uu.seUppsala University Publications
Change search
Refine search result
12 1 - 50 of 95
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 1.
    Andersson, Peter
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Jacobsson Svärd, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Andersson Sundén, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Sjöstrand, Henrik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Neutron tomography of axially symmetric objects using 14 MeV neutrons from a portable neutron generator2014In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 85, no 8, p. 085109-Article in journal (Refereed)
    Abstract [en]

    In nuclear boiling water reactor cores, the distribution of water and steam (void) is essential for both safety and efficiency reasons. In order to enhance predictive capabilities, void distribution assessment is performed in two-phase test-loops under reactor-relevant conditions. This article proposes the novel technique of fast-neutron tomography using a portable deuterium-tritium neutron generator to determine the void distribution in these loops.Fast neutrons have the advantage of high transmission through the metallic structures and pipes typically concealing a thermal-hydraulic test loop, while still being fairly sensitive to the water/void content. However, commercially available fast-neutron generators also have the disadvantage of a relatively low yield and fast-neutron detection also suffers from relatively low detection efficiency. Fortunately, some loops are axially symmetric, a property which can be exploited to reduce the amount of data needed for tomographic measurement, thus limiting the interrogation time needed.In this article, three axially-symmetric test objects depicting a thermal-hydraulic test loop have been examined; steel pipes with outer diameter 24 mm, thickness 1.5 mm and with three different distributions of the plastic material POM inside the pipes. Data recorded with the FANTOM fast-neutron tomography instrument have been used to perform tomographic reconstructions to assess their radial material distribution. Here, a dedicated tomographic algorithm that exploits the symmetry of these objects has been applied, which is described in the paper.Results are demonstrated in 20 rixel (radial pixel) reconstructions of the interior constitution and 2D visualization of the pipe interior is demonstrated. The local POM attenuation coefficients in the rixels were measured with errors (RMS) of 0.025, 0.020 and 0.022 cm-1, solid POM attenuation coefficient. The accuracy and precision is high enough to provide a useful indication on the flow mode, and a visualization of the radial material distribution can be obtained. A benefit of this system is its potential to be mounted at any axial height of a two-phase test section without requirements for pre-fabricated entrances or windows. This could mean a significant increase in flexibility of the void distribution assessment capability at many existing two-phase test loops.

  • 2.
    Andersson, Peter
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Sundén, E. Andersson
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Jacobsson Svärd, Staffan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Sjöstrand, Henrik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Correction for dynamic bias error in transmission measurements of void fraction2012In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 83, no 12, p. 125110-Article in journal (Refereed)
    Abstract [en]

    Dynamic bias errors occur in transmission measurements, such as X-ray, gamma, or neutron radiography or tomography. This is observed when the properties of the object are not stationary in time and its average properties are assessed. The nonlinear measurement response to changes in transmission within the time scale of the measurement implies a bias, which can be difficult to correct for. A typical example is the tomographic or radiographic mapping of void content in dynamic two-phase flow systems. In this work, the dynamic bias error is described and a method to make a first-order correction is derived. A prerequisite for this method is variance estimates of the system dynamics, which can be obtained using high-speed, time-resolved data acquisition. However, in the absence of such acquisition, a priori knowledge might be used to substitute the time resolved data. Using synthetic data, a void fraction measurement case study has been simulated to demonstrate the performance of the suggested method. The transmission length of the radiation in the object under study and the type of fluctuation of the void fraction have been varied. Significant decreases in the dynamic bias error were achieved to the expense of marginal decreases in precision.

  • 3.
    Backlin, Eric
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine.
    A comparator for spectroscopic work1930In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 1, no 11, p. 662-666Article in journal (Refereed)
  • 4.
    Batistoni, Paola
    et al.
    ENEA, Dept Fus & Technol Nucl Safety & Secur, I-00044 Frascati, Rome, Italy..
    Popovichev, S.
    Culham Sci Ctr, CCFE, Abingdon OX14 3DB, Oxon, England..
    Conroy, Sean
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Lengar, I.
    Jozef Stefan Inst, Reactor Phys Div, Jamova Cesta 39, SI-1000 Ljubljana, Slovenia..
    Cufar, A.
    Jozef Stefan Inst, Reactor Phys Div, Jamova Cesta 39, SI-1000 Ljubljana, Slovenia..
    Abhangi, M.
    Inst Plasma Res, Gandhinagar 382428, Gujarat, India..
    Snoj, L.
    Jozef Stefan Inst, Reactor Phys Div, Jamova Cesta 39, SI-1000 Ljubljana, Slovenia..
    Horton, L.
    Culham Sci Ctr, JET Exploitat Unit, Abingdon OX14 3DB, Oxon, England..
    Calibration of neutron detectors on the Joint European Torus2017In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 88, no 10, article id 103505Article in journal (Refereed)
    Abstract [en]

    The present paper describes the findings of the calibration of the neutron yield monitors on the Joint European Torus (JET) performed in 2013 using a Cf-252 source deployed inside the torus by the remote handling system, with particular regard to the calibration of fission chambers which provide the time resolved neutron yield from JET plasmas. The experimental data obtained in toroidal, radial, and vertical scans are presented. These data are first analysed following an analytical approach adopted in the previous neutron calibrations at JET. In this way, a calibration function for the volumetric plasma source is derived which allows us to understand the importance of the different plasma regions and of different spatial profiles of neutron emissivity on fission chamber response. Neutronics analyses have also been performed to calculate the correction factors needed to derive the plasma calibration factors taking into account the different energy spectrum and angular emission distribution of the calibrating (point) Cf-252 source, the discrete positions compared to the plasma volumetric source, and the calibration circumstances. All correction factors are presented and discussed. We discuss also the lessons learnt which are the basis for the on-going 14 MeV neutron calibration at JET and for ITER.

  • 5.
    Bielecki, J.
    et al.
    Polish Acad Sci, Inst Nucl Phys, PL-31342 Krakow, Poland..
    Giacomelli, L.
    CCFE, Culham Sci Ctr, Abingdon OX14 3DB, Oxon, England.;Ist Fis Plasma P Caldirola, Milan, Italy..
    Kiptily, V.
    CCFE, Culham Sci Ctr, Abingdon OX14 3DB, Oxon, England..
    Scholz, M.
    Polish Acad Sci, Inst Nucl Phys, PL-31342 Krakow, Poland..
    Drozdowicz, K.
    Polish Acad Sci, Inst Nucl Phys, PL-31342 Krakow, Poland..
    Conroy, Sean
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy. CCFE, Culham Sci Ctr, Abingdon OX14 3DB, Oxon, England..
    Craciunescu, T.
    Natl Inst Laser Plasma & Radiat Phys, IAP, Bucharest, Romania..
    Kempenaars, M.
    CCFE, Culham Sci Ctr, Abingdon OX14 3DB, Oxon, England..
    Phillips-Tikhonov regularization with a priori information for neutron emission tomographic reconstruction on Joint European Torus2015In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 86, no 9, article id 093505Article in journal (Refereed)
    Abstract [en]

    A method of tomographic reconstruction of the neutron emissivity in the poloidal cross section of the Joint European Torus (JET, Culham, UK) tokamak was developed. Due to very limited data set (two projection angles, 19 lines of sight only) provided by the neutron emission profile monitor (KN3 neutron camera), the reconstruction is an ill-posed inverse problem. The aim of this work consists in making a contribution to the development of reliable plasma tomography reconstruction methods that could be routinely used at JET tokamak. The proposed method is based on Phillips-Tikhonov regularization and incorporates a priori knowledge of the shape of normalized neutron emissivity profile. For the purpose of the optimal selection of the regularization parameters, the shape of normalized neutron emissivity profile is approximated by the shape of normalized electron density profile measured by LIDAR or high resolution Thomson scattering JET diagnostics. In contrast with some previously developed methods of ill-posed plasma tomography reconstruction problem, the developed algorithms do not include any post-processing of the obtained solution and the physical constrains on the solution are imposed during the regularization process. The accuracy of the method is at first evaluated by several tests with synthetic data based on various plasma neutron emissivity models (phantoms). Then, the method is applied to the neutron emissivity reconstruction for JET D plasma discharge #85100. It is demonstrated that this method shows good performance and reliability and it can be routinely used for plasma neutron emissivity reconstruction on JET.

