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Hellesen, Carl
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Publications (10 of 99) Show all publications
Hellesen, C., Mantsinen, M., Conroy, S., Ericsson, G., Eriksson, J., Kiptily, V. & Nabais, F. (2018). Analysis of resonant fast ion distributions during combined ICRF and NBI heating with transients using neutron emission spectroscopy. Nuclear Fusion, 58(5), Article ID 056021.
Open this publication in new window or tab >>Analysis of resonant fast ion distributions during combined ICRF and NBI heating with transients using neutron emission spectroscopy
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2018 (English)In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 58, no 5, article id 056021Article in journal (Refereed) Published
Abstract [en]

ICRF heating at the fundamental cyclotron frequency of a hydrogen minority ion species also gives rise to a partial power absorption by deuterium ions at their second harmonic resonance. This paper studies the deuterium distributions resulting from such 2nd harmonic heating at JET using neutron emission spectroscopy data from the time of flight spectrometer TOFOR. The fast deuterium distributions are obtained over the energy range 100 keV to 2 MeV. Specifically, we study how the fast deuterium distributions vary as ICRF heating is used alone as well as in combination with NBI heating. When comparing the different heating scenarios, we observed both a difference in the shapes of the distributions as well as in their absolute level. The differences are most pronounced below 0.5 MeV. Comparisons are made with corresponding distributions calculated with the code PION. We find a good agreement between the measured distributions and those calculated with PION, both in terms of their shapes as well as their amplitudes. However, we also identified a period with signs of an inverted fast ion distribution, which showed large disagreements between the modeled and measured results. Resonant interactions with tornado modes, i.e. core localized toroidal alfven eigenmodes (TAEs), are put forward as a possible explanation for the inverted distribution.

National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:uu:diva-319414 (URN)10.1088/1741-4326/aab4ab (DOI)000428454700003 ()
Available from: 2017-04-04 Created: 2017-04-04 Last updated: 2018-06-20Bibliographically approved
Salewski, M., Nocente, M., Jacobsen, A. S., Binda, F., Cazzaniga, C., Eriksson, J., . . . Tardocchi, M. (2018). Bayesian Integrated Data Analysis of Fast-Ion Measurements by Velocity-Space Tomography. Paper presented at 2nd International Atomic Energy Agency (IAEA) Technical Meeting (TM) on Fusion Data Processing, Validation, and Analysis (IAEA-TM), MAY 30-JUN 02, 2017, Massachusetts Inst Technol Campus, Samberg Conf Ctr, Cambridge, MA. Fusion science and technology, 74(1-2), 23-36
Open this publication in new window or tab >>Bayesian Integrated Data Analysis of Fast-Ion Measurements by Velocity-Space Tomography
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2018 (English)In: Fusion science and technology, ISSN 1536-1055, E-ISSN 1943-7641, Vol. 74, no 1-2, p. 23-36Article in journal (Refereed) Published
Abstract [en]

Bayesian integrated data analysis combines measurements from different diagnostics to jointly measure plasma parameters of interest such as temperatures, densities, and drift velocities. Integrated data analysis of fast-ion measurements has long been hampered by the complexity of the strongly non-Maxwellian fast-ion distribution functions. This has recently been overcome by velocity-space tomography. In this method two-dimensional images of the velocity distribution functions consisting of a few hundreds or thousands of pixels are reconstructed using the available fast-ion measurements. Here we present an overview and current status of this emerging technique at the ASDEX Upgrade tokamak and the JET toamak based on fast-ion D-alpha spectroscopy, collective Thomson scattering, gamma-ray and neutron emission spectrometry, and neutral particle analyzers. We discuss Tikhonov regularization within the Bayesian framework. The implementation for different types of diagnostics as well as the uncertainties are discussed, and we highlight the importance of integrated data analysis of all available detectors.

