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

2. TESLA 500 RF Requirements

3. Specifications of the Power Supply

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

5. Layout of RF System

6. 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+

7. 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

8. 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

9. Long Pulse Modulator Options
Sine wave
Poor flat to ± 3.5% over Hz
5 times wasted power (4.6 MW peak power)
Hard tube
Large capacitor bank (0.5% droop  130 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

10. 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

11. 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 ( kV)
19" control rack
Switchgear, SCR control head, power distribution panel, panel view display, control chassis with IGBT gating, Interlock chassis, PLC chassis

12. Pulse Waveform Comparison
SNS modulator
TESLA modulator

13. SNS Modulator Circuit

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

15. 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

16. Experiences and Potentials of PAL (2)
Peak output power 111 MW
Peak voltage 350 kV
Peak current 317 A
Load impedance 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 kW
C-band Smart Modulator No. 1

17. 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