Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Dual view FIDA measurements on MAST   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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The categories of this paper are: plasm-ph
18
The categories of this paper are: econ
11
The categories of this paper are: hep-lat
30
The categories of this paper are: q-alg
24
The categories of this paper are: dg-ga
1
The categories of this paper are: cs
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The categories of this paper are: mtrl-th
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The categories of this paper are: bayes-an
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The categories of this paper are: atom-ph
13
The categories of this paper are: quant-ph
9
The categories of this paper are: nlin
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The categories of this paper are: funct-an
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The categories of this paper are: q-fin
10
The categories of this paper are: q-bio
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The categories of this paper are: acc-phys
12
The categories of this paper are: nucl-th