1. Member of the Helmholtz Association Page 1 Gerald Staats | ELBE| www.hzdr.de SRF-Gun Dark Current Chopper or taking the remains from other projects Gerald Staats for the ELBE-Team

2. Member of the Helmholtz Association Page 2 Gerald Staats | ELBE| www.hzdr.de Requirements for SRF-Gun dark current chopper 13MHz PRF for CW operation Short pulse length High stability 1.Stripline kicker structures – stolen from ELBE kicker design 2.Fast 13MHz pulse driver – stolen from positron kicker design 3. Pulse power combiner – reused from home 4.TEM ring resonator stripline kicker structure – something must be new 5.Problems Topics

3. Member of the Helmholtz Association Page 3 Gerald Staats | ELBE| www.hzdr.de 1. Two Stripline-Kicker-Geometries - stolen from ELBE kicker design From ELBE-Kicker design we have two parametric models for stripline kicker First: the normal geometry well known from literature with Krashnykh-Fender Second: a inverse geometry Both a modeled and optimized with CST Microwave Studio and CST Particle Studio (in progress) Both have nonlinear taper functions, the first transversal and longitudinal the second only longitudinal Matching for both is better than SLAC values

4. Member of the Helmholtz Association Page 4 Gerald Staats | ELBE| www.hzdr.de 1. First: classical kicker-geometry, beamline tube not shown

5. Member of the Helmholtz Association Page 5 Gerald Staats | ELBE| www.hzdr.de 1. E-field inside the kicker structure for odd-mode excitation

6. Member of the Helmholtz Association Page 6 Gerald Staats | ELBE| www.hzdr.de 1. Matching for odd-mode excitation

7. Member of the Helmholtz Association Page 7 Gerald Staats | ELBE| www.hzdr.de 1. PIC simulation – 5MeV Bunch

8. Member of the Helmholtz Association Page 8 Gerald Staats | ELBE| www.hzdr.de 1. Second: kicker-geometry with beamline tube taper

9. Member of the Helmholtz Association Page 9 Gerald Staats | ELBE| www.hzdr.de 1. E-field inside the kicker structure for odd-mode excitation

10. Member of the Helmholtz Association Page 10 Gerald Staats | ELBE| www.hzdr.de 1. Matching for odd-mode excitation

11. Member of the Helmholtz Association Page 11 Gerald Staats | ELBE| www.hzdr.de 1. PIC simulation – 5MeV Bunch

12. Member of the Helmholtz Association Page 12 Gerald Staats | ELBE| www.hzdr.de 2. Driver schematics – half bridge – stolen from positron kicker design

13. Member of the Helmholtz Association Page 13 Gerald Staats | ELBE| www.hzdr.de 2. Driver board – water cooled - delivers 250V 5ns pulses on 50 Ohms

14. Member of the Helmholtz Association Page 14 Gerald Staats | ELBE| www.hzdr.de 2. Measured output signal from test bench with 13MHz PRF

15. Member of the Helmholtz Association Page 15 Gerald Staats | ELBE| www.hzdr.de 3. Transmission line combiner (non isolating) – stolen from home

16. Member of the Helmholtz Association Page 16 Gerald Staats | ELBE| www.hzdr.de 3. S-Parameter

17. Member of the Helmholtz Association Page 17 Gerald Staats | ELBE| www.hzdr.de 3. Hybride combiner (isolating) – also stolen from home

18. Member of the Helmholtz Association Page 18 Gerald Staats | ELBE| www.hzdr.de 3. S-Parameter

19. Member of the Helmholtz Association Page 19 Gerald Staats | ELBE| www.hzdr.de 4. TEM ring resonator stripline kicker structure Using a TEM ring resonator to made the stripline kicker resonant Kicker pulse circulating in the ring resonator gives higher Q and saves power Higher Q means slower kicking -> could be a problem ???

20. Member of the Helmholtz Association Page 20 Gerald Staats | ELBE| www.hzdr.de 13MHz PRF in CW operation, circulating time is 76.92ns Ring structure needs about 100µs for filling -> to slow ??? 4. Filling the resonant TEM ring structure with power

21. Member of the Helmholtz Association Page 21 Gerald Staats | ELBE| www.hzdr.de Directional couplers need high bandwidth Q depends from the directional coupler, seen up to 500 No DC can be coupled in, therefore a offset must compensated Higher Q made LLRF control loop possible 106.8MHz PRF, 1ns Pulsbreite 106.8MHz PRF, 8ns Pulsbreite 4. Some first experiments with a Flexwell coaxial cable at 106.8MHz PRF

22. Member of the Helmholtz Association Page 22 Gerald Staats | ELBE| www.hzdr.de 4. TEM ring resonator with bypass for fast switching -> fast kicking

23. Member of the Helmholtz Association Page 23 Gerald Staats | ELBE| www.hzdr.de 4. 13MHz PRF, every second pulse suppressed

24. Member of the Helmholtz Association Page 24 Gerald Staats | ELBE| www.hzdr.de 5. Conclusion, problems and next steps. Stripline kicker structure caused bunch deformation, better kick the waste Kicker driver module must be tested CW operation leads to high power consumption in known kicker/chopper concepts Combiner must be build and tested CW operation made RF control loops possible for higher stability TEM ring resonator with bypass could be a solution

25. Member of the Helmholtz Association Page 25 Gerald Staats | ELBE| www.hzdr.de 6. References (1)Development of a Fast High-Power Pulser and ILC DR Injection/Extraction Kicker, Anatoly Krasnykh (SLAC), ILC Damping Ring R&D Workshop, Cornell University, September 26-28, 2006 (2)DRF Series Design Guide, Application Note 1815, Microsemi Power Products Group (former APT), January 2011. (3)3kW and 5kW half-bridge Class-D RF generators at 13.56 MHz with 89% efficiency and limited frequency agility, IXYS Corporation, 2002. (4)Ultra Fast Hybrid MOSFET/Driver Switch Module R&D for a Broadband Chopper, Tao Tang, Craig Burkhart, Power Conversion Department, SLAC National Accelerator Laboratory (5)Hybrid MOSFET/Driver for Ultra-Fast Switching, T. Tang, and C. Burkhart, Stanford Linear Accelerator Center