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Laser Compton Polarized
+
e Source for ILC
Tsunehiko OMORI (KEK)
CavityComptonMeeting
26/Jul/2005
ILC: International Linear Collider
DR
e- lineac
e+ lineac
DRs
~ 50 km
Ecm = 500 - 1000 GeV
start experiment at ~2015
Polarized Beams play important role
Suppress back ground
Increase rate of interaction (if both beam pol)
Solve Week mixing of final state
Two ways to get pol.
(1) Helical Undurator
e- beam
E >150 GeV
Undulator
L > 150 m
(2) Laser Compton
+
e
Two ways to get pol.
+
e
(1) Helical Undurator
e- beam
E >150 GeV
Undulator
L > 150 m
Our Proposal
(2) Laser Compton
Why Laser Compton ?
i) Positron Polarization.
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
ILC Undulator-base e+ Source
150 GeV
250 GeV
250 GeV
Experiments
Today’s talk
1. Proof-of-Principle demonstration
at KEK-ATF
Experiment at KEK, just finished
2. Concept of Laser Based Polarized
e+ Source for ILC
Simulation study &
Plan of Experimental R/D
1. Experiment at KEK-ATF
ATF: Accelerator Test Facility for ILC built at KEK
Experiment done by Waseda-TMU-KEK collaboration
120 m
Experiment@KEK
i) proof-of-principle demonstration
ii) accumulate technical imformation:
polarimetry, beam diagnosis, …
Compton Chamber
g-ray Measured Asymmetry
A= -0.93±
0.15
laser%
pol. = - 79 %
A= 1.18± 0.15 %
laser pol. = + 79 %
M. Fukuda et al., PRL 91(2003)164801
Ne+ = 3 x 104/bunch
Pol(expected) = 77%
Asym (expected) = 0.95%
Measure e+ polarization :
use Bremsstrahlung g-ray
g-ray
polarized e+
E = 40 MeV
Pb conveter
calculation
e+ polarization (e+ run )
T. Omori et al., PRL 96 (2006) 114801
e- spin in Iron
e+ beam spin
A(R)= +0.60 ± 0.25%
e- spin in Iron
e+ beam spin
A(L)= -1.18 ± 0.27%
e-
spin in Iron
e+ beam spin
non
A(0)= -0.02 ± 0.25%
e+ run
T. Omori et al., PRL 96 (2006) 114801
A = 0.90 ±
0.18 %
Pol. = 73 %
We did e- run, also.
e+
run
e- run
e-
e+
Separation
magnet
e+
e-
W- target
W- target
e+
Separation
magnet
polarized
e-
e- polarization (e- run)
e- spin in Iron
e- beam spin
A(R)= +0.78 ± 0.27%
e- spin in Iron
e- beam spin
A(L)= -0.97 ± 0.27%
e-
spin in Iron
e- beam spin
non
A(0)= -0.23 ± 0.27%
e- run
A = 0.89 ±
0.19 %
Asymmetry Measurements
e- run
e+ run
A = 0.90 ±
0.18 %
T. Omori et al., PRL 96 (2006) 114801
A = 0.89 ±
0.19 %
Summary of Experiment
1) The experiment was successful.
High intensity short pulse polarized
e+ beam was firstly produced.
Pol. ~ 73 ± 15(sta) ± 19(sys) %
T. Omori et al., PRL 96 (2006) 114801
2) We confirmed propagation of the
polarization from laser photons ->
g-rays -> and pair created e+s & e-s.
3) We established polarimetry of
short pulse & high intensity g-rays,
positrons, and electrons.
2. Concept of Compton
+
polarized e source
for ILC
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
Summer 2004
ITRP(International Technology Recommendation Panel)
technology choice : cold LC (ILC)
cold LC : super conduction RF cavity for accel.
Before Summer 2004
Conceptual Design for warm LC
T. Omori et al., NIM A500 (2003) 232-252
+
10
Ne =1.2x10 /bunch
After Summer 2004
Study Compton applied to a cold LC.
New and Improved design
Full use of slow repetition rate (5Hz)
ILC requirements
ILC requirements
2x1010 e+/bunch (hard)
2800 bunches/train (hard)
5 Hz (we have time to store e + s)
Strategy
Old: Design for warm LC
T. Omori et al.,
NIM A500 (2003)
make positrons at once.
232-252
both electron & laser beams: throw away
New: Design for cold LC (ILC) Basic Idea:
Moenig
make positrons in 100 m sec. K.
P. Rainer
Electron storage ring,
laser pulse stacking cavity : Re-use !!!
positron stacking ring.
Laser Pulse Stacking Cavity
Fabry-perot Resonator
Input laser (YAGlaser)
Energy 1.2 mJ/bunch
3.077 nsec bunch spacing
train length = 50 msec
Cavity
Enhancement Factor =500
Laser pulse in cavity
600 mJ/bunch
single bunch in a cavity
Schematic View of Whole System
ILC: International Linear Collider
DR
e- lineac
e+ lineac
~ 50 km
DRs
Schematic View of Whole System
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
Cavity Compton Collab.: Hiroshima-Waseda-LAL-Kyoto-CERN-KEK
Make a fist
prototype
single cavity
Lcav = 420 mm
Put it in
ATF ring
Nov. 2006
.
Summary of ILC source design
Laser based scheme is good candidate of
ILC polarized e+ source.
We have new Idea
make positrons in 100 m sec.
Electron storage ring
laser pulse stacking cavitys
positron stacking ring (= e+ DRs)
1.6x1010 e+/bunch x 2800 bunches @ 5Hz
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
e+ beam pol.
(laser pol)
R
L
0 non (Liner)
e- spin in iron
(magnet pol.)
expected value
(MC)
Calculate A A(R) : A(R) ~ + 0.95 %
)
) Calculate A
) Calculate A
A(L) : A(L) ~ - 0.95 %
A(0) : A(0) = 0
Ng/electron/turn (in all energy of g-ray)
Compton Ring (e storage Ring)
-
2.0
CO2 ring
1.6
1.6
YAG ring
1.2
1.2
0.8
0.8
0.4
0.4
0
10
20 30 40 50
Turns
Average Ng/turn (in 23-29 MeV)
CO2 : 1.78x1010 /turn
(average in 50 turns)
0
20
40 60 80 100
Turns
YAG : 1.36x1010 /turn
(average in 100 turns)
0.03
-0.03
dEnergy/Energy
e+ stacking in Damping Ring (simulation)
i-th bunch on
j-th DR turn
1st bnch on 1st trn
5th bnch on 5th trn
10th bnch
on 10th trn
e+ in a bucket
Time
-0.4
0.4
Longitudinal Pos. (m)
~110 msec
T=0
before 11th bnch on
941st trn
11th bnch on 942nd trn
15th bnch on 946th trn
~10 msec
20th bnch
on 951st trn
before 21st bnch on
1882nd trn
~10 msec + 110 msec
~20 msec
100 bnchs on 9410th trn
100th bnch
~100 msec + 110 msec
100 bnchs on 18820th trn
stacking loss = 18%
in total
~110 msec
on 8479th trn
~200 msec