Laser Compton Polarized e + e + Source for ILC CavityComptonMeeting 26/Jul/2005 Tsunehiko OMORI (KEK)

ILC : International Linear Collider e + lineace - lineacDRsDR E cm = 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 GeV250 GeV Experiments

Today ’ s talk 2. Concept of Laser Based Polarized e + Source for ILC Simulation study & Plan of Experimental R/D 1. Proof-of-Principle demonstration at KEK-ATF Experiment at KEK, just finished

1. Experiment at KEK-ATF 120 m Experiment done by Waseda-TMU-KEK collaboration ATF: Accelerator Test Facility for ILC built at KEK

i) proof-of-principle demonstration ii) accumulate technical imformation: polarimetry, beam diagnosis, …

Compton Chamber

 -ray  Measured 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 10 4 /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 + beam spin non A(R)= ± 0.25% A(L)= ± 0.27% A(0)= ± 0.25% T. Omori et al., PRL 96 (2006)

A = 0.90 ± 0.18 % Pol. = 73 % e + run T. Omori et al., PRL 96 (2006)

e + run e - run We did e - run, also.

e - polarization (e - run) e - spin in Iron e - beam spin non A(L)= ± 0.27% A(0)= ± 0.27% A(R)= ± 0.27%

A = 0.89 ± 0.19 % e - run

A = 0.90 ± 0.18 % e + run A = 0.89 ± 0.19 % e - run Asymmetry Measurements T. Omori et al., PRL 96 (2006)

Summary of Experiment 1) 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)

Collaborating Institutes: BINP, CERN, DESY, Hiroshima, IHEP, IPN, KEK, Kyoto, LAL, NIRS, NSC-KIPT, SHI, and Waseda Sakae  Araki  Yasuo  Higashi  Yousuke  Honda  Masao  Kuriki  Toshiyuki  Okugi  Tsunehiko  Omori  Takashi  Taniguchi  Nobuhiro  Terunuma,  Junji  Urakawa  X  Artru  M  Chevallier, V  Strakhovenko, Eugene  Bulyak  Peter  Gladkikh  Klaus  Meonig, Robert  Chehab  Alessandro  Variola  Fabian  Zomer  Frank  Zimmermann, Kazuyuki  Sakaue  Tachishige  Hirose  Masakazu  Washio  Noboru  Sasao  Hirokazu  Yokoyama  Masafumi  Fukuda  Koichiro  Hirano  Mikio  Takano  Tohru  Takahashi  Hiroki  Sato  Akira  Tsunemi  and Jie  Gao 2. Concept of Compton polarized e + source for ILC

Summer 2004 ITRP (International Technology Recommendation Panel) technology choice : cold LC (ILC) cold LC : super conduction RF cavity for accel.

Conceptual Design for warm LC T. Omori et al., NIM A500 (2003) Ne + =1.2x10 10 /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

2x10 10 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)

Laser Pulse Stacking Cavity Input laser (YAGlaser) Energy 1.2 mJ/bunch nsec bunch spacing train length = 50  sec Cavity Enhancement Factor =500 Laser pulse in cavity 600 mJ/bunch single bunch in a cavity Fabry-perot Resonator

Schematic View of Whole System

ILC : International Linear Collider e + lineace - lineacDRsDR ~ 50 km

Schematic View of Whole System

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

We also have Experimental R/D Plan for Comptom Pol. e + Source Cavity-Compton

Plan: Exprmntl R/D at KEK. Put it in ATF ring Nov Cavity Compton Collab.: Hiroshima-Waseda-LAL-Kyoto-CERN-KEK Make a fist prototype single cavity L cav = 420 mm

Laser based scheme is good candidate of ILC polarized e + source. Summary of ILC source design We have new Idea make positrons in 100 m sec. Electron storage ring laser pulse stacking cavitys positron stacking ring (= e + DRs) 1.6x10 10 e + /bunch x Hz with 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 ) ) e + beam pol. (laser pol) e - spin in iron (magnet pol.) A(0) : A(0) = 0 A(R) : A(R) ~ % A(L) : A(L) ~ % R L 0 expected value (MC)

Compton Ring (e - storage Ring) Turns Turns CO2 ringYAG ring N  /electron/turn (in all energy of  -ray) Average N  /turn (in MeV) CO2 : 1.78x10 10 /turn YAG : 1.36x10 10 /turn (average in 50 turns) (average in 100 turns)

e + stacking in Damping Ring (simulation) 1st bnch on 1st trn5th bnch on 5th trn 100 bnchs on 18820th trn 10th bnch on 10th trn before 11th bnch on 941st trn 11th bnch on 942nd trn15th bnch on 946th trn 20th bnch on 951st trn before 21st bnch on 1882nd trn 100th bnch on 8479th trn 100 bnchs on 9410th trn ~110  sec ~10 msec ~10 msec  sec ~20 msec ~100 msec  sec ~110 msec~200 msec T= Longitudinal Pos. (m)  Energy/Energy i-th bunch on j-th DR turn Time e+ in a bucket stacking loss = 18% in total