2-DIMENSIONAL HARD X-RAY-IMAGING DIAGNOSTIC FOR LOWER HYBRID CURRENT DRIVE EXPERIMENTS IN PBX-M

The efficiency of plasma current drive with lower hybrid waves is reflected in the distribution of suprathermal electrons formed during this process. Past measurements of the bremsstrahlung radiation from these electrons depended on arrays of hard x-ray detectors at different toroidal and poloidal locations around tokamaks [Nucl. Fusion 25, 1515 (1985)]. To avoid the space requirements and the complex correlation and inversion procedures associated with such systems, a single 23-cm-diam hard x-ray image intensifier tube is being installed for two-dimensional imaging on PBX-M. It will be optically coupled to an image processor already in place for a soft x-ray pinhole camera [Rev. Sci. Instrum. 59, 1831 (1988)], and analysis algorithms similar to those already developed for this diagnostic will be used.