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  • 1.
    Al-Adili, Ali
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Investigation of 234U(n,f) with a Frisch-grid ionization chamber2011Licentiate thesis, monograph (Other academic)
    Abstract [en]

    This work treats three topics. The main topic concerns neutron-induced fission of 234U. The main goal is to investigate the fission-fragments properties  as a function of the incident neutron energy. The study was carried out using a twin Frisch-grid ionization chamber. The first fluctuations on fragment properties are presented, in terms of strong angular anisotropy oscillation.

    The second part of the work treats the data-acquisition systems in use, particularly for neutron-induced fission experiments. Modern digital systems are studied and compared with the conventional analogue systems. It was shown that the digital systems are superior in drift stability, pile-up correction and extended the possibilities of offline analysis.

    The third part of the work concerns the Frisch-grid inefficiency. The Frisch grid was introduced in the chamber to remove the angular dependency from the induced charge. However, the shielding is not perfect and a correction is needed for the small angular dependency. Two contradicting methods have been presented in literature, one adding, and the second subtracting the angular-dependent part from the detected signal. An experiment with Cf(sf) was designed and performed to solve the pending ambiguity. The results support the additive model.

  • 2.
    Al-Adili, Ali
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Hambsch, Franz-Josef
    EC-JRC, IRMM, Geel, Belgium.
    Oberstedt, Stephan
    EC-JRC, IRMM, Geel, Belgium.
    Pomp, Stephan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Zeynalov, Shakir
    JINR, Dubna, Russia.
    Comparison of digital and analogue data acquisition systems for nuclear spectroscopy2010In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 624, no 3, p. 684-690Article in journal (Refereed)
    Abstract [en]

    In the present investigation the performance of digital data acquisition (DA) and analogue data acquisition (AA) systems are compared in neutron-induced fission experiments. The DA results are practically identical to the AA results in terms of angular-, energy- and mass-resolution, and both compare very well with literature data. However, major advantages were found with the digital techniques. DA allows for a very efficient αparticle pile-up correction. This is important when considering the accurate measurement of fission-fragment characteristics of highly αactive actinide isotopes relevant for the safe operation of Generation IV reactors and the successful reduction of long-lived radioactive nuclear waste. In case of a strong αemitter, when applying the αparticle pile-up correction, the peak-to-valley ratio of the energy distribution was significantly improved. In addition, DA offers a very flexible expanded off-line analysis and reduces the number of electronic modules drastically, leading to an increased stability against electronic drifts when long measurement times are required.

  • 3.
    Andersson Sundén, Erik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Neutron Spectrometry Techniques for Fusion Plasmas: Instrumentation and Performance2010Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Neutron are emitted from a deuterium plasma with energies around 2.5 MeV. The neutron spectrum is intimately related to the ion velocity distribution of the plasma. As a consequence, the analysis of neutron energy spectra can give information of the plasma rotation, the ion temperature, heating efficiency and fusion power.

    The upgraded magnetic proton recoil spectrometer (MPRu), based on the thin-foil technique, is installed at the tokamak JET. The upgrade of the spectrometer was done to allow for measurements of deuterium plasmas. This thesis describes the hardware, the data reduction scheme and the kind of fusion plasma parameters that can be estimated from the data of the MPRu. The MPRu data from 3rd harmonic ion cyclotron resonance and beam heating are studied.

    Other neutron spectrometer techniques are reviewed as well, in particular in the aspect of suitability for neutron emission spectrometry at ITER. Each spectrometer technique is evaluated using synthetic data which is obtained from standard scenarios of ITER. From this evaluation, we conclude that the thin-foil technique is the best technique to measure, e.g., the ion temperature in terms of time resolution.

    List of papers
    1. The thin-foil magnetic proton recoil neutron spectrometer MPRu at JET
    Open this publication in new window or tab >>The thin-foil magnetic proton recoil neutron spectrometer MPRu at JET
    Show others...
    2009 (English)In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 610, no 3, p. 682-699Article in journal (Refereed) Published
    Abstract [en]

    Neutrons are produced in fusion energy experiments with both deuterium (D) and deuterium–tritium (DT) plasmas. Neutron spectroscopy is a valuable tool in the study of the underlying fuel ion populations. The magnetic proton recoil neutron spectrometer, originally installed at JET in 1996 for 14-MeV neutron measurements, has been upgraded, with the main aim of improving its signal-to-background ratio (S/B), making measurements of the 2.5-MeV neutron emission in D plasmas possible. The upgrade includes a new focal-plane detector, based on the phoswich technique and consequently less sensitive to background, and a new custom-designed digital data acquisition system based on transient recorder cards. Results from JET show that the upgraded MPRu can measure 2.5-MeV neutrons with S/B=5, an improvement by a factor of 50 compared with the original MPR. S/B of 2.8×104 in future DT experiments is estimated. The performance of the MPRu is exemplified with results from recent D plasma operations at JET, concerning both measurements with Ohmic, ion cyclotron resonance (ICRH) and neutral beam injection (NBI) plasma heating, as well as measurements of tritium burn-up neutrons. The upgraded instrument allows for 2.5-MeV neutron emission and deuterium ion temperature measurements in plasmas with low levels of tritium, a feature necessary for the ITER experiment.

