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Progress of SC RF Cavity during the 2006-2007

Progress of SC RF Cavity during the 2006-2007. RF Group May 10, 2007. Topics. Final assembly of SC cavity module. Module horizontal test and its performance. Tunnel installation and on-site alignment. Machine commissioning for SR mode. for Physics mode.

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Progress of SC RF Cavity during the 2006-2007

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  1. Progress of SC RF Cavityduring the 2006-2007 RF Group May 10, 2007

  2. Topics • Final assembly of SC cavity module. • Module horizontal test and its performance. • Tunnel installation and on-site alignment. • Machine commissioning • for SR mode. • for Physics mode. • Puzzles of the vacuum I/L of the east module，and where is the solution? • Spare SC cavity module and key components development

  3. Final Module Assembling from March to May 2006 • 2006 Mar. 23~30, the IHEP #2 SCC module was assembled in the clean room of building 6. Prof. Mitsunobu came to IHEP and instruct us to perform this work, MELCO sent one S.V, Mr. Arakawa, to witness the whole procedure and give us some suggestions in advance. • 2006 April. 26~May 3, the IHEP #1 SCC module was assembled. Prof. Furuya and Mitsunobu came to IHEP and instruct us, MELCO sent two S.V, Dr. Kijima and Mr. Okada, to witness this procedure.

  4. 1. Cavities are ready for final assembly in building six 2. Assemble the damper with the beam taper 3. Mount the damper on the cryostat 6. Some of participators 4. Mount the coupler on the cryostat 5. Pre-assemble doorknob on to the coupler port

  5. Log for Horizontal Test from May to August 2006 • 2006 May~ June, the horizontal test for the IHEP #2 SC module. • Coupler aging at room temperature, instructed by Prof. Furuya. • To cool down SC module to 4.5K. • Coupler aging at 4.5K. • 2006.06.26~30, we carried out final performance test under the instruction of Prof. Furuya, two S.V, Ms. Kijima and Mr. Arakawa, came to IHEP to check our equipment and witness this procedure. • During the conditioning period of the cavity, a B.D happen at 1.5MV, B.D detector miss to take an action，the pressure of LHe vessel increases up to more than 1.3bar, and the spring valve was opened automatically and a amount of cooled helium gas leaked from pipe of the spring valve. • 2006 July~ August, the horizontal test for the IHEP #1 SC module. • Coupler aging at room temperature by us. • To cool down SC module to 4.5K. • Coupler aging at 4.5K. • 2006.08.24~26, the final performance tested by us, one S.V, Mr. Okada, came to IHEP to check our equipment and witness this procedure. • During the cooling down period of the cavity, we forgot to close the by-pass valve of the cooling helium gas for the coupler, the flow rate of the helium gas is extremely high and a great lot of cooled helium gas pass through the return line, and some ice was frozen around the coupler port.

  6. Horizontal Test 1. Dummy tank test for cryogenic system commissioning 2. Move the cavity module to horizontal test room 3. Clean up the ceramic windows of the coupler 4. Added a compensating spring to detune the frequency 5. Coupler frozen by a huge amount of cold helium gas 6. the coupling of coupler changes from under to over matching

  7. Horizontal test performance of the IHEP-#1 SCC

  8. Horizontal test performance of the IHEP-#2 SCC

  9. Shrinking length of the beam pipe during cooling down of the cavity module 1. SBP of IHEP #1 SC cavity 3. SBP of IHEP #2 SC cavity 2. LBP of IHEP #1 SC cavity 4. LBP of IHEP #1 SC cavity

  10. Tunnel installation from August to Nov. 2006 • Cryogenic group run the dummy load at the site of the tunnel, to test the LHe and LN2 transfer line and cryogenic system. • Measure the itself alignment data of the SC cavity module at off-line. • Move Cavity module to the beam line. • Adjust and align the cavity on to the beam line • Connect cavity with the neighboring beam chamber by RF-shielded bellow in a local clean booth. • Prepare and connect cooling water system for HOM damper and high power coupler. • Prepare and mount temperature sensor, pressure sensor and flow meter for each SC module.