  • 6.
    Binda, Federico
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Andersson Sundén, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Eriksson, Jacob
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Hellesen, Carl
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Ericsson, Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Absolute calibration of the JET neutron profile monitorIn: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623Article in journal (Refereed)
  • 7.
    Binda, Federico
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Ericsson, Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Eriksson, Jacob
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Hellesen, Carl
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Conroy, Sean
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Sundén, Erik Andersson
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Forward fitting of experimental data from a NE213 neutron detector installed with the magnetic proton recoil upgraded spectrometer at JET2014In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 85, no 11, p. 11E123-Article in journal (Refereed)
    Abstract [en]

    In this paper, we present the results obtained from the data analysis of neutron spectra measured with a NE213 liquid scintillator at JET. We calculated the neutron response matrix of the instrument combining MCNPX simulations, a generic proton light output function measured with another detector and the fit of data from ohmic pulses. For the analysis, we selected a set of pulses with neutral beam injection heating (NBI) only and we applied a forward fitting procedure of modeled spectral components to extract the fraction of thermal neutron emission. The results showed the same trend of the ones obtained with the dedicated spectrometer TOFOR, even though the values from the NE213 analysis were systematically higher. This discrepancy is probably due to the different lines of sight of the two spectrometers (tangential for the NE213, vertical for TOFOR). The uncertainties on the thermal fraction estimates were from 4 to 7 times higher than the ones from the TOFOR analysis.

  • 8.
    Bohlin, K
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Interface circuit between a capacitance meter (PAR 401) and a microcomputer (Apple II)1985In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 56, no 11Article in journal (Refereed)
  • 9.
    Boye, Shawn A.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Rosén, Daniel
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Lazor, Peter
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, Solid Earth Geology.
    Katardjiev, Ilia
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Precise magnetoresistance and Hall resistivity measurements in the diamond anvil cell2004In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 75, no 11, p. 5010-5015Article in journal (Refereed)
    Abstract [en]

    An experimental system in combination with a technique for creating samples has been developed for conducting magnetotransport measurements of 3d ferromagnets as a function of temperature and pressure. Polycrystalline Ni0.985O0.015 thin film samples have been manufactured for experiments at zero pressure and in the diamond anvil cell (DAC) such that the contacts are of a predetermined size. This ensures that the placement of the leads in the pressure chamber of the DAC does not affect the quality of the measurement. Magnetoresistance and Hall resistivity measurements are preformed using the van der Pauw technique and the constant current method. The performance of the experimental apparatus is demonstrated by magnetotransport measurements of Ni0.985O0.015 thin films between 285 and 455 K in applied magnetic fields up to 10 T. The change in magnetic resistivity measured in the transverse configuration at zero pressure in the DAC, −0.0162(2) μΩ  cm T−1 at 297 K, is observed to be negative and linear up to the maximum applied field. The extraordinary Hall coefficient measured at zero pressure and 297 K is found to be RE = −30.4(1)×10−10 m3 C−1.

  • 10. Cazzaniga, C.
    et al.
    Sundén, Erik Andersson
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Binda, Federico
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Croci, G.
    Ericsson, Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Giacomelli, L.
    Gorini, G.
    Griesmayer, E.
    Grosso, G.
    Kaveney, G.
    Nocente, M.
    Cippo, E. Perelli
    Rebai, M.
    Syme, B.
    Tardocchi, M.
    Single crystal diamond detector measurements of deuterium-deuterium and deuterium-tritium neutrons in Joint European Torus fusion plasmas2014In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 85, no 4, p. 043506-Article in journal (Refereed)
    Abstract [en]

    First simultaneous measurements of deuterium-deuterium (DD) and deuterium-tritium neutrons from deuterium plasmas using a Single crystal Diamond Detector are presented in this paper. The measurements were performed at JET with a dedicated electronic chain that combined high count rate capabilities and high energy resolution. The deposited energy spectrum from DD neutrons was successfully reproduced by means of Monte Carlo calculations of the detector response function and simulations of neutron emission from the plasma, including background contributions. The reported results are of relevance for the development of compact neutron detectors with spectroscopy capabilities for installation in camera systems of present and future high power fusion experiments.

  • 11.
    Cecconello, Marco
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics. EURATOM VR Assoc, Uppsala, Sweden.
    Sperduti, Andrea
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics. EURATOM VR Assoc, Uppsala, Sweden.
    Fitzgerald, I.
    Culham Sci Ctr, EURATOM CCFE Fus Assoc, Abingdon, Oxon, England.
    Conroy, Sean
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics. EURATOM VR Assoc, Uppsala, Sweden.
    Holm, Stefan Jarl
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics. EURATOM VR Assoc, Uppsala, Sweden.
    Weiszflog, Matthias
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics. EURATOM VR Assoc, Uppsala, Sweden.
    The neutron camera upgrade for MAST Upgrade2018In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 89, no 10, article id 10I110Article in journal (Refereed)
    Abstract [en]

    The Neutron Camera Upgrade (NCU) is a neutron flux monitor consisting of six lines of sight (LoSs) under installation on Mega Ampere Spherical Tokamak (MAST) Upgrade. The NCU is expected to contribute to the study of the confinement of fast ions and on the efficiency of non-inductive current drive in the presence of on-axis and off-axis neutral beam injection by measuring the neutron emissivity profile along the equatorial plane. This paper discusses the NCU main design criteria, the engineering and interfacing issues, and the solutions adopted. In addition, the results from the characterization and performance studies of the neutron detectors using standard gamma-rays sources and a Cf-252 source are discussed. The proposed design has a time resolution of 1 ms with a statistical uncertainty of less than 10% for all MAST Upgrade scenarios with a spatial resolution of 10 cm: higher spatial resolution is possible by moving the LoSs in-between plasma discharges. The energy resolution of the neutron detector is better than 10% for a light output of 0.8 MeVee, and the measured pulse shape discrimination is satisfactory.

  • 12.
    Cecconello, Marco
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Turnyanskiy, M.
    Conroy, S.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Ericsson, G.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Ronchi, Emanuel
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Sangaroon, S.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Akers, R.
    Fitzgerald, I.
    Cullen, A.
    Weiszflog, Matthias
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    A neutron camera system for MAST2010In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 81, no 10, p. 10D315-Article in journal (Refereed)
    Abstract [en]

    A prototype neutron camera has been developed and installed at MAST as part of a feasibility study for a multichord neutron camera system with the aim to measure the spatial and time resolved 2.45 MeV neutron emissivity profile. Liquid scintillators coupled to a fast digitizer are used for neutron/gamma ray digital pulse shape discrimination. The preliminary results obtained clearly show the capability of this diagnostic to measure neutron emissivity profiles with sufficient time resolution to study the effect of fast ion loss and redistribution due to magnetohydrodynamic activity. A minimum time resolution of 2 ms has been achieved with a modest 1.5 MW of neutral beam injection heating with a measured neutron count rate of a few 100 kHz.

  • 13. Cherigier-Kovacic, L.
    et al.
    Ström, Petter
    KTH, Fusionsplasmafysik.
    Lejeune, A.
    Doveil, F.
    Electric field induced Lyman-alpha emission of a hydrogen beam for electric field measurements2015In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 86, no 6, article id 063504Article in journal (Refereed)
    Abstract [en]

    Electric field induced Lyman-alpha emission is a new way of measuring weak electric fields in vacuum and in a plasma. It is based on the emission of Lyman-alpha radiation (121.6 nm) by a low-energy metastable H atom beam due to Stark-quenching of the 2s level induced by the field. In this paper, we describe the technique in detail. Test measurements have been performed in vacuum between two plates polarized at a controlled voltage. The intensity of emitted radiation, proportional to the square of the field modulus, has been recorded by a lock-in technique, which gives an excellent signal to noise ratio. These measurements provide an in situ calibration that can be used to obtain the absolute value of the electric field. A diagnostic of this type can help to address a long standing challenge in plasma physics, namely, the problem of measuring electric fields without disturbing the equilibrium of the system that is being studied.

