ILC accelerator related R&D in Japan2nd ASIA ILC R&D Seminar at KNU, Daegu, KoreaJunji Urakawa , KEK*

1. Pol. e- source R&D at Nagoya U., Hiroshima U., and KEKProduction of nanosecond pol.e- beam for ILC Photocathode: GaAs-GaAsP SL (Pol.max > 85%)Laser energy : 6mJ10HzBunch width(FWHM): 1.6nsBunch charge : 8nC

Lasere-beamThe SL active layer grown ona laser cutting GaAs waferILC:6.4nC/bunch

Extracted charge of 30nC/bunch was obtained.Space charge limit Experiments & SimulationsThe experimental data is a measurement of supply current to the electrode.Both results are corresponding well, therefore this simulation is almost appropriate for calculatingSC effect.Experimental dataSimulation dataGPTExtracted charge is estimated from the number of macro-particlesat 10mm downstream PC.

Characteristics of SUS and Ti-Mo electrodeDark current characteristic isnt degraded even if many breakdowns were occurred. Hardly observed dark current until breakdown was occurred.Advantages of Ti-Mo electrode

Photocathode LifetimePreliminaryThe photocathode lifetime seems no problem under the condition of a few micro amps beam emission.Gun:2.7x10-9Pa2NEG:2.0x10-9Pa

Long-term 200keV operation became possible by employing the titanium anode and molybdenum cathode electrode. Remaining R&D : A laser system which meets fully ILC requirements.SLAC isdeveloping.Hiroshima,and KEK areconsidering.

Cs2Te Photo-cathode, 1.6 Cell S-band RF GunMulti-bunch beam generation6. Photo-cathode RF gun

Fig.5 Momentum distribution of bunch train

Fig. 7 Upper-left : ICT signal of 100 bunches, upper-right : 100 bunches on the OTR screen, bottom figure : energy of each bunch in the train100 bunches/pulse energyspread is less than 0.5%.

Emittance measurementx: 3.0 [mmmrad]y: 4.7 [mmmrad]Collision pointQF1QD1CP1G(OTR)x: 86umy: 36umBeam profile at Collision pointBeam current : 2.5nC/train, 3bunches

Optical Circuite- beam

X-ray GenerationPulsed laser stacking chamber43MeV end station to separate X-rayand e-beam. 33keV X-ray is deflectedby Crystals.

Laser Undulator Compact X-ray (LUCX) Project at KEK-ATFMulti-bunch photo-cathode RF GunS-band Acc. StructureStorageLaser power40kW, 7psec(FWHM), next step :1MWBeam size at CP 60mm in sMulti-bunch e- beam 300nC at gun43MeV Multi-bunch beam+ Super-Cavity = 33keV X-ray.X-rayDetectorAt present, laser waist size is 30mm ins. We should reduce both beam size at CPdown to 30mm.33keV X-ray generation based on inverse Compton scattering was started from May 2007 with Super-Cavity.

laser beame- beam7. Pulsed laser storage cavityFrom two-mirror cavity to four-mirror cavity under International collaboration with LAL.

Considering two-mirror cavity,reflectance R, transmissivity T, and losses L where R+T+L = 1 by energy conservation.The bounce number b which is defined from the round-trip power loss in a cavity, e1/b.FSR : free spectral rangeIf R=R1=R2

Storage of laser pulseResonance condition :The relationship with laser and cavity :

The enhancement factor is the function of reflectivity, l and laser pulse width.

CW Laser wire beam size monitor in DR 14.7m laser wire for X scan 5.7m for Y scan(whole scan: 15min for X,6min for Y)300mW 532nm Solid-state Laserfed into optical cavityJFY2003Achievement on related technique

Laser wire block diagram optical cavity resonance is kept by piezo actuatorFree spectral range:532nm/2=266nmLine width=0.3nm

Laser: Mode Lock:PassiveSESAMFrequency:357MHzCavity length:0.42 mPulse width:7.3 p sec(FWHM)Wave Length:1064 nmPower: ~ 6W SESAM: SEmi-conductor Saturable Absorber Mirrors Experimental resultsPulse Laser Storage

