Triaxial diode on HYDRAMITE

In 1982, members of Sandia National Laboratories' Department 1230 performed triaxial diode experiments on the HYDRAMITE accelerator. These experiments demonstrated the viability of the triaxial concept, and established the multiple, concentric diode (several, nested, triaxial diodes) as the leading candidate for the radiation-production diode for the Saturn accelerator. A triaxial diode consists of three, coaxial cylinders and a perpendicular, planar anode connecting the downstream ends of the inner and outer cylinders. The intermediate cylinder is the cathode, and the space between the end of the cathode and the planar anode is the axial, anode-cathode gap. HYDRAMITE, with a long self-magnetically-insulated transmission line, provided the electrical pulse to drive the triaxial diode. A post-hole convolute inside the diode housing split the incoming, electromagnetic wave into the two waves needed to feed the triaxial diode. An inductively-corrected, vacuum-voltage monitor measured the diode voltage, and B dot probes and Rogowski coils measured all the anode and cathode currents. Nuclear activation measurements indicated that less than 0.5% of the diode current consisted of protons moving from the anode to the cathode, and particle-in-cell computer simulations support this measurement. Moreover, the impedance was consistent with the cathode tip emitting in the one-dimensional, space-charge-limited mode with unipolar flow. Although the beam deposited enough energy in the anode to generate an anode plasma, probably the electrical pulse was too short for the plasma to form and begin emitting ions into the anode-cathode gap. Finally, no charge flowed in the inner radial gap, and the outer gap current, which was constant from shot to shot, probably originated from the post-hole convolute. 35 refs., 40 figs