Improvement in the performance statistics of a Blumlein in double pulse mode

The paper presents the results of studies on shot-to-shot performance of a water Blumlein line of 1-1.2 kJ of stored energy. The experiments were carried using the TEMP- 4M pulsed ion accelerator during its operation in both single pulse mode (150 ns, 250 kV to 300 kV) and double-pulse mode with the first negative (300 - 600 ns ,100 kV - 150 kV) followed by a second positive (120 ns, 250 kV - 300 kV) pulse. The analysis was carried out for two cases when the Blumlein was terminated with a resistive load and with a self-magnetically insulated ion diode. It was found that in double pulse mode operation the shot-to-shot variation in breakdown voltage of a preliminary spark gap is small, the standard deviation does not exceed 2 %. At the same time, the shot-to-shot variation in the breakdown voltage of the main spark gap in both double-pulse and single pulse mode is 3-4 times higher than that for the preliminary spark gap. To improve the statistics performance of the main spark gap we changed the regime of its operation from a self-triggering mode to a forced triggering mode. In the new arrangement the first voltage pulse applied to the load form Blumlein is used to trigger the main spark gap. The new (controlled) regime of the main spark gap operation showed a good stability of breakdown voltage and thus allowed to stabilize the duration of the first pulse. The standard deviation of the breakdown voltage and duration of the first pulse did not exceed 2% for the set of 50 pulses. This regime also allowed for a decrease in the charging voltage of the Blumlein to a 0.9-0.95 of self-breakdown voltage of the main spark while the energy stored in Marx generator was decreased from 4 kJ to 2.5 kJ. At the same time the energy stored in Blumlein remained the same.