Title :
High peak power RF processing studies of 3 GHz niobium cavities
Author :
Graber, J. ; Barnes, P. ; Kirchgessner, J. ; Moffat, D. ; Padamsee, H. ; Rubin, D. ; Sears, J. ; Shu, Q.S.
Author_Institution :
Lab. of Nucl. Studies, Cornell Univ., Ithaca, NY, USA
Abstract :
The effects and benefits of high peak power RF processing as a means of reducing field emission loading in 3-GHz niobium accelerator cavities are being investigated. The test apparatus includes 3-GHz klystron capable of delivering RF pulses of up to 200-kW peak power with pulse lengths up to 2.5 ms at a repetition rate of approximately 1 Hz. The test apparatus has variable coupling such that the input external Q varies between 10/sup 5/ and 10/sup 10/ without breaking the cavity vacuum. Low-power, continuous-wave (CW) tests before and after HPP show that HPP is effective in removing emissions which are unaffected by low-power RF processing. CW measurements show that field emission reduction is dependent on maximum field reached during HPP. HPP fields of E/sub peak/ = 70-72 MV/m have been attained. These tests showed FE elimination to E/sub peak/ = 40 MV/m, and maximum fields of E/sub peak/=50-55 MV/m. Temperature mapping is now available. A cavity which showed strong FE loading and had extensive temperature mapping is now being investigated in a scanning electron microscope. A nine-cell cavity has been successfully tested, and, through HPP, reached E/sub acc/=15 MV/m, with Q/sub 0/=6.0*10/sup 9/.<>
Keywords :
cavity resonators; klystrons; niobium; particle accelerators; superconducting devices; 3 GHz; Nb cavities; cavity vacuum.; field emission loading; high peak power RF processing; klystron; nine-cell cavity; scanning electron microscope; superconducting RF cavities; temperature mapping; Business continuity; Circuit testing; Etching; Iron; Klystrons; Niobium; Radio frequency; Resistors; Surface contamination; Temperature;
Conference_Titel :
Particle Accelerator Conference, 1991. Accelerator Science and Technology., Conference Record of the 1991 IEEE
Conference_Location :
San Francisco, CA, USA
Print_ISBN :
0-7803-0135-8
DOI :
10.1109/PAC.1991.164983
