Power flow studies with HERMES-III, 300-ns pulse operation

Recent experiments with HERMES III confirmed that the accelerator can operate very successfully in a 300-ns, 8-MV, 400-kA mode. This was accomplished by shorting the PFLs and pulse sharpening switching and transferred the output power from the gas switches directly to the voltage adder cavities. The observed voltage and current are consistent with the parapotential and pressure balance theories. Extensive numerical simulations with TWOQUICK were done to study the power flow in the voltage adder and the 4-m extension coaxial transmission line. Apparently even for these low operating voltages (8 MV), the adder becomes MITL in a relatively short time. The precursor pulse is small (∼ 35-kA peak) and ∼40 ns duration. The MITL operation can be numerically simulated by assuming an electron emission threshold of ∼ 100 kV/cm. Results of the experiments and numerical simulations as well as plans for future experimentation are presented