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A new 5 kV, 1.5 MJ modular capacitor bank has been designed for the Sustained Spheromak Physics Experiment (SSPX) at LLNL. The new bank consists of thirty 4 mF capacitors that are independently controlled by light-triggered thyristors. By closing all switches simultaneously, the bank will provide a mega-ampere discharge. The new bank will also allow additional capabilities to SSPX, including higher peak gun current, longer current pulses, and multi-pulse plasma buildup. Experiment results for a single stage prototype will be presented.

We have used the improved ETA-II linear induction accelerator (ETA-III) and the IMP steady-state wiggler to generate high power (1-2 GW) microwaves at 140 GHz. The FEL was used in an amplifier configuration with a gyrotron driver. Improved control of energy sweep and computerized magnetic alignment in ETA-III resulted in small beam corkscrew motion ( >

Summary form only given. An experiment is being designed to measure the single-pass propagation and absorption of electron cyclotron heating (ECH) waves in dense plasmas and to compare the results with theoretical predictions. Calculations of microwave transmission through the MTX (Microwave Tokamak Experiment) access port, propagation of the waves through the plasma, and the resulting power deposition profile on a calorimeter located on the tokamak inside wall have been performed. Ray-tracing calculations show substantial refractive spreading of the beam in the poloidal direction at densities above 1.5t1020 m-3, well within the range of the experiments. Future experiments with the free-electron laser (FEL) will also explore the nonlinear absorption of high-power ECH pulses. Calculations of the nonlinear absorption, including the spread in N || across the beam, have been done using approximate analytic absorption coefficients and with an orbit code. The calculations are compared with data from refraction/diffraction experiments using a high toroidal field, B 0=6.5 T, so that the cyclotron resonance is outside the plasma, and with absorption experiments at B 0 =5.0 T, using a range of plasma densities. Detailed analysis of the density and temperature profiles from the FIR interferometer and ECE data, respectively, for several of these FEL shots was used to calculate the transmitted power fraction reaching a small microwave horn on the inside wall of the tokamak