Measurements of Escaping Fast Particles Using a Thin-Foil Charge Collector

Jarvis, O.N.; Belle, P. van; Hone, M.; Sadler, G.; Whitfield, G.; Cecil, F. E.; Darrow, D. S.; Esposito, B.

doi:10.13182/fst01-a154

Cited by 20 publications

(12 citation statements)

References 9 publications

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“…3 Following this preliminary testing, two devices, one consisting of four Ni foils, each a thickness of 2.5 m and one consisting of two Ni foils, 250 m thick, were installed near the plasma edge on JET and operated throughout the 1997 d-t campaign and continued operation until decommissioning in 2001. 4 …”

Section: Introductionmentioning

confidence: 99%

Thin foil Faraday collectors as a radiation hard fast lost-ion diagnostic

Cecil

Aakhus-Witt

Hawbaker

et al. 2003

Review of Scientific Instruments

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We are investigating thin foil Faraday collectors as a diagnostic for lost fast ions from tokamak fusion plasmas. Prototype devices have been recently installed in the National Spherical Torus Experiment and DIII-D. Initial results from these devices indicate a loss of energetic ions from a variety of plasma conditions. Results from a device installed immediately outside a thin Be window on ALCATOR C-mod, as a test on the response to moderately intense fluxes of soft x rays indicate an upper limit of about 2ϫ10 Ϫ22 A/photon/cm 2 at a plasma electron temperature of 1.8 keV. An important property of the diagnostic is the expected ability to operate under fairly high neutron/ gamma radiation backgrounds. We have tested this expectation by measuring the current from a thin ͑2.5 m͒ Ni foil placed in the core of a TRIGA fission reactor. At a maximum steady-state power of 950 kW (10 13 n/cm 2 /s), a current of 1.2 nA/cm 2 was measured.

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Section: Introductionmentioning

confidence: 99%

Thin foil Faraday collectors as a radiation hard fast lost-ion diagnostic

Cecil

Aakhus-Witt

Hawbaker

et al. 2003

Review of Scientific Instruments

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“…Such losses are diagnosed, for example, by Faraday cup [18] and scintillator Fast Loss Ion Probe (sFLIP) [19] diagnostics that detect ions on loss orbits. Resonant interaction of high-energy particles with magnetic perturbations in toroidal devices can produce large-scale modification of the particle distribution, sometimes leading to particle loss.…”

Section: Global and Compressional Alfvén Eigenmodes (Gae And Cae Resmentioning

confidence: 99%

“…The HEF has not been clearly observed on NSTX energetic ion diagnostics other than the E||B NPA, such as the vertical Fast-ion D-alpha (vFIDA) [49,50], scintillator Fast-Loss Ion Probe, (sFLIP) [18] and the solid state Neutral Particle Analyzer (ssNPA) [45].…”

Section: Nstx Energetic Ion Diagnosticsmentioning

confidence: 99%

Investigation Of A Transient Energetic Charge Exchange Fux Enhancement ('spike-on-tail') Observed In Neutral-beam-heated H-mode Discharges In The National Spherical Torus Experiment

Medley¹

2011

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In the National Spherical Torus Experiment (NSTX), a large increase in the charge exchange neutral flux localized at the Neutral Beam (NB) injection full energy is measured by the E||B (superimposed parallel electric and magnetic fields) Neutral Particle Analyzer (NPA). Termed the High-Energy Feature (HEF), it appears on the NB-injected energetic ion spectrum only in discharges where tearing or kink-type modes (f < 50 kHz) are absent, % in the measured neutron yield and total stored energy that are observed to coincide with the feature appear to be driven by concomitant broadening of measured Te(r), Ti(r) and n e (r) profiles and not the HEF itself. While the HEF has minimal impact on plasma performance, it nevertheless poses a challenging wave-particle interaction phenomenon to understand. Candidate mechanisms for HEF formation are developed based on quasilinear theory of wave-particle interaction. The only mechanism found to lead to the large NPA flux ratios, € H = F max /F min , observed in NSTX is the quasilinear evolution of the energetic ion distribution, , in phase space and the concomitant loss of some particles, which occurs due to the cyclotron interaction of the particles with destabilized modes having sufficiently high frequencies, kHz, in the plasma frame that are tentatively identified as Global Alfvén Eigenmodes.

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“…Energetic ion losses can be measured by a number of means, including Faraday cups [2][3][4] , surface barrier diode detectors [5][6][7][8][9] , track detectors 10 , exposure samples [11][12][13][14] , infrared imaging 15 , and scintillators [16][17][18][19][20][21][22][23][24] , and calorimeter probes 25 . Scintillator detectors have the advantage that they can provide the pitch angles and energies of the lost ions as a function of time during a discharge.…”

Section: Introductionmentioning

confidence: 99%

Scintillator based energetic ion loss diagnostic for the National Spherical Torus Experiment

Darrow

2008

Review of Scientific Instruments

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A scintillator based energetic ion loss detector has been built and installed on the National Spherical Torus Experiment 1 (NSTX) to measure the loss of neutral beam ions. The detector is able to resolve the pitch angle and gyroradius of the lost energetic ions. It has a wide acceptance range in pitch angle and energy, and is able to resolve the full, one-half, and one-third energy components of the 80 keV D neutral beams up to the maximum toroidal magnetic field of NSTX. Multiple Faraday cups have been embedded behind the scintillator to allow easy absolute calibration of the diagnostic and to measure the energetic ion loss to several ranges of pitch angle with good time resolution. Several small, vacuum compatible lamps allow simple calibration of the scintillator position within the field of view of the diagnostic's video camera.

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Measurements of Escaping Fast Particles Using a Thin-Foil Charge Collector

Cited by 20 publications

References 9 publications

Thin foil Faraday collectors as a radiation hard fast lost-ion diagnostic

Thin foil Faraday collectors as a radiation hard fast lost-ion diagnostic

Investigation Of A Transient Energetic Charge Exchange Fux Enhancement ('spike-on-tail') Observed In Neutral-beam-heated H-mode Discharges In The National Spherical Torus Experiment

Scintillator based energetic ion loss diagnostic for the National Spherical Torus Experiment

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