Power flow modeling for RITS-6

Summary form only given. Sandia National Laboratories began commissioning the six-stage inductive voltage adder (IVA) configuration of its Radiographic Integrated Test Stand (RITS-6) in 2006. The lower impedance IVA technology results in excess power-flow from the transmission line to the diode region. Schemes to divert the excess flow include attaching a large-radius field shaper ("knob") to the transmission line immediately upstream from the diode region with a correspondingly larger anode radius ("dustbin"). The RITS-6 commissioning includes a series of shots with a blade-diode load for configurations with and without the dustbin and knob. Numerical modeling of each configuration was conducted prior to commissioning using the particle-in-cell code LSP. Modeling included power flow from the transmission line to a blade-diode load with load impedances ranging from under- to over-matched. Simulation results for transmission line currents and impedances for each blade-diode configuration are presented. These results identified geometries which result in cavity resonances and undesirable voltage fluctuations. Efforts to understand and mitigate these resonances are discussed