e + ソースの現状 大森 GDE 活動報告会 2008 年 6 月 23 日 シカゴ GDE meeting に向けて 大森 GDE 活動報告会 2008 年 10 月 6 日 かなりの数のスライドが、栗木さんが先ごろ大邱 "2nd Asia ILC R&D Seminar, Sep 29-30, 2008" で行った公演のスライドからの、借用です

Working Groups and Conveners ILC08 - Accelerator 1. Sources Axel Brachmann, Jim Clarke

ILC and Positron Source Undulator is the baseline design. Two alternatives: ─Conventional (electron driven) is a fall back. ─Laser Compton is an advanced alternative. Any schemes are not fully established. Need a certain amount of R&D for ILC positron source. M. Kuriki, 2nd Asia ILC R&D Seminar, Sep 29-30, 2008

Baseline Design It relies upon gamma rays generated by passing 150 GeV electron through 168m undulator. Undulator is “inserted” to part way of ML (150GeV). A positron source driven by 0.5 GeV electron is a back up for high availability and machine commissioning. M. Kuriki, 2nd Asia ILC R&D Seminar, Sep 29-30, 2008

Undulator Parameters M. Kuriki, 2nd Asia ILC R&D Seminar, Sep 29-30, 2008

Matching Device The generated positrons is a point like with a large transverse momentum spread. That should be converted to a parallel beam for further acceleration; The matching device does it. Depending on the matching device, it increases capture efficiency from 10% to 40%. M. Kuriki, 2nd Asia ILC R&D Seminar, Sep 29-30, 2008

DC Solenoid High field (6T) and high capture efficiency(30%). Similar to other DC SC magnets; It is technically matured. It is not feasible for ILC since 100's of kW of eddy current in a fast rotating metal target. M. Kuriki, 2nd Asia ILC R&D Seminar, Sep 29-30, 2008

Shielded Flux Concentrator Ramping from 0T to 7 T in 2cm (no field on target). Capture Efficiency ~21% Difficult technically to sustain 1ms pulse train length. Further study needed to prove feasibility (prototype). M. Kuriki, 2nd Asia ILC R&D Seminar, Sep 29-30, 2008

Quarter Wave Transformer Ramping from 0T to 1 T in 5cm (no field on target). Capture efficiency ~ 15%. Technically matured and realizable (actual baseline). M. Kuriki, 2nd Asia ILC R&D Seminar, Sep 29-30, 2008

Summary for baseline R&D efforts for critical devices are in progress (undulator, target, etc). Although Matching device is one of the most important, the R&D is stopped. QWT is the only realistic solution at this moment and it should be actual baseline as long as there is no big progress on R&D for MD. M. Kuriki, 2nd Asia ILC R&D Seminar, Sep 29-30, 2008

Alternative Design e- driven scheme (conventional) and Laser Compton scheme are considered to be alternative schemes. ─e- driven scheme is a back-up alternative. ─Laser Compton is an advanced alternative. Because the baseline design is a totally new approach, a conservative alternative is very important as a technical backup. Laser Compton is attractive, but it is technically immature; It is advanced alternative. M. Kuriki, 2nd Asia ILC R&D Seminar, Sep 29-30, 2008

e- driven scheme e- drive beam impinges on a conversion target. ─6 GeV 2E+10 e- bunch. ─Amorphous W (W-Re alloy), crystalline W, diamond, liquid Pb- Sn,etc. Capture devices. E+ booster up to 5 GeV: The technology depends on the pulse structure; SC for long pulse case (~1ms) and NC for short pulse case (<50μs). The most important and difficult issue is conversion target. M. Kuriki, 2nd Asia ILC R&D Seminar, Sep 29-30, 2008

CHANNELING FOR ILC & CLIC e+ source R. Chehab A single target works for CLIC, but multi-target is needed for ILC limited by PEDD. A single target might work for ILC in Low P parameter. e-e- Crystal Amorphous e +, e -,  γ e-e- e+e+ “x” meters Only the photons are impinging on the converter: that limits the energy deposition in the amorphous target. RadiatorConverter M. Kuriki, 2nd Asia ILC R&D Seminar, Sep 29-30, 2008

Driving motor Vacuum pump Cog-wheel pump transport tubes Target head Liquid lead target A prototype in BINP has been operated 20000h without any troubles. ─Pb 90% Sn 10%, 300˚C, Cog- wheel pump. Brazing technique for BN window has been established. Liquid Pb-Sn jet in vacuum M. Kuriki, 2nd Asia ILC R&D Seminar, Sep 29-30, 2008

