FAST-ELECTRON TRANSPORT AND LOWER-HYBRID ABSORBED POWER PROFILES FROM HARD X-RAY-IMAGING IN THE PRINCETON BETA-EXPERIMENT-MODIFIED

Recent hardware improvements on the hard x-ray camera of the Princeton Beta Experiment-Modified (PBX-M) expand the capabilities for observing bremsstrahlung radiation from fast electrons during lower hybrid current drive (LHCD) experiments, thereby allowing accurate fast electron transport studies. Developed methods to directly invert two-dimensional x-ray images reveal radial profiles of the emitted intensity and isotropy. Such profiles extracted from lower hybrid (LH) modulation experiments permit computation of the lower hybrid power absorption profile. Results from application to the LH phase scans demonstrate the ability to control the peak location of the driven current. Incorporating these results into simulations using both a three-dimensional Fokker-Planck code and a simple modulation model provides lower and upper bound estimates for the hot electron diffusion coefficient D*. © 1995 American Institute of Physics.