Status of self-magnetic pinch diode investigations on RITS-6

Abstract

The electron beam-driven self-magnetic pinch diode is presently fielded on the RITS-6 accelerator at Sandia National Laboratories and is a leading candidate for future flash x-ray radiographic sources. The diode is capable of producing sub 3-mm radiation spot sizes and greater than 350 rads measured at 1 m from the x-ray source. While RITS-6 is capable of delivering up to 11.5 MV using a magnetically insulated transmission line (MITL), the diode typically operates between 6 – 7 MV. Because the radiation dose has a power-law dependence on diode voltage, this limits the dose production on RITS. Coupling this low-impedance (∼ 40–60 ohms) diode to a MITL with similar or higher impedance affects its radiographic potential. The sensitivity in diode operation is compounded by the interaction of evolving plasmas from the cathode and anode, which seem to limit stable diode operation to a narrow regime. To better quantify the diode physics, high-resolution, time-resolved diagnostics have been utilized which include plasma spectroscopy, fast-gated imaging, x-ray p-i-n diodes, x-ray spot size, and diode and accelerator current measurements. Data from these diagnostics are also used to benchmark particle-in-cell simulations in order to better understand the underlying diode physics. An overview of these experiments and simulations is presented.