SRF-Gun Dark Current Chopper
or
taking the remains from other
projects
Gerald Staats for the ELBE-Team
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Member of the Helmholtz Association
Gerald Staats | ELBE| www.hzdr.de
Requirements for SRF-Gun dark current chopper
13MHz PRF for CW operation
Short pulse length
High stability
Topics
1.
2.
3.
4.
5.
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Stripline kicker structures – stolen from ELBE kicker design
Fast 13MHz pulse driver – stolen from positron kicker design
Pulse power combiner – reused from home
TEM ring resonator stripline kicker structure – something must be new
Problems
Member of the Helmholtz Association
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
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Member of the Helmholtz Association
Gerald Staats | ELBE| www.hzdr.de
1. First: classical kicker-geometry, beamline tube not shown
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Member of the Helmholtz Association
Gerald Staats | ELBE| www.hzdr.de
1. E-field inside the kicker structure for odd-mode excitation
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Member of the Helmholtz Association
Gerald Staats | ELBE| www.hzdr.de
1. Matching for odd-mode excitation
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Member of the Helmholtz Association
Gerald Staats | ELBE| www.hzdr.de
1. PIC simulation – 5MeV Bunch
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Member of the Helmholtz Association
Gerald Staats | ELBE| www.hzdr.de
1. Second: kicker-geometry with beamline tube taper
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Member of the Helmholtz Association
Gerald Staats | ELBE| www.hzdr.de
1. E-field inside the kicker structure for odd-mode excitation
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Member of the Helmholtz Association
Gerald Staats | ELBE| www.hzdr.de
1. Matching for odd-mode excitation
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Member of the Helmholtz Association
Gerald Staats | ELBE| www.hzdr.de
1. PIC simulation – 5MeV Bunch
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Member of the Helmholtz Association
Gerald Staats | ELBE| www.hzdr.de
2. Driver schematics – half bridge – stolen from positron kicker design
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Member of the Helmholtz Association
Gerald Staats | ELBE| www.hzdr.de
2. Driver board – water cooled - delivers 250V 5ns pulses on 50 Ohms
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Member of the Helmholtz Association
Gerald Staats | ELBE| www.hzdr.de
2. Measured output signal from test bench with 13MHz PRF
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Member of the Helmholtz Association
Gerald Staats | ELBE| www.hzdr.de
3. Transmission line combiner (non isolating) – stolen from home
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Member of the Helmholtz Association
Gerald Staats | ELBE| www.hzdr.de
3. S-Parameter
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Member of the Helmholtz Association
Gerald Staats | ELBE| www.hzdr.de
3. Hybride combiner (isolating) – also stolen from home
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Member of the Helmholtz Association
Gerald Staats | ELBE| www.hzdr.de
3. S-Parameter
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Member of the Helmholtz Association
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 ???
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Member of the Helmholtz Association
Gerald Staats | ELBE| www.hzdr.de
4. Filling the resonant TEM ring structure with power
13MHz PRF in CW operation, circulating time is 76.92ns
Ring structure needs about 100µs for filling -> to slow ???
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Member of the Helmholtz Association
Gerald Staats | ELBE| www.hzdr.de
4. Some first experiments with a Flexwell coaxial cable at 106.8MHz PRF
106.8MHz PRF, 8ns Pulsbreite
106.8MHz PRF, 1ns Pulsbreite
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
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Member of the Helmholtz Association
Gerald Staats | ELBE| www.hzdr.de
4. TEM ring resonator with bypass for fast switching -> fast kicking
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Member of the Helmholtz Association
Gerald Staats | ELBE| www.hzdr.de
4. 13MHz PRF, every second pulse suppressed
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Member of the Helmholtz Association
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
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Member of the Helmholtz Association
Gerald Staats | ELBE| www.hzdr.de
6. References
(1)
(2)
(3)
(4)
(5)
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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
DRF Series Design Guide, Application Note 1815, Microsemi Power Products Group (former
APT), January 2011.
3kW and 5kW half-bridge Class-D RF generators at 13.56 MHz with 89% efficiency and limited
frequency agility, IXYS Corporation, 2002.
Ultra Fast Hybrid MOSFET/Driver Switch Module R&D for a Broadband Chopper, Tao Tang,
Craig Burkhart, Power Conversion Department, SLAC National Accelerator Laboratory
Hybrid MOSFET/Driver for Ultra-Fast Switching, T. Tang, and C. Burkhart, Stanford Linear
Accelerator Center
Member of the Helmholtz Association
Gerald Staats | ELBE| www.hzdr.de