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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.