Scintillator probe for lost alpha measurements in JET

Baeumel, S.; Werner, A.; Semler, R.; Mukherjee, S.; Darrow, D.S.; Ellis, R.; Cecil, F. E.; Pedrick, L.; Altmann, H.; Kiptily, V.; Gafert, J.; Contributors, Jet‐Efda

doi:10.1063/1.1787916

Cited by 65 publications

(57 citation statements)

References 10 publications

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“…A theoretical explanation has been proposed in [8], but to our knowledge detailed comparisons with experiment have not been made. This paper reports on measurements of MeV range fishbone-induced fast ion losses obtained on JET with a 2-D scintillation detector [12] and its numerical simulation. The losses have been detected in a variety of discharge scenarios, but for the purpose of this article one particularly well diagnosed discharge was selected for an in-depth analysis.…”

Section: Introductionmentioning

confidence: 99%

MeV-range fast ion losses induced by fishbones on JET

et al. 2010

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Abstract. Energy and pitch angle resolved measurements of highly energetic (megaelectronvolt range) suprathermal ions ejected from the plasma through interaction with fishbone oscillations are presented. The measurements are obtained with a 2-D scintillator probe diagnostic installed on JET, which is designed to detect lost ions only above a certain energy threshold (E min,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 (max. 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 NPA 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 nonresonant type. The simulated energy and pitch angle distribution of the losses, the ‡ See the Appendix of F. Romanelli et al., Proceedings of the 22nd IAEA Fusion Energy Conference, Geneva, Switzerland, 2008 MeV-range fast ion losses induced by fishbones on JET 2 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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Section: Introductionmentioning

confidence: 99%

MeV-range fast ion losses induced by fishbones on JET

et al. 2010

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“…FILDs have been used to measure escaping α-particles resulting from DT-fusion in TFTR, 10 and energetic ions produced by auxiliary heating methods (and lost due to various plasma instabilities or equilibrium effects) in NSTX, 11 AUG, 12 DIII-D, 13 and JET. 14 space observations possible with a FILD are encouraging design studies for a reciprocating probe on ITER. 15 Alcator C-Mod (Refs.…”

Section: Introductionmentioning

confidence: 99%

Energetic ion loss detector on the Alcator C-Mod tokamak

Pace

Granetz

Vieira

et al. 2012

Review of Scientific Instruments

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A scintillator-based energetic ion loss detector has been successfully commissioned on the Alcator C-Mod tokamak. This probe is located just below the outer midplane, where it captures ions of energies up to 2 MeV resulting from ion cyclotron resonance heating. After passing through a collimating aperture, ions impact different regions of the scintillator according to their gyroradius (energy) and pitch angle. The probe geometry and installation location are determined based on modeling of expected lost ions. The resulting probe is compact and resembles a standard plasma facing tile. Four separate fiber optic cables view different regions of the scintillator to provide phase space resolution. Evolving loss levels are measured during ion cyclotron resonance heating, including variation dependent upon individual antennae.

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“…8 Now many devices are equipped with various forms of fast ion loss detectors with different names (e.g., FILD, FIL, SLIP, SP, sFILP, etc.). [9][10][11][12][13][14][15][16] ("FILD" will be used in the rest of the paper.) A common fast ion loss detector is a scintillator-based detector with a charge-coupled device (CCD) camera and/or photomultiplier (PMT) detection system.…”

Section: Principle Of Libpmentioning

confidence: 99%

Using neutral beams as a light ion beam probe (invited)

Chen

Heidbrink

Zeeland

et al. 2014

Review of Scientific Instruments

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By arranging the particle first banana orbits to pass near a distant detector, the light ion beam probe (LIBP) utilizes orbital deflection to probe internal fields and field fluctuations. The LIBP technique takes advantage of (1) the in situ, known source of fast ions created by beam-injected neutral particles that naturally ionize near the plasma edge and (2) various commonly available diagnostics as its detector. These born trapped particles can traverse the plasma core on their inner banana leg before returning to the plasma edge. Orbital displacements (the forces on fast ions) caused by internal instabilities or edge perturbing fields appear as modulated signal at an edge detector. Adjustments in the q-profile and plasma shape that determine the first orbit, as well as the relative position of the source and detector, enable studies under a wide variety of plasma conditions. This diagnostic technique can be used to probe the impact on fast ions of various instabilities, e.g., Alfvén eigenmodes (AEs) and neoclassical tearing modes, and of externally imposed 3D fields, e.g., magnetic perturbations. To date, displacements by AEs and by externally applied resonant magnetic perturbation fields have been measured using a fast ion loss detector. Comparisons with simulations are shown. In addition, nonlinear interactions between fast ions and independent AE waves are revealed by this technique.

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Scintillator probe for lost alpha measurements in JET

Cited by 65 publications

References 10 publications

MeV-range fast ion losses induced by fishbones on JET

MeV-range fast ion losses induced by fishbones on JET

Energetic ion loss detector on the Alcator C-Mod tokamak

Using neutral beams as a light ion beam probe (invited)

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