1. Klystron Modulator for Proton Driver
Chris Jensen
Why does Proton Driver need modulators
Overview of pulse power concepts
Description of three possible modulators
Update on status of SMTF modulators
Pictures of FNAL and DESY/PPT

2. Why modulators ? Need high power RF to accelerate beam
Need RF amplifiers
Klystron (e- Beam - RF Converter)
Require high voltage ( 130 kV )
Limited Spark Energy ( 20 J )
Need Peak Power to drive klystron
Modulator converts wall power to peak power
Klystron Efficiency is 50%
Limit average power dissipated
Feburary 2, 2005

3. Pulse Power Concepts Two time regimes Peak vs. Average
Pulse Compression
Peak vs. Average
Components Ratings
Some need Peak
Some need Average
How many need both?
Reliable Operation
Feburary 2, 2005

4. Pulse Forming Network Linac is one example Output shaped by network
Each capacitor section provides peak energy for fraction of pulse length
Pulse Length is 125 us
How can size / cost be reduced for long pulses
Feburary 2, 2005

5. Pulse Forming Network
Feburary 2, 2005

6. Pulse Switching Mode Supply
SNS Modulator one example
1.3 ms, 60 Hz, 10 MW peak
Output shaped by switching / regulating
High voltage output needs filter and rectifier
High Frequency / Voltage Transformer
Feburary 2, 2005

7. Feburary 2, 2005

8. Bouncer Modulator Built for Tesla Test Facility in 1994
Output shaped by bouncer network
Invented by Quentin Kerns
Feburary 2, 2005

9. Bouncer Modulator
Switch connects main capacitor bank to transformer during pulse.
Transformer steps up voltage to 120kV/130A (12:1)
Main capacitor bank discharges by 20% during pulse
“Bouncer” circuit compensates for cap bank droop.
Feburary 2, 2005

10. FNAL Original Modulator Circuit
Step for operation: 1) Turn On Bouncer Switch 2) Switch connects main capacitor bank to transformer for flat top 3) Transformer steps up to 120 kV 4) Main Capacitor Bank Discharges 20% 4) Bouncer Circuit has low impedance and voltage compensates for droop 5) Switch must open during a spark to remove energy stored in pulse transformer
Feburary 2, 2005

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15. Improved Bouncer Modulator Built for DESY by industry
Feburary 2, 2005

16. Feburary 2, 2005

17. Bouncer Modulator for SMTF
Incorporate New Capacitor Technology
Self Healing Hazy Polypropylene
Incoporate New Switch Technology
IGBTs have improved over 10 years
Pulse Length increased to 4 ms (from 2ms)
Modular construction for flexibility
Feburary 2, 2005

18. Feburary 2, 2005

19. SMTF Modulator Status • Pulse Transformers for SMTF on order
Main Capacitor Bank from AVX / TPC
Volume is 20% of original film/paper
Cost is 50% of original film/paper
Bouncer Capacitors and Inductors out for bid
No significant change in requirements or size
Added power saved cost incentive to inductor
Switch is in Design Stage
SLAC collaborating with design
Feburary 2, 2005