Effect of sparkgap breakdown and current buildup speed on the pinch dynamics in Filippov-type plasma focus experiments

Summary form only given. We have studied the relation between the spark-gap operation parameters and the plasma pinch and neutron yield in our Filippov-type plasma focus, Dena, with 90 kJ energy storage bank (25 kV, 0.288 mF). It has been found that better pinches with regard to their neutron yield, generally are associated with a faster breakdown in the triggerable spark-gap as well as higher current buildup rate. We have measured the current buildup speed at various operating conditions and derived the experimental primary ionization parameter and drift velocity of electrons, at extremely high field to pressure ratios. Also, an elaborate axisymmetric variational time-domain finite element simulation code has been developed, in support of the experimental measurements. The code takes the effect of primary, secondary, and photoionization mechanisms in discharge evolution of the spark-gap.