Laser Compton Polarized ee++ Source for ILC

Compton meeting@LAL 24/Apr/2006

Tsunehiko OMORI (KEK)

ILC: International Linear Collidere+ lineace- lineac DRsDR

Ecm = 500 - 1000 GeV

Polarized Beams play important role Suppress back ground Increase rate of interaction (if both beam pol) Solve Week mixing of final state

start experiment at ~2015

~ 50 km

Two ways to get pol. e+

(1) Helical Undurator

(2) Laser Compton

e- beam E >150 GeV

Undulator L > 150 m

Two ways to get pol. e+

(1) Helical Undurator

(2) Laser Compton

e- beam E >150 GeV

Undulator L > 150 m

Our Proposal

Why Laser Compton ?

ii) Independence Undulator-base e+ : use e- main linac Problem on design, construction, commissioning, maintenance, Laser-base e+ : independent Easier construction, operation, commissioning, maintenance iii) Low energy operation

Undulator-base e+ : need deccelation Laser-base e+ : no problem

i) Positron Polarization.

ILC Undulator-base e+ Source

150 GeV 250 GeV 250 GeV

Experiments

Today’s talk

2. Concept of Laser Based Polarized e+ Source for ILC

Simulation study & Plan of Experimental R/D(Cavity-Compton)

1.Proof-of-Principle demonstration at KEK-ATF (ATF-Compton collab.)

Experiment at KEK, just finished

1. Experiment at KEK-ATF

120 m

ATF-Compton collaboration: Waseda, TMU, NRIS, AIST, and KEKATF: Accelerator Test Facility for ILC built at KEK

i) proof-of-principle demonstration

ii) accumulate technical imformation: polarimetry, beam diagnosis, …

ATF Experiment@KEK

No Optical Cavity at Collision Point

Compton Chamber

-rayMeasured Asymmetry

A= -0.93± 0.15 % A= 1.18± 0.15 %laser pol. = - 79 % laser pol. = + 79 %

M. Fukuda et al., PRL 91(2003)164801

Ne+ = 3 x 104/bunch Asym (expected) = 0.95%Pol(expected) = 77%

polarized e+

Measure e+ polarization : use Bremsstrahlung -ray

Pb conveter

-ray

E = 40 MeV

calculation

e+ polarization (e+ run )e- spin in Iron

e- spin in Iron

e- spin in Iron

e+ beam spin

e+ beam spin

e+ beam spinnon

A(R)= +0.60 ± 0.25%

A(L)= -1.18 ± 0.27%

A(0)= -0.02 ± 0.25%

T. Omori et al., PRL 96 (2006) 114801

A = 0.90 ± 0.18 %

Pol. = 73 %

e+ run T. Omori et al., PRL 96 (2006) 114801

Summary of Experiment1) The experiment was successful. High intensity short pulse polarized e+ beam was firstly produced. Pol. ~ 73 ± 15(sta) ± 19(sys) %

3) We established polarimetry of short pulse & high intensity -rays, positrons, and electrons.

2) We confirmed propagation of the polarization from laser photons -> -rays -> and pair created e+s & e-s.

T. Omori et al., PRL 96 (2006) 114801

Collaborating Institutes:BINP, CERN, DESY, Hiroshima, IHEP, IPN, KEK, Kyoto,

LAL, NIRS, NSC-KIPT, SHI, and Waseda

SakaeArakiYasuoHigashiYousukeHondaMasaoKurikiToshiyukiOkugi TsunehikoOmoriTakashiTaniguchiNobuhiroTerunuma,

JunjiUrakawaXArtruMChevallier, VStrakhovenko, EugeneBulyakPeterGladkikhKlausMeonig, RobertChehabAlessandroVariolaFabianZomerFrankZimmermann, KazuyukiSakaueTachishigeHiroseMasakazuWashioN

oboruSasaoHirokazuYokoyamaMasafumiFukudaKoichiroHiranoMikioTakanoTohruTakahashiHirokiSatoAkiraTsunemiand JieGao

2. Concept of Compton polarized e+ source

for ILC

Summer 2004ITRP(International Technology Recommendation Panel)

technology choice : cold LC (ILC) cold LC : super conduction RF cavity for accel.

Conceptual Design for warm LCT. Omori et al., NIM A500 (2003) 232-252

Ne+=1.2x1010/bunch

Before Summer 2004

Study Compton applied to a cold LC.

