MeV-range fast ion losses induced by fishbones on JET

C. Perez von Thun, A. Perona, T. Johnson, S.E. Sharapov, M. Reich, V.G. Kiptily, M. Cecconello, Antti Salmi, V.Ya. Goloborod'ko, S.D. Pinches, M. García-Muñoz, D. Darrow, M. Brix, I. Voitsekhovitch, JET EFDA contributors

Research output: Contribution to journalArticleScientificpeer-review

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Abstract

Energy and pitch angle resolved measurements of highly energetic (megaelectronvolt (MeV) range) suprathermal ions ejected from the plasma through interaction with fishbone oscillations are presented. The measurements are obtained with a 2D scintillator probe diagnostic installed on JET, which is designed to detect lost ions only above a certain energy threshold (Emin,D ~ 200 keV). In the case reported here the lost ions are identified as fast protons which had been accelerated to high energies by ICRF minority heating. The energy of the lost protons (~0.5–4 MeV) is approximately one order of magnitude higher than the energy of the injected beam ions (maximum 130 keV) driving the fishbone. Losses arriving at the probe are enhanced by about a factor 10–20 with respect to MHD-quiescent levels, and are found to increase quadratically with the fishbone amplitude. Using a number of simplifying assumptions, numerical simulations have been performed which combine the HAGIS, MISHKA and SELFO codes (where the distribution function predicted by SELFO has been validated against neutral particle analyser measurements). The losses are found to originate from orbit stochastic diffusion of trapped protons near the plasma boundary or from counter-passing protons deep in the plasma core, which transit under the influence of the fishbone into an unconfined trapped orbit. The simulations show further that the losses are of non-resonant type. The simulated energy and pitch angle distribution of the losses, the temporal behaviour of the losses during a fishbone cycle and the scaling of the losses with the fishbone amplitude are compared with experiment. The simulation results are mostly in broad agreement with experiment, but some of the predictions could not be reconciled with experiment using this model.
Original languageEnglish
Article number084009
JournalNuclear Fusion
Volume50
Issue number8
DOIs
Publication statusPublished - 2010
MoE publication typeA1 Journal article-refereed

Fingerprint

ions
protons
pitch (inclination)
energy
orbits
plasma interactions
simulation
probes
neutral particles
minorities
transit
scintillation counters
counters
distribution functions
ion beams
scaling
oscillations
cycles
heating
thresholds

Keywords

  • plasma physics
  • tokamaks
  • simulation
  • fusion energy

Cite this

Perez von Thun, C., Perona, A., Johnson, T., Sharapov, S. E., Reich, M., Kiptily, V. G., ... contributors, JET. EFDA. (2010). MeV-range fast ion losses induced by fishbones on JET. Nuclear Fusion, 50(8), [084009]. https://doi.org/10.1088/0029-5515/50/8/084009
Perez von Thun, C. ; Perona, A. ; Johnson, T. ; Sharapov, S.E. ; Reich, M. ; Kiptily, V.G. ; Cecconello, M. ; Salmi, Antti ; Goloborod'ko, V.Ya. ; Pinches, S.D. ; García-Muñoz, M. ; Darrow, D. ; Brix, M. ; Voitsekhovitch, I. ; contributors, JET EFDA. / MeV-range fast ion losses induced by fishbones on JET. In: Nuclear Fusion. 2010 ; Vol. 50, No. 8.
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title = "MeV-range fast ion losses induced by fishbones on JET",
abstract = "Energy and pitch angle resolved measurements of highly energetic (megaelectronvolt (MeV) range) suprathermal ions ejected from the plasma through interaction with fishbone oscillations are presented. The measurements are obtained with a 2D scintillator probe diagnostic installed on JET, which is designed to detect lost ions only above a certain energy threshold (Emin,D ~ 200 keV). In the case reported here the lost ions are identified as fast protons which had been accelerated to high energies by ICRF minority heating. The energy of the lost protons (~0.5–4 MeV) is approximately one order of magnitude higher than the energy of the injected beam ions (maximum 130 keV) driving the fishbone. Losses arriving at the probe are enhanced by about a factor 10–20 with respect to MHD-quiescent levels, and are found to increase quadratically with the fishbone amplitude. Using a number of simplifying assumptions, numerical simulations have been performed which combine the HAGIS, MISHKA and SELFO codes (where the distribution function predicted by SELFO has been validated against neutral particle analyser measurements). The losses are found to originate from orbit stochastic diffusion of trapped protons near the plasma boundary or from counter-passing protons deep in the plasma core, which transit under the influence of the fishbone into an unconfined trapped orbit. The simulations show further that the losses are of non-resonant type. The simulated energy and pitch angle distribution of the losses, the temporal behaviour of the losses during a fishbone cycle and the scaling of the losses with the fishbone amplitude are compared with experiment. The simulation results are mostly in broad agreement with experiment, but some of the predictions could not be reconciled with experiment using this model.",
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author = "{Perez von Thun}, C. and A. Perona and T. Johnson and S.E. Sharapov and M. Reich and V.G. Kiptily and M. Cecconello and Antti Salmi and V.Ya. Goloborod'ko and S.D. Pinches and M. Garc{\'i}a-Mu{\~n}oz and D. Darrow and M. Brix and I. Voitsekhovitch and contributors, {JET EFDA}",
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language = "English",
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Perez von Thun, C, Perona, A, Johnson, T, Sharapov, SE, Reich, M, Kiptily, VG, Cecconello, M, Salmi, A, Goloborod'ko, VY, Pinches, SD, García-Muñoz, M, Darrow, D, Brix, M, Voitsekhovitch, I & contributors, JETEFDA 2010, 'MeV-range fast ion losses induced by fishbones on JET', Nuclear Fusion, vol. 50, no. 8, 084009. https://doi.org/10.1088/0029-5515/50/8/084009

