A tangentially viewing fast ion D-alpha diagnostic for NSTX

Bortolon, A.; Heidbrink, W. W.; Podestà, M.

doi:10.1063/1.3495768

Cited by 31 publications

(25 citation statements)

References 7 publications

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“…Although the results obtained in [127] and [128] predict possible stochastic non-adiabatic diffusion experimentally, it was not studied in detail. However, experimental studies of EP confinement in NSTX did not find an effect from the non-adiabatic behaviour of the EP magnetic moment, at least within the measured accuracy of 20-30% [131,132]. These studies were done in so-called MHD quiescent plasmas.…”

Section: Conservation Of Magnetic Moment In Low Field Machinesmentioning

confidence: 79%

Energetic particle physics in fusion research in preparation for burning plasma experiments

2014

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The area of energetic particle (EP) physics in fusion research has been actively and extensively researched in recent decades. The progress achieved in advancing and understanding EP physics has been substantial since the last comprehensive review on this topic by Heidbrink and Sadler (1994 Nucl. Fusion 34 535). That review coincided with the start of deuterium-tritium (DT) experiments on the Tokamak Fusion Test Reactor (TFTR) and full scale fusion alphas physics studies. Fusion research in recent years has been influenced by EP physics in many ways including the limitations imposed by the 'sea' of Alfvén eigenmodes (AEs), in particular by the toroidicity-induced AE (TAE) modes and reversed shear AEs (RSAEs). In the present paper we attempt a broad review of the progress that has been made in EP physics in tokamaks and spherical tori since the first DT experiments on TFTR and JET (Joint European Torus), including stellarator/helical devices. Introductory discussions on the basic ingredients of EP physics, i.e., particle orbits in STs, fundamental diagnostic techniques of EPs and instabilities, wave particle resonances and others, are given to help understanding of the advanced topics of EP physics. At the end we cover important and interesting physics issues related to the burning plasma experiments such as ITER (International Thermonuclear Experimental Reactor).

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Section: Conservation Of Magnetic Moment In Low Field Machinesmentioning

confidence: 79%

Energetic particle physics in fusion research in preparation for burning plasma experiments

2014

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“…A new tangentially viewing installation is planned for NSTX. 40 FIDA is a powerful diagnostic on existing machines. The spectra provide information on one velocity coordinate, the spatial resolution can be a few centimeters in the transverse direction, the temporal resolution can be submillisecond, and calibrated measurements of the radiance permit absolute comparisons with theory.…”

Section: Applicationsmentioning

confidence: 99%

Fast-ion Dα measurements of the fast-ion distribution (invited)

Heidbrink

2010

Review of Scientific Instruments

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127

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The fast-ion Dα (FIDA) diagnostic is an application of charge-exchange recombination spectroscopy. Fast ions that neutralize in an injected neutral beam emit Balmer-α light with a large Doppler shift. The spectral shift is exploited to distinguish the FIDA emission from other bright sources of Dα light. Background subtraction is the main technical challenge. A spectroscopic diagnostic typically achieves temporal, energy, and transverse spatial resolution of ∼1 ms, ∼10 keV, and ∼2 cm, respectively. Installations that use narrow-band filters achieve high spatial and temporal resolution at the expense of spectral information. For high temporal resolution, the bandpass-filtered light goes directly to a photomultiplier, allowing detection of ∼50 kHz oscillations in FIDA signal. For two-dimensional spatial profiles, the bandpass-filtered light goes to a charge-coupled device camera; detailed images of fast-ion redistribution at instabilities are obtained. Qualitative and quantitative models relate the measured FIDA signals to the fast-ion distribution function. The first quantitative comparisons between theory and experiment found excellent agreement in beam-heated magnetohydrodynamics (MHD)-quiescent plasmas. FIDA diagnostics are now in operation at magnetic-fusion facilities worldwide. They are used to study fast-ion acceleration by ion cyclotron heating, to detect fast-ion transport by MHD modes and microturbulence, and to study fast-ion driven instabilities.

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“…The first application of a charge exchange diagnostic to infer details of the fast ion distribution used He spectroscopy on JET [29], while the first true FIDA experiments were carried out on DIII-D [30]. Since then the technique has been applied to various machines [31][32][33][34][35]. Modelling of FIDA signals has advanced over the years with the development of the FIDASIM code [36].…”

Section: Introductionmentioning

confidence: 99%

Dual view FIDA measurements on MAST

Michael¹,

Conway²,

Crowley³

et al. 2013

Plasma Phys. Control. Fusion

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A Fast Ion Deuterium Alpha (FIDA) spectrometer was installed on MAST to measure radially resolved information about the fast ion density and its distribution in energy and pitch angle.Toroidally and vertically-directed collection lenses are employed, to detect both passing and trapped particle dynamics, and reference views are installed to subtract the background. This background is found to contain a substantial amount of passive FIDA emission driven by edge neutrals, and to depend delicately on viewing geometry. Results are compared with theoretical expectations based on the codes NUBEAM (for fast ion distributions) and FIDASIM. Calibrating via the measured beam emission peaks, the toroidal FIDA signal profile agrees with classical simulations in MHD quiescent discharges where the neutron rate is also classical. Long-lived modes (LLM) and chirping modes decrease the core FIDA signal significantly, and the profile can be matched closely to simulations using anomalous diffusive transport; a spatially uniform diffusion coefficient is sufficient for chirping modes, while a core localized diffusion is better for a LLM. Analysis of a discharge with chirping mode activity shows a dramatic drop in the core FIDA signal and rapid increase in the edge passive signal at the onset of the burst indicating a very rapid redistribution towards the edge. Vertical viewing measurements show a discrepancy with simulations at higher Doppler shifts when the neutron rate is classical, which, combined with the fact that the toroidal signals agree, means that the difference must be occurring for pitch angles near the trapped-passing boundary.Further evidence of an anomalous transport mechanism for these particles is provided by the fact that an increase of beam power does not increase the higher energy vertical FIDA signals, while the toroidal signals do increase.

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A tangentially viewing fast ion D-alpha diagnostic for NSTX

Cited by 31 publications

References 7 publications

Energetic particle physics in fusion research in preparation for burning plasma experiments

Energetic particle physics in fusion research in preparation for burning plasma experiments

Fast-ion Dα measurements of the fast-ion distribution (invited)

Dual view FIDA measurements on MAST

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