Reflex Diode Experiments on Gamble II

Summary form only given. Previous experiments on the NRL Gamble II generator (2 Omega, 2 MV, 100 ns) demonstrated reflexing of MeV electrons through thin tantalum foil anodes whose thickness (13 mum) was a small fraction of the electron range (CSDA range of 1 MeV electrons in tantalum is 460 mum). The total bremsstrahlung was comparable to that from thick foils, indicating that the electrons passed (reflexed) many times through the thin foil. The reduced attenuation of low-energy (10-100 keV) photons in the thin tantalum resulted in an increased surface dose of a factor of four compared with the surface dose from the spectrum produced from thick foils. Renewed interest in this technique led to the present series of reflex diode experiments on Gamble II, where two new approaches are under investigation to enhance reflex diode capabilities. Plasma-filled reflex diodes, similar to those fielded on the Saturn generator, demonstrate the ability to operate at very low impedance and radius, potentially producing low-endpoint bremsstrahlung from high-current reflexing configurations with intensities impossible with vacuum diodes. Pulsed heating prior to and during the generator pulse is investigated as a way to degas the tantalum, delay ion formation and increase the number of passes electrons make through the tantalum, allowing thinner tantalum to be used efficiently for enhanced emission of low-energy X-rays. Results of these experiments and computer simulations will be presented