Place, publisher, year, edition, pages
TAYLOR & FRANCIS INC, 2018
Keywords
Tokamaks, fast ions, velocity-space tomography
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:uu:diva-361010 (URN)10.1080/15361055.2017.1380482 (DOI)000436997000004 ()
Conference
2nd International Atomic Energy Agency (IAEA) Technical Meeting (TM) on Fusion Data Processing, Validation, and Analysis (IAEA-TM), MAY 30-JUN 02, 2017, Massachusetts Inst Technol Campus, Samberg Conf Ctr, Cambridge, MA
Available from: 2018-09-25 Created: 2018-09-25 Last updated: 2018-09-25Bibliographically approved
Åberg Lindell, M., Andersson, P., Grape, S., Hellesen, C., Håkansson, A. & Eriksson, M. (2018). Discrimination of irradiated MOX fuel from UOX fuel by multivariate statistical analysis of simulated activities of gamma-emitting isotopes. Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 885, 67-78
Open this publication in new window or tab >>Discrimination of irradiated MOX fuel from UOX fuel by multivariate statistical analysis of simulated activities of gamma-emitting isotopes
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2018 (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. 885, p. 67-78Article in journal (Refereed) Published
Abstract [en]

This paper investigates how concentrations of certain fission products and their related gamma-ray emissions can be used to discriminate between uranium oxide (UOX) and mixed oxide (MOX) type fuel. Discrimination of irradiated MOX fuel from irradiated UOX fuel is important in nuclear facilities and for transport of nuclear fuel, for purposes of both criticality safety and nuclear safeguards. Although facility operators keep records on the identity and properties of each fuel, tools for nuclear safeguards inspectors that enable independent verification of the fuel are critical in the recovery of continuity of knowledge, should it be lost. A discrimination methodology for classification of UOX and MOX fuel, based on passive gamma-ray spectroscopy data and multivariate analysis methods, is presented. Nuclear fuels and their gamma-ray emissions were simulated in the Monte Carlo code Serpent, and the resulting data was used as input to train seven different multivariate classification techniques. The trained classifiers were subsequently implemented and evaluated with respect to their capabilities to correctly predict the classes of unknown fuel items. The best results concerning successful discrimination of UOX and MOX-fuel were acquired when using non-linear classification techniques, such as the k nearest neighbors method and the Gaussian kernel support vector machine. For fuel with cooling times up to 20 years, when it is considered that gamma-rays from the isotope  134Cs can still be efficiently measured, success rates of 100% were obtained. A sensitivity analysis indicated that these methods were also robust.

Keywords
Spent nuclear fuel, MOX, Gamma spectroscopy, Multivariate analysis, Classification
National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-337676 (URN)10.1016/j.nima.2017.12.020 (DOI)000424740800009 ()
Funder
Swedish Research Council, VR 621-2009-3991Swedish Radiation Safety Authority, SSM2016-661
Available from: 2018-01-03 Created: 2018-01-03 Last updated: 2018-04-19Bibliographically approved
Krasilnikov, A. V., Kiptily, V., Lerche, E., Van Eester, D., Afanasyev, V. I., Giroud, C., . . . Mironov, M. I. (2018). Evidence of Be-9 + p nuclear reactions during 2 omega(CH) and hydrogen minority ICRH in JET-ILW hydrogen and deuterium plasmas. Nuclear Fusion, 58(2), Article ID 026033.
Open this publication in new window or tab >>Evidence of Be-9 + p nuclear reactions during 2 omega(CH) and hydrogen minority ICRH in JET-ILW hydrogen and deuterium plasmas
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2018 (English)In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 58, no 2, article id 026033Article in journal (Refereed) Published
Abstract [en]

The intensity of Be-9 + p nuclear fusion reactions was experimentally studied during second harmonic (2 omega CH) ion-cyclotron resonance heating (ICRH) and further analyzed during fundamental hydrogen minority ICRH of JET-ILW hydrogen and deuterium plasmas. In relatively low-density plasmas with a high ICRH power, a population of fast H+ ions was created and measured by neutral particle analyzers. Primary and secondary nuclear reaction products, due to Be-9 + p interaction, were observed with fast ion loss detectors, gamma-ray spectrometers and neutron flux monitors and spectrometers. The possibility of using Be-9(p, d)2 alpha and Be-9(p, alpha)Li-6 nuclear reactions to create a population of fast alpha particles and study their behaviour in non-active stage of ITER operation is discussed in the paper.

