RF measurements of a C-band cavity beam position monitor

Abstract

RF measurements of a C-band cavity beam position monitor *CHU Jian-Hua( ) 1,2 TONG De-Chun( ) 3 ZHAO Zhen-Tang( ) 1;1)

Simulation and experiments for the Q ext of a cavity beam position monitor

“…The reflection method was also used to measure Q [2]. When measuring each adapter's reflection, the other three were terminated by 50 Ω loads.…”

“…According to Ref. [2], when the beam is pass-ing through the position cavity, the TM110 mode is excited and coupled into waveguides, and this is the first-stage coupling. Then the excited TE10 mode in the waveguide is coupled out by the waveguide to the coaxial cable adapter, and this is the second-stage coupling.…”

“…Each stage has its β and Q and this paper deals mainly with Q ext . In CBPM designs people found that it was difficult to simulate the two stages of coupling together, so they did not consider the second-stage coupling in the physics design, but tried to solve it in experiments after brazing waveguides [2,3]. In Ref.…”

“…In Ref. [2], the position cavity's Q 0 is about 10000, and β of the first-stage coupling is about 5. However, the total β of the two stages is only 0.75 and Q ext increases from 2000 to 13000 unpredictably.…”

Design and cold test of a rectangular cavity beam position monitor

“…The most commonly used CBPMs now are cylindrical ones, which are easy to design and make. Many labs have designed cylindrical CBPMs whose resolution have reached micron and even sub-micron levels [1][2][3][4][5][6][7][8]. However, because of processing limits, for a cylindrical CBPM, the transverse section will always be an elliptical one.…”