    Keywords
    Neutron, Spectrometer, 14 MeV neutrons, 2.5 MeV neutrons, MPR, MPRu, Fusion, Diagnostic
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:uu:diva-129551 (URN)10.1016/j.nima.2009.09.025 (DOI)000273157600010 ()
    Available from: 2010-08-19 Created: 2010-08-18 Last updated: 2017-12-12Bibliographically approved
    2. Gain stabilization control system of the upgraded magnetic protonrecoil neutron spectrometer at JET
    Open this publication in new window or tab >>Gain stabilization control system of the upgraded magnetic protonrecoil neutron spectrometer at JET
    Show others...
    2009 (English)In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 80, no 6, p. 063505-Article in journal (Refereed) Published
    Abstract [en]

    Burning plasma experiments such as ITER and DEMO require diagnostics capable of withstanding the harsh environment generated by the intense neutron flux and to maintain stable operating conditions for times longer than present day systems. For these reasons, advanced control and monitoring (CM) systems will be necessary for the reliable operation of diagnostics. This paper describes the CM system of the upgraded magnetic proton recoil neutron spectrometer installed at the Joint European Torus focusing in particular on a technique for the stabilization of the gain of the photomultipliers coupled to the neutron detectors. The results presented here show that this technique provides good results over long time scales. The technique is of general interest for all diagnostics that employ scintillators coupled to photomultiplier tubes.

    Keywords
    fusion reactor instrumentation, neutron detection, neutron flux, neutron spectrometers, photomultipliers, plasma diagnostics, plasma toroidal confinement, scintillation counters, Tokamak devices
    National Category
    Physical Sciences
    Identifiers
    urn:nbn:se:uu:diva-121514 (URN)10.1063/1.3109682 (DOI)000267600600016 ()
    Available from: 2010-03-24 Created: 2010-03-24 Last updated: 2017-12-12Bibliographically approved
    3. Neutron emission spectroscopy diagnosis of JET D and DT plasmas with the new MPRu instrument
    Open this publication in new window or tab >>Neutron emission spectroscopy diagnosis of JET D and DT plasmas with the new MPRu instrument
    Show others...
    2006 (English)In: 33rd EPS Conference on Plasma Phys. and Contr. Fusion, 2006, p. 30I P-1.071Conference paper, Published paper (Refereed)
    Identifiers
    urn:nbn:se:uu:diva-24830 (URN)
    Available from: 2007-02-07 Created: 2007-02-07 Last updated: 2017-01-25
    4. Evaluation of Spectral Unfolding for Neutron Spectroscopy
    Open this publication in new window or tab >>Evaluation of Spectral Unfolding for Neutron Spectroscopy
    Show others...
    2007 (English)Report (Other (popular scientific, debate etc.))
    Identifiers
    urn:nbn:se:uu:diva-13737 (URN)
    Note
    and JET EFDA contributors (EFD -C(07)04/10)Available from: 2008-06-05 Created: 2008-06-05 Last updated: 2017-01-25
    5. Instrumentation for neutron emission spectrometry in use at JET
    Open this publication in new window or tab >>Instrumentation for neutron emission spectrometry in use at JET
    Show others...
    2010 (English)In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 623, no 2, p. 681-685Article in journal (Refereed) Published
    Abstract [en]

    The present contribution discusses two neutron spectrometers: the time-of-flight spectrometer (TOFOR) and the magnetic proton recoil spectrometer (MPRu). TOFOR uses fast plastic scintillators equipped with digital time-stamping electronics to register the time of each eligible scintillation event. The time trace for each detector is acquired practically dead-time free. The detectors of the MPRu are of phoswich type and each detector is connected to a digital transient recorder card that stores the full waveform for an event. By using phoswich detectors, pulse-shape discrimination techniques can be applied offline to distinguish signal events from background. A future upgrade of TOFOR could be digital “hybrid” cards, which store correlated time and waveform information. This information can be used to decrease the background level in the ttof spectrum, thereby increasing the operating range.

    Keywords
    Fusion diagnostic, Neutron emission spectrometry, MPRu, TOFOR, Data acquisition systems
    National Category
    Physical Sciences
    Identifiers
    urn:nbn:se:uu:diva-121517 (URN)10.1016/j.nima.2010.02.255 (DOI)000284343600010 ()
    Available from: 2010-03-24 Created: 2010-03-24 Last updated: 2017-12-12Bibliographically approved
    6. Evaluation of neutron spectrometer techniques for ITER using synthetic data
    Open this publication in new window or tab >>Evaluation of neutron spectrometer techniques for ITER using synthetic data
    Show others...
    2013 (English)In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 701, p. 17p. 62-71Article in journal (Refereed) Published
    Abstract [en]

    A neutron spectrometer at ITER is expected to provide estimates of plasma parameters such as ion temperature, Ti, fuel ion ratio, nt/nd, and Qthermal/Qtot, with 10-20% precision at a time resolution, Δt, of at least 100 ms. The present paper describes a method for evaluating different neutron spectroscopy techniques based on their instrumental response functions and synthetic measurement data. We include five different neutron spectrometric techniques with realistic response functions, based on simulations and measurements where available. The techniques are magnetic proton recoil, thin-foil proton recoil, gamma discriminating organic scintillator, diamond and time-of-flight. The reference position and line of sight of a high resolution neutron spectrometer on ITER are used in the study. ITER plasma conditions are simulated for realistic operating scenarios. The ITER conditions evaluated are beam and radio frequency heated and thermal deuterium-tritium plasmas. Results are given for each technique in terms of the estimated time resolution at which the parameter determination can be made within the required precision (here 10% for Ti and the relative intensities of NB and RF emission components). It is shown that under the assumptions made, the thin-foil techniques out-perform the other spectroscopy techniques in practically all measurement situations. For thermal conditions, the range of achieved Δt in the determination of Ti varies in time scales from ms (for the magnetic and thin-foil proton recoil) to s (for gamma discriminating organic scintillator).

