1. Progress of the sub-harmonic bunching system (i.e. upgrading progress of BEPCII present bunching system) Pei Shilun for the SHBS team Accelerator center, IHEP May 10, 2007

2. Outline Beam dynamics simulation and mechanical layout Design and study of the two sub-harmonic bunching cavities Design and study of the two RF power source Construction schedule

3. Beam dynamics simulation and mechanical layout (1)

4. Schematic layout of the bunching system 1.6ns 10ps ~9nC(total) SHB2 Buncher Standard accelerate section Gun 571.2MHz 2856MHz e- Schematic layout of the upgraded pre-injector with 2 SHBs (Design Scheme) 10nC SHB1 142.8MHz Schematic layout of the present pre-injector (Present Scheme) e- 1.6ns PB Buncher Standard accelerate section Gun 2856MHz 1.6ns 10ps350ps ~7nC(total) 10nC

5. layout of the bunching system Keep the location and arrangement of devices Keep the arrangement of devices but move northward for 113.4cm Remove PB 、 GUF6 and GUF7 Install SHB1 、 SHB2 and 11 new coils

6. Arrangement of devices for the new sub- harmonic bunching system Solenoids Gun BPM&BCT Vacuum valve Vacuum chamber Profile BPMSHB1SHB2Bellow Bellows Solenoids

7. Beam pulse structure at the bunching system exit Starting with the beam parameters at the gun exit calculated with EGUN, a 150kV/10A/10nC/1.6ns(Bottom width)/0.95ns(FWHM) electron bunch is used as an input of PARMELA to simulate and optimize the beam performance of the primary electron beam at the present and the sub-harmonic bunching system exit. enlarged Present bunching system Sub- harmonic bunching system

8. Emittance variation along the bunching system

9. Bunching efficiency of the bunching system (charge within 10ps at the A0 exit) Present bunching system Sub- harmonic bunching system

10. Beam envelope variation along the bunching system Present bunching system Sub- harmonic bunching system

11. Solenoid field strength variation along the bunching system Present bunching system Sub- harmonic bunching system

12. Physical tolerance of the new sub-harmonic bunching system InstrumentTolerance Gun beam timing±50 ps Gun high voltage±0.4 % SHB1 phase±1.5 o SHB1 power±1.5% SHB2 phase±1.5 o SHB2 power±1.5% Buncher phase±2.0 o A0 phase±2.0 o According to the simulation results with PARMELA, the physical tolerance of the new sub-harmonic bunching system can be obtained. If the physical tolerance shown in the following table cann’t be satisfied, the reduction of the bunching efficiency will be larger than 10%.

13. Design and study of the two sub- harmonic bunching cavities (2)

14. Main parameters of SHB1: Resonant frequency: 142.8MHz Tuning range: ~400kHz(length of tuner: 40mm 、 radius of tuner: 10mm) Q 0 value: ~8175 Shunt impedance: ~1.4MOhm E surface,max /E gap,max =2.53 When P in =10kW, E gap,max =2.70MV/m, E surface,max =6.85MV/m, V gap,max =118kV. Main parameters and structure of SHB1 water channel Structure of SHB1

15. SHB1 assembly SHB1 cut view Tuner cut view Long drift tube assembly Mechanical design of the SHB1

16. Monitor Coupler Short drift tube Long drift tube end-plate Mechanical design of the SHB1 Bought from HITACHI High- Technologies Corporation

17. Main parameters and structure of SHB2 Main parameters of SHB2: Resonant frequency: 571.2MHz Tuning range: ~2MHz (length of tuner: 30mm 、 radius of tuner: 8mm) Q 0 value: ~13629 Shunt impedance: ~3.7MOhm E surface max /E gap,max =2.44 When P in =4.5kW, E gap,max =3.68MV/m, E surface,max =8.98MV/m, V gap,max =129kV. Structure of SHB2

18. Mechanical design of the SHB2 test cavity

19. Cold test of the SHB2 test cavity Frequency: 571.2MHz (Simulation: 571.2MHz) Unloaded Q value: >10605 (Simulation: 12370) Tuning range: 1.60MHz (Simulation: 1.40MHz) VSWR: <1.05 (Simulation: <1.05) The measurement and the simulation consistent well!

