Study of High Intensity Multi-Bunch -rayGeneration by Compton Scattering

ATF TB meeting@KEK 28/May/2006

presented by Tsunehiko OMORI (KEK)

on behalf of Cavity-Compton collaboration

Sakae Araki, Yasuo Higashi, Yousuke Honda, Yoshimasa Kurihara, Masao Kuriki,Toshiyuki Okugi, Tsunehiko Omori, Takashi Taniguchi, Nobuhiro Terunuma,

Junji Urakawa, and Kaoru YokoyaKEK, Ibaraki, Japan

Ronic Chiche, Marie Jacquet, Alessandro Variola, and Fabian Zomer*IN2P3/CNRS and LAL, Orsay, France (*also University of Paris 11)

Xavier Artru, Robert Chehab, and Michel ChevallieIN2P3/CNRS and IPN/Lyon France

Frank ZimmermannCERN, Geneva, Switzerland

Kazuyuki Sakaue, Tachishige Hirose, and MasakazuWashioWaseda University, Tokyo, Japan

Noboru Sasao and Hirokazu YokoyamaKyoto University, Kyoto, Japan

Tohru Takahashi and Hiroki SatoHiroshima University, Hiroshima, Japan

Cavity-Compton Collaboration

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 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

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

Ne+=1.2x1010/bunch

Old design

Electron storage ring

laser pulse stacking cavities

po

sitron

stacking

in m

ain D

R

Re-use Concept

to main linac

Compton ring

New design

Laser Pulse Stacking Cavity

Input laser (YAGlaser) Energy 0.75 mJ / bunch 3.077 nsec bunch spacing train length = 50 sec

Cavity Enhancement Factor =1000

Laser pulse in cavity 750 mJ/bunch single bunch in a cavity

Fabry-perot Resonator

Schematic View of Whole System

R/D items(1) Compton ring

(2) Laser Pulse Stacking Cavity (Optical Cavity)

(4) Laser

(3) e+ stacking in DRsimulation study

simulation studyhardware R/D for bunch length modulation (optional / in future)

experimental R/D

We need cooporation with companeis.Progresses of lasers are very rapid.

R/D items(1) Compton ring

(2) Laser Pulse Stacking Cavity (Optical Cavity)

(4) Laser

(3) e+ stacking in DRsimulation study

simulation studyhardware R/D for bunch length modulation (optional / in future)

experimental R/D <- this proposal (Cavity-Compton collaboration)

We need cooporation with companeis.Progresses of lasers are very rapid.

Laser Pulse Stacking Cavity is a key.

a) One of the most uncertain parts of the current design. b) The efficiency of whole system highly depends on the cavity design. c) The reqirements to other parts highly depends on the cavity design.

cavity design : enhancement factor, laser spot size, and collision angle

Simulation alone is not effective in desiging cavity. We need experimental R/D.

Plan: Exprmntl R/D at ATF

.

Make a fist prototype single cavity

Put it in ATF ring

Hiroshima-LAL-IPN-CERN-Kyoto-Waseda-KEK

Lcav = 420 mm

Points of R/D

Points for high enhancement factor

Points for small spot

remove/suppress vibrationestablish feed back technology

2- Lcav --> +0

all are common in pol. e+ and laser wire

good matching between laser and cavityparabola mirrors (option)

Achieve both high enhancement & small spot

(less stabile) & (less stabile)

Points of R/D (continued)

Number of g-rays strongly depend of crossing angle

This in NOT common in pol. e+ and laser wire

Achieve smaller crossing angle

10W, 357MHz

02000400060008000

0 10 20 30crossing angle

Counts

/cro

ssin

g

--> Small crossing angle is preferable--> constraint in chamber design

ATF

e- bench length = 9 mm (rms)

Ne = 1x1010/bunch

.

Collision point is at between QM13R and QM14R (s = 40 m)

Collision Point

DR North Straight Section by T. Okugi

e- beam optics

alpha_x = -0.092 mbeta_x = 6.155 meta_x = 0 m

alpha_y = -0.232 mbeta_y = 6.546 meta_y = 0 m

s = 40 m (=s0) （ between QM13R and QM14R)

eps_x = 1.0E-09 meps_y = 0.5E-11 m

Assume

e- beam spot sizesig_x (s0) = 78 umsig_y (s0) = 6 um Stay almost constant in S = +- 1 m

Twiss Parameter

e- beam optics and spot size

Mirror R (mm)

rms laser spot size (micron)

250 88

211 35

210.5 30

210.1 20

210.01 11

210.001 6

L

R

Laser stacking cavity with Two Spherical Mirrors

Choice of R and spot size

our choice for 1st prototype

L = 420.00 mm

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Preparation and ScheduleSep/2005 X-ray generation cavity achieved Enh.~1000 But large spot size ~ 100 m

Oct Install prototype cavity into ATF ringNov-Dec test apparatuses using parasitic running

Apr/2006 We started assemble of test cavity (Not compatible to install ATF) Aug Start fabrication of prototype cavity

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Sep Complete prototype cavity

Jan/2007 First gamma-ray generation test

Expected Number of -raysNumber of -rays/bunch

Electron :Ne = 2x1010 (single bunch operation)Laser : 10 W (28 nJ/bunch)Optical Cavity: Enhancement = 1000

N=1300/bunch X-ing angle = 10 degN= 900/bunch X-ing angle = 15 deg

Number of -rays/second

Electron :Ne =1x1010 (multi-bunch and multi-train operation)Electron 20 bunches/train, 3 trains/ringLaser : 10 W (28 nJ/bunch)Optical Cavity: Enhancement = 1000

N = 8.5x1010/sec X-ing angle = 10 degN = 5.7x1010/sec X-ing angle = 15 deg

2nd & 3rd Prototype Cavities?

Longer cavityLcav = 840 mm, 2100 mm

Cavity using parabolic mirrors

Possible candidates (not decided yet)

Goal of the ProjectResults of prototype cavity(s)

Design cavity of ILC Compton Ring(CR)

Decide number of cavities, laser power, number of lasers used in CR.Design Compton Ring & other details.