Low-Level RF of BEPCII Sun YI IMAC’07 May. 11, 2007 IHEP

Review the past one year The Hardest and key time was from Apr.06 to Dec.06 West LLRF was used for the horizontal test and the Q0 measurement at the test room; All the Q0, both East and West SCC, are higher than the design target. ( June~Sep. 2006) The first time on the high power test of SCC in China made a big challenge on the LLRF LLRF installation 、 cabling 、 and calibration (Mar.~Oct. 2006) Commissioning 2 stations of SRF ( Oct.~Nov ) The East station join in the beam commissioning ( Nov. 2006) SR run with only East station ( Dec ~ Feb. 2007) West station was used for the e+ ring commissioning ( Feb. 2007) Two stations have been used for physic collision run ( Apr. 2007)

During the past one year, 2 LLRF stations have been finished, installation 、 cabling 、 calibration 、 high power test and Q0 measurement 、 commissioning SRF, now e+/e- beam run perfectly.

God and the Double Interlock prevent SRF from damage High power INTL: cooling water & wind 、 temperature 、 Klystron & circulator, etc. LLRF INTL: quench 、 arc 、 RF power limitation 、 vacuum 、 cryogenic 、 tuner ， etc.

Calibration Vc by 3 methods Determine Vc by RF forwarding power P+ R/Q=95.3 Q L ≈2E+5 P+=13kw →Vc=1MV Confirm Vc by RF field inside the SCC Q15D≈1.09E+11 P15D=90mw → Vc=1MV Calibration Vc by synchrotron oscillation frequency measured result: fs=22.3KHz at Vc=0.6MV

Beam and RF power matched in a typical SR run

Vc oscillation result in the beam trip by LLRF 60mA e- lost at Dec.4, 2006 RF voltage recovered and the oscillation disappeared after the beam lost Vc=0.6MV, the oscillation period=3ms After adjusting the ALC feedback loop parameter, this problem was cured, the beam current can be increased to 200mA in Dec.2006 This is not the Robinson instability, I still set the cavity frequency detune angle=0 degree till 200mA

First high power test of #2 SCC at June 06 Apr 29~May 11 finished the room temperature RF aging to coupler 150KW May 23 purify GHe May 30 cold down SCC 、 June 7 LHe level=46% 、 June 13 level=95% June 1~18 LLRF commissioning with Klytron 、 calibration RF power June 19 LLRF test the frequency tuner and piezo for cavity June 20 RF aging on the coupler 100kw 、 cavity detune at 4K temperature June 21 quench protection test 、 tuning the cavity June 22 detune±1KHz 、 ±45 0 、 cavity frequency locked 、 measured Q L =2.1E5 June 23 first reached 1MV 、 calibration Vc 、 RF power 、 setting LLRF loops June MV 、 measurement Q0=1×10 9 June 25 LLRF test the RF pulse aging 、 5 radiation sensors test OK June 26 Sino-Japan confirmed the safty and the Vc calibration June MV first quench happened June MV 、 36.5KW 、 radiation 32mSv/hr June 29 reached 2MV in the first time June 30 RF pulse aging, at 2MV measurement Q0=5.4×10 8 July 1 measureQ0 at 1.8MV 、 1.5MV 、 1.4MV 、 1.3MV July 3 warm up the #2 SCC July 11 #2 SCC reached room temperature

Using LHe consumption to measure Q0 Function Vc—RF voltage P C —RF power consumed by the cavity wall P totalloss —the whole module heat loss under a Vc P staticloss —cryostat heat loss without RF field P heater —the heater power inside the cryostat Liquid Helium parameters: at 1.2bar 、 4.2K liquid Helium→Gas potential heat=19.4 KJ/Kg LHe proportion gravity = 122Kg/m 3 after closing the input valve, LHe level will be reduced from 96% to 85% within a time LHe volume vs level = 2.73Liter/1% (roughly) with a given Vc, to determine the P C by the reducing of the LHe

First measurement of Q0 for #2SCC Vc—over 2MV 、 heater=0w 、 LHe level=red

High power test and Q0 measurement

RF pulse aging to increase the quench Vc and reduce the radiation before the aging: quench happened at 1.7MV, radiation 35mSv/hr after RF aging: quench at 2MV, radiation=10mSv/hr at 1.7MV At 2MV ， the radiation intensity maybe 300~500mSv/hr （ over the meter range ）

Summary 1) West LLRF finished the high power test for #2 & #1 SCC ( June~Sep.) at 2MV: Q0=5.8E8 (East SC) Q0=1E9 (West SC) Vacuum gate valves were not damaged by the dark current 2) East LLRF joined in the beam run at Nov.2006 ( on time) 3) East station was dedicated the SR run ( Dec.06~Feb.07) reached e- beam ~64kw 4) West station was put in the e+ ring commissioning ( Feb ) reached e+ beam ~18kw 5) frf=499.8MHz±14KHz were shifted by 0.2KHz step without beam loss 6) fs 、 φs 、 Vc 、 and RF power are matched 7) RF power limitation at LLRF were released over 80KW ( Apr.2007 ) LLRF will be test under the heavy Beam loading in the Thanks to Prof. K. Akai, T. Furuya, S. Mitsunobu for help. Thanks to Dr. Wang Chaoen of TLS, and Dr.Zhao zhentang of SSRF for the useful discussions. Thanks to Prof. S. Kurokawa for pushing on the co-operation. Thanks every expert and colleague