Enhanced Emission Cathodes for High Intensity Electron Beam Diodes

Experiments are underway to investigate an enhanced emission cathode on the Short Pulse, High Intensity Nanosecond X-radiator (SPHINX) at Sandia National Laboratories (SNL). SPHINX is a 2MV, 22kA, 10nsec pulsewidth, electron beam accelerator used for radiation effects testing. The SPHINX cathode consists of a planar graphite disk inserted in the center of an anodized, aluminum cap at the end of a 60-Ohm vacuum transmission line. As part of the University of New Mexico’s work on novel cathode designs, laser etched aluminum cathodes are being tested at SPHINX. Laser etching (~100-micron scalelengths) provides a means of controlling the location of microscopic enhanced emission sites leading to faster turn-on times (<2ns) and more uniform beam profiles. Diagnostics include radiochromic film, thermoluminescent detectors, and fast scintillator imaging. Testing of various patterns are planned and recent results will be presented. Such cathodes may prove beneficial in higher energy accelerators such as HERMES III (18MV, 650kA, 30ns FWHM), where fast turn-on times lead to greater power delivery and higher overall efficiencies.

* Sandia National Laboratories is managed and operated by NTESS under DOE NNSA contract DE-NA0003525.