First Mini-workshop on IHEP 1.3GHZ SRF

LLRF and Tuner

Sun YI （孙 毅）

Accelerator Center, IHEPJune 10, 2009

content• Review on BEPC RF & BEPCII S

RF

• Block diagram of 1.3GHZ LLRF

• Tuner and piezo of 9-cell cavity

• Problems

• Summary

Beijing Electron Positron Collider (BEPC)Institute of High Energy Physics, CAS

The old BEPC was one Ring machine before the upgrade at 20054 cavities of 200MHz in BEPC tunnel

4 transmitters ( tetrode ) inside West RF hall2×30KW to feed one cavity ( 200MHz )

LLRF station for 4 cavities

2 LLRF stations are located respectively at the East/west RF hall beside each Klystron & PS, the cryogenic hall is above the test room

PLC touch panel for each SRF station

In a station: Superconducting cavity,250KW klystron and LLRF control system

PLC touch panelshow different pages:1) RF system interlock2) main parameters3) plot 4) cryogenic & cavity Q0

Part 2 block diagram of 1.3GHZ LLRF

F-1 signal generation

Prof. Wang Guangwei is in charge of the R&D of the FB loops of LLRF.

Liu Rong ( PH.D student ) will visit KEK and work at STF for the digital LLRF feedback loops on Sep., 2009

LLRF workshop will be hold on Oct.,2009 at KEK, A chance of discussion and working for the FB loops at STF.

CW Pulse

Feed-Back Feed-Forward

Micro-phonics ±0.50 ±3HZ

Beam Loading

QL~1.7×106 BW~764HZ

Lorentz Detune K~1.1 18MV/m ~230 153HZ

Part 3 tuner and piezo target for Q0~1010 、 QL~106→BW~1000HZ 1.3GHZ cavity freq. <±0.10 ，→ ±1HZ →dynamic range±~3nm

STF target : →±50HZ ( with beam?)

4 kinds of tuner

Coaxial Ball Screw 500N/mm (Saito)

Blade 25N/um ( INFN for TTF )

Slide Jack 290N/mm (STF)

Cam+lever 60N/um (Saclay-2)

First try to test a slide jack tuner

• IHEP case: one cavity in one cryostat

• Spring compensation for BEPCII cavity

• STF cavity only rely on elastic force ? (without compensation spring)

• How to “pre-tuning” under 2K?

BEPCII 超导腔调谐补偿弹簧示意图

Conception design of tuner and cryostat is on the way

IHEP 1.3GHZ SCC tuner

STF freq. vs tuner position ≈300KHZ/mm

IHEP need more Simulation and calculation

cavity freq. ~ tuner force ~ Ti jacket Stiffness

IHEP should reduce the mistakes and risks before the fabrication of the tuner.

Stiffness of the Tuner System

KCavity

KJacket KTuner

80 N / m 220 N / m

59 N / m

Improvement in the STF Baseline Cavities

Stiffness of Cavity Fixing Support 72 kN/mm 　 22 kN/mmLorentz Detuning -520 Hz -870 Hz (31.5 MV/m)

TTF Cavity

Inside M – Shield. Thick Titanium Baseplate,Thick Nb Beam Tube & Thick Nb End-cell

STF Baseline Cavity

Cell Taper13 deg. → 10 deg.

Beam Tube78 → 84

Input Port40 →

STF Baseline Cavity TTF CavityＦｚ

Ｆｒ

Part 4 problems: Location of Tuner ( in the middle or in one side of cryostat ? )

直线导轨Linear guider

丝杠螺母机构

齿轮传动机构

Piezo孔

参考面

基准面

Upgrade to STF tuner is possible?

Other questions• STF tuner had been test at RT , cold test on the

tuner is needed?• The motor screw is too long, why STF did not

set the motor inside the tank? • How to measure the tuner position? • The materials of roller wedge and ball?• Details of the taper gear, and motor gear box• Materials of tuner flange and 4 supporting rod?

summary• IHEP have collected experience on the KEKB

superconducting cavity, and have a happy history of the co-operation with KEK

• the design on 1.3GHZ tuner and LLRF has been begun since the end of 2008, there is a hard way to reach the test with cavity.

• IHEP still keep a lot of questions and hope the help from STF experts

THANKS!