ISSN:
1089-7623
Source:
AIP Digital Archive
Topics:
Physics
,
Electrical Engineering, Measurement and Control Technology
Notes:
The modification and control of the plasma current profile by lower hybrid current drive is considered one of the most promising avenues to control MHD instabilities and improve the high beta performance of tokamaks. The Hard X-ray Camera on PBX-M records images of the bremsstrahlung emitted by suprathermal electrons that carry part of the plasma current during lower hybrid current drive. The Hard X-ray Camera is a pinhole camera that uses a 9 in. diam x-ray intensifier as detector. It provides a tangential view of the tokamak plasma and delivers 64 images with 128×128 pixels per plasma shot. The spatial resolution in the plasma is approximately 2 cm, and the time resolution 3 ms. The camera is sensitive to x rays between 30 and 200 keV. The photon energy (and the energy of the suprathermal electrons) is measured with an absorber foil method. Modeling of the x-ray emission has reproduced the experimental images with a better than 10% accuracy. In addition, two inversion techniques have been developed: one of these can be performed on line between shots. Illustrative examples of important applications of hard x-ray imaging will be given. The hard x-ray images provide information on the radial location of the absorption of the lower hybrid waves, on the velocity distribution of the suprathermal electrons, on the diffusion of superthermal electrons, and on anomalous hot electron transport induced by MHD instabilities. © 1995 American Institute of Physics.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.1146291
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