  11. Tunnel installation Alignment Data for East & West SCC Module 1. Transverse direction (X_Y-axes) 2. Longitudinal direction (Z-axes)

  12. 1. West SC module in positron beam line 2. East SC module in electron beam line 3. A local clean booth used for cavity tunnel installation 4. Monitors array of temperature, pressure and flow meter for cavity 5. Chiller for the coupler 6. Cavity vacuum gauge controller

  13. Machine Commissioning • During beginning commissioning, RF trip happen frequently during several days, the signal is recorded by a scope as right. Final we found that it is due to the instability of amplitude feedback loop, the loop damping is not sufficient, by adjusting the loop damping knob, we settle down this problem. Accelerating Voltage Incident Power Reflected Power Beam Current Density • Once time, the east cavity vacuum goes bad, even applying a low cavity voltage, vacuum I/L happens frequently, we decide to aging the cavity to degas the cell surface. Final a breakdown occurs, by a mass analyzer, we found a great of hydrogen released, and cavity recovered from this breakdown.

  14. Commissioning cont’... • During a routine cavity conditioning on Jan. 30 2006, a breakdown occurred for east module, since the B.D detector miss to cut off RF power, the pressure of LHe vessel rises up, the electric safety valve was opened. After taking this action, but the electric valve didn’t close after a short time, the rotation shaft of the valve was frozen and couldn’t be closed by operator, we use a heater to warm up the frozen shaft, and close the electric valve.

  15. Difficulties... • 2006 Nov. 12~2007 Feb. 5, the BEPCII start to commissioning to clean up the vacuum chamber by beam, only the east cavity module used in SR commissioning. • Nov. 18, 2006, first time the beam caught by RF bucket and accumulate in storage ring. • Dec. 13, 2006, the max beam current reach to 90mA at 2.5GeV in SR operation. • From Jan 22~26 ,2007, Prof. Furuya visited IHEP, the BEPCII accumulated beam current up to 178mA at 2.5GeV in SR mode on 23rd Jan., while a accelerating voltage of 1.3MV applied to accelerate the beam by the east accelerating module.

  16. Difficulties cont’... • From 2007 Feb. 8 to now, the BEPCII start to commissioning in colliding mode. • For positron storage ring (West SC module), the beam current increased smoothly, up to now, it can accumulated beam current of 150mA stably. • For electron storage ring (East SC module), the beam current increased slowly, the vacuum I/L occurred frequently. • Since the condition of the vacuum of east module went bad gradually, we decided to warm up both SC cavity during the period of spring holiday, from Feb. 20 to 22, the cavities warmed up to max 88K and keep several hours to degas condensed gas. • In order to find the reason that the vacuum went bad quickly during injection, on mar. 23, 2007, the BEPCII changed to S.R run mode temporary, the beam current of 100mA can be accumulated by the east module, while the west module is offset from resonant frequency, no vacuum I/L happen.

  17. We recorded the mass analyzer signal during injection and operation period of both module, the period is from 22nd to 23nd April, 2007. 1. East SC module in positron beam line (injected beam 80~100mA) 2. West SC module in electron beam line (injected beam 50~150mA)

  18. Again from 2007 April 24 to 26, we warmed up both cavity to 100K to release condensed gas on cavity surface, also mass analyzer signal were recorded. 1. Mass analyzer signal during warming up east SC module up to 100K 2. Mass analyzer signal during warming up west SC module up to 100K

  19. Budget for Spare Module *** This project already got the permission of government, and it will be performed from 2007 to 2009.

  20. Acknowledgement • During the past year, several time, Prof. Furuya, Mitsunobu and Akai visited IHEP to instruct us in module assembling, horizontal test and final success RF commissioning. Supervisors from MELCO help us check our equipments and tools, and deliver necessary technique document to us. and thanks Prof. Kurokawa for his concern on SC cavity. • Now the spare SC module already started up, we wish KEK can supported us as before, RF group of KEKB, SSRF and BEPCII should be collaborated very tightly in future SRF technology development, especially in the aspects of niobium cavity fabrication and test, high power coupler research and HOM damper construction.

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