High Power Co-Axial Coupler

Johnson, Rolland¹  Neubauer, Michael¹ 

[1] Muons, Inc., Batavia, IL (United States)

关键词: Radio Frequency;    couplers;    high-power;    Cavity;    Superconducting;    particle acclerators;   

DOI  :  10.2172/1233735
RP-ID  :  DOE-MUONSINC--2969
PID  :  OSTI ID: 1233735

美国|英语

来源: SciTech Connect

【 摘 要 】

A superconducting RF (SRF) power coupler capable of handling 500 kW CW RF power at 750 MHz is required for present and future storage rings and linacs. There are over 35 coupler designs for SRF cavities ranging in frequency from 325 to 1500 MHz. Coupler windows vary from cylinders to cones to disks and RF power couplers will always be limited by the ability of ceramic windows and their matching systems to withstand the stresses due to non-uniform heating from dielectric and wall losses, multipactor, and mechanical flexure. In the Phase II project, we built a double window coaxial system with materials that would not otherwise be useable due to individual VSWRs. Double window systems can be operated such that one is cold (LN2) and one is warm. They can have different materials and still have a good match without using matching elements that create problematic multipactor bands. The match of the two windows will always result from the cancellation of the two window???s reflections when they are located approximately a quarter wavelength apart or multiples of a quarter wavelength. The window assemblies were carefully constructed to put the window material and its braze joint in compression at all times. This was done using explosion bonding techniques which allow for inexpensive fabrication of the vacuum / compression ring out of stainless steel with copper plating applied to the inner surface. The EIA 3-1/8??? double window assembly was then successfully baked out and tested to 12 kW in a 3-1/8??? co-axial system. The thermal gradient across the window was measured to be 90 C which represents about 15 ksi tensile stress in an uncompressed window. In our design the compression was calculated to be about 25 ksi, so the net compressive force was 5 ksi at full power.