Keywords
beryllium, proton, nuclear reactions, ICRH, alpha-particles
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:uu:diva-341566 (URN)10.1088/1741-4326/aa90c3 (DOI)000419796500003 ()
Available from: 2018-02-14 Created: 2018-02-14 Last updated: 2018-05-09Bibliographically approved
Hellesen, C. & Qvist, S. (2017). Benchmark and demonstration of the CHD code for transient analysis of fast reactor systems. Annals of Nuclear Energy, 109, 712-719
Open this publication in new window or tab >>Benchmark and demonstration of the CHD code for transient analysis of fast reactor systems
2017 (English)In: Annals of Nuclear Energy, ISSN 0306-4549, E-ISSN 1873-2100, Vol. 109, p. 712-719Article in journal (Refereed) Published
Abstract [en]

In this paper the dynamic thermal hydraulic fast reactor simulation code CHD is presented. The code is built around a scriptable object-oriented framework in the programming language Python to be able to flexibly describe different reactor geometries including thermal-hydraulics models of an arbitrary number of coolant channels as well as pumps, heat-exchangers and pools etc. In addition, custom objects such as the Autonomous Reactivity Control (ARC) system for enhanced passive safety are modeled in detail. In this paper we compare the performance of the CHD code with other similar fast reactor dynamics codes using a benchmark study of the European Sodium cooled Fast Reactor (ESFR). The results agree well, both qualitatively and quantitatively with the code benchmark. In addition, we demonstrate the code's ability to simulate the long-term asymptotic behavior of a neutronically shut down reactor in an unprotected loss of flow scenario using a model of the Advanced Burner Reactor (ABR). (C) 2017 Elsevier Ltd. All rights reserved.

Place, publisher, year, edition, pages
Elsevier, 2017
Keywords
Fast reactor, Thermal-hydraulics, Point-kinetics, Transient, Passive safety, ULOF
National Category
Energy Engineering
Identifiers
urn:nbn:se:uu:diva-339705 (URN)10.1016/j.anucene.2017.05.031 (DOI)000418211500071 ()
Available from: 2018-01-26 Created: 2018-01-26 Last updated: 2018-01-26Bibliographically approved
Hellesen, C., Andersson Sundén, E., Conroy, S., Dzysiuk, N., Ericsson, G., Hjalmarsson, A., . . . Marcinkevicius, B. (2017). Conceptual design of a BackTOF neutron spectrometer for fuel ion ratio measurements at ITER. Nuclear Fusion, 57(6), Article ID 066021.
Open this publication in new window or tab >>Conceptual design of a BackTOF neutron spectrometer for fuel ion ratio measurements at ITER
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2017 (English)In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 57, no 6, article id 066021Article in journal (Refereed) Published
Abstract [en]

In this paper we present a conceptual design of a back scattering neutron time of flight spectrometer (BackTOF) for use at ITER. The proposed BackTOF design aims at fulfilling the requirements set on a neutron spectrometer system to be used for inferring the core fuel ion ratio in a DT plasma. Specifically we have investigated the requirements on the size, energy resolution, count rate capability, efficiency and signal to background ratio. These requirements are a compact size that fits in roughly 1 m3, an energy resolution of 4% or better, a count rate capability of at least 100 kHz, an efficiency of at least 10−5 and a signal to background ratio of 1000 or better.