    Publisher
    p. 17
    National Category
    Physical Sciences
    Identifiers
    urn:nbn:se:uu:diva-121519 (URN)10.1016/j.nima.2012.10.041 (DOI)000313721400010 ()
    Available from: 2010-04-12 Created: 2010-03-24 Last updated: 2017-12-12Bibliographically approved
  • 4.
    Andersson Sundén, Erik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Ballabio, Luigi
    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.
    Ericsson, Göran
    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.
    Gorini, Giuseppe
    Hellesen, Carl
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Ognissanto, Flora
    Ronchi, Emanuele
    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.
    Tardocchi, Marco
    Weiszflog, Matthias
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Evaluation of neutron spectrometer techniques for ITER using synthetic data2013In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 701, p. 17p. 62-71Article in journal (Refereed)
    Abstract [en]

    A neutron spectrometer at ITER is expected to provide estimates of plasma parameters such as ion temperature, Ti, fuel ion ratio, nt/nd, and Qthermal/Qtot, with 10-20% precision at a time resolution, Δt, of at least 100 ms. The present paper describes a method for evaluating different neutron spectroscopy techniques based on their instrumental response functions and synthetic measurement data. We include five different neutron spectrometric techniques with realistic response functions, based on simulations and measurements where available. The techniques are magnetic proton recoil, thin-foil proton recoil, gamma discriminating organic scintillator, diamond and time-of-flight. The reference position and line of sight of a high resolution neutron spectrometer on ITER are used in the study. ITER plasma conditions are simulated for realistic operating scenarios. The ITER conditions evaluated are beam and radio frequency heated and thermal deuterium-tritium plasmas. Results are given for each technique in terms of the estimated time resolution at which the parameter determination can be made within the required precision (here 10% for Ti and the relative intensities of NB and RF emission components). It is shown that under the assumptions made, the thin-foil techniques out-perform the other spectroscopy techniques in practically all measurement situations. For thermal conditions, the range of achieved Δt in the determination of Ti varies in time scales from ms (for the magnetic and thin-foil proton recoil) to s (for gamma discriminating organic scintillator).

  • 5.
    Andersson Sundén, Erik
    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.
    Conroy, Sean
    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.
    Giacomelli, Luca
    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.
    Hjalmarsson, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Källne, Jan
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Ronchi, Emanuelle
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy.
    Sangaroon, Siriyaporn
    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.
    Instrumentation for neutron emission spectrometry in use at JET2010In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 623, no 2, p. 681-685Article in journal (Refereed)
    Abstract [en]

    The present contribution discusses two neutron spectrometers: the time-of-flight spectrometer (TOFOR) and the magnetic proton recoil spectrometer (MPRu). TOFOR uses fast plastic scintillators equipped with digital time-stamping electronics to register the time of each eligible scintillation event. The time trace for each detector is acquired practically dead-time free. The detectors of the MPRu are of phoswich type and each detector is connected to a digital transient recorder card that stores the full waveform for an event. By using phoswich detectors, pulse-shape discrimination techniques can be applied offline to distinguish signal events from background. A future upgrade of TOFOR could be digital “hybrid” cards, which store correlated time and waveform information. This information can be used to decrease the background level in the ttof spectrum, thereby increasing the operating range.

  • 6.
    Andersson Sundén, Erik
    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.
    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.
    Gatu Johnson, Maria
    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.
    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.
    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, Applied Nuclear Physics.
    Källne, Jan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Electricity.
    Gorini, G
    Univ Milano -Bicocca, Milano, Italy.
    Tardocchi, M
    Univ Milano -Bicocca, Milano, Italy.
    Combo, A
    IST, Portugal.
    Cruz, N
    Batista, A
    Pereira, R
    Fortuna, R
    Sousa, J
    Popovichev, S
    The thin-foil magnetic proton recoil neutron spectrometer MPRu at JET2009In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 610, no 3, p. 682-699Article in journal (Refereed)
    Abstract [en]

    Neutrons are produced in fusion energy experiments with both deuterium (D) and deuterium–tritium (DT) plasmas. Neutron spectroscopy is a valuable tool in the study of the underlying fuel ion populations. The magnetic proton recoil neutron spectrometer, originally installed at JET in 1996 for 14-MeV neutron measurements, has been upgraded, with the main aim of improving its signal-to-background ratio (S/B), making measurements of the 2.5-MeV neutron emission in D plasmas possible. The upgrade includes a new focal-plane detector, based on the phoswich technique and consequently less sensitive to background, and a new custom-designed digital data acquisition system based on transient recorder cards. Results from JET show that the upgraded MPRu can measure 2.5-MeV neutrons with S/B=5, an improvement by a factor of 50 compared with the original MPR. S/B of 2.8×104 in future DT experiments is estimated. The performance of the MPRu is exemplified with results from recent D plasma operations at JET, concerning both measurements with Ohmic, ion cyclotron resonance (ICRH) and neutral beam injection (NBI) plasma heating, as well as measurements of tritium burn-up neutrons. The upgraded instrument allows for 2.5-MeV neutron emission and deuterium ion temperature measurements in plasmas with low levels of tritium, a feature necessary for the ITER experiment.

