Transcript E166 “Polarized Positrons for Future Linear Colliders” John C. Sheppard E166 Co-spokesman SLAC: August 31, 2004

E166
“Polarized Positrons for
Future Linear Colliders”
John C. Sheppard
E166 Co-spokesman
SLAC: August 31, 2004
Introduction
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Overview and purpose of E166
Experimental Setup
Status & Milestones
Collaboration
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About 45+2
members from
16+1 institutions
from all three
regions
(Asia, Europe,
the Americas,
and Daresbury)
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John Sheppard,
Kirk McDonald
(co-spokesmen)
Overview of E166
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Demonstration experiment for production of polarized e+
FFTB at SLAC with 50 GeV, 1010 e-/pulse , 30 Hz
1 m long helical undulator produces circular polarized
radiation 0-10 MeV
Conversion of photons to positrons in 0.5 rad Ti-target
Measurement of polarization of positrons by Compton
transmission method
Idea from
Alexander Michailichenko
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Polarized positrons
at linear colliders
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The >150 GeV electron beam itself is used for the production
of polarized positrons
Electron beam passes a 200m helical undulator (50% surplus)
After conversion, the positrons are captured and accelerated
They collide with a subsequent bunch train
E-166 Experiment
E-166 is a demonstration of undulator-based
production of polarized positrons for linear colliders:
- Photons are produced in the same energy range and
polarization characteristics as for a linear collider;
-The same target thickness and material are used as in
the linear collider;
-The polarization of the produced positrons is expected
to be in the same range as in a linear collider.
-The simulation tools are the same as those being used
to design the polarized positron system for a linear
collider.
- However, the intensity per pulse is low by a factor of
2000.
TESLA, NLC/USLCSG, and E-166 Positron Production
ILC/
Table 1: TESLA, NLC/USLCSG,
E-166 Polarized Positron Parameters
Parameter
Units
TESLA*
NLC
E-166
ILC
GeV
150-250
150
50
Beam Energy, Ee
10
9
3x10
8x10
1x1010
Ne/bunch
2820
190
1
Nbunch/pulse
Hz
5
120
30
Pulses/s
planar
helical
helical
Undulator Type
1
1
0.17
Undulator Parameter, K
cm
1.4
1.0
0.24
Undulator Period u
st
MeV
9-25
11
9.6
1 Harmonic Cutoff, Ec10
photons/m/e
1
2.6
0.37
dN/dL
m
135
132
1
Undulator Length, L
Ti-alloy Ti-alloy Ti-alloy, W
Target Material
r.l.
0.4
0.5
0.5
Target Thickness
%
1-5
1.8†
0.5
Yield
%
25
20
Capture Efficiency
12
12
8.5x10
1.5x10
2x107
N+/pulse
3x1010
8x109
2x107
N+/bunch
%
40-70
40-70
Positron Polarization
*TESLA baseline design; TESLA polarized e+ parameters (undulator and
polarization) are the same as for the NLC/USLCSG
† Including the effect of photon collimation at  = 1.414.
E166 Equipment
E166 Undulator Area
Spectrometer Area
Beam Intensities &
Energies
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1010 electrons/bunch @ 50GeV into the undulator
5x106 phE
4 x 109 photons @ < 10 MeV
5 x 104 phE
4 x 109 photons
2 x 107 e+
4 x 107 photons ~ 500 TeV
4 x 105 e+
1 x 103 photons of total ~ 5 GeV
(~ 5 MeV)
The helical
undulator
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Rotating magnetic field
Wire winded helically
Inner diameter 0.89 mm
Magnetic field: 0.76 T
Pulsed current: 2300 A
Rate 30 Hz
1010 e-/pulse incident
Parameter
NLC
E166
Length
240 m
1m
Beam
150 GeV
50 GeV
Period
10 mm
2.4 mm
Strength K
1
0.17
Cutoff
~10 MeV
9.6 MeV
Positrons
3 x 1010
2 x 107
Undulator radiation
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Produced photons, cutoff and polarization
30.6
K 2 phot
phot



0
.
37
dL  mm 1  K 2 m e 
m e
dN
2

Ee / 50 GeV  
EC  24 MeV 
 9.6 MeV
2
 mm1  K 
Energy spectrum
Polarization
+1
5 MeV
5 MeV
-1
Target and
spectrometer
Material
Polarization
Ti 0.25 rad.
52 %
Ti 0.5 rad.
53 %
W-Re 0.5 rad.
49 %
With Photons from Undulator
Polarization / dN/dE
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Target: Ti or W-Re, yield 0.5 %
Energy spectrometer: spread 20%
Positron energy (MeV)
5 MeV
Extraction
Counts
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Pos. energy (MeV)
CsI Calorimeter
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„DESY Zeuthen and Humboldt University Berlin“
Pack 3 x 3 crystals in a stack
CsI crystals: ~ 6 cm X 6 cm X 28 cm from DESY
~1000 Re-converted photons -> Max 5 GeV
Readout by PIN diodes (large linear dynamic range)
14 degrees aparture
Magnet

e+
W-Target
Aerogel flux counters
and Si-W calorimeter
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Aerogel energy threshold: 4.3 MeV
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Photon flux measurement
Si-W calorimeter
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4 x 4 Stack of 20 plates of W
(1 rad. length thickness)
Up to 500 TeV signal
Total energy of undulator photons
Status of
Subcomponents
Component
Status
Helical undulator
1.0 m prototype „Cornell University“
Positron transport
system
In design
Institution
„Princeton University“
Analyzer magnets
In construction „DESY Hamburg“
CsI calorimeter
Prototype,
„DESY Zeuthen/
In construction Humboldt Unversity
Berlin
Si-W calorimeter
Ready
„University Tenessee“
Aerogel counters
Ready
„Princeton University“
DAQ and Readout
Ready
„SLAC“
In Discussion
„E166“
Data Analysis
E166 Milestones
E166 Schedule
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Now thru October 1, 2004:
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October 1st thru November 1st :
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Develop DAQ (T467)
Develop/build equipment
Install Equipment
PreBeam Equipment Check
Checkout, Backgrounds, Initial Data Run
January 1st thru February 1st, 2005 :
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Checkout, Backgrounds, Initial Data Run
E-166 Beamline Schematic
50 GeV, low emittance electron beam
2.4 mm period, K=0.17, helical
undulator
10 MeV, polarized photons
0.5 r.l. converter target
51%-54% positron polarization
Moffeit/Woods
E-166 Beam Request
E-166 Beam Parameters
Ee
GeV
50
frep
Hz
30
Ne
e1x1010
ex=ey
m-rad
3x10-5
xy
m
5.2, 5.2
sx,sy
mm

sE/E


The SLAC FFTB:
•Built to Demonstrate LC FFS: 60-70 nm rms spot
•28- 50 GeV Beam Energy
• e = 1.5x10-5/ 1.5x10-6 m-rad (x/y)
• sz = 50-500 mm
• Nb = 0.1-4x1010 e-/bunch
• 2.5 kW Power Limit (1x