
Characterization of Fast Ion Absorption of the High Harmonic Fast Wave in the National Spherical Torus Experiment
Author(s) -
A. Rosenberg,
J. Ménard,
J. R. Wilson,
S. Medle,
C. K. Phillips,
R. André,
D. S. Darro,
R. Dümont,
B.P. LeBlanc,
M. H. Redi,
T. K. Mau,
E. F. Jaeger,
P. M. Ryan,
D. W. Swain,
R. W. Harvey,
J. Egedal,
the NSTX Team
Publication year - 2003
Language(s) - English
Resource type - Reports
DOI - 10.2172/814742
Subject(s) - atomic physics , population , ion , neutron , absorption (acoustics) , torus , physics , computational physics , optics , nuclear physics , demography , geometry , mathematics , quantum mechanics , sociology
Ion absorption of the high harmonic fast wave in a spherical torus is of critical importance to assessing the viability of the wave as a means of heating and driving current. Analysis of recent National Spherical Torus Experiment (NSTX) shots has revealed that under some conditions when neutral beam and radio-frequency (RF) power are injected into the plasma simultaneously, a fast ion population with energy above the beam injection energy is sustained by the wave. In agreement with modeling, these experiments find the RF-induced fast ion tail strength and neutron rate at lower B-fields to be less enhanced, likely due to a larger beta profile, which promotes greater off-axis absorption where the fast ion population is small. Ion loss codes find the increased loss fraction with decreased B insufficient to account for the changes in tail strength, providing further evidence that this is an RF interaction effect. Though greater ion absorption is predicted with lower k(sub)||, surprisingly little variation in the tail was observed, along with a small neutron rate enhancement with higher k(sub)||. Data from the neutral particle analyzer, neutron detectors, X-ray crystal spectrometer, and Thomson scattering is presented, along with results from the TRANSP transport analysis code, ray-tracing codes HPRT and CURRAY, full-wave code and AORSA, quasi-linear code CQL3D, and ion loss codes EIGOL and CONBEAM