  • 7.
    Ehrengren, Kajsa
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Large scale introduction of wind power in an electricity productionsystem: Estimated effects on the carbon dioxide emissions2010Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This thesis considers the effect of a large scale wind power introduction into an electricity system and the focus has been on the carbon dioxide emissions. Two different systems were studied, the Swedish and the Danish electricity system. When studying the Swedish electricity system different scenarios were created to see what might happen with the CO2 emissions with an introduction of a large amount of wind power. The model that was used is based on parameters such as regulating power, transmission capacity, export possibility, and the electricity generation mixes in the Nordic countries. Given that the transmission capacity is good enough, the conclusion is that the carbon dioxide emissions will be reduced with a large scale introduction of wind power. In the Danish electricity system wind power is already introduced to a large extent. The main purpose here was to investigate the development of the CO2 emissions and if it is possible to decide the actual change in carbon dioxide emissions due to the large scale introduction of wind power. The conclusions to this part are that the CO2 emissions per kWh produced electricity have decreased since the electricity generation mix has changed but the total amount of CO2 emissions fluctuates depending on weather, in a dry year less hydro power from Norway and Sweden can be used and more electricity from the fossil fuelled CHPs are generated. It has not been possible to determine the influence of the wind power on the CO2 emissions.

  • 8.
    Ericsson, Göran
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Pomp, S
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Sjöstrand, H
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Traneus, E
    Comment on "Piezonuclear decay of thorium" [Phys. Lett. A 373 (2009) 1956]2009In: Physics Letters A, ISSN 0375-9601, E-ISSN 1873-2429, Vol. 373, no 41, p. 3795-3796Article in journal (Refereed)
  • 9.
    Ericsson, Göran
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Pomp, Stephan
    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.
    Traneus, E.
    Raysearch AB, Stockholm.
    Piezonuclear reactions - do they really exist?2010In: Physics Letters A, ISSN 0375-9601, E-ISSN 1873-2429, Vol. 374, no 5, p. 750-753Article in journal (Refereed)
    Abstract [en]

    In a number of recent articles in this journal F. Cardone and collaborators have claimed the observation of several striking nuclear phenomena which they attribute to "piezonuclear reactions". One such claim [F. Cardone, R. Mignani, A. Petrucci, Phys. Lett. A 373 (2009) 1956] is that subjecting a solution of 228Th to cavitation leads to a "transformation" of thorium nuclei that is 104 times faster than the normal nuclear decay for this isotope. In a "Comment" [G. Ericsson, S. Pomp, H. Sjöstrand, E. Traneus, Phys. Lett. A 373 (2009) 3795] to the thorium work, we have criticized the evidence provided for this claim. In a "Reply" [F. Cardone, R. Mignani, A. Petrucci, Phys. Lett. A 373 (2009) 3797] Cardone et al. answer only some minor points but avoid addressing the real issue. The information provided in their Reply displays a worrying lack of control of their experimental situation and the data they put forward as evidence for their claims. We point out several shortcomings and errors in the described experimental preparations, set-up and reporting, as well as in the data analysis. We conclude that the evidence presented by Cardone et al. is insufficient to justify their claims of accelerated thorium decay (by "piezonuclear reactions" or otherwise).

  • 10.
    Eriksson, Jacob
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Calculations of neutron energy spectra from fast ion reactions in tokamak fusion plasmas2010Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    A MATLAB code for calculating neutron energy spectra from JET discharges was developed. The code uses the fuel ion distribution calculated by the computer code SELFO to generate the spectrum through a Monte-Carlo simulation. The calculated spectra were then compared against experimental results from the neutron spectrometer TOFOR. In the calculations, the exact orbits of the fuel ions are taken into account, in order to investigate what effects this has on the spectrum. The reason for this is that, for certain plasma heating scenarios, large populations of fast fuel ions are formed. These fast ions may have Larmor radii of the order of decimeters, which is comparable to the width of the sight line of TOFOR, and may therefore affect the recorded neutron spectrum. A JET discharge with both NBI and 3rd harmonic ICRF heating was analyzed. The results show that the details of the line of sight of the detector indeed affects the neutron spectrum. This effect is probably important for other diagnostics techniques, such as gamma-ray spectroscopy and neutral particle analysis, as well. Good agreement with TOFOR data is observed, but not for the exact same time slice of the discharge, which leaves some questions yet to be investigated.

  • 11.
    Frassinetti, L
    et al.
    Alfven lab, KTH, Stockholm, Sweden.
    Brunsell, R
    Alfven lab, KTH, Stockholm, Sweden.
    Cecconello, M
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Drake, R
    Alfven lab, KTH, Stockholm, Sweden.
    Heat transport modelling in EXTRAP T2R2009In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 49, no 2, p. 025002-Article in journal (Refereed)
    Abstract [en]

    A model to estimate the heat transport in the EXTRAP T2R reversed field pinch (RFP) is described. The model, based on experimental and theoretical results, divides the RFP electron heat diffusivity χ e into three regions, one in the plasma core, where χ e is assumed to be determined by the tearing modes, one located around the reversal radius, where χ e is assumed not dependent on the magnetic fluctuations and one in the extreme edge, where high χ e is assumed. The absolute values of the core and of the reversal χ e are determined by simulating the electron temperature and the soft x-ray and by comparing the simulated signals with the experimental ones. The model is used to estimate the heat diffusivity and the energy confinement time during the flat top of standard plasmas, of deep F plasmas and of plasmas obtained with the intelligent shell.

