Initial powerflow studies on KITS

Sandia National Laboratories is investigating and developing high-dose and high-brightness flash radiographic sources. In collaboration with colleagues from MRC, AWE and Titan Pulsed Sciences Division, Sandia is conducting powerflow studies into paraxial diodes on the Radiographic Integrated Test Stand (RITS)¹. Historically high-impedance accelerators have driven these diodes with little excess powerflow into the diode. However, a number of facilities now under design will use lower impedance Inductive Voltage Adder (IVA) technology to drive these diodes resulting in additional excess powerflow into the diode. The goals of these recent experiments conducted at Sandia were to assess these powerflow issues and to help benchmark LSP², the Particle-in-Cell code being used as a design tool for studying the coupling of powerflow from the accelerator into the diode. An integral part of the AWE-style paraxial diode is the non-emitting “knob”. LSP was used early in the design of the experiments to study the effects of different size knobs on the powerflow into the diode region for both a hollow cathode load and a radiographic diode. These simulation results suggested that larger knobs are more effective in retrapping the upstream MITL bound current while keeping the excess power flow out of the diode region. Initial experiments were performed with a hollow cathode to diagnose how well each size knob works in diverting the excess powerflow. Preliminary results of these experiments and comparisons to LSP simulations are presented.