Beam Chopper R & D for Next Generation High Power Proton Drivers

1. Beam Chopper R & D forNext GenerationHigh Power Proton Drivers Michael A. Clarke-Gayther RAL / ASTeC / HIPPI

2. Project planning / Overview:

3. Project planning / Detail:

4. HIPPI WP4: The RAL† Fast Beam Chopper Development Programme Progress Report for the period: January 2004 – June 2005 M. A. Clarke-Gayther † † CCLRC Rutherford Appleton Laboratory, Didcot, Oxfordshire, UK

5. Outline See: Giulia Bellodi’s talk later in this session • ‘Fast – Slow’ chopping • RAL Front-End Test Stand (FETS) chopping schemes • High voltage pulse generator development • Fast Pulse Generator (FPG) • Slow Pulse Generator (SPG) • Slow – wave structure development • Helical structure B • Helical structure C

6. ‘Fast – Slow’ chopping

8. Fast and slowchoppermodules Chopper 1 (fast transition) BEAM Chopper 2 / Beam dump(slower transition)

9. RAL FETS chopping schemes

12. Fast Pulse Generator (FPG) Development

13. Phase 1 FPG system Single polarity @ 1.4 kV max. High peak power load Control and interface Combiner 9 x Pulse generator cards 9 x Pulse generator cards Power supply 13 M. A. Clarke-Gayther RAL/ASTeC/HIPPI

14. Phase 2 FPG system Dual polarity @ 1.4 kV max. High peak power loads Control and interface Power supply 9 x Pulse generator cards 9 x Pulse generator cards Combiner 9 x Pulse generator cards 9 x Pulse generator cards 14 M. A. Clarke-Gayther RAL/ASTeC/HIPPI

16. Phase 2 FPG waveform measurement FPG Waveforms at ± 1.4 kV peak & 5 ns / div. FPG Waveforms at ± 1.4 kV peak & 2 μs / div. FPG Waveforms at ± 1.4 kV peak & 100 ns / div. FPG Waveforms at ± 1.4 kV peak & 0. 2 ms / div.

17. Phase 2 FPG waveform measurement FPG timing jitter at 10 ps / div.

18. Measured performance parameters for the Phase 2 FPG system

19. Time & amplitude dependent FPG waveform analysis / 324 MHz FETS scheme

20. FPG duty cycle and LF droop for the ESS and FETS schemes † Assumes 4 kV SPG with ~ 9 ns transition time (10 – 90 %) †† Assumes 8 kV SPG with ~ 12 ns transition time (10 – 90%)

21. FPG duty cycle droop compensation

22. FPG duty cycle droop compensation OFF I.S. RAMPING (100 % CHOPPING) 30 % CHOPPING

23. FPG duty cycle droop compensation OFF I.S. RAMPING (100 % CHOPPING) 30 % CHOPPING

24. FPG duty cycle droop compensation OFF I.S. RAMPING (100 % CHOPPING) 30 % CHOPPING

25. FPG duty cycle droop compensation I.S. RAMPING CH BEAM CH BEAM CH BEAM CH BEAM CH 805 ns

26. FPG duty cycle droop compensation I.S. RAMPING CH BEAM CH BEAM CH BEAM CH BEAM CH 805 ns

27. Slow Pulse Generator (SPG) Development

28. SPG beam line layout and load analysis Slow chopper electrodes Beam 16 close coupled ‘slow’ pulse generator modules

29. SPG prototype system / Electronic implementation

30. SPG prototype system / Modular construction SPG Module 0.8 m 0.28 m

31. Prototype SPG module / Side view Axial cooling fans Air duct 0.26 m 8 kV push-pull MOSFET switch module Non-inductive damping resistors High voltage feed-through (output port)

32. SPG pre-prototype ‘Breadboard’ system - 8 kV~ 5 μF LF cap.bank HVdamping resistor 8 kV push-pullMOSFETswitch + 8 kV~ 5 μF LF cap.bank + 8 kV~ 3 nF HF cap.bank - 8 kV~ 3 nF HF cap.bank Two turn load inductance ~ 50 nH Load capacitance ~ 30 pf 6 kV, 400 MHz ÷ 1000 probe Trigger input Auxiliary power supplies Cooling fan

33. ‘Breadboard’ SPG waveform measurement • SPG waveforms at ± 6 kV peak & 50 ns / div. • SPG waveforms at ± 6 kV peak & 0.2 ms / div. • SPG waveforms at ± 6 kV peak & 0.5 μs / div. • SPG timing jitter at 100ps / div.

34. Measured performance parameters for the ‘Breadboard’ SPG system

35. Slow – Wave structure Development

36. Helical structure B with L - C trimmers and adjustable delay Adjustable L-C trimmer Adjust cable lengths to change delay

37. Helical structure C with L - C trimmers Quadrupole bore diameter

38. Summary • Three candidate chopping schemes for RAL FETS • Schemes A & B ready for first engineering analysis • FPG can meet ESS and RAL FETS requirements • Duty cycle droop compensation scheme to be tested • SPG prototype system designed and part constructed • Pre - prototype measurements show PRF limitation • Slow – wave structure engineering concepts refined • L – C impedance trimming and adjustable delay

39. ‘ ‘Fast-Slow’ Beam Chopping for next generation high power proton drivers’,M.A. Clarke-Gayther, Proc. of PAC 2005, Knoxville, Tennessee, USA, 16-20 May, 2005, at press.CARE-Conf-05-015-HIPPI ‘Re-design of the RAL chopper line’ F Gerigk, G Bellodi CCLRC, ASTeC, Intense Beams Group HIPPI-WP5 meeting, Coseners House, Abingdon, UK 13th April 2005 http://gerigk.home.cern.ch/gerigk/talks/hippi_ral_bd_0405.pdf ‘A fast beam chopper for next generation high power proton drivers’,M. A. Clarke-Gayther, Proc. of the Ninth EPAC, Lucerne, Switzerland, 5-9 July, 2004, p. 1449-1451CARE-Conf-04-009-HIPPI ‘A new 180 MeV H- Linac for Upgrades of ISIS’, F. Gerigk Proc. of the ninth EPAC, Lucerne, Switzerland, 5-9 July, 2004, p. 153-155

40. ‘A review of fast beam chopping’, F. Caspers,Proc. of Linac 04, Lubeck, Germany, 16-20 August, 2004, p. 578-582.CARE-Conf-04-???-HIPPI ‘Slow-wave electrode structures for the ESS 2.5 MeV fast chopper’,M.A. Clarke-Gayther, Proc. of PAC 2003, Portland, Oregon, USA, 12-16 May, 2003, p. 1473-1475 ‘A Fast Chopper for the ESS 2.5 MeV Beam Transport Line’, M. A. Clarke-Gayther Proc. of the eighth EPAC, Paris, France, 3-7 June, 2002, p. 2136-2138 ‘Slow-wave electrode structures for the ESS 2.5 MeV fast chopper’, M.A Clarke-Gayther,Proc. of the Eighth EPAC, Paris, France, 3-7 June, 2002, p.2133-2135 ‘Modulator systems for the ESS 2.5 MeV Fast Chopper’, M.A Clarke-Gayther,Proc. of PAC 2001, Chicago, 18-22 June 2001, p. 4062-4065.

41. Unipolar AC coupled FPG baseline ‘droop’