20. Design and study of the two RF power source (3)

21. Schematic diagram of the RF system for BEPCII Future Linac

22. Specification of the six reference signal generator Input signal: 571.2MHz 、 -8dBm-4dBm Output signal: f1=571.2MHz 、 f2=142.8MHz 、 f3=2856MHz 、 f4=17.85MHz 、 f5=71.4MHz 、 f6=499.8MHz Output power: f1, f2, f3 >13dBm, f4, f5, f6 >10dBm Input phase noise: >130dBc/Hz (5kHz) Output phase noise: f1, f2, f4, f5 >110dBc/Hz (5kHz) f3, f6 >105dBc/Hz (5kHz) Phase shift: <=±2ps/ ℃ Non-harmonic restrain: >=50dBc Harmonic restrain: >=25dBc Output signal isolation: >=20dB Stably operating temperature: 0~50 Degree

23. SHB1 solid-state amplifier 1) Specification: Frequency 142.8MHz  5.0MHz Pulse width 10 to 70  s Repetition 1 to 100Hz RF input power (cw) 10mW Phase noise － 110dBc/Hz (1kHz) RF output power 20kW Phase variation  1.5˚ (max. ) Phase drift during pulse <1˚ Pulse rise/fall time <1  s RF pulse flatness 2 % (max.) RF power stability  1.5 % 2) Operation requirement: Monitor of the output power. Monitor of the power supply and power amplifier modules. VSWR protection when output mismatch occurs. 3) Environment requirement: Air conditioning, < 25 ℃

24. SHB2 solid-state amplifier 1) Specification: Frequency 571.2MHz  5.0MHz Pulse width 10 to 70  s Repetition 1 to 100Hz RF input power (cw) 10mW Phase noise － 110dBc/Hz (1kHz) RF output power 10kW Phase variation  1.5˚ (max. ) Phase drift during pulse <1˚ Pulse rise/fall time <1  s RF pulse flatness 2 % (max.) RF power stability  1.5 % 2) Operation requirement: Monitor of the output power. Monitor of the power supply and power amplifier modules. VSWR protection when output mismatch occurs. 3) Environment requirement: Air conditioning, < 25 ℃

25. 571.2MHz/1.5kW solid state test module for SHB2 ParametersMeasured Frequency571.2MHz Pulse width 10  s Repetition400Hz RF input power10dBm Rise time70.8 ns Fall time98.0 ns RF pulse flatness0.48% Output power1888W Phase drift during pulse 0.738°

26. Requirements to the LLRF Phase and amplitude stability of the SHB cavities. Fast interlock of the SHB cavities and the power amplifiers. Frequency tuning of the SHB cavities. Ethernet interface for remote control. Fast data acquisition and history recording.

27. Construction schedule 2006.12: Detailed engineering design 2007.1~07.10: Fabrication of all SHB components 2007.11~07.12: Acceptance test 2008.1~08.5: High power test in laboratory 2008.6~08.8: Installation and commissioning 2008.9: Operation in Linac (4)

28. Summary(1) Established in the future development of BEPCII Linac, the optimized physical design of BEPCII future sub-harmonic bunching system and the optimized structure of the two SHBs are developed. Design, fabrication and cold test of the SHB2 test cavity has been performed, the test results is consistent with the simulation. Study of the two RF power source have been done. One test module of the solid state amplifier has been designed and tested with satisfied results.

29. Thank the colleagues from KEKB-Linac and SLAC for their help in the past several years. Summary(2) Recently, the upgrading of BEPCII present bunching system to sub-harmonic bunching system has been approved by IHEP’s experts and directors. The detailed design scheme has been decided. The construction will start in this year, correspondingly, the commissioning will be started in summer of 2008 according to the construction plan. The revolution is not success, everybody in the SHBS team should continue to work hard.