Low-Level RF of BEPCII

Sun YI

IMAC’07May. 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. 2006 )

• The East station join in the beam commissioning ( Nov. 2006)• SR run with only East station ( Dec. 2006 ~ Feb. 2007)• West station was used for the e+ ring commissioning ( Feb. 2007)• Two stations have been used for physic collision run ( Apr. 2007)

e+

e+ e-

e-One machine / two purposes:

1 SCC / ring physic run2 SCC / outside ring dedicate the SR users

Harmonic number 398 ( Phy.) / 402 ( SR)

by pass chamber (SR run)

West SC East SC

RF hall (E)RF hall (W)

Refrigerator/ valve box500W / 2SC Test room for SC

Down side

SR run

IP-2#hall

Frf 499.8 MHzIb 900mA/ring 300mAPb 123kw ~80kwSCC 1/ring 2Kly. 250KW/ring 2*250KWHOMs ~5kw/scQL 1.7E5 1.7E5Q0 ( 2.0MV ) 5E8 5E8 (1.5MV) 1E9 1E9

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 damageHigh power INTL: cooling water & wind 、 temperature 、 Klystron & circulator, etc.LLRF INTL: quench 、 arc 、 RF power limitation 、 vacuum 、 cryogenic 、 tuner ，etc.

超导高频系统状态显示面板

紧急停机

本地 远控

控制选择

对撞 同步

运行模式

速调管

主振信号源fRF = 499.8MHz

VSWR

M

Vc set

LLRF ON

DRFB

入射功率

反射功率

门钮

P+ P-

真空e+束流

RESET

系统恢复

负载

环行器

功率

高压电源

High Power Interlock

e-束流

氦气压力

低温槽

液氦液面

LHe Flow

陶瓷窗

PLL-kly AGC

下限位

调谐器

上限位压电陶瓷

F loop ONTuned

ALC-kly

ALC-Vc

PLL-Vc

GV

失超保护

Heater

GV

Calibration Vc by 3 methods

• Determine Vc by RF forwarding power P+

R/Q=95.3 QL≈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

0

cos

2p c s

s

heV

E

4 LRVc Q PQ

15 150.266 36.72 D DEacc Vc P Q 6

80

2 499.8 10

/ 2 / 2 2.99792458 10 0.266C C C C

acc Ceff g

V V V VE V

L C f m

0

3L

dB

fQ

BW

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 t

he 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 、 ±450 、 cavity frequency locked 、 measured QL=2.1E

5 • June 23 first reached 1MV 、 calibration Vc 、 RF power 、 setting LLRF loops• June 24 1.2MV 、 measurement Q0=1×109

• 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 27 1.55MV first quench happened• June 28 1.7MV 、 36.5KW 、 radiation 32mSv/hr• June 29 reached 2MV in the first time• June 30 RF pulse aging , at 2MV measurement Q0=5.4×108

• 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 PC—RF power consumed by the cavity wall Ptotalloss—the whole module heat loss under a Vc Pstaticloss—cryostat heat loss without RF field Pheater—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/m3

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 PC by the reducing of the LHe

2 21 1

095.3

C C

C totalloss staticloss heater

V VQ

R P P P PQ

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

High power test and Q0 measurement

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

辐射剂量与超导腔高频老练前后的腔压关系

1. 55 , 11. 60 , 5

1. 70 , 10

1. 80 , 25

1. 90 , 50

1. 95 , 74

1. 97 , 80

0

10

20

30

40

50

60

70

80

90

100

0. 80 1. 00 1. 20 1. 40 1. 60 1. 80 2. 00 2. 20 2. 40

MV高频超导腔电压（ ）

mSv/

辐射剂量（

小时）

老练前辐射剂量一轮脉冲老练后二轮脉冲老练后三轮脉冲老练后

Summary1) 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 current2) 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 160mA@2.5GeV ~64kw4) West station was put in the e+ ring commissioning ( Feb. 2007 ) reached e+ beam 150mA@1.89GeV ~18kw5) frf=499.8MHz±14KHz were shifted by 0.2KHz step without beam loss6) fs、 φs 、 Vc 、 and RF power are matched7) RF power limitation at LLRF were released over 80KW ( Apr.2007 ) LLRF will be test under the heavy Beam loading in the future

• 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 use

ful discussions.• Thanks to Prof. S. Kurokawa for pushing on the co-operation.

Thanks every expert and colleague