Liquid Pb-Sn Target Liquid Pb target + BN window is very strong against high peak power, but less average power. Pulsed operation (e.g. 100 bunches with 6.2ns spacing, 0.6μs, 150Hz) moderates thermal effects. In the pulse operation, capture efficiency is higher and incident electron can be fewer. P. Logachov et al. in APAC2007 Energy/100ps GeV/mm Average power (kW) Operation point M. Kuriki, 2nd Asia ILC R&D Seminar, Sep 29-30, 2008

Laser Compton Scheme A few GeV (1.8GeV for example) electron bunch collides with 1μm laser photon stored in optical cavity. Several 10s MeV gamma impinges in a conversion target. A dedicated electron driver is reasonable. Obtaining enough positron, is a technical challenge. ─High intensity electron beam: Linac, Storage ring, ERL ─High intensity photon beam: High power laser, optical cavity. ─Stacking scheme: DR stacking, Pre-DR, etc. M. Kuriki, 2nd Asia ILC R&D Seminar, Sep 29-30, 2008

Compton Ring A storage ring for electron driver:5.3nC, 6.2ns, 1ps, 1.8GeV, 0.6Jx5CP. Positron bunch(Ne+:2.0E+8) is generated. 10 bunches are stacked on a same bucket. This process is repeated 10 times with 10ms interval for beam cooling. Finally, Ne+:2E+10 is obtained. M. Kuriki, 2nd Asia ILC R&D Seminar, Sep 29-30, 2008

ERL ERL(Energy Recovery Linac) is employed as the dedicated electron driver. ─0.48nC, 18.5ns (54MHz) ~ 26mA, E=1.8GeV ─N γ =2.3E+9 by 0.6 Jx5 CP, N e+ =2.0E+7 By a semi-CW operation (50ms), 1000 times stacking in DR is performed and Ne+=2.0E+10 is obtained. M. Kuriki, 2nd Asia ILC R&D Seminar, Sep 29-30, 2008

Stacking Simulation # of positron by a single collision is not sufficient -> need stacking. Stacking simulation in DR (multi-turn injection) shows 10.6% of injected e+ are lost! stacking efficiency ~90%. The tolerance of the injection loss would be qualified. F. Zimmermann M. Kuriki, 2nd Asia ILC R&D Seminar, Sep 29-30, 2008

CLIC Compton Scheme Collaboration on Positron Generation strongly supported by CLIC and ILC managements (J.P. M. Kuriki, 2nd Asia ILC R&D Seminar, Sep 29-30, 2008 by F. Zimmermann & L. Rinolfi

ILC Positron Source:MM Undulator is moved to the end of ML (250GeV). ─ Energy scan <100GeV is difficult. ─ Dedicated pulse for e+ generation with ½L. QWT instead of AMD, which has lower capture efficiency; The undulator length is 350m. KAS share the common target with gamma1 source; yield is only 1% of the nominal intensity. M. Kuriki, 2nd Asia ILC R&D Seminar, Sep 29-30, 2008

Further Considerations on MM Improved Low P parameter : half # of bunches in a pulse. It is a big fair wind for the electron driven. ─ Potential target damage, which is the most serious issue on electron driven scheme, is relaxed. ─ There are active R&D on noble ideas. No doubts that Conventional is really “conventional”. M. Kuriki, 2nd Asia ILC R&D Seminar, Sep 29-30, 2008

TDP Summary Basic R&D is very important in TDP1. Re-baseline at the end of TDP-1 is the mile- stone. According to the investigation based on the latest technology, the status is: The conventional method is important as a fall- back. Low P parameter and noble target technologies make it feasible and reliable. Technical difficulty forces the undulator system bigger and bigger and it does not seem “mimimal machine”. From the pure technical point of view, the baseline is the electron driven and undulator and laser compton are upgrade alternatives. M. Kuriki, 2nd Asia ILC R&D Seminar, Sep 29-30, 2008

Summary R&D status of ILC positron source is reviewed. Undulator scheme is the baseline design. ─SC helical Undulator, rotating rim target prototype. ─Need study for matching device. e- driven scheme is important as a backup. ─There are several active R&Ds based on noble ideas. It is the best scheme for MM. Laser Compton is an advanced alternative. ─Aggressive R&D efforts. ─Still need more technical maturity. ─ILC-CLIC collaboration. M. Kuriki, 2nd Asia ILC R&D Seminar, Sep 29-30, 2008