Using a Monte Carlo model of the BackTOF spectrometer we find that the proposed BackTOF design is compact enough to be installed at ITER while being capable of achieving a resolution of about 4% FWHM with a count rate capability of 300 kHz and an efficiency at 1.25 10−3. This is sufficient for achieving the requirements on the fuel ion ratio at ITER. We also demonstrate how data acquisition systems capable of providing both timing and energy information can be used to effectively discriminate random background at high count rates.

Keywords
neutron spectroscopy, time of flight, burning plasma, fuel ion ratio
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:uu:diva-348803 (URN)10.1088/1741-4326/aa6937 (DOI)000425870000001 ()
Available from: 2018-05-04 Created: 2018-05-04 Last updated: 2018-05-04Bibliographically approved
Kazakov, Y. O. O., Possnert, G., Sjöstrand, H., Skiba, M., Weiszflog, M., Andersson Sundén, E., . . . Kazantzidis, V. (2017). Efficient generation of energetic ions in multi-ion plasmas by radio-frequency heating. Nature Physics, 13(10), 973-978
Open this publication in new window or tab >>Efficient generation of energetic ions in multi-ion plasmas by radio-frequency heating
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2017 (English)In: Nature Physics, ISSN 1745-2473, E-ISSN 1745-2481, Vol. 13, no 10, p. 973-978Article in journal (Refereed) Published
Abstract [en]

We describe a new technique for the efficient generation of high-energy ions with electromagnetic ion cyclotron waves in multi-ion plasmas. The discussed three-ion scenarios are especially suited for strong wave absorption by a very low number of resonant ions. To observe this effect, the plasma composition has to be properly adjusted, as prescribed by theory. We demonstrate the potential of the method on the world-largest plasma magnetic confinement device, JET (Joint European Torus, Culham, UK), and the high-magnetic-field tokamak Alcator C-Mod (Cambridge, USA). The obtained results demonstrate efficient acceleration of He-3 ions to high energies in dedicated hydrogendeuterium mixtures. Simultaneously, effective plasma heating is observed, as a result of the slowing-down of the fast He-3 ions. The developed technique is not only limited to laboratory plasmas, but can also be applied to explain observations of energetic ions in space-plasma environments, in particular, He-3-rich solar flares.

National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:uu:diva-359272 (URN)10.1038/NPHYS4167 (DOI)000412181200018 ()
Note

For a complete list of authors see http://dx.doi.org/10.1038/NPHYS4167

Available from: 2018-09-05 Created: 2018-09-05 Last updated: 2018-09-05Bibliographically approved
Binda, F., Eriksson, J., Ericsson, G., Hellesen, C., Conroy, S., Nocente, M. & Andersson Sundén, E. (2017). Generation of the neutron response function of an NE213 scintillator for fusion applications. Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 866, 222-229
Open this publication in new window or tab >>Generation of the neutron response function of an NE213 scintillator for fusion applications
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2017 (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. 866, p. 222-229Article in journal (Refereed) Published
Abstract [en]

In this work we present a method to evaluate the neutron response function of an NE213 liquid scintillator. This method is particularly useful when the proton light yield function of the detector has not been measured, since it is based on a proton light yield function taken from literature, MCNPX simulations, measurements of gammarays from a calibration source and measurements of neutrons from fusion experiments with ohmic plasmas. The inclusion of the latter improves the description of the proton light yield function in the energy range of interest (around 2.46 MeV). We apply this method to an NE213 detector installed at JET, inside the radiation shielding of the magnetic proton recoil (MPRu) spectrometer, and present the results from the calibration along with some examples of application of the response function to perform neutron emission spectroscopy (NES) of fusion plasmas. We also investigate how the choice of the proton light yield function affects the NES analysis, finding that the result does not change significantly. This points to the fact that the method for the evaluation of the neutron response function is robust and gives reliable results.