New and Improved design

Full use of slow repetition rate (5Hz)

After Summer 2004

ILC requirements

ILC requirements2x1010 e+/bunch (hard)2800 bunches/train (hard)5 Hz (we have time to store e + s)

Strategy

New: Design for cold LC (ILC) make positrons in 100 m sec. Electron storage ring, laser pulse stacking cavity : Re-use !!! positron stacking ring.

Old: Design for warm LC make positrons at once. both electron & laser beams: throw away

Basic Idea: K. Moenig P. Rainer

T. Omori et al., NIM A500 (2003) 232-252

Laser Pulse Stacking Cavity

Input laser (YAGlaser) Energy 0.7 mJ/bunch 3.077 nsec bunch spacing train length = 50 sec

Cavity Enhancement Factor =1000

Laser pulse in cavity 700 mJ/bunch single bunch in a cavity

Fabry-perot Resonator

Schematic View of Whole System

ILC: International Linear Collidere+ lineace- lineac DRsDR

~ 50 km

Schematic View of Whole System

Schematic View of Whole System

This part is necessary for ILC, This part is necessary for ILC, no matter what eno matter what e++ production production scheme is chosen.scheme is chosen.

We also haveExperimental R/D Plan

for Comptom Pol. e+ Source

Plan: Exprmntl R/D at KEK

.Put it in ATF ringOct. 2006

Hiroshima-Waseda-LAL-Kyoto-CERN-KEK Collaboration

Make a fist prototype single cavityLcav = 420 mm

.Put it in ATF ringOct. 2006

Make a fist prototype single cavityLcav = 420 mm

detail Sato's talk

Laser based scheme is good candidate of ILC polarized e+ source.

Summary of ILC source design

We have new Ideamake positrons in 100 m sec. Electron storage ring laser pulse stacking cavities positron stacking ring (= e+ DRs)

2x1010 e+/bunch x 2800 bunches @ 5Hzwith polarization ( ~ 60%)

Some values are extrapolation from old design.We need detailed simulation.

We plan to put prototype laser cavity in ATF.

Slides to answer questions

Polarization Measurement

non (Liner)

)Calculate A

)Calculate A

)Calculate A

e+ beam pol.(laser pol)

e- spin in iron (magnet pol.)

A(0) : A(0) = 0

A(R) : A(R) ~ + 0.95 %

A(L) : A(L) ~ - 0.95 %

R

L

0

expected value

(MC)

W- target

Separationmagnet

e+

e+

e-

W- target

e+Separation

magnet

polarized

e-

e-

e+ run e- run

We did e- run, also.

e- polarization (e- run)e- spin in Iron

e- spin in Iron

e- spin in Iron

e- beam spin

e- beam spin

e- beam spinnon

A(L)= -0.97 ± 0.27%

A(0)= -0.23 ± 0.27%

A(R)= +0.78 ± 0.27%

A = 0.89 ± 0.19 %

e- run

A = 0.90 ± 0.18 %

T. Omori et al., arXiv:hep-ex/0508026 KEK Preprint 2005-56

e+ run

A = 0.89 ± 0.19 %

e- run

Asymmetry Measurements

Compton Ring (e- storage Ring)

0 10 20 30 40 50 Turns

0 20 40 60 80 100 Turns

CO2 ring YAG ring

N/

elec

tron

/turn

(in

all

ener

gy o

f -

ray)

2.0

1.6

1.2

0.8

0.4

1.6

1.2

0.8

0.4

Average N/turn (in 23-29 MeV) CO2 : 1.78x1010 /turn YAG : 1.36x1010 /turn (average in 50 turns) (average in 100 turns)

e+ stacking in Damping Ring (simulation)1st bnch on 1st trn

5th bnch on 5th trn

100 bnchs on 18820th trn

10th bnch on 10th trn

before 11th bnch on 941st trn

11th bnch on 942nd trn

15th bnch on 946th trn

20th bnch on 951st trn

before 21st bnch on1882nd trn

100th bnch on 8479th trn

100 bnchs on 9410th trn

~110 sec

~10 msec

~10 msec + 110 sec ~20 msec ~100 msec + 110 sec

~110 msec

~200 msec

T=0

-0.4 0.4Longitudinal Pos. (m)

-0.0

3

0.

03E

nerg

y/En

ergy

i-th bunch on j-th DR turn

Time

e+ in a bucket

stacking loss = 18% in total