Foil implosion studies with a plasma flow switch

A plasma flow switch has been developed for the 1.5 MJ Pegasus capacitor bank to efficiently utilize the bank energy to drive a foil implosion. The object of this activity is to generate an intense burst of soft x-rays when the foil stagnates and thermalizes on axis. The peak current of the Pegasus bank, determined from the charge voltage divided by the characteristic impedance of the capacitor bank is -- 10 MA. When used to perform direct-drive, foil implosion experiments, the foil collapses to the axis when the current has risen to only -- 3 MA. The kinetic energy of the imploding foil for the direct-drive configuration cannot exceed -- 25% of the bank energy (lossless calculation). The plasma flow switch has been designed to have a conduction time of -- 4 μsec and a commutation time of -- 0.2 μsec. This permits flow implosion experiments to be performed at peak current. The soft x-ray output, as determined by volometry and by an array of filtered x-ray diodes, is compared for the two modes of operation