  • 12.
    Fridström, Richard
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Response of the Gamma TIP Detectorsin a Nuclear Boiling Water Reactor2010Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In order to monitor a nuclear boiling water reactor fixed and movable detectors are used, such as the neutron sensitive LPRM (Local Power Range Monitors) detectors and the gamma sensitive TIP (Traversing Incore Probe) detectors. These provide a mean to verify the predictions obtained from core simulators, which are used for planning and following up the reactor operation. The core simulators calculate e.g. the neutron flux and power distribution in the reactor core. The simulators can also simulate the response in the LPRM and TIP detectors. By comparing with measurements the accuracy of the core simulators can be quantified. The core simulators used in this work are PHOENIX4 and POLCA7. Because of the complexity of the calculations, each fuel assembly is divided axially into typically 25 nodes, which are more or less cubic with a side length of about 15 cm. Each axial segment is simulated using a 2D core simulator, in this work PHOENIX4, which provides data to the 3D code, in this case POLCA7, which in turn perform calculations for the whole core. The core simulators currently use both radial pin weights and axial node weights to calculate the gamma TIP detector signal. A need to bring forward new weight factors has now been identified because of the introduction of new fuel designs. Therefore, the gamma TIP detector response has been simulated using a Monte Carlo code called MCNPX for a modern fuel type, SVEA-96 Optima2, which is manufactured by Westinghouse. The new weights showed some significant differences compared to the old weights, which seem to overestimate the radial weight of the closest fuel pins and the axial weight of the node in front of the detector. The new weights were also implemented and tested in the core simulators, but no significant differences could be seen when comparing the simulated detector response using new and old weights to authentic TIP measurements.

  • 13.
    Gatu Johnson, Maria
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Fusion Plasma Observations at JET with the TOFOR Neutron Spectrometer: Instrumental Challenges and Physics Results2010Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The neutron spectrometer TOFOR was installed at JET in 2005 for high-rate observation of neutrons from reactions between two deuterium (D) ions. Neutron spectrometry as a fusion plasma diagnostic technique is invoked to obtain information about the velocity states of fusion fuel ions. Based on neutron spectrometry data, conclusions can be drawn on the efficiency of plasma heating schemes as well as optimization of fuel ion confinement. The quality of TOFOR analysis is found to depend on how well the instrument response function is known; discriminator threshold levels, detector time alignment and electronics broadening are identified as crucial issues.

    About 19 percent of the neutrons observed with TOFOR have scattered off the JET vessel wall or other structures in the line-of-sight before reaching the instrument, as established through simulations and measurements. A method has been developed to take these neutrons into account in the analysis. TOFOR measurements of fast deuterium distributions are seen to agree with distributions deduced from NPA data, obtained based on an entirely different principle. This serves as validation of the modeling and analysis.

    Extraordinary statistics in the TOFOR measurements from JET pulses heated with 3rd harmonic RF heating on D beams allow for study of instabilities using neutron emission spectrometry. At ITER, similar studies should be possible on a more regular basis due to higher neutron rates.

    Observations of neutrons from Be+3He reactions in the TOFOR spectrum from D plasmas heated with fundamental RF tuned to minority 3He raise the question of beryllium neutrons at JET after installation of the ITER-like wall, and at ITER, with beryllium as the plasma facing component. This is especially important for the first few years of ITER operation, where the machine will not yet have been certified as a nuclear facility and should be run in zero-activation mode.

    List of papers
    1. The TOFOR neutron spectrometer and its first use at JET
    Open this publication in new window or tab >>The TOFOR neutron spectrometer and its first use at JET
    Show others...
    2006 In: Review of Scientific Instruments, Vol. 77, no 10E702, p. 3-Article in journal (Refereed) Published
    Identifiers
    urn:nbn:se:uu:diva-96184 (URN)
    Available from: 2007-09-13 Created: 2007-09-13 Last updated: 2010-02-11Bibliographically approved
    2. The 2.5-MeV neutron time-of-flight spectrometer TOFOR for experiments at JET
    Open this publication in new window or tab >>The 2.5-MeV neutron time-of-flight spectrometer TOFOR for experiments at JET
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    2008 (English)In: Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, ISSN 0168-9002, E-ISSN 1872-9576, Vol. 591, no 2, p. 417-430Article in journal (Refereed) Published
    Abstract [en]

    A time-of-flight (TOF) spectrometer for measurement of the 2.5-MeV neutron emission from fusion plasmas has been developed and put into use at the JET tokamak. It has been optimized for operation at high rates (TOFOR) for the purpose of performing advanced neutron emission spectroscopy (NES) diagnosis of deuterium plasmas with a focus on the fuel ion motional states for different auxiliary heating scenarios. This requires operation over a large dynamic range, including high rates of > 100 kHz with a maximum value of 0.5 MHz for the TOFOR design. This paper describes the design principles and their technical realization. The performance is illustrated with recent neutron TOF spectra recorded for plasmas subjected to different heating scenarios. A true event count rate of 39 kHz has been achieved at about a tenth of the expected neutron yield limit of JET, giving a projected maximum of 400 kHz at peak JET plasma yield. This means that the count rate capability for NES diagnosis of D plasmas has been improved more than an order of magnitude. Another important performance factor is the spectrometer bandwidth, where data have been acquired and analyzed successfully with a response function for neutrons over the energy range 1 to > 5 MeV. The implications of instrumental advancement represented by TOFOR are discussed.

    National Category
    Physical Sciences Engineering and Technology
    Identifiers
    urn:nbn:se:uu:diva-16750 (URN)10.1016/j.nima.2008.03.010 (DOI)000257529700011 ()
    Note

    Conference Information: 21st IAEA Fusion Energy Conference Chengdu, PEOPLES R CHINA, OCT 16-21, 2006

    Available from: 2008-06-05 Created: 2008-06-05 Last updated: 2017-12-08Bibliographically approved
    3. Modeling and TOFOR measurements of scattered neutrons at JET
    Open this publication in new window or tab >>Modeling and TOFOR measurements of scattered neutrons at JET
    Show others...
    (English)Manuscript (preprint) (Other academic)
    Abstract [en]

