Research and Development Status and Programs for ILC at KEK-ATF We are going to research and develop on advanced accelerator technology under International Collaboration (ATF-MoU) for ILC at KEK-ATF. I will report the highlight of present research programs and prospect the future, especially the results of ATF2 project in 2008. Junji Urakawa (KEK) 1 at Oxford, 10/27
ATF Status and Prospect Emittance status, BPM Improvement, Laser wire results, Pulsed laser wire development, ODR monitor results, Fast kicker R&D, Laser Interferometer in an Optical Cavity New device for nm beam control. 2
ATF Introduction Wire scanner Extraction Line MW1X MW1X MW2X MW3X Beam Dump MW4X Seputum Magnets Wiggler Extraction Kicker East Arc Injection Kicker North Straight ATF Damping Ring BH1R BH1R.18 ML5T QF1R.14 ZV24R BPM.2 ZH23R QF2R.14 BPM.1 QF2R BPM.48 ZH48R BPM.49 ZV51R QF1R.28 BH1R.19 BH1R.36 BT ( Beam Transport Line ) QF31T ZH30T QD31T ZV30T South Straight RF Cavity West Arc E=1.28GeV SR Monitor Wiggler Ne=1x10 10 e-/bunch Electoron Linac 1 ~ 20 bunches Rep=3.125Hz X emit=2.5x10 -6 Y emit=1.25x10 -8 as normalized emittance 3
Multibunch emittance study • Scrubbing of DR was started DR pressure should be < 7 x10 -7 Pa for 1% emittance ratio for 1.0 x10 10 e - , 20 bunches, (=67mA, beam scrubbing with 210mA is necessary.) 0.78Hz repetition so far, >1 x10 -6 Pa - < 5x x10 -7 Pa • Monitors of MB emittance MB (or projected) Laser-wire Projected SR interference monitor, X-ray SR monitor MB (or projected) wire scanner: (EXT-line coupling problem?) • Problem of MB emittance 4 Fast Ion Instability ? Energy fluctuation ( coupled bunch longitudinal oscillation ?)
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Fast Ion Instability: Experimental Results at ATF Required vertical emittance : 2pm rad for ILC Y_emittance(00mode, 1.6E9intensity) Y emi(1.1e9/bunch intensity) Y_emittance(00mode, 3.7E9intensity) Y emi(4.1e9/bunch intensity) Y_emittance(01mode, 6.3E9intensity) Y emi(5.2e9/bunch intensity) MB emittance after 5.5A.hour scrubbing Vertical Emittance of Multibunch 5.0 10 -11 5 10 -11 Vertical Emittance of each bunch 6.3x10 9 Y emittance of each bunch 4.0 10 -11 4 10 -11 3 10 -11 3.0 10 -11 3.7x10 9 2 10 -11 2.0 10 -11 9 5.2x10 4.1x10 9 1 10 -11 1.0 10 -11 GLC Design 9 1.1x10 1.6x10 9 0.0 10 0 0 0 5 10 15 20 0 5 10 15 20 bunch number Bunch Number Vacuum Pressure<10 -8 Pa (0.1nTorr) in ILC 6
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ATF Damping Ring BPM reference EBW plane flange (A3003) HIP transition top block (Ti) reference reference button (SUS304) brazing (Al) plane plane SMA connector ø24mm ceramics brazing (Ag-Cu) pin (Kovar) 19.5 mm 70mm cross section of BPM camber Button electrode assembly Button BPM for Damping Ring Electronics: single pass detection for 96 BPMs DC-50MHz BW, base line clip & charge ADC, min. resolution ~20µm 8
Spectrum of DR BPM DR button BPM beam signal spectrum out from 40m RG223/u cable 65 DR BPM(MB30R) spectrum [dB µ V] 60 55 50 45 40 10 7 10 8 10 9 10 10 Freqency [Hz] Signal peak at ~ 1GHz 9
BPM electronics improvement Gain change Microwave diode detector signal to signal from BPM 600 ~ 1000MHz charge ADC single bunch ch 1 ch 1 HPF 50MHz LPF1000MHz LPF135MHz SMA QLA ATT RF combiner ch 2 -20dB ch 2 SMA LF amp RF amp multibunch QLA DC~ 155MHz 40 ~ 1000MHz ch 3 ch 3 Gain 15dB Gain 28.5dB SMA QLA 19dBm output 25dBm output ch 4 ch 4 SMA QLA ch 2 ch 3 calibration pulse ch 4 SMA 4-way splitter gain change control flat Improved BPM Circuit ( simplified diagram ) Electronics: 40MHz - 1GHz BW, base line clip & low noise LF amp min. resolution ~2µm 10
Resolution Improvement 100 Existing circuit (estimated by beam) Estimated Resolution [ µ m] 10 Improved circuit (estimated by calibration pulser) 1 10 8 10 9 10 10 10 11 Bunch Intensity [electrons/bunch] 11 Min. resolution ~ 2µm
Vertical orbit Improvement Y orbit before BPM improvement (26Nov2002) 1.5 1.0 Y C.O.D. [mm] 0.5 0.0 -0.5 -1.0 -1.5 0 20 40 60 80 100 BPM number Y orbit after BPM improvement (20May2003) 1.5 1.0 Y C.O.D. [mm] 0.5 0.0 -0.5 -1.0 -1.5 12 0 20 40 60 80 100 BPMnumber
Vertical dispersion Improvement Y dispersion before BPM improvement (26Nov2002) 15.0 10.0 Y dispersion [mm] 5.0 0.0 -5.0 -10.0 -15.0 0 20 40 60 80 100 BPMnumber Y dispersion after BPM improvement (20May2003) 15.0 10.0 Y dispersion [mm] 5.0 0.0 -5.0 -10.0 -15.0 13 0 20 40 60 80 100 BPMnumber