  • 14. Ciavola, G.
    et al.
    Gammino, S.
    Barbarino, S.
    Celona, L.
    Consoli, F.
    Gallo, G.
    Maimone, F.
    Mascali, D.
    Passarello, S.
    Galata, A.
    Tinschert, K.
    Spaedtke, P.
    Lang, R.
    Maeder, J.
    Rossbach, J.
    Koivisto, H.
    Savonen, M.
    Koponen, T.
    Suominen, P.
    Ropponen, T.
    Barue, C.
    Lechartier, M.
    Beijers, J. P. M.
    Brandenburg, S.
    Kremers, H. R.
    van Rooyen, Daniel
    Uppsala University, The Svedberg Laboratory.
    Kuchler, D.
    Scrivens, R.
    Schachter, L.
    Dobrescu, S.
    Stiebing, K.
    Status report of the multipurpose superconducting electron cyclotron resonance ion source2008In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 79, no 2, p. 02A326-Article in journal (Refereed)
    Abstract [en]

    Intense heavy ion beam production with electron cyclotron resonance (ECR) ion sources is a common requirement for many of the accelerators under construction in Europe and elsewhere. An average increase of about one order of magnitude per decade in the performance of ECR ion sources was obtained up to now since the time of pioneering experiment of R. Geller at CEA, Grenoble, and this trend is not deemed to get the saturation at least in the next decade, according to the increased availability of powerful magnets and microwave generators. Electron density above 1013 cm(-3) and very high current of multiply charged ions are expected with the use of 28 GHz microwave heating and of an adequate plasma trap, with a B-minimum shape, according to the high B mode concept [S. Gammino and G. Ciavola, Plasma Sources Sci. Technol. 5, 19 (1996)]. The MS-ECRIS ion source has been designed following this concept and its construction is underway at GSI, Darmstadt. The project is the result of the cooperation of nine European institutions with the partial funding of EU through the sixth Framework Programme. The contribution of different institutions has permitted to build in 2006-2007 each component at high level of expertise. The description of the major components will be given in the following with a view on the planning of the assembly and commissioning phase to be carried out in fall 2007. An outline of the experiments to be done with the MS-ECRIS source in the next two years will be presented.

  • 15.
    Conroy, Sean W.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Weiszflog, Matthias
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Andersson-Sunden, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Ericsson, Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Gatu-Johnson, Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Hellesen, Carl
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Ronchi, Emanuel
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Sjöstrand, Henrik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Neutron spectrometer for ITER using silicon detectors2008In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 79, no 10, p. 10E508-Article in journal (Refereed)
    Abstract [en]

    High resolution neutron spectrometers provide information about plasma parameters at existing fusion experiments. Such a system may also be employed at ITER. Proton recoil telescopes have classically been used to detect neutrons with good energy resolution but poor efficiency. Using annular silicon detectors, it is possible to greatly increase the solid angle coverage and hence improve efficiency. Based on a simulation (MCNPX) study, the scaling of energy resolution, efficiency, and time to determine an ion temperature to 10% accuracy on foil thickness and detector location is shown. The latter quantity is used to determine the optimum foil thickness and detector geometry for specific plasma temperatures. For a 20 keV deuterium-tritium (DT) plasma, 5.3% resolution with efficiency of 2.9x10(-4) n cm(2) is attainable using the available detectors. This gives a temperature measurement with 10% accuracy in 1.1 ms for a neutron flux of 2x10(9) n cm(-2). Multiple detectors can be used to further increase the efficiency if needed. A system of this kind could be tested in a future DT campaign at, for example, JET.

  • 16. Craciunescu, Teddy
    et al.
    Andersson Sundén, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Asp, E.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Binda, Federico
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Cecconello, Marco
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Conroy, Sean
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Dzysiuk, Nataliia
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Ericsson, Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Eriksson, Jacob
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Hellesen, Carl
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Hjalmarsson, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Possnert, Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Sjöstrand, Henrik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Skiba, Mateusz
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Weiszflog, Matthias
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Zychor, I.
    Evaluation of reconstruction errors and identification of artefacts for JET gamma and neutron tomography2016In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 87, no 1, article id 013502Article in journal (Refereed)
    Abstract [en]

    The Joint European Torus (JET) neutron profile monitor ensures 2D coverage of the gamma and neutron emissive region that enables tomographic reconstruction. Due to the availability of only two projection angles and to the coarse sampling, tomographic inversion is a limited data set problem. Several techniques have been developed for tomographic reconstruction of the 2-D gamma and neutron emissivity on JET, but the problem of evaluating the errors associated with the reconstructed emissivity profile is still open. The reconstruction technique based on the maximum likelihood principle, that proved already to be a powerful tool for JET tomography, has been used to develop a method for the numerical evaluation of the statistical properties of the uncertainties in gamma and neutron emissivity reconstructions. The image covariance calculation takes into account the additional techniques introduced in the reconstruction process for tackling with the limited data set (projection resampling, smoothness regularization depending on magnetic field). The method has been validated by numerically simulations and applied to JET data. Different sources of artefacts that may significantly influence the quality of reconstructions and the accuracy of variance calculation have been identified.

  • 17.
    Craciunescu, Teddy
    et al.
    National Institute for Laser, Plasma and Radiation Physics, Magurele, Bucharest, Romania.
    Andersson Sundén, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Binda, Federico
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Cecconello, Marco
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Conroy, Sean
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Dzysiuk, Nataliia
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Ericsson, Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Eriksson, Jacob
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Hellesen, Carl
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Hjalmarsson, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Possnert, Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Sjöstrand, Henrik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Skiba, Mateusz
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Weiszflog, Matthias
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Zychor, I.
    Natl Ctr Nucl Res, Otwock, Poland.
    Maximum likelihood bolometric tomography for the determination of the uncertainties in the radiation emission on JET TOKAMAK2018In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 89, no 5, article id 053504Article in journal (Refereed)
    Abstract [en]

    The total emission of radiation is a crucial quantity to calculate the power balances and to understand the physics of any Tokamak. Bolometric systems are the main tool to measure this important physical quantity through quite sophisticated tomographic inversion methods. On the Joint European Torus, the coverage of the bolometric diagnostic, due to the availability of basically only two projection angles, is quite limited, rendering the inversion a very ill-posed mathematical problem. A new approach, based on the maximum likelihood, has therefore been developed and implemented to alleviate one of the major weaknesses of traditional tomographic techniques: the difficulty to determine routinely the confidence intervals in the results. The method has been validated by numerical simulations with phantoms to assess the quality of the results and to optimise the configuration of the parameters for the main types of emissivity encountered experimentally. The typical levels of statistical errors, which may significantly influence the quality of the reconstructions, have been identified. The systematic tests with phantoms indicate that the errors in the reconstructions are quite limited and their effect on the total radiated power remains well below 10%. A comparison with other approaches to the inversion and to the regularization has also been performed.

  • 18.
    Céolin, D.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science.
    Forsell, J-O
    Wannberg, B.
    Legendre, S.
    Palaudoux, J.
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmacy.
    Öhrwall, Gunnar
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science.
    Svensson, Svante
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science.
    Piancastelli, Maria Novella
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science.
    A rotatable electron spectrometer for multicoincidence experiments2010In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 81, no 6, p. 063112-Article in journal (Refereed)
    Abstract [en]

    We have developed a rotatable hemispherical spectrometer with good energy and angular resolution, which can be positioned with the lens axis arbitrarily within a solid angle of 1 pi. The collection angle of the emitted electrons with respect to the polarization axis of the light is set by means of a three-axes goniometer, operating under vacuum. An important requirement for this setup was the possibility to perform coincidences between the electron analyzed by the spectrometer and one or several other particles, such as ions, electrons, or photons. The lens system and the hemispheres have been designed to accommodate such experimental demands, regarding parameters such as the resolving power, the acceptance angle, or the width of the kinetic energy window which can be recorded for a given pass energy. We have chosen to detect the impact position of the electron at the focal plane of the hemispherical analyzer with a delay line detector and a time-to-digital converter as acquisition card rather than using a conventional charge-coupled device camera.

  • 19.
    Dal Molin, A.
    et al.
    Univ Milano Bicocca, Dipartimento Fis G Occhialini, Milan, Italy.
    Andersson Sundén, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Binda, Federico
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Cecconello, Marco
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Conroy, Sean
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Dzysiuk, Nataliia
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Ericsson, Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Eriksson, Jacob
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Hellesen, Carl
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Hjalmarsson, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Possnert, Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Sjöstrand, Henrik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Skiba, Mateusz
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Weiszflog, Matthias
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Zychor, I.
    Development of a new compact gamma-ray spectrometer optimised for runaway electron measurements2018In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 89, no 10, article id 10I134Article in journal (Refereed)
    Abstract [en]

    A new compact gamma-ray spectrometer was developed in order to optimise the measurement of bremsstrahlung radiation emitted from runaway electrons in the MeV range. The detector is based on a cerium doped lutetium-yttrium oxyorthosilicate (LYSO:Ce) scintillator coupled to a silicon photomultiplier and is insensitive to magnetic fields. Adedicated electronic board was developed to optimise the signal readout as well as for online control of the device. The detector combines a dynamic range up to 10 MeV with moderate energy non-linearity, counting rate capabilities in excess of 1 MHz, and an energy resolution that extrapolates to a few % in the MeV range, thus meeting the requirements for its application to runaway electron studies by bremsstrahlung measurements in the gamma-ray energy range.