    In this paper, the scattered and direct neutron fluxes in the line-of-sight of the TOFOR neutron spectrometer at JET are simulated and the simulations compared with measurement results. The Monte Carlo code MCNPX is used in the simulations, with a vessel material composition obtained from the JET drawing office and neutron emission profiles calculated from TRANSP simulations of beam ion density profiles. The MCNPX simulations show that the material composition of the scattering wall has a large effect on the shape of the scattered neutron spectrum. Neutron source profile shapes as well as radial and vertical source displacements in the TOFOR line-of-sight are shown to only marginally affect the scatter, while having a larger impact on the direct neutron flux. A matrix of simulated scatter spectra for mono-energetic source neutrons is created which is folded with an approximation of the source spectrum for each JET pulse studied to obtain a scatter component for use in the data analysis. The scatter components thus obtained are shown to describe the measured data. It is also demonstrated that the scattered flux is approximately constant relative to the total neutron yield as measured with the JET fission chambers, while there is a larger spread in the direct flux, consistent with simulations. The simulated effect on the integrated scattered/direct ratio of an increase with movements outward along the radial direction and a drop at higher values of the vertical plasma position is also reproduced in the measurements. Finally, the quantitative agreement found in scatter/direct ratios between simulations (0.185±0.005) and measurements (0.187±0.050) serves as a solid benchmark of the MCNPX model used.

    Research subject
    Physics with specialization in Applied Nuclear Physics
    Identifiers
    urn:nbn:se:uu:diva-114036 (URN)
    Note
    To be submitted to Plasma Physics and Controlled FusionAvailable from: 2010-02-08 Created: 2010-02-08 Last updated: 2010-02-11
    4. Cross-validation of JET fast deuterium results from TOFOR and NPA
    Open this publication in new window or tab >>Cross-validation of JET fast deuterium results from TOFOR and NPA
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    2009 (English)In: 36th EPS Conference on Plasma Physics, Sofia, June 29 - July 3, 2009 ECA Vol.33E, 2009, p. P-2.151-Conference paper, Published paper (Other academic)
    National Category
    Physical Sciences
    Research subject
    Physics with specialization in Applied Nuclear Physics
    Identifiers
    urn:nbn:se:uu:diva-114038 (URN)
    Conference
    36th EPS Conference on Plasma Physics
    Available from: 2010-02-08 Created: 2010-02-08 Last updated: 2010-02-18Bibliographically approved
    5. Neutron emission generated by fast deuterons accelerated with ion cyclotron heating at JET
    Open this publication in new window or tab >>Neutron emission generated by fast deuterons accelerated with ion cyclotron heating at JET
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    2010 (English)In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 50, no 2, p. 022001-Article in journal, Letter (Refereed) Published
    Abstract [en]

    For the first time, the neutron emission from JET plasmas heated with combined deuterium neutral beam injection and third harmonic ion cyclotron radio frequency heating have been studied with neutron emission spectroscopy (NES). Very high DD neutron rates were observed with only modest external heating powers, which was attributed to acceleration of deuterium beam ions to energies of about 2-3 MeV, where the DD reactivity is on a par of that of the DT reaction. Fast deuterium energy distributions were derived from analysis of NES data and confirm acceleration of deuterium beam ions up to energies around 3 MeV, in agreement with theoretical predictions. The high neutron rates allowed for observations of changes in the fast deuterium populations on a time scale of 50 ms. Correlations were seen between fast deuterium ions at different energies and magnetohydrodynamic activities, such as monster sawtooth crashes and toroidal Alfvén eigenmodes.

    National Category
    Physical Sciences
    Identifiers
    urn:nbn:se:uu:diva-114441 (URN)10.1088/0029-5515/50/2/022001 (DOI)000275322200002 ()
    Available from: 2010-02-16 Created: 2010-02-16 Last updated: 2017-12-12Bibliographically approved
    6. Neutron emission from beryllium reactions in JET deuterium plasmas with 3He minority
    Open this publication in new window or tab >>Neutron emission from beryllium reactions in JET deuterium plasmas with 3He minority
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    2010 (English)In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 50, no 4, p. 045005-Article in journal (Refereed) Published
    Abstract [en]

    Recent fast ion studies at JET involve ion cyclotron resonance frequency (ICRF) heating tuned to minority He-3 in cold deuterium plasmas, with beryllium evaporation in the vessel prior to the session. During the experiments, the high-resolution neutron spectrometer TOFOR was used to study the energy spectrum of emitted neutrons. Neutrons of energies up to 10MeV, not consistent with the neutron energy spectrum expected from d(d,n)He-3 reactions, were observed. In this paper, we interpret these neutrons as a first-time observation of a Be-9(He-3, n)C-11 neutron spectrum in a tokamak plasma, a conclusion based on a consistent analysis of experimental data and Monte Carlo simulations. Be-9(a, n)C-12 and Be-9(p, n)B-9 reactions are also simulated for p and a fusion products from d(He-3, a) p reactions; these two-step processes are seen to contribute on a level of about 10% of the single-step process in Be-9(He-3, n) C-11. Contributions to the total neutron yield from the Be-9(3He, n)C-11 reaction are found to be in the range 13 +/- 3 to 57 +/- 5%. We demonstrate how TOFOR can be used to simultaneously (i) probe the deuterium distribution, providing reliable measurements of the bulk deuterium temperature, here in the range 3.2 +/- 0.4 to 6.3 +/- 1.0 keV and (ii) provide an estimate of the beryllium concentration (in the range 0.48 +/- 0.17 to 6.4 +/- 1.7% of n(e) assuming T-3He = 300 keV). The observation of Be-9 related neutrons is relevant in view of the upcoming installation of a beryllium-coated ITER-like wall on JET and for ITER itself. An important implication is possible neutron-induced activation of the ITER vessel during the low-activation phase with ICRF heating tuned to minority He-3 in hydrogen plasmas.

