Optically monitoring of the Marx switches to characterize AWE´s flash x-ray machines

The Marx bank in THE Single Pulse Forming Line, 1-10MV, X-ray generators at AWE are connected to pulse forming lines which comprise of a folded Blumlein and a balance circuit to limit the prepulse. The first three or four switches are triggered then, detrimentally, charge leaks though the balance circuit during the time taken for the remaining Marx switches to close (Marx erection time). Most critically, this charge contributes to pre-pulse which crucially must be kept low for optimum X-ray diode operation. The investigation was performed on the EROS simulator, a 40-150U Marx assembled from 66times1.3 muF capacitors. Depending on the charge level, the erection time for this Marx increases from 0.4mus to 0.7mus at lowest operating voltage. This study optically monitors the timing sequence which the Marx bank switches close and, using electrical circuit models the results compare the predictions to the measured electrical results.