Cavity:Super InvarCavity length:420mmMirrors:Reflectivity:99.9%, 99.9% (maybe, 99.98%)Curvature:250 mm (0 = 180m)Ext. Cavity: 62super invar

Finesse: R = 99.98%Finesse =c/l:decay timec: light verocityl: cavity lengthF ~ 6300 ~ 3.0secPDTrans.P.C.PBSPBSJFY 2004

e- beamlaser beampulse stacking cavity in vacuum chamber1.Achieve high enhancement & small spot size2.Establish feedback technology3.Achieve small crossing angle 4.Get experinence with e- beam-ray Generation with Laser Pulse Stacking Cavity (Hiroshima-Waseda-IHEP-KEK)We should detect 20 gs/collision.

Mirror damage which is caused by peak power density on the mirror.Storage averagepower 40kW or more(maybe 120kW)Laser size on mirror440 mm

Then, reduce waistsize from 160 mm to60 mm.Laser size on mirror1174 mmGood coating spherical mirror damage threshold :Average power density on mirror ~10 MW/cm2Peak power density on mirror ~10 GW/cm2Waist size in sigma from 80 mm to 30 mmdamaged coating size ~100 mmDepth (p-p) 5.5 mm

REO and SOC mirror threshold are a little small :6.7 GW/cm2 and 1.6 GW/cm2

We designed asymmetric reflective mirror configuration to increase the coupling : 99.7% and 99.9% .Then, we found damaged mirror was low reflective one.When we introduced burst mode operation for x-ray generation with F.L. pumped amplifier, we might increase average power in the cavity until 120kW. It means ~20GW/cm2.Now we keep 40kW average power with larger beam size 1174 mm on the mirror ,which corresponds 0.8GW/cm2.

R/D Status in JapanModerate Enhancement ~ 1000Moderate spot size ~ 30 micronSimple cavity stucture with two mirrorsGet experinence with 43MeV and 1.3GeV e- beam Laser Undulator Compact X-ray (LUCX) Project at KEK-ATF43MeV Multi-bunch beam+ Super-Cavity = 33keV X-ray.Expected X-ray is generated.

Key technology isCompact(less than 10m)quasi-monochromatic (less than 1%) High Flux ( 100 times than Compact normal Linac X-ray1011 photons/sec 1% b.w.High Brightness (1017 photons/sec mrad2 mm2 0.1% b.w.Ultra-short pulse X-ray40 fs ~8. Quantum beam project Characteristic of proposed machine

Pulsed laser storage

Storage energy : 100 timesBeam size < 8 mPhoto-cathode RF gun

Low emittance beam 3mmmradShort pulse, 162.5MHz bunch trainSCRF Cavity

Ultra-low loss(10n)long pulse accelerationhigh intensity and low emittance*

Pulsed Laser Storage Laser wire waist ~ 3 mElectron beam size ~ 2 mBeam orbit control Achieved by ATFFrom 2-mirror cavity to 4-mirror cavity*

Organization & ResponsibilityCommittee for project evaluation*

Annual Schedule and Budget*

Item20082009201020112012S. Cavity Development($1.5M/year),HRF + Cly($0.8M/year)Upgrade of SC Cavity performance

Compact RF power source system Control system for SCRF

Construction of Test AcceleratorConfirm the performance Electron Source($0.5M/year)High Q and long life photo-cathode500 kV DC High Voltage High Intensity Beam GenerationPulsed Laser Storage System ($0.4M/year)X-ray Detector($0.1M/year)Design and R&D on laser storage

X-ray Detector

Impact by Compact High Brightness Photon Beam1) 2 2) X )*

Target of component technology*

technologyPresent statusTarget Key pointsElectron source300 nC/pulse

10,000nC/pulse(2008-2009)48,000 nC/pulse(2010-2012)Pulse laser, new photo-cathode 1 msec pulse lengthSC CavityPulse: 25 MV/mCW: 12 MV/mPulse: 30 MV/mCW: 20 MV/m Pulsed laser storage0.5 mJ/pulse, Waist: 30 m50 mJ/pulse, Waist: 8 m4-mirror optical cavityColliding controlm beam orbit controlSub- m beam orbit control

Quantum beam project(2008-2012) approved by MEXTCompact high brightness X-ray source using SC Cavity*

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