X to Y coupling Improvement 200.0 200.0 dY by ZH4R 26Nov2002 150.0 150.0 dY by ZH2R 26Nov2002 100.0 100.0 dY[micron] dY[micron] 50.0 50.0 0.0 0.0 -50.0 -50.0 -100.0 -100.0 -150.0 -150.0 -200.0 -200.0 0 20 40 60 80 100 0 20 40 60 80 100 BPMnumber BPMnumber 200.0 200.0 dY by ZH2R 20May2003 dY by ZH4R 20May2003 150.0 150.0 100.0 100.0 dY[micron] dY[micron] 50.0 50.0 0.0 0.0 -50.0 -50.0 -100.0 -100.0 -150.0 -150.0 -200.0 -200.0 0 20 40 60 80 100 0 20 40 60 80 100 BPMnumber BPMnumber 14
Laser wire beam size monitor in DR 14.7µm laser wire for X scan 5.7µm for Y scan 300mW 532nm Solid-state Laser (whole scan: 15min for X, Fed into optical cavity 6min for Y) 15
Laser wire block diagram optical cavity resonance is kept by piezo actuator 16
Two important cavity parameters • There are two important parameters Observed Airy which characterize the cavity. function – Finess (F): sharpness of resonance transmittance • proportional to power gain (G) • determined by mirror reflectivity • measured by its transmitted light. – Waist (w 0 ): thinness of the beam Half of wavelength • measure of spatial resolution or Peak width: 0.3nm luminosity Timing accuracy :1asec • determined by cavity geometry • measured by phase difference between two modes (or e - beam itself) 17 – F.o.m: G/(w 0 ) n (n=1~2) • F and w contradict technically.
Beam profile by Laser wire σ e 2 = σ meas 2 - σ lw 2 β: measured by Q-trim excitation εβ = σ e 2 – [ η ( ∆ p/p)] 2 18
Energy Spread Bunch Length by beam size monitor at EXT dispersive by SR monitor with streak camera point Energy Spread (runD) bunch length(runD') [psec] 40 -4 8.5 10 Energy Spread (run E) bunch length(runE') [psec] simulation (0.4% coupling) bunch length(runF') [psec] simulation (0.4% coupling) simulation (6% coupling) -4 simulation (6% coupling) 8.0 10 simulation (3% coupling) 35 Bunch Length (rms) [psec] -4 7.5 10 Energy Spread 30 -4 7.0 10 -4 6.5 10 25 -4 6.0 10 20 -4 5.5 10 -4 5.0 10 15 10 1.2 10 9 9 9 9 10 0 2 10 4 10 6 10 8 10 1 10 -4 4.5 10 10 1.2 10 9 9 9 9 10 0 2 10 4 10 6 10 8 10 1 10 Bunch Intensity [electrons/bunch] Bunch Intensity [electrons/bunch] 19
Emittance by Laser wire Y emittance (single bunch) X emittance (single bunch) emitt_x Y emittance (15bunch projected) emitt_y X emittance by LW Y emittance by LW 2 10 -9 1 10 -11 0.5% coupling Calculation 1.8 10 -9 8 10 -12 0.5% coupling Calculation X emittance Y emittance 1.6 10 -9 6 10 -12 1.4 10 -9 4 10 -12 1.2 10 -9 2 10 -12 LW Y emit(single 16APR03) LW X emit(single 16APR03) LW Y emit(15 bunch 6JUN03) 1 10 -9 0 2 10 9 4 10 9 6 10 9 8 10 9 1 10 10 2 10 9 4 10 9 6 10 9 8 10 9 1 10 10 0 0 Bunch Intensity Bunch Intensity < 0.5% y/x emittance ratio Y emittance =4pm at small 20 intensity
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Results with higher transverse mode How to make TE01 mode? 00 01 00 TEM01 mode was produced • Resolution may be with efficiency of 60% by improved by ~x3 with the inserting phase converter. same w 0 . 22
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Experimental results （ Pulse Laser Storage ） Laser: Mode Lock: Passive SESAM Frequency: 357MHz Cavity length: 0.42 m Pulse width: 7.3 p sec (FWHM) Wave Length: 1064 nm SESAM: SEmi-conductor Saturable Absorber Mirrors Power: ~ 6W 24
Ext. Cavity : Cavity: Super Invar Cavity length: 0.42 m Mirrors: Reflectivity: 99.7%, 99.9% Curvature: 250 mm ( 0 = 180 m) super invar 62φ 25
Finesse: R = 99.9% : decay time Finesse = c/l c: light verocity PD PBS PBS l: cavity length P.C. Trans. ~ 3.0 sec F ~ 6300 (Preliminary) 26
Plused Laser and Electron Beam Collision to measure bunch length Pulse Laser Wire (Storage laser pulses in optical cavity ): The systems for New X-ray source & New bunch length monitor at a storage ring 27
714MHz Cavity Scattered Laser Repetition rate : Gamma beam 357MHz laser pulses Phase Scan Compton Scattering in every 357MHz Electron repetition rate : 357MHz As an X-ray source : Electron bunches An optical cavity stores higher peak power and gets higher flux X-ray with pulse laser than CW laser. As Beam monitor : By scanning the laser pulse’s phase in the cavity and measuring the Compton signal count rate ; an electron bunch length profile is obtained. 28
Storage of laser pulse Resonance condition : Perfect resonance : L = L laser cavity The relationship with laser and cavity : Imperfect Resonance : L ～ laser cavity L The enhancement factor is the function of Not resonance : L ≠ L reflectivity, l and laser laser cavity pulse width. 29
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