Klystron Power Supplies for ILC 2nd Korean ILC Workshop December 28-29, 2004 Pohang Accelerator Laboratory Jong-Seok Oh PAL/POSTECH

TESLA 500 RF Requirements

Specifications of the Power Supply

Power Requirements of the RF System Peak RF power per RF station 9.7 MW Duty cycle 0.685% Average RF power available per RF station 66 kW Klystron efficiency 65% Modulator efficiency 85% Total efficiency 55% AC power per RF station 120 kW Auxiliary power per RF station 14 kW Total wall plug power per station 134 kW Number of active stations 560 Total wall plug power 75MW

Layout of RF System

Overall Layout of the RF System 572 (1144) klystrons in total 6 stations for two linacs ~100 (~200) modulators per station 12.5 MW ( 25MW) per station e- e+

Principle of TESLA Modulator Pulse cable : 4 parallel, 6.45 Ohm, max. ~2.8 km Pulser unit : 2.8m(L) x 1.6m(W) x 2.0 m(H) Pulse transformer tank : 2m(L) x 1.2m(W) x 1.4m(H), 6.5 ton

TESLA Modulator Status 10 Modulators have been built, 3 by FNAL and 7 by industry 8 modulators are in operation 10 years operation experience exists Work towards a more cost efficient and compact design has started Many vendors for modulator components are available

Long Pulse Modulator Options Sine wave Poor flat to ± 3.5% over 1.4 ms @ 50 Hz 5 times wasted power (4.6 MW peak power) Hard tube Large capacitor bank (0.5% droop  130 uF @140 kV  1.3 MJ) High voltage series switch PFN/Tr. Fixed pulse width, fast switching at moderate voltages Large VxTp transformer DTI Series IGBT switch No regulation possible Complex voltage distribution and protection TESLA Series IGBT switch + pulse transformer + bouncer circuit Complex voltage distribution, Multiple switches, Large HV pulse transformer SNS High frequency switching (20 kHz) by IGBT Minimize series IGBT Significantly reduced pulse transformer No crowbar circuit needed 1

Specifications of TESLA and SNS Modulator Parameters TESLA I TESLA II SNS Pulse width [ms] 2.0 1.4 Output voltage [kV] 130 110 140 Output current [A] 95 79 Repetition rate [pps] 10 60 Peak power [MW] 12.35 14.3 11 Average power [kW] 247 200 924 Solid state switch GTO IGBT DC link voltage [kV] 10.6  1.2 Transformer step-up ratio 13 12 18 Flattop ripple [%]  0.5 Efficiency [%] 86 89 (?) > 93 RF Frequency [MHz] 1300 805 Peak RF power [MW] 5

Features of SNS Modulator AC power Use industry standard 3 phase 13.8/2.1 kV 1.5MVA transformer Dry type transformer with 5th and 7th harmonic traps 3 phase SCR voltage controller Coarse adjustment of DC voltage Limit in-rush current at turn-on DC storage capacitor Self-cleaning design 110 mF per polarity  160 kJ stored energy IGBT switch + H-bridge Tradeoff between switching losses and size of magnetic device 20 kHz H-bridge in 3 phase PWM to control and regulate output voltage Bipolar switching to simply magnetic design Switching losses of ~ 5 kW/device Boost transformer + DC rectifier 1:18 voltage step-up with triple-resonant filter  1:47 voltage gain Amorphous nano-crystalline cores with zero-magnetostiction Low stored energy in the output filter (2.25 J @ 140 kV) 19" control rack Switchgear, SCR control head, power distribution panel, panel view display, control chassis with IGBT gating, Interlock chassis, PLC chassis

Pulse Waveform Comparison SNS modulator TESLA modulator

SNS Modulator Circuit

Converter Modulator Assembly IGBT Mounting Oil Pump / Heat XChgR HV Conn. Output Diode Rectifier Stepup XFMR Output Choke Shunt Capacitor Low Inductance Primary Bus

Experiences and Potentials of PAL (1) PLS 200 MW Modulator Max. Peak Power (MW) 200 Peak Output Voltage (kV) 400 Pulse Repetition Rate (Hz) Operating 10 Max. 60 Equi. Pulse Width (ms) 7.5 Flat - top Pulse Width (ms) 4.4 PFN Impedance (W) 2.8 Input Voltage (V, 3f, 60Hz) 480

Experiences and Potentials of PAL (2) Peak output power 111 MW Peak voltage 350 kV Peak current 317 A Load impedance 1104 W Flat top width 2.5 ms HV pulse length 3.5 ms Pulse energy 389 J Pulse repetition rate 100 pps Average output power 38.9 kW C-band Smart Modulator No. 1

Summary Bouncer modulator is a reasonable baseline design Units have been tested over many years Efficiency is ~ 86% and can be improved Cost estimates 300k$ ~ 400k$ each for 576 units Upgrades still being investigated Other operating designs exist New designs are also of interest Charging supply technology and power distribution are important issues PAL has enough potential and experiences for ILC modulator