Numerical simulations of the TriMeV and SABRE rod-pinch electron beam diodes

Summary form only given. High-power rod-pinch diodes are presently being investigated as high-brightness X-ray sources. A thin annular cathode surrounds a small-diameter rod (anode) that can extend through the plane of the cathode. Electrons impinging on the high-atomic-number, range-thin rod generate a bremsstrahlung radiation spectrum that is used as a radiographic source. Positive and negative polarity rod-pinch designs have been successfully operated on the TriMeV generator at V/spl ges/1.5 MV and I/spl ges/25 kA yielding radiographic spot sizes /spl les/1 mm. Numerical simulations of both polarity rod-pinch diodes have been carried out using LSP, a two- and three-dimensional particle-in-cell (PIC) code. LSP presently utilizes Moliere multiple scattering and an energy-loss model for treating the interaction of high energy electrons with the range-thin anode (rod). A new model utilizing the ITS series of Monte Carlo algorithms is being implemented to simulate energy loss, scattering and production of secondary electrons in the anode. High-density anode and cathode plasma evolution, which may ultimately limit the impedance lifetime, is modeled with a fluid-PIC hybrid approach. The LSP simulation results are compared with experimental diagnostic information such as voltage, current, and X-ray pin-hole-camera images for a variety of configurations including solid and hollow rods at different anode-cathode gap spacings. The comparisons provide insight into electron angular distributions striking the anode, impedance collapse mechanisms, etc. The new rod-pinch diode design for the recently reconfigured SABRE generator, a 5-cavity inductive voltage adder, will be presented and LSP simulations will be compared with experimental results.