Enhancing the radiographic capabilities of the GREC Accelerator using plasma erosion switches and a two-m, 150-ohm MITL

Recently we performed experiments to enhance the radiographic capabilities of the GREC Accelerator. Previous experiments using a 2-m 56 ohm MITL routinely achieved average dose levels of 250 ± 50 R at a distance of 1 m from the source. By employing a higher impedance MITL (free space impedance 150 ohm), plasma erosion switches to eliminate prepulse and increase the rate of rise on the input current, shaped cathodes to improve pinch quality and a low Z, thin foil over the high Z (tantalum) target, output dose levels of 550 ± 50 R were routinely obtained. Using stainless steel current shunts at the input and output of the 2-m MITL, we measured excellent current transport to the diode. Using plasma erosion switches, an average increase of two in the rate of rise of the input current was observed. Spot size measurements are discussed in the text.