High power Cusp guns

This paper presents the final test results of a 3.5-A Cusp gun (original design) and the status of the development of an 8-A Cusp gun (high perveance design). Both guns are designed to operate at 70 kV with beam alpha (transverse to axial velocity ratio) = 1.5, beam ripple < 10%, and axial velocity spread < 5%. The Cusp gun produces the axis encircling electron beam required for high harmonic gyrotrons and peniotrons. Cooperative experiments are planned at the University of California - Davis (UCD) to test devices operating at 35 GHz in the 2^nd harmonic and at 94 GHz in the 6^th harmonic, using these Cusp guns. The long-term goal is to develop a compact, sixth harmonic, 25-50 kW, 94 GHz peniotron or gyrotron that is focused by permanent magnets and uses the high perveance Cusp gun.