    Keywords
    PACS codes: 29.30.Hs, 29.25.Dz, 52.55.-s, 52.55.Fa, 25.55.-e, 52.55.Pi
    National Category
    Physical Sciences
    Research subject
    Physics with specialization in Applied Nuclear Physics
    Identifiers
    urn:nbn:se:uu:diva-114040 (URN)10.1088/0029-5515/50/4/045005 (DOI)000276475600009 ()
    Available from: 2010-02-08 Created: 2010-02-08 Last updated: 2017-12-12Bibliographically approved
    7. Neutron emission levels during the ITER zero activation phase
    Open this publication in new window or tab >>Neutron emission levels during the ITER zero activation phase
    Show others...
    2010 (English)In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 50, no 8, p. 084020-Article in journal (Refereed) Published
    Abstract [en]

    In recent experiments at JET, a contribution to the neutron emission from reactions between beryllium and 3He, 4He and H has been identified. With the beryllium walled planned for ITER, this raises the question of possible neutron activation during the ITER zero activation phase. Here, we estimate the neutron emission rates for various heating scenarios foreseen for this ITER phase using Monte Carlo simulations. The emission is seen to be strongly dependent on the scenario chosen and the assumptions involved. We find that fundamental minority heating can contribute on the scale of low temperature deuterium plasmas, depending on minority concentration and ICRH power applied. Harmonic ICRH leads to production of tails that can give rise to significant neutron emission rates, while rates from hydrogen beams will be near zero. Better knowledge of the zero activation phase conditions, and more sophisticated ICRH codes, would be needed to give exact rate predictions. We conclude that rates from so-called zero activation plasmas will be significantly lower than expected for the DD or DT phases, but far from zero.

    Keywords
    PACS codes: 29.30.Hs, 29.25.Dz, 52.55.-s, 52.55.Fa, 25.55.-e, 52.55.Pi
    National Category
    Natural Sciences
    Research subject
    Applied Nuclear Physics
    Identifiers
    urn:nbn:se:uu:diva-114041 (URN)10.1088/0029-5515/50/8/084020 (DOI)000280505800021 ()
    Available from: 2010-02-08 Created: 2010-02-08 Last updated: 2017-12-12Bibliographically approved
  • 14.
    Gatu Johnson, Maria
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Cecconello, Marco
    Hellesen, Carl
    Andersson Sundén, Erik
    Conroy, Sean
    Ericsson, Göran
    Ronchi, Emanuele
    Weiszflog, Matthias
    Gorini, Giuseppe
    Physics Department, Milano-Bicocca University, and Instituto di Fisica del Plasma del CNR, Milan, Italy (EURATOM-ENEA-CNR Association).
    Tardocchi, Marco
    Cross-validation of JET fast deuterium results from TOFOR and NPA2009In: 36th EPS Conference on Plasma Physics, Sofia, June 29 - July 3, 2009 ECA Vol.33E, 2009, p. P-2.151-Conference paper (Other academic)
  • 15.
    Gatu Johnson, Maria
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Conroy, Sean
    Andersson Sundén, Erik
    Cecconello, Marco
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Ericsson, Göran
    Hellesen, Carl
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Gherendi, Mihaela
    Association EURATOM-MEdC, National Institute for Laser, Plasma and Radiation Physics, Bucharest, Romania.
    Hjalmarsson, Anders
    Murari, Andrea
    Consorzio RFX-Associazione EURATOM ENEA per la Fusione, I-35127 Padova, Italy.
    Popovichev, Sergei
    EURATOM/CCFE Association, Culham Science Centre, Abingdon, United Kingdom.
    Ronchi, Emanuele
    Weiszflog, Matthias
    Zoita, Liviu Vasile
    Association EURATOM-MEdC, National Institute for Laser, Plasma and Radiation Physics, Bucharest, Romania.
    Modeling and TOFOR measurements of scattered neutrons at JETManuscript (preprint) (Other academic)
    Abstract [en]

    In this paper, the scattered and direct neutron fluxes in the line-of-sight of the TOFOR neutron spectrometer at JET are simulated and the simulations compared with measurement results. The Monte Carlo code MCNPX is used in the simulations, with a vessel material composition obtained from the JET drawing office and neutron emission profiles calculated from TRANSP simulations of beam ion density profiles. The MCNPX simulations show that the material composition of the scattering wall has a large effect on the shape of the scattered neutron spectrum. Neutron source profile shapes as well as radial and vertical source displacements in the TOFOR line-of-sight are shown to only marginally affect the scatter, while having a larger impact on the direct neutron flux. A matrix of simulated scatter spectra for mono-energetic source neutrons is created which is folded with an approximation of the source spectrum for each JET pulse studied to obtain a scatter component for use in the data analysis. The scatter components thus obtained are shown to describe the measured data. It is also demonstrated that the scattered flux is approximately constant relative to the total neutron yield as measured with the JET fission chambers, while there is a larger spread in the direct flux, consistent with simulations. The simulated effect on the integrated scattered/direct ratio of an increase with movements outward along the radial direction and a drop at higher values of the vertical plasma position is also reproduced in the measurements. Finally, the quantitative agreement found in scatter/direct ratios between simulations (0.185±0.005) and measurements (0.187±0.050) serves as a solid benchmark of the MCNPX model used.

