r&d status of ilc positron source kuriki masao (hiroshima/kek) 구리기 마사오 (...

ASIA ILC R&D seminarKympok National University, Taegu, Korea 129-30 October 2008

R&D status of ILC Positron Source

KURIKI Masao (Hiroshima/KEK)구리기　마사오 ( 히로시마　대학 )


Table of Contents

IntroductionRDR baseline configuration and its R&D. Alternative configuration and its R&D.TDP for ILC positron sourceSummary

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Baseline

Alternative

TDP

Summary


ILC and Positron Source

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

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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.


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.

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Baseline

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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)

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Baseline

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TDP

Summary


R&D efforts for the baseline (1)This system is a totally new approach; Feasibility of the system should be confirmed in various levels.─ Devices ─ System and sub-system

In addition, the ILC baseline e+ source is not an isolated system from the whole ILC and has inter-system dependencies.Careful considerations are necessary from the system point of view.─ E+ is generated at the same time for the collision. ─ E+ time structure is identical to that in ML.

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Baseline

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TDP

Summary


R&D efforts for the baseline (2)The R&D efforts for critical devices are on going.─ Super-conducting helical undulator.─ Rotating conversion target.─ Capture devices (pending due to no budget).

Several considerations from the system engineering point of view have been made. ─ E+ timing issue : a mathematical puzzle among DR

harmonic number, bunch spacing in ML, round trip duration from e- DR to e+ DR, etc.

─ Keep Alive e+ source : machine commissioning, fast recovery from the system failure,etc.

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Summary


Undulator Cryo-module OverviewStainless steel vacuum vessel with Central turret

50K Al Alloy Thermal shield. Supported from He bath

Stainless Steel He bath contains100L liq He. Supported by 4 rods attached to the vacuum vessel

U Beam used to support/align the magnet.

U beam Support rod

Magnet cooled to 4.2K by liq He in bath.

Beam Tube

S Carr


Undulator Cryomodule

U Beam

He Vessel

Heat Shield

Helical Undulator


0

50

100

150

200

250

300

350

0 10 20 30 40

Quench number

Que

nch

curr

ent (

A)

magnet 1

magnet 2

nominal current

Quench Test & Field Measurement

All two magnets finally satisfied the specification.Field profile is measured by hall probe, showing a good quality.


Conversion TargetK

en D

avie

s -

Dar

esbu

ry L

abor

ator

y

Water-cooled electromagnet Variable pole gap (0mm to 160mm) Peak field > 1 T at wheel

15 kW drive motor

Ti alloy wheel.

L Jenner

Torque Sensor

Photon beam


Target Prototype

Experiment will start when personnel guards are in place

Should be completed by end of 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%.

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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.

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Baseline

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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.

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Baseline

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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

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Baseline

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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

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Baseline

Alternative

TDP

Summary


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.

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Baseline

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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.

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Baseline

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TI P

Summary


Pulse Stacking Optical Cavity


Pulsed Laser Injected CavityR. Chiche

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Baseline

Alternative

TI P

Summary


High power ps fiber amplifier E. Cormier

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Baseline

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TDP

Summary


Experiment at KEK-ATF

Electron beamCSI

γray

e beam

PD

16~28MeV420mm

Collision angle 12 degree

λ:1064nm 10W=28nJ , 2.8ns spacing Pulse length : 7ps

= 30 μm

Mode lock laser

Finess = 780γ/

colli

son

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Baseline

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TDP

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

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Baseline

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TDP

Summary

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


PosiPol-Collaboration

Laser-Compton has a large potential as a future technology. Many common efforts can be shared in a context of various applications.─ X-ray/SR sources for industrial and medical

applications,─ Beam diagnostics with Laser,─ Polarized Positron Generation for ILC, CLIC,

SuperB, ..State-of-the-art technologies are quickly evolved with world-wide synergy.PosiPol collaboration has been started in 2006. The last annual meeting was held at Hiroshima in July 08. The next meeting will be held at near CERN in 2009.

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Summary


WWW of PosiPol R&Ds

Laser Compton

Optical Cavity

High powerlaser

X-raysource

e- sourceILC, ERL

Medicalapplications

Industrialapplications

ERL/Ring4th Generationlight source

LW monitor/Polarimetry

ILC e+

CLIC e+

SuperB

e+source

MaterialScienceScientific

Application

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Baseline

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TDP

Summary


Minimum machine studiesRe-baseline in 2010(publish in interim report)

Minimum machine studiesRe-baseline in 2010(publish in interim report)

TDP is a multi-phase approach towards TDR.TDP-1 is focused on

Risk mitigationCost reduction

TDP-2 is a real technical design phase based on the design established on TDP-1.

Technical Design Phase


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.

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Baseline

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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”.

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Baseline

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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

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TDP

Summary


Thank you for your attention.

귀하의 관심을 주셔서 감사합니다

I ntroduction

Baseline

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TDP

Summary


TDP-2

TDP-2:-Technical requirements documentation-Technical design work cost update-Value Engineering-Cost & Schedule-18 month period

TDP-2:-Technical requirements documentation-Technical design work cost update-Value Engineering-Cost & Schedule-18 month period


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


RDR Source Layout

Ti-alloy fast rotating target for gamma -> e+ conversion.Capture devices : AMD or QWT + L-band NC accelerator with solenoid focusing.Backup source (500MeV e-, 10% intensity).

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Baseline

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TDP

Summary


Flux Concentrator for KEB upgrade

I ntroduction

Baseline

Alternative

TI P

Summary

r&d status of ilc positron source kuriki masao (hiroshima/kek) 구리기 마사오 (...

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