Keywords
NE213 scintillator, Neutron spectroscopy, Response function, Proton light yield
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:uu:diva-330537 (URN)10.1016/j.nima.2017.04.023 (DOI)000407863700029 ()
Available from: 2017-10-04 Created: 2017-10-04 Last updated: 2018-04-23Bibliographically approved
Salewski, M., Nocente, M., Jacobsen, A. S., Binda, F., Cazzaniga, C., Ericsson, G., . . . Tardocchi, M. (2017). MeV-range velocity-space tomography from gamma-ray and neutron emission spectrometry measurements at JET. Nuclear Fusion, 57(5), Article ID 056001.
Open this publication in new window or tab >>MeV-range velocity-space tomography from gamma-ray and neutron emission spectrometry measurements at JET
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2017 (English)In: Nuclear Fusion, ISSN 0029-5515, E-ISSN 1741-4326, Vol. 57, no 5, article id 056001Article in journal (Refereed) Published
Abstract [en]

We demonstrate the measurement of a 2D MeV-range ion velocity distribution function by velocity-space tomography at JET. Deuterium ions were accelerated into the MeV-range by third harmonic ion cyclotron resonance heating. We made measurements with three neutron emission spectrometers and a high-resolution gamma-ray spectrometer detecting the gamma-rays released in two reactions. The tomographic inversion based on these five spectra is in excellent agreement with numerical simulations with the ASCOT-RFOF and the SPOT-RFOF codes. The length of the measured fast-ion tail corroborates the prediction that very few particles are accelerated above 2 MeV due to the weak wave-particle interaction at higher energies.

Place, publisher, year, edition, pages
IOP PUBLISHING LTD, 2017
Keywords
gamma-ray spectrometry, neutron emission spectrometry, velocity-space tomography, fast ions, tokamak
National Category
Subatomic Physics
Identifiers
urn:nbn:se:uu:diva-321793 (URN)10.1088/1741-4326/aa60e9 (DOI)000398746700001 ()
Available from: 2017-05-11 Created: 2017-05-11 Last updated: 2018-04-23Bibliographically approved
Hellesen, C., Grape, S., Jansson, P., Jacobsson, S., Åberg Lindell, M. & Andersson, P. (2017). Nuclear Spent Fuel Parameter Determination using Multivariate Analysis of Fission Product Gamma Spectra. Annals of Nuclear Energy, 110, 886-895
Open this publication in new window or tab >>Nuclear Spent Fuel Parameter Determination using Multivariate Analysis of Fission Product Gamma Spectra
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2017 (English)In: Annals of Nuclear Energy, ISSN 0306-4549, E-ISSN 1873-2100, Vol. 110, p. 886-895Article in journal (Refereed) Published
Abstract [en]

In this paper, we investigate the application of multivariate data analysis methods to the analysis of gamma spectroscopy measurements of spent nuclear fuel (SNF). Using a simulated irradiation and cooling of nuclear fuel over a wide range of cooling times (CT), total burnup at discharge (BU) and initial enrichments (IE) we investigate the possibilities of using a multivariate data analysis of the gamma ray emission signatures from the fuel to determine these fuel parameters. This is accomplished by training a multivariate analysis method on simulated data and then applying the method to simulated, but perturbed, data.

We find that for SNF with CT less than about 20 years, a single gamma spectrum from a high resolution gamma spectrometer, such as a high-purity germanium spectrometer, allows for the determination of the above mentioned fuel parameters.

Further, using measured gamma spectra from real SNF from Swedish pressurized light water reactors we were able to confirm the operator declared fuel parameters. In this case, a multivariate analysis trained on simulated data and applied to real data was used.

Keywords
Multivariate analysis, principal component analysis, partial least squares regression, gamma ray, nuclear fuel, safeguards
National Category
Subatomic Physics
Research subject
Physics with specialization in Applied Nuclear Physics
Identifiers
urn:nbn:se:uu:diva-327108 (URN)10.1016/j.anucene.2017.07.035 (DOI)000412251000078 ()
Funder
Swedish Radiation Safety Authority
Available from: 2017-08-03 Created: 2017-08-03 Last updated: 2018-04-19Bibliographically approved
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