MeV-range fast ion losses induced by fishbones on JET. / Perez von Thun, C.; Perona, A.; Johnson, T.; Sharapov, S.E.; Reich, M.; Kiptily, V.G.; Cecconello, M.; Salmi, Antti; Goloborod'ko, V.Ya.; Pinches, S.D.; García-Muñoz, M.; Darrow, D.; Brix, M.; Voitsekhovitch, I.; contributors, JET EFDA.

In: Nuclear Fusion, Vol. 50, No. 8, 084009, 2010.

Research output: Contribution to journalArticleScientificpeer-review

TY - JOUR

T1 - MeV-range fast ion losses induced by fishbones on JET

AU - Perez von Thun, C.

AU - Perona, A.

AU - Johnson, T.

AU - Sharapov, S.E.

AU - Reich, M.

AU - Kiptily, V.G.

AU - Cecconello, M.

AU - Salmi, Antti

AU - Goloborod'ko, V.Ya.

AU - Pinches, S.D.

AU - García-Muñoz, M.

AU - Darrow, D.

AU - Brix, M.

AU - Voitsekhovitch, I.

AU - contributors, JET EFDA

PY - 2010

Y1 - 2010

N2 - Energy and pitch angle resolved measurements of highly energetic (megaelectronvolt (MeV) range) suprathermal ions ejected from the plasma through interaction with fishbone oscillations are presented. The measurements are obtained with a 2D scintillator probe diagnostic installed on JET, which is designed to detect lost ions only above a certain energy threshold (Emin,D ~ 200 keV). In the case reported here the lost ions are identified as fast protons which had been accelerated to high energies by ICRF minority heating. The energy of the lost protons (~0.5–4 MeV) is approximately one order of magnitude higher than the energy of the injected beam ions (maximum 130 keV) driving the fishbone. Losses arriving at the probe are enhanced by about a factor 10–20 with respect to MHD-quiescent levels, and are found to increase quadratically with the fishbone amplitude. Using a number of simplifying assumptions, numerical simulations have been performed which combine the HAGIS, MISHKA and SELFO codes (where the distribution function predicted by SELFO has been validated against neutral particle analyser measurements). The losses are found to originate from orbit stochastic diffusion of trapped protons near the plasma boundary or from counter-passing protons deep in the plasma core, which transit under the influence of the fishbone into an unconfined trapped orbit. The simulations show further that the losses are of non-resonant type. The simulated energy and pitch angle distribution of the losses, the temporal behaviour of the losses during a fishbone cycle and the scaling of the losses with the fishbone amplitude are compared with experiment. The simulation results are mostly in broad agreement with experiment, but some of the predictions could not be reconciled with experiment using this model.

AB - Energy and pitch angle resolved measurements of highly energetic (megaelectronvolt (MeV) range) suprathermal ions ejected from the plasma through interaction with fishbone oscillations are presented. The measurements are obtained with a 2D scintillator probe diagnostic installed on JET, which is designed to detect lost ions only above a certain energy threshold (Emin,D ~ 200 keV). In the case reported here the lost ions are identified as fast protons which had been accelerated to high energies by ICRF minority heating. The energy of the lost protons (~0.5–4 MeV) is approximately one order of magnitude higher than the energy of the injected beam ions (maximum 130 keV) driving the fishbone. Losses arriving at the probe are enhanced by about a factor 10–20 with respect to MHD-quiescent levels, and are found to increase quadratically with the fishbone amplitude. Using a number of simplifying assumptions, numerical simulations have been performed which combine the HAGIS, MISHKA and SELFO codes (where the distribution function predicted by SELFO has been validated against neutral particle analyser measurements). The losses are found to originate from orbit stochastic diffusion of trapped protons near the plasma boundary or from counter-passing protons deep in the plasma core, which transit under the influence of the fishbone into an unconfined trapped orbit. The simulations show further that the losses are of non-resonant type. The simulated energy and pitch angle distribution of the losses, the temporal behaviour of the losses during a fishbone cycle and the scaling of the losses with the fishbone amplitude are compared with experiment. The simulation results are mostly in broad agreement with experiment, but some of the predictions could not be reconciled with experiment using this model.

KW - plasma physics

KW - tokamaks

KW - simulation

KW - fusion energy

U2 - 10.1088/0029-5515/50/8/084009

DO - 10.1088/0029-5515/50/8/084009

M3 - Article

VL - 50

JO - Nuclear Fusion

JF - Nuclear Fusion

SN - 0029-5515

IS - 8

M1 - 084009

ER -

Perez von Thun C, Perona A, Johnson T, Sharapov SE, Reich M, Kiptily VG et al. MeV-range fast ion losses induced by fishbones on JET. Nuclear Fusion. 2010;50(8). 084009. https://doi.org/10.1088/0029-5515/50/8/084009