Thermal/structural analysis of a SCRF photocathode electron gun cavity

The all niobium superconducting RF photocathode electron gun being developed by Advanced Energy Systems and Brookhaven National Laboratory was analyzed to determine an optimum cavity configuration. An overview of this program appears under a separate title [M. Cole, this conference, ref 1]. Details of the thermal and structural analysis and results for the final configuration are presented in this paper. A 1.8 K superfluid helium bath was assumed on the outside of the cavity. The assumptions that were used on the superfluid side as well as the thermal and structural properties of RRR 250 niobium are given. Heat loads were developed from a SUPERFISH model and were included for surface temperatures between 1.8 and 8 K. Thermal conductivity, RF heat loads, and Kapitza resistance all being highly non-linear require an iterative thermal solution. Laser power and power density limits were determined and are presented. The final cavity wall thickness provides adequate structural stiffness and a broad enough thermal path to decrease the superfluid side heat flux to acceptable levels