  • 20. Devishvili, A.
    et al.
    Zhernenkov, K.
    Dennison, Andrew J. C.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Toperverg, B. P.
    Wolff, Max
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Hjörvarsson, Björgvin
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Materials Physics.
    Zabel, H.
    SuperADAM: Upgraded polarized neutron reflectometer at the Institut Laue-Langevin2013In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 84, no 2, p. 025112-Article in journal (Refereed)
    Abstract [en]

    A new neutron reflectometer SuperADAM has recently been built and commissioned at the Institut Laue-Langevin, Grenoble, France. It replaces the previous neutron reflectometer ADAM. The new instrument uses a solid state polarizer/wavelength filter providing a highly polarized (up to 98.6%) monochromatic neutron flux of 8 x 10(4) n cm(-2) s(-1) with monochromatization Delta lambda/lambda = 0.7% and angular divergence Delta alpha = 0.2 mrad. The instrument includes both single and position sensitive detectors. The position sensitive detector allows simultaneous measurement of specular reflection and off-specular scattering. Polarization analysis for both specular reflection and off-specular scattering is achieved using either mirror analyzers or a He-3 spin filter cell. High efficiency detectors, low background, and high flux provides a dynamic range of up to seven decades in reflectivity. Detailed specifications and the instrument capabilities are illustrated with examples of recently collected data in the fields of thin film magnetism and thin polymer films.

  • 21.
    Englund, Carl-Johan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Agåker, Marcus
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Fredriksson, Pierre
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Olsson, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Johansson, Niklas
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Rubensson, Jan-Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Nordgren, Joseph
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    An ultra-high vacuum chamber for scattering experiments featuring in-vacuum continuous in-plane variation of the angle between entrance and exit vacuum ports2015In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 86, no 9, article id 095110Article in journal (Refereed)
    Abstract [en]

    A concept that enables in-vacuum continuous variation of the angle between two ports in one plane has been developed and implemented. The vacuum chamber allows for measuring scattering cross sections as a function of scattering angle and is intended for resonant inelastic X-ray scattering experiments. The angle between the ports can be varied in the range of 30 degrees-150 degrees, while the pressure change is less than 2 x 10(-10) mbars.

  • 22.
    Ericsson, G.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Conroy, S.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Johnson, M. Gatu
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Andersson Sundén, E.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Cecconello, Marco
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Eriksson, Jacob
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Hellesen, Carl
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Sangaroon, S.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Weiszflog, Matthias
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Neutron spectroscopy as a fuel ion ratio diagnostic: Lessons from JET and prospects for ITER2010In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 81, no 10, p. 10D324-Article in journal (Refereed)
    Abstract [en]

    The determination of the fuel ion ratio n(t)/n(d) in ITER is required at a precision of 20%, time resolution of 100 ms, spatial resolution of a/10, and over a range of 0.01<10. We use simplified but realistic Monte Carlo models of ITER to assess the possibility to use neutron emission spectroscopy ((NES) for such measurements. We show that NES meets the requirements for ion temperatures T-i>6 keV and for n(T)/n(D)<0.6. A crucial issue is the signal-to-background situation in the measurement of the weak 2.5 MeV emission from DD reactions in the presence of a background of scattered 14 MeV DT neutrons. Important experimental input and corroboration for this assessment are presented from the time-of-flight neutron spectrometer at JET where the presence of a strong component of backscattered neutrons is observed. Neutron emission components on ITER due to beam-thermal and tritium-tritium reactions can further enhance the prospects for NES.

  • 23.
    Eriksson, Jacob
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Castegnetti, Giuseppe
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Conroy, Sean
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Ericsson, Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Luca, Giacomelli
    Department of Physics, Università degli Studi di Milano-Bicocca, Milano, Italy.
    Hellesen, Carl
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Deuterium density profile determination at JET using a neutron camera and a neutronspectrometer2014In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 85, no 11, p. 11E106-Article in journal (Refereed)
    Abstract [en]

    In this work we estimate the fuel ion density profile in deuterium plasmas at JET, using the JET neutron camera, the neutron time-of-flight spectrometer TOFOR, and fusion reactivities modeled by the transport code TRANSP. The framework has been tested using synthetic data, which showed that the density profile could be reconstructed with an average accuracy of the order of 10 %. The method has also been applied to neutron measurements from a neutral beam heated JET discharge, which gave nd/ne ≈ 0.6 ± 0.3 in the plasma core and nd/ne ≈ 0.4 ± 0.3 towards the edge. Correction factors for detector efficiencies, neutron attenuation, and back-scattering are not yet included in the analysis; future work will aim at refining the estimated density.

  • 24.
    Eriksson, Susanna K
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Hahlin, Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Kahk, Juhan Matthias
    Villar-Garcia, Ignacio J
    Webb, Matthew J
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Physical Organic Chemistry.
    Grennberg, Helena
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - BMC, Physical Organic Chemistry.
    Yakimova, Rositza
    Rensmo, Håkan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Edström, Kristina
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Structural Chemistry.
    Hagfeldt, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Physical Chemistry.
    Siegbahn, Hans
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Edwards, Mårten O M
    Karlsson, Patrik G
    Backlund, Klas
    Ahlund, John
    Payne, David J
    A versatile photoelectron spectrometer for pressures up to 30 mbar2014In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 85, no 7, p. 075119-Article in journal (Refereed)
    Abstract [en]

    High-pressure photoelectron spectroscopy is a rapidly developing technique with applications in a wide range of fields ranging from fundamental surface science and catalysis to energy materials, environmental science, and biology. At present the majority of the high-pressure photoelectron spectrometers are situated at synchrotron end stations, but recently a small number of laboratory-based setups have also emerged. In this paper we discuss the design and performance of a new laboratory based high pressure photoelectron spectrometer equipped with an Al Kα X-ray anode and a hemispherical electron energy analyzer combined with a differentially pumped electrostatic lens. The instrument is demonstrated to be capable of measuring core level spectra at pressures up to 30 mbar. Moreover, valence band spectra of a silver sample as well as a carbon-coated surface (graphene) recorded under a 2 mbar nitrogen atmosphere are presented, demonstrating the versatility of this laboratory-based spectrometer.

  • 25. Figueiredo, J.
    et al.
    Andersson Sundén, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Binda, Federico
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Cecconello, Marco
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Conroy, Sean
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Dzysiuk, Nataliia
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Ericsson, Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Eriksson, Jacob
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Hellesen, Carl
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Hjalmarsson, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Possnert, Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Sjöstrand, Henrik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Skiba, Mateusz
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Weiszflog, Matthias
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Zoletnik, S.
    JET diagnostic enhancements testing and commissioning in preparation for DT scientific campaigns2018In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 89, no 10, article id 10K119Article in journal (Refereed)
    Abstract [en]

    In order to optimize the scientific exploitation of JET (Joint European Torus) during the upcoming deuterium-tritium experiments, a set of diagnostic systems is being enhanced. These upgrades focus mainly on the experimental and operational conditions expected during tritium campaigns. It should be stressed that measurements relevant for burning plasmas are specifically targeted. Previously non-available capabilities, such as a current measurement system fully covering all poloidal field circuits, are described in detail. Instrument descriptions, performance prediction, testing, and initial commissioning results of these systems are presented.

  • 26.
    Forsberg, Johan
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Duda, Laurent-Claudius
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Olsson, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Schmitt, Thorsten
    Swiss Light Source, Paul Scherrer Institute.
    Andersson, Joakim
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Nordgren, Joseph
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Hedberg, Jonas
    Leygraf, Christofer
    Aastrup, Teodor
    Wallinder, Daniel
    Guo, Jinghua
    System for in situ studies of atmospheric corrosion of metal films using soft x-ray spectroscopy and quartz crystal microbalance2007In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 78, no 8, p. 083110-Article in journal (Refereed)
    Abstract [en]

    We present a versatile chamber (“atmospheric corrosion cell”) for soft x-ray absorption/emission spectroscopy of metal surfaces in a corrosive atmosphere allowing novel in situ electronic structure studies. Synchrotron x rays passing through a thin window separating the corrosion cell interior from a beamline vacuum chamber probe a metal film deposited on a quartz crystal microbalance (QCM) or on the inside of the window. We present some initial results on chloride induced corrosion of iron surfaces in humidified synthetic air. By simultaneous recording of QCM signal and soft x-ray emission from the corroding sample, correlation between mass changes and variations in spectral features is facilitated.

