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
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
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
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
Pulse Forming Network Feburary 2, 2005
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
Feburary 2, 2005
Bouncer Modulator Built for Tesla Test Facility in 1994 Output shaped by bouncer network Invented by Quentin Kerns Feburary 2, 2005
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
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
Feburary 2, 2005
Feburary 2, 2005
Feburary 2, 2005
Feburary 2, 2005
Improved Bouncer Modulator Built for DESY by industry Feburary 2, 2005
Feburary 2, 2005
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
Feburary 2, 2005
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