  • 16.
    Gatu Johnson, Maria
    et al.
    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.
    Cecconello, Marco
    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.
    Ericsson, Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Gherendi, M
    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.
    Murari, A
    Popovichev, S
    Ronchi, Emanuele
    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.
    Zoita, L
    JET-EFDA Contributors,
    Modelling and TOFOR measurements of scattered neutrons at JET2010In: Plasma Physics and Controlled Fusion, ISSN 0741-3335, E-ISSN 1361-6587, Vol. 52, no 8, p. 085002-Article in journal (Refereed)
    Abstract [en]

    In this paper, the scattered and direct neutron fluxes in the line of sight (LOS) of the TOFOR neutron spectrometer at JET are simulated and the simulations compared with measurement results. The Monte Carlo code MCNPX is used in the simulations, with a vessel material composition obtained from the JET drawing office and neutron emission profiles calculated from TRANSP simulations of beam ion density profiles. The MCNPX simulations show that the material composition of the scattering wall has a large effect on the shape of the scattered neutron spectrum. Neutron source profile shapes as well as radial and vertical source displacements in the TOFOR LOS are shown to only marginally affect the scatter, while having a larger impact on the direct neutron flux. A matrix of simulated scatter spectra for mono-energetic source neutrons is created which is folded with an approximation of the source spectrum for each JET pulse studied to obtain a scatter component for use in the data analysis. The scatter components thus obtained are shown to describe the measured data. It is also demonstrated that the scattered flux is approximately constant relative to the total neutron yield as measured with the JET fission chambers, while there is a larger spread in the direct flux, consistent with simulations. The simulated effect on the integrated scattered/direct ratio of an increase with movements outward along the radial direction and a drop at higher values of the vertical plasma position is also reproduced in the measurements. Finally, the quantitative agreement found in scatter/direct ratios between simulations (0.185 ± 0.005) and measurements (0.187 ± 0.050) serves as a solid benchmark of the MCNPX model used.

  • 17.
    Gatu Johnson, Maria
    et al.
    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.
    Andersson Sundén, Erik
    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.
    Ericsson, Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Gorini, Giuseppe
    Physics Department, Milano-Bicocca University, and Istituto di Fisica del Plasma del CNR, Milan, Italy (EURATOM-ENEA-CNR Association).
    Kiptily, Vasily
    Euratom / UKAEA Fusion Association, Culham Science Centre, Abingdon, United Kingdom.
    Nocente, Massimo
    Physics Department, Milano-Bicocca University, and Istituto di Fisica del Plasma del CNR, Milan, Italy (EURATOM-ENEA-CNR Association).
    Pinches, Simon
    Euratom / UKAEA Fusion Association, Culham Science Centre, Abingdon, United Kingdom.
    Ronchi, Emanuele
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Sharapov, Sergei
    Euratom / UKAEA Fusion Association, Culham Science Centre, Abingdon, United Kingdom.
    Sjöstrand, Henrik
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Tardocchi, Marco
    Physics Department, Milano-Bicocca University, and Istituto di Fisica del Plasma del CNR, Milan, Italy (EURATOM-ENEA-CNR Association).
    Weiszflog, Matthias
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Neutron emission from beryllium reactions in JET deuterium plasmas with 3He minority2010In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 50, no 4, p. 045005-Article in journal (Refereed)
    Abstract [en]

    Recent fast ion studies at JET involve ion cyclotron resonance frequency (ICRF) heating tuned to minority He-3 in cold deuterium plasmas, with beryllium evaporation in the vessel prior to the session. During the experiments, the high-resolution neutron spectrometer TOFOR was used to study the energy spectrum of emitted neutrons. Neutrons of energies up to 10MeV, not consistent with the neutron energy spectrum expected from d(d,n)He-3 reactions, were observed. In this paper, we interpret these neutrons as a first-time observation of a Be-9(He-3, n)C-11 neutron spectrum in a tokamak plasma, a conclusion based on a consistent analysis of experimental data and Monte Carlo simulations. Be-9(a, n)C-12 and Be-9(p, n)B-9 reactions are also simulated for p and a fusion products from d(He-3, a) p reactions; these two-step processes are seen to contribute on a level of about 10% of the single-step process in Be-9(He-3, n) C-11. Contributions to the total neutron yield from the Be-9(3He, n)C-11 reaction are found to be in the range 13 +/- 3 to 57 +/- 5%. We demonstrate how TOFOR can be used to simultaneously (i) probe the deuterium distribution, providing reliable measurements of the bulk deuterium temperature, here in the range 3.2 +/- 0.4 to 6.3 +/- 1.0 keV and (ii) provide an estimate of the beryllium concentration (in the range 0.48 +/- 0.17 to 6.4 +/- 1.7% of n(e) assuming T-3He = 300 keV). The observation of Be-9 related neutrons is relevant in view of the upcoming installation of a beryllium-coated ITER-like wall on JET and for ITER itself. An important implication is possible neutron-induced activation of the ITER vessel during the low-activation phase with ICRF heating tuned to minority He-3 in hydrogen plasmas.

  • 18.
    Gatu Johnson, Maria
    et al.
    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.
    Andersson Sundén, Erik
    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.
    Ericsson, Göran
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Gorini, Giuseppe
    Physics Department, Milano-Bicocca University, and Istituto di Fisica del Plasma del CNR, Milan, Italy (EURATOM-ENEA-CNR Association).
    Nocente, Massimo
    Physics Department, Milano-Bicocca University, and Istituto di Fisica del Plasma del CNR, Milan, Italy (EURATOM-ENEA-CNR Association).
    Ronchi, Emanuele
    Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Applied Nuclear Physics.
    Tardocchi, Marco
    Physics Department, Milano-Bicocca University, and Istituto di Fisica del Plasma del CNR, Milan, Italy (EURATOM-ENEA-CNR As