     

  • 27.
    Gatu Johnson, Maria
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Giacomelli, Luca
    Hjalmarsson, Anders
    Weiszflog, Matthias
    Andersson Sundén, Erik
    Conroy, Sean
    Ericsson, Göran
    Hellesen, Carl
    Källne, Jan
    Ronchi, Emanuele
    Gorini, Giuseppe
    EURATOM-ENEA-CNR Association, Instituto di Fisica del Plasma, I-20126 Milan, Italy.
    Tardocchi, Marco
    Murari, Andrea
    EURATOM-ENEA-CNR Association, Consorzio RFX, I.35127 Padua, Italy.
    Popovichev, Sergei
    EURATOM-UKAEA Association, JET, Culham Science Centre, Abingdon, Oxfordshire, GB OX14 3DB, United Kingdom.
    Sousa, Jorge
    Associação EURATOM/Instituto Superior Técnico (IST), Centro de Fusão Nuclear, Avenida Rovisco Pais 1, P1049-001 Lisboa, Portugal.
    Pereira, Rita
    Combo, Alvaro
    Cruz, Nuno
    The TOFOR neutron spectrometer and its first use at JET2006In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 77, no 10E702, p. 1-3Article in journal (Refereed)
    Abstract [en]

    A time-of-flight neutron spectrometer (TOFOR) has been developed to measure the 2.45  MeV  d+d3He+n neutron emission from D plasmas. The TOFOR design features the capability to operate at high rates in the 100  kHz range, data collection with fast time digitizing and storing, and monitoring of the signals from the scintillation detectors used. This article describes the principles of the instrument and its installation at JET and presents preliminary data to illustrate the TOFOR performance as a neutron emission spectroscopy diagnostic.

  • 28. Gherendi, M.
    et al.
    Zoita, V. L.
    Craciunescu, T.
    Johnson, M. G.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Pantea, A.
    Baltog, I.
    Edlington, T.
    Hellesen, Carl
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Kiptily, V.
    Conroy, Sean
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Murari, A.
    Popovichev, S.
    Neutron field parameter measurements on the JET tokamak by means of super-heated fluid detectors2012In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 83, no 10, p. 10E124-Article in journal (Refereed)
    Abstract [en]

    The neutron field parameters (fluence and energy distribution) at a specific location outside the JET Torus Hall have been measured by means of super-heated fluid detectors (or bubble detectors) in combination with an independent, time-of-flight, technique. The bubble detector assemblies were placed at the end of a vertical line of sight at about 16 m from the tokamak mid plane. Spatial distributions of the neutron fluence along the radial and toroidal directions have been obtained using two-dimensional arrays of bubble detectors. Using a set of three bubble detector spectrometers the neutron energy distribution was determined over a broad energy range, from about 10 keV to above 10 MeV, with an energy resolution of about 30% at 2.5 MeV. The very broad energy response allowed for the identification of energy features far from the main fusion component (around 2.45 MeV for deuterium discharges).

  • 29.
    Giacomelli, L.
    et al.
    CNR, Ist Fis Plasma P Caldirola, Milan, Italy.
    Belli, F.
    ENEA CR Frascati, Dipartimento FSN, Rome, Italy.
    Binda, Federico
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Conroy, Sean
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Eriksson, Jacob
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Milocco, A.
    Univ Milano Bicocca, Dipartimento Fis G Occhialini, Milan, Italy;Culham Sci Ctr, CCFE, Abingdon, Oxon, England.
    Popovicev, S.
    Culham Sci Ctr, CCFE, Abingdon, Oxon, England.
    Syme, D. B.
    Culham Sci Ctr, CCFE, Abingdon, Oxon, England.
    Neutron emission spectroscopy of D plasmas at JET with a compact liquid scintillating neutron spectrometer2018In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 89, no 10, article id 10I113Article in journal (Refereed)
    Abstract [en]

    Neutron emission spectroscopy is a diagnostic technique that allows for energy measurements of neutrons born in nuclear reactions. The JET tokamak fusion experiment (Culham, UK) has a special role in this respect as advanced spectrometers for 2.5 MeV and 14 MeV neutrons have been developed here for the first time for measurements of the neutron emission spectrum from D and DT plasmas with unprecedented accuracy. Twin liquid scintillating neutron spectrometers were built and calibrated at the Physikalisch-Technische Bundesanstalt (PTB) (Braunschweig, Germany) and installed on JET in the recent years with tangential-equatorial (KM12) and vertical-radial (KM13) view lines, with the latter only recently operational. This article reports on the performance of KM12 and on the development of the data analysis methods in order to extract physics information upon D ions kinematics in JET auxiliary-heated D plasmas from 2.5 MeV neutron measurements. The comparison of these results with the correspondents from other JET neutron spectrometers is also presented: their agreement allows for JET unique capability of multi-lines of sight neutron spectroscopy and for benchmarking other 14 MeV neutron spectrometers installed on the same lines of sight in preparation for the DT experimental campaign at JET.

  • 30. Giacomelli, L.
    et al.
    Conroy, Sean
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Gorini, G.
    Horton, L.
    Murari, A.
    Popovichev, S.
    Syme, D. B.
    Tomographic analysis of neutron and gamma pulse shape distributions from liquid scintillation detectors at Joint European Torus2014In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 85, no 2, p. 023505-Article in journal (Refereed)
    Abstract [en]

    The Joint European Torus (JET, Culham, UK) is the largest tokamak in the world devoted to nuclear fusion experiments of magnetic confined Deuterium (D)/Deuterium-Tritium (DT) plasmas. Neutrons produced in these plasmas are measured using various types of neutron detectors and spectrometers. Two of these instruments on JET make use of organic liquid scintillator detectors. The neutron emission profile monitor implements 19 liquid scintillation counters to detect the 2.45 MeV neutron emission from D plasmas. A new compact neutron spectrometer is operational at JET since 2010 to measure the neutron energy spectra from both D and DT plasmas. Liquid scintillation detectors are sensitive to both neutron and gamma radiation but give light responses of different decay time such that pulse shape discrimination techniques can be applied to identify the neutron contribution of interest from the data. The most common technique consists of integrating the radiation pulse shapes within different ranges of their rising and/or trailing edges. In this article, a step forward in this type of analysis is presented. The method applies a tomographic analysis of the 3-dimensional neutron and gamma pulse shape and pulse height distribution data obtained from liquid scintillation detectors such that n/gamma discrimination can be improved to lower energies and additional information can be gained on neutron contributions to the gamma events and vice versa.

  • 31.
    Giacomelli, L.
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Hjalmarsson, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Kallne, J.
    Hellesen, Carl
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Tardocchi, M.
    Gorini, G.
    Van Eester, D.
    Lerche, E.
    Johnson, T.
    Kiptily, V.
    Conroy, Sean
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Sunden, E. Andersson
    Ericsson, Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Johnson, Maria Gatu
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Sjöstrand, Henrik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Weiszflog, Matthias
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Neutron emission spectroscopy results for internal transport barrier and mode conversion ion cyclotron resonance heating experiments at JET2008In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 79, no 10, p. 10E514-Article in journal (Refereed)
    Abstract [en]

    The effect of ion cyclotron resonance heating (ICRH) on (He-3)D plasmas at JET was studied with the time of flight optimized rate (TOFOR) spectrometer dedicated to 2.5 MeV dd neutron measurements. In internal transport barrier (ITB) plasma experiments with large He-3 concentrations (X(He-3)>15%) an increase in neutron yield was observed after the ITB disappeared but with the auxiliary neutral beam injection and ICRH power still applied. The analysis of the TOFOR data revealed the formation of a high energy (fast) D population in this regime. The results were compared to other mode conversion experiments with similar X(He-3) but slightly different heating conditions. In this study we report on the high energy neutron tails originating from the fast D ions and their correlation with X(He-3) and discuss the light it can shed on ICRH-plasma power coupling mechanisms.

  • 32.
    Gorini, G
    et al.
    CNISM, Dipartimento di Fisica, Università degli Studi di Milano-Bicocca, Milano, Italien.
    Källne, Jan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Ognissanto, F
    CNISM, Dipartimento di Fisica, Università degli Studi di Milano-Bicocca, Milano, Italien.
    Tardocchi, M
    Istituto di Fisica del Plasma "Piero Caldirola", Associazione EURATOM-ENEA-CNR, Milano Italien.
    Relationship between neutron yield rate of tokamak plasmas and spectrometer measured flux for different sight lines2011In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 82, no 3, p. 033507-Article in journal (Refereed)
    Abstract [en]

    A parametric relationship between total neutron yield rate and collimated fluxes related to the brightness (B) of plasma chords (lambda) is developed for different emissivity distributions of tokamak plasmas. Specifically, the brightness was expressed as a function of chord coordinates of radial position using a simple model for the emissivity profiles of width parameter w. The functional brightness dependence B(lambda,w) was calculated to examine the relationship between measured flux and deduced yield rate, and its plasma profile dependence. The results were used to determine the chord range of minimum profile sensitivity in order to identify the preferred collimator sight for the determination of yield rate from neutron emission spectroscopy (YNES) measurements. The YNES method is discussed in comparison to conventional methods to determine the total neutron yield rates and related plasma fusion power relying on uncollimated flux measurements and a different calibration base for the flux-yield relationship. The results have a special bearing for tokamaks operating with both deuterium and deuterium-tritium plasmas and future high power machines such as for ITER, DEMO, and IGNITOR.

