e + ソースの現状

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

Parameter Value# of positron/bunch 2.00E+10Bunch spacing 369ns# of bunch/Pulse 2625Pulse repetition rate 5Hz

I ntroduction

Baseline

Alternative

TDP

SummaryUndulator 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.

I ntroduction

Baseline

Alternative

TDP

Summary


Undulator Parameters

Parameter ValueElectron drive energy 150 GeVElectron beam energy loss 4.5 GeVUndulator length 147 m (168m)Undulator period 11.5mmUndulator Field 0.86 TUndulator strength 0.92

10 MeVPhoton energy (1st hrmc)

I ntroduction

Baseline

Alternative

TDP

Summary


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%.

I ntroduction

Baseline

Alternative

TDP

Summary


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.


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).


Quarter Wave Transformer

Ramping from 0T to 1 T in 5cm (no field on target).Capture efficiency ~ 15%. Technically matured and realizable (actual baseline).


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.

I ntroduction

Baseline

Alternative

TDP

Summary


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.

I ntroduction

Baseline

Alternative

TDP

Summary


e- driven schemee- 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.

I ntroduction

Baseline

Alternative

TDP

Summary


CHANNELING FOR ILC & CLIC e+ source

R. ChehabA 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-

Crystal Amorphous

e+, e-, γe-

e+

“x” meters

Only the photons are impinging on the converter: that limits the energy deposition in the amorphous target.

Radiator Converter

I ntroduction

Baseline

Alternative

TDP

Summary


Driving motor

Vacuum pump

Cog-wheel pump

transport tubes

Target head

Liquid lead targetA 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

I ntroduction

Baseline

Alternative

TDP

Summary


Liquid Pb-Sn TargetLiquid 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/mm21012

A

vera

ge p

ower

(kW

)

Operation point


Laser Compton SchemeA 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.

I ntroduction

Baseline

Alternative

TI P

Summary


Compton RingA 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.

I ntroduction

Baseline

Alternative

TI P

Summary


ERLERL(Energy Recovery Linac) is employed as the dedicated electron driver.─ 0.48nC, 18.5ns (54MHz) ~ 26mA, E=1.8GeV─ Nγ=2.3E+9 by 0.6 Jx5 CP, Ne+=2.0E+7

By a semi-CW operation (50ms), 1000 times stacking in DR is performed and Ne+=2.0E+10 is obtained.

I ntroduction

Baseline

Alternative

TI P

Summary


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. ZimmermannI ntroduction

Baseline

Alternative

TDP

Summary


CLIC Compton Scheme

I ntroduction

Baseline

Alternative

TDP

Summary

Collaboration on Positron Generation strongly supported by CLIC and ILC managements (J.P. Delahaye@PosiPol08)


by F. Zimmermann & L. Rinolfi

ILC Positron Source:MMUndulator 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.

I ntroduction

Baseline

Alternative

TDP

Summary


Further Considerations on MMImproved 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”.

I ntroduction

Baseline

Alternative

TDP

Summary


TDP SummaryBasic 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.

I ntroduction

Baseline

Alternative

TDP

Summary


SummaryR&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.

I ntroduction

Baseline

Alternative

TDP

Summary


Documents

e + ソースの現状