C-band Accelerator system for XFEL / SPring-8 C. Kondo, T. Inagaki, T. Shintake for XFEL project in SPring-8 6/Oct/2008 Seminar at SLAC

8 GeV XFEL Machine Layout Injector S-band 4 units C-band (42  off-crest) 12 units C-band (crest) 52 units Undulators 30 MeV 100 A 500 keV 1 A x 1 ns 1.4 GeV 3 kA 8 GeV 3 kA 400 MeV 1 kA Bunch compression Acceleration X-ray Laser min < 0.1 nm E a = 35 MV/m  V/V ~ 0.01% rms  ~ 0.2 deg. rms  V/V ~ 0.01% rms  ~ 0.5 deg. rms

C-band (5712 MHz) RF system HV Charger

Pulse-to-pulse jitter from the klystron voltage HV Charger AC 420 V XFEL requires (rms) - Intensity  0.01% - Phase  0.2 ° Modulator Charging 50 kV Klystron Pulse -350 kV Pulse Comp. RF 50 MW RF 70 MW  2 Accel. Struct.  0.01 % high precision HV charger with <0.01% (100 ppm) stability

Improvement of High Voltage Charger Specification: ・ Switching deviceIGBT ・ Charging voltageMax. 50 kV ・ Charging current ~ 2 A ・ Average output power 36 kW ・ Repetition 60 Hz ・ Voltage stability (jitter) 0.01 %rms Aug. 2006, Nichicon Corp. Used at prototype acc. Feb. 2008, Nichicon Corp. Nov. 2007, Toshiba electro-wave,

Block Diagram of HV Charger Full-wave rectification AC 420 V Full bridge switching Main Sub Resonance High voltage rectification DC 600 V Max. 50 kV We use Main charger and Sub charger. “Main” charges 99.5%, fast but roughly “Sub” charges up to the target voltage, slowly but accurately.

Feedback Control of Charged Voltage HV charger Modulator PFN Capacitors HV probe Japan finechem inc Feedback of the voltage Error amp. Reference voltage Stray capacitance delays the response Main resistor : 1 G  →100 M  ・ Time constant: 1 msec→100  sec ・ Heat loss: Fluorinert, Cooling water.

New HV charger with 10 ppm (rms) stability Prototype model Feb. 2008, Nichicon Corp. This stability satisfies the requirement at XFEL (<100 ppm). Typical HV charging cycle (Tens of waveforms are overlaid)

C-band (5712 MHz) RF system Compact “all-in-one” modulator

“New” modulator One tank including the pulse transformer and modulator Pulse Transformer PFN circuit Capacitor x16 (General Atomics) Thyratron e2v CX-1836 EOL circuit Diode & Resistor Klystron cathode Nihon Koshuha Co. Ltd., Oct./2007 Compact size: 1.7m x 1m x 1.2m, EM noise shielding, etc.

Thyratron and PFN Circuit (Detail) Thyratron e2v, CX-1836 ・ Deuterium filled ・ Impregnated cathode ・ Double gap, twin trigger ・ Cooled by natural oil flow Omit forced oil flow. Pulse Forming Network circuit Z PFN = 4  ・ Capacitor : General Atomics, Max. 50 kV  F ×16 series ・ Coil 0.6  H ×16 series Replace Other circuit EOL, tail clipper, shunt diode, discharging resistor, etc

Pulse Transformer (detail) RISHO Co. (Japan) Turn ratio: 1:16 （ Prim=6 turn 、 Sec=96 turn ） Primary voltage: -22 kV Secondary voltage: -350 KV Epoxy-molded winding ・ High voltage insulation ・ Suppression of wire vibration

Oil cooling system of the modulator Concept Fan-less cooling for viscous insulation oil Low cost, Compact Requirements Heat generation: ~3kW Heater ~1kW ( thyratron cathode, Klystron cathode) Current 45kV,60pps ( EOL, thy. Anode, Core Loss, etc) Oil temperature : < 45 ℃ We measured the practical heat transfer coefficient by model tank. And, we designed the optimum cooling system for the modulator.

View of Cooling system 2 panel type on partition wall Cooling panel 1 pipe type on top board Cooling pipe 2 panel type on side board Cooling panel (side board)

Oil temperature Oil temperature on nominal operation Operation: 45 kV charging 60 pps Cooling water: 26 ℃, 8 L/min Oil temperature: < 43 ℃ Oil Temperature ( ℃ )

C-band (5712 MHz) RF system C-band Klystron

50MW pulse klystron Output power :50 MW Frequency:5712 MHz RF pulse width:2.5  sec Beam Voltage:-350 kV Beam Current:310 A Repetition:60 pps TOSHIBA ELECTRON TUBES & DEVICES CO.LTD. Model No. E37202 In the test accelerator, no trouble for 3,000 hours

C-band (5712 MHz) RF system Pulse compressor C-band accelerator structure

RF pulse compressor Fabricated by Mitsubishi Heavy Industries Ltd. High-Q cavities mode: TE 0,1,15 Q0 : 190,000  : 9.5 Mode converters (Shintake 1996) - Waveguide(TE 10 )  Circular(TE 0,1,x ) - 4 coupling holes  Lower rf field at the coupling hole Input 50 MW 2.5  s 200 MW peak 0.5  s Output Directional coupler

Accelerating structure (Shintake structure) Choke mode cavity (Shintake 1992) - traps the accel. mode (5712 MHz) - eliminate HOM (not 5712 MHz)  multi-bunch operation High acceleration gradient R~ 54 M  /m,  ~ 0.53, L=1.8 m Ea = 35 MV/m with 63 MW x 300 nsec rf power Fabricated by Mitsubishi Heavy Industries Ltd SiC absorber

Mass production of the accelerating Mitsubishi Heavy Industries Ltd. Precise lathe Shipping Dr. Miura (Mitsubishi) Cells

High power rf test bunker (July 2008 ~) Accel. struct.WaveguideRF pulse compressorModulator Klystron In order to check quality of the delivered components, we constructed the test bunker. Now, rf processing is in progress.

Modulator development team 白澤 近藤 櫻井 稲垣 武部 新竹 T. Inagaki C. Kondo T. Shintake S. Indo K. Nakajima T. SakuraiK. Shirasawa

Summary Highly precise charger Parallel charging system New HV probe of fast response-time. Stability of charging voltage ~10 ppm (rms) New “all-in-one” modulator power supply Compact oil-filled power supply. EM noise shielding, fan-less oil-cooling system … No trouble operation for 700 hours Schedule High power rf components were delivered on schedule. Quality will be checked at the rf test bunker. 2009~2010 installation 2011~ Beam commissioning

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