  • 33.
    Hawkes, N. C.
    et al.
    UKAEA, CCFE, Culham Sci Ctr, Abingdon OX14 3DB, Oxon, England.
    Andersson Sundén, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Binda, Federico
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Cecconello, Marco
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Conroy, Sean
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Dzysiuk, Nataliia
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Ericsson, Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Eriksson, Jacob
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Hellesen, Carl
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Hjalmarsson, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Possnert, Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Sjöstrand, Henrik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Skiba, Mateusz
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Weiszflog, Matthias
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Zychor, I.
    Natl Ctr Nucl Res, PL-05400 Otwock, Poland.
    Instrumentation for the upgrade to the JET core charge-exchange spectrometers2018In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 89, no 10, article id 10D113Article in journal (Refereed)
    Abstract [en]

    Charge-exchange spectroscopy on JET has become particularly challenging with the introduction of the ITER-like wall. The line intensities are weaker and contaminated by many nuisance lines. We have therefore upgraded the instrumentation to improve throughput and allow the simultaneous measurement of impurity and fuel-ion charge exchange by splitting the light between two pairs of imaging spectrometers using dichroic beam splitters. Imaging instruments allow us to stack 11 x 1 mm diameter fibres on the entrance slits without cross talk. CCD cameras were chosen to have 512 x 512 pixels to allow frame transfer times <0.2 ms which with minimum exposure times of 5 ms give tolerable smearing even without a chopper. The image plane is optically demagnified 2:1 to match the sensor size of these cameras. Because the image plane of the spectrometer is tilted, the CCD must also be tilted to maintain focus over the spectrum (Scheimpflug condition). To avoid transverse keystoning (causing the vertical height of the spectra to change across the sensor), the configuration is furthermore designed to be telecentric by a suitable choice of the lens separation. The lens configuration is built almost entirely from commercial off-the-shelf components, which allowed it to be assembled and aligned relatively rapidly to meet the deadline for in-vessel calibration in the JET shutdown.

  • 34.
    Helgesson, Petter
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Sjöstrand, Henrik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Fitting a defect non-linear model with or without prior, distinguishing nuclear reaction products as an example2017In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 88, article id 115114Article in journal (Refereed)
    Abstract [en]

    Fitting parametrized functions to data is important for many researchers and scientists. If the model is non-linear and/or defect, it is not trivial to do correctly and to include an adequate uncertainty analysis. This work presents how the Levenberg-Marquardt algorithm for non-linear generalized least squares fitting can be used with a prior distribution for the parameters, and how it can be combined with Gaussian processes to treat model defects. An example, where three peaks in a histogram are to be distinguished, is carefully studied. In particular, the probability r1 for a nuclear reaction to end up in one out of two overlapping peaks is studied. Synthetic data is used to investigate effects of linearizations and other assumptions. For perfect Gaussian peaks, it is seen that the estimated parameters are distributed close to the truth with good covariance estimates. This assumes that the method is applied correctly; for example, prior knowledge should be implemented using a prior distribution, and not by assuming that some parameters are perfectly known (if they are not). It is also important to update the data covariance matrix using the fit if the uncertainties depend on the expected value of the data (e.g., for Poisson counting statistics or relative uncertainties). If a model defect is added to the peaks, such that their shape is unknown, a fit which assumes perfect Gaussian peaks becomes unable to reproduce the data, and the results for r1 become biased. It is, however, seen that it is possible to treat the model defect with a Gaussian process with a covariance function tailored for the situation, with hyper-parameters determined by leave-one-out cross validation. The resulting estimates for r1 are virtually unbiased, and the uncertainty estimates agree very well with the underlying uncertainty.

  • 35.
    Hellesen, Carl
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Andersson Sundèn, E.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Conroy, S.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Ericsson, G.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Eriksson, J.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Johnson, M. Gatu
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Weiszflog, Matthias
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Neutron spectroscopy results of JET high-performance plasmas and extrapolations to DT performance2010In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 81, no 10, p. 10D337-Article in journal (Refereed)
    Abstract [en]

    In a fusion reactor with high energy gain, the fusion power will be mainly thermonuclear (THN). Measurements of the THN neutron rate are a good performance indicator of a fusion plasma, requiring neutron emission spectroscopy (NES) measurements to distinguish thermal and nonthermal contributions. We report here on recent NES results from JET high-performance plasmas with high fractions (about 65%) of THN emission. The analysis is made with a framework for analyzing NES data, taking into account THN reactions and beam-target reactions. The results are used to extrapolate to the equivalent DT rates. Finally, we discuss the applicability of using NES in the deuterium phase of ITER, both for the extrapolations to ITER's future DT performance as well as for the measurements of confined energetic ions.

  • 36.
    Hellesen, Carl
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Andersson Sundén, E
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Conroy, Sean
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Ericsson, Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Giacomelli, L
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Hjalmarsson, Andersson
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Gatu Johnson, Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Källne, J
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Ronchi, E
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Weiszflog, Matthias
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Ballabio, L
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Gorini, G
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Tardocchi, M
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Sjöstrand, Henrik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Voitsekovitch, I
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Validation of TRANSP Simulations Using Neutron emission Spectroscopy with Dual Sight Lines2008In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 79, no 10, p. 10E510-Article in journal (Refereed)
    Abstract [en]

    A method to generate modeled neutron spectra from bulk and fast ion distributions simulated by TRANSP has been developed. In this paper, modeled data generated from fuel ion distrubutions modeled with TRANSP is compared to measured data from two neutron spectrometers with different lines of sight; TOFOR with a radial one and the MPRu with a tangential one. The information obtained from the analysis of the measured neutron spectra such as the relative intensity of the emission from different ion populations places additional constraints on the simulation and can be used to adjust the parameters of the simulation.

  • 37. Hellesen, Carl
    et al.
    Andersson Sundén, Erik
    Conroy, Sean
    Ericsson, Göran
    Giacomelli, Luca
    Hjalmarsson, Anders
    Gatu Johnson, Maria
    Källne, Jan
    Ronchi, Emanuelle
    Weiszflog, Matthias
    Ballabio, Luigi
    Gorini, Giuseppe
    Tardocchi, Marco
    Voitsekhovitch, Irina
    Validating TRANSP simulations Using Neutron Emission Spectroscopy with Dual Sight Lines2008In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 79, no 10, p. E510-Article in journal (Refereed)
  • 38.
    Hellesen, Carl
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Eriksson, Jacob
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Conroy, Sean
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Ericsson, Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Skiba, Mateusz
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Weiszflog, Matthias
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Fuel ion ratio measurements in reactor relevant neutral beam heated fusion plasmas2012In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 83, no 10, p. 10D916-Article in journal (Refereed)
    Abstract [en]

    In this paper, we present a method to derive n tn d using the ratio of the thermonuclear neutron emission to the beam-target neutron emission. We apply it to neutron spectroscopy data from the magnetic proton recoil spectrometer taken during the deuterium tritium experiment at JET. n tn d-values obtained using neutron spectroscopy are in qualitative agreement with those from other diagnostics measuring the isotopic composition of the exhaust in the divertor.

  • 39.
    Hellesen, Carl
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Skiba, Mateusz
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Dzysiuk, N.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Weiszflog, Matthias
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Hjalmarsson, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Ericsson, Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Conroy, Sean
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Sundén, Erik Andersson
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Eriksson, Jacob
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Binda, Federico
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Prospects for measuring the fuel ion ratio in burning ITER plasmas using a DT neutron emission spectrometer2014In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 85, no 11, p. 11D825-Article in journal (Refereed)
    Abstract [en]

    The fuel ion ratio n(t)/n(d) is an essential parameter for plasma control in fusion reactor relevant applications, since maximum fusion power is attained when equal amounts of tritium (T) and deuterium (D) are present in the plasma, i.e., n(t)/n(d) = 1.0. For neutral beam heated plasmas, this parameter can be measured using a single neutron spectrometer, as has been shown for tritium concentrations up to 90%, using data obtained with the MPR (Magnetic Proton Recoil) spectrometer during a DT experimental campaign at the Joint European Torus in 1997. In this paper, we evaluate the demands that a DT spectrometer has to fulfill to be able to determine n(t)/n(d) with a relative error below 20%, as is required for such measurements at ITER. The assessment shows that a back-scattering time-of-flight design is a promising concept for spectroscopy of 14 MeV DT emission neutrons.

  • 40. Helou, W.
    et al.
    Andersson Sundén, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Asp, E.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Binda, Federico
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Cecconello, Marco
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Conroy, Sean
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Dzysiuk, Nataliia
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Ericsson, Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Eriksson, Jacob
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Hellesen, Carl
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Hjalmarsson, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Possnert, Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Sjöstrand, Henrik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Skiba, Mateusz
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Weiszflog, Matthias
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Zychor, I.
    ITER-like antenna capacitors voltage probes: Circuit/electromagnetic calculations and calibrations2016In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 87, no 10, article id 104705Article in journal (Refereed)
    Abstract [en]

    The analyses illustrated in this manuscript have been performed in order to provide the required data for the amplitude-and-phase calibration of the D-dot voltage probes used in the ITER-like antenna at the Joint European Torus tokamak. Their equivalent electrical circuit has been extracted and analyzed, and it has been compared to the one of voltage probes installed in simple transmission lines. A radio-frequency calibration technique has been formulated and exact mathematical relations have been derived. This technique mixes in an elegant fashion data extracted from measurements and numerical calculations to retrieve the calibration factors. The latter have been compared to previous calibration data with excellent agreement proving the robustness of the proposed radio-frequency calibration technique. In particular, it has been stressed that it is crucial to take into account environmental parasitic effects. A low-frequency calibration technique has been in addition formulated and analyzed in depth. The equivalence between the radio-frequency and low-frequency techniques has been rigorously demonstrated. The radio-frequency calibration technique is preferable in the case of the ITER-like antenna due to uncertainties on the characteristics of the cables connected at the inputs of the voltage probes. A method to extract the effect of a mismatched data acquisition system has been derived for both calibration techniques. Finally it has been outlined that in the case of the ITER-like antenna voltage probes can be in addition used to monitor the currents at the inputs of the antenna.

  • 41.
    Hoang Duc, Long
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Electrical Engineering, Solid-State Electronics.
    Jobs, Magnus
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA.
    Lofnes, Tor
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA.
    Ruber, Roger
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA.
    Olsson, Jörgen
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Electrical Engineering, Solid-State Electronics.
    Dancila, Dragos
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Electrical Engineering, Solid-State Electronics.
    Feedback compensated 10 kW solid-state pulsed power amplifier at 352 MHz for particle accelerators2019In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 90, no 10, article id 104707Article in journal (Refereed)
    Abstract [en]

    This paper presents the first results of an in-house developed low-level radio frequency (LLRF) system and a 10 kW solid state power amplifier (SSPA). The design approach for the SSPA is based on eight resonant single-ended kilowatt modules combined using a planar Gysel combiner. Each of the single-ended modules is based on a two-stepped impedance resonant matching, allowing for harmonic suppression, simple design for massive production, and high-performance design. A design methodology to tune SSPA modules for optimum combining efficiency is presented thoroughly in the time domain. We characterize the power droop due to capacitor banks in the time domain. In open loop of compensation, it is about 1 kW within the pulse of peak value 10 kW and a duration of 3.5 ms. This may lead to the beam instability of the accelerator as particles are not provided with the same energy during the pulse. By incorporating our LLRF system, it is demonstrated that the objective of amplitude and phase stability is satisfied, as required in the European Spallation Source proton accelerator. The presented design also offers the advantages of compact form factor, low complexity, and better performance. In closed loop compensation, the variation of amplitude (pulse droop) is measured on the order of 20 W, which is equivalent to 0.2% at 10 kW peak output power.

  • 42.
    Hoang, Long
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics. Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, FREIA. Uppsala University.
    Feedback compensated 10 kW solid-state pulsed power amplifier at 352 MHz for particle accelerators2019In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 90, no 10, p. 104707-1-104707-10, article id 4707Article in journal (Refereed)
  • 43. Ibek, Mateusz
    et al.
    Leitner, Torsten
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and condensed matter physics.
    Erko, Alexei
    Firsov, Alexander
    Wernet, Philippe
    Monochromatizing and focussing femtosecond high-order harmonic radiation with one optical element2013In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 84, no 10, p. 103102-Article in journal (Refereed)
    Abstract [en]

    A novel approach for monochromatizing and focussing the Vacuum-Ultraviolet and soft x-ray radiation from high-order harmonic generation of a femtosecond optical laser with only one optical element is presented. We demonstrate that off-axis reflection zone plates applied as focussing monochromators allow for efficiently optimizing the trade-off between energy resolution and temporal dispersion of the femtosecond pulses. In the current experimental realization, we show how the temporal dispersion can be varied between 2 fs and 16 fs with a correlating variation of the energy resolution E/Delta E between 20 and 90 for an off-axis reflection zone plate optimized for harmonic 13 at 20.41 eV. We also show how the focal spot size varies correspondingly between 80 x 90 mu m(2) and 290 x 140 mu m(2) as determined with a computational fitting approach based on a 3D Gaussian model. The diffraction efficiency for the tested zone plates amounts to up to 10%. We furthermore evaluate the influence of pointing stability on the performance of the zone plates. Based on our results we propose an optimized realization of a dedicated beam line for femtosecond pulses from high-order harmonic generation with an off-axis reflection zone plate. 

  • 44.
    Ismail, I.
    et al.
    UPMC Univ Paris 06, Sorbonne Univ, CNRS, UMR 7614,Lab Chim Phys Matiere & Rayonnement, F-75005 Paris 05, France.
    Guillemin, R.
    UPMC Univ Paris 06, Sorbonne Univ, CNRS, UMR 7614,Lab Chim Phys Matiere & Rayonnement, F-75005 Paris 05, France.
    Marchenko, T.
    UPMC Univ Paris 06, Sorbonne Univ, CNRS, UMR 7614,Lab Chim Phys Matiere & Rayonnement, F-75005 Paris 05, France.
    Travnikova, O.
    UPMC Univ Paris 06, Sorbonne Univ, CNRS, UMR 7614,Lab Chim Phys Matiere & Rayonnement, F-75005 Paris 05, France.
    Ablett, J. M.
    Synchrotron SOLEIL, Orme Merisiers, F-91192 Gif Sur Yvette, France.
    Rueff, J. -P
    Piancastelli, Maria Novella
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Simon, M.
    Synchrotron SOLEIL, Orme Merisiers, F-91192 Gif Sur Yvette, France;UPMC Univ Paris 06, Sorbonne Univ, CNRS, UMR 7614,Lab Chim Phys Matiere & Rayonnement, F-75005 Paris 05, France.
    Journel, L.
    UPMC Univ Paris 06, Sorbonne Univ, CNRS, UMR 7614,Lab Chim Phys Matiere & Rayonnement, F-75005 Paris 05, France.
    Experimental setup for the study of resonant inelastic X-ray scattering of organometallic complexes in gas phase2018In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 89, no 6, article id 063107Article in journal (Refereed)
    Abstract [en]

    A new setup has been designed and built to study organometallic complexes in gas phase at the third-generation Synchrotron radiation sources. This setup consists of a new homemade computer-controlled gas cell that allows us to sublimate solid samples by accurately controlling the temperature. This cell has been developed to be a part of the high-resolution X-ray emission spectrometer permanently installed at the GALAXIES beamline of the French National Synchrotron Facility SOLEIL. To illustrate the capabilities of the setup, the cell has been successfully used to record high-resolution K alpha emission spectra of gas-phase ferrocene Fe(C5H5)(2) and to characterize their dependence with the excitation energy. This will allow to extend resonant X-ray emission to different organometallic molecules.

  • 45.
    Jacobsen, A. S.
    et al.
    Culham Sci Ctr, EUROfus Consortium, JET, Abingdon OX14 3DB, Oxon, England.;Max Planck Inst Plasma Phys, Garching, Germany..
    Binda, Federico
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics. Culham Sci Ctr, EUROfus Consortium, JET, Abingdon OX14 3DB, Oxon, England.
    Cazzaniga, C.
    Culham Sci Ctr, EUROfus Consortium, JET, Abingdon OX14 3DB, Oxon, England.;Sci & Technol Facil Council, Rutherford Appleton Lab, ISIS Facil, Didcot OX11 0QX, Oxon, England..
    Eriksson, Jacob
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics. Culham Sci Ctr, EUROfus Consortium, JET, Abingdon OX14 3DB, Oxon, England.
    Hjalmarsson, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics. Culham Sci Ctr, EUROfus Consortium, JET, Abingdon OX14 3DB, Oxon, England.
    Nocente, M.
    Culham Sci Ctr, EUROfus Consortium, JET, Abingdon OX14 3DB, Oxon, England.;Univ Milano Bicocca, Dipartimento Fis G Occhialini, Milan, Italy..
    Salewski, M.
    Culham Sci Ctr, EUROfus Consortium, JET, Abingdon OX14 3DB, Oxon, England.;Tech Univ Denmark, Dept Phys, Kongens Lyngby, Denmark..
    Tardini, G.
    Culham Sci Ctr, EUROfus Consortium, JET, Abingdon OX14 3DB, Oxon, England.;Max Planck Inst Plasma Phys, Garching, Germany..
    Velocity-space sensitivities of neutron emission spectrometers at the tokamaks JET and ASDEX Upgrade in deuterium plasmas2017In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 88, no 7, article id 073506Article in journal (Refereed)
    Abstract [en]

    Future fusion reactors are foreseen to be heated by the energetic alpha particles produced in fusion reactions. For this to happen, it is important that the energetic ions are sufficiently confined. In present day fusion experiments, energetic ions are primarily produced using external heating systems such as neutral beam injection and ion cyclotron resonance heating. In order to diagnose these fast ions, several different fast-ion diagnostics have been developed and implemented in the various experiments around the world. The velocity-space sensitivities of fast-ion diagnostics are given by so-called weight functions. Here instrument-specific weight functions are derived for neutron emission spectrometry detectors at the tokamaks JET and ASDEX Upgrade for the 2.45 MeV neutrons produced in deuterium-deuterium reactions in deuterium plasmas. Using these, it is possible to directly determine which part of velocity space each detector observes.

  • 46. Jacobsen, A. S.
    et al.
    Salewski, M.
    Eriksson, Jacob
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Ericsson, Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Hjalmarsson, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Korsholm, S. B.
    Leipold, F.
    Nielsen, S. K.
    Rasmussen, J.
    Stejner, M.
    Velocity-space sensitivity of the time-of-flight neutron spectrometer at JET2014In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 85, no 11, p. 11E103-Article in journal (Refereed)
    Abstract [en]

    The velocity-space sensitivities of fast-ion diagnostics are often described by so-called weight functions. Recently, we formulated weight functions showing the velocity-space sensitivity of the often dominant beam-target part of neutron energy spectra. These weight functions for neutronemission spectrometry (NES) are independent of the particular NES diagnostic. Here we apply these NES weight functions to the time-of-flight spectrometer TOFOR at JET. By taking the instrumental response function of TOFOR into account, we calculate time-of-flight NES weight functions that enable us to directly determine the velocity-space sensitivity of a given part of ameasured time-of-flight spectrum from TOFOR.

  • 47.
    Jana, Somnath
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Terschlüsen, Joachim A.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Stefanuik, Robert
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Plogmaker, Stefan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics. MAX VI Lab, Lund, Sweden..
    Troisi, Sara
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Malik, Rameez S.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Svanqvist, Mathias
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics. Swedish Def Res Agcy, FOI, SE-14725 Tumba, Sweden..
    Knut, Ronny
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Söderström, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    Karis, Olof
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Molecular and Condensed Matter Physics.
    A setup for element specific magnetization dynamics using the transverse magneto-optic Kerr effect in the energy range of 30-72 eV2017In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 88, no 3, article id 033113Article in journal (Refereed)
    Abstract [en]

    In this paper, we present a spectrometer that is designed for element-specific and time-resolved transverse magneto-optic Kerr effect experiments at the high-harmonic generation pump-probe facility High Energy Laser Induced Overtone Source (HELIOS) laboratory. HELIOS delivers photons with energies between 30 eV and 72 eV with an overall time resolution of less than 40 fs. The spectrometer is based on a Rowland-circle geometry and allows for simultaneous measurements of all magnetic transition-metal elements. The setup also features easy sample transfer and alignment, and it combines high photon throughput, optimized data acquisition, and a fast switching of the magnetic field at the sample. The spectrometer performance is demonstrated by measuring the ultrafast demagnetization of permalloy. Our data are, for all practical purposes, identical to what have been reported in the earlier high-order harmonic generation work of a similar sample by Mathias et al. [Proc. Natl. Acad. Sci. U.S.A. 109, 4792-4797 (2012)], however, obtained within 15% of the acquisition time compared to their study. Furthermore, our data show a shift of the demagnetization curve of Ni relative to Fe, which has previously been interpreted as a delay of the Ni demagnetization to that of Fe [S. Mathias et al., Proc. Natl. Acad. Sci. U. S. A. 109, 4792-4797 (2012)].

  • 48. Janhunen, P.
    et al.
    Toivanen, P. K.
    Polkko, J.
    Merikallio, S.
    Salminen, P.
    Haeggstrom, E.
    Seppänen, H.
    Kurppa, R.
    Ukkonen, J.
    Kiprich, S.
    Thornell, Greger
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Kratz, Henrik
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Richter, L.
    Krömer, O.
    Rosta, R.
    Noorma, M.
    Envall, J.
    Lätt, S.
    Mengali, G.
    Quarta, A. A.
    Koivisto, H.
    Tarvainen, O.
    Kalvas, T.
    Kauppinen, J.
    Nuottajärvi, A.
    Obraztsov, A.
    Invited Article: Electric solar wind sail: Toward test missions2010In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 81, no 11, p. 111301-Article in journal (Refereed)
    Abstract [en]

    The electric solar wind sail (E-sail) is a space propulsion concept that uses the natural solar wind dynamic pressure for producing spacecraft thrust. In its baseline form, the E-sail consists of a number of long, thin, conducting, and centrifugally stretched tethers, which are kept in a high positive potential by an onboard electron gun. The concept gains its efficiency from the fact that the effective sail area, i.e., the potential structure of the tethers, can be millions of times larger than the physical area of the thin tethers wires, which offsets the fact that the dynamic pressure of the solar wind is very weak. Indeed, according to the most recent published estimates, an E-sail of 1 N thrust and 100 kg mass could be built in the rather near future, providing a revolutionary level of propulsive performance (specific acceleration) for travel in the solar system. Here we give a review of the ongoing technical development work of the E-sail, covering tether construction, overall mechanical design alternatives, guidance and navigation strategies, and dynamical and orbital simulations.

  • 49.
    Johnson, M. Gatu
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Andersson Sundén, E.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Cecconello, Marco
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Conroy, S.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Ericsson, G.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Eriksson, Jacob
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Gorini, G.
    Hellesen, Carl
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Kiptily, V.
    Nocente, M.
    Sangaroon, S.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Sharapov, S. E.
    Tardocchi, M.
    van Eester, D.
    Weiszflog, Matthias
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Neutron spectrometry of JET discharges with ICRH-acceleration of helium beam ions2010In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 81, no 10, p. 10D336-Article in journal (Refereed)
    Abstract [en]

    Recent experiments at JET aimed at producing He-4 ions in the MeV range through third harmonic ion cyclotron resonance heating (ICRH) acceleration of He-4 beams in a He-4 dominated plasma. MeV range D was also present through parasitic ICRH absorption on residual D. In this contribution, we analyze TOFOR neutron spectrometer data from these experiments. A consistent description of the data is obtained with d(d, n)(3) He and Be-9(alpha, n)C-12 neutron components calculated using Stix distributions for the fast D and He-4, taking finite Larmor radius effects into account and with a ICRH power partition of P-D(RF) = 0.01 X P-4He(RF), in agreement with TOMCAT simulations.

  • 50.
    Klimek, Iwona
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Cecconello, Marco
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Sharapov, S. E.
    Harrison, J.
    Ericsson, Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Determination of hydrogen/deuterium ratio with neutron measurements on MAST2014In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 85, no 11, p. 11E109-Article in journal (Refereed)
    Abstract [en]

    On MAST, compressional Alfven eigenmodes can be destabilized by the presence of a sufficiently large population of energetic particles in the plasma. This dependence was studied in a series of very similar discharges in which increasing amounts of hydrogen were puffed into a deuterium plasma. A simple method to estimate the isotopic ratio n(H)/n(D) using neutron emission measurements is here described. The inferred isotopic ratio ranged from 0.0 to 0.6 and no experimental indication of changes in radial profile of n(H)/n(D) were observed. These findings are confirmed by TRANSP/NUBEAM simulations of the neutron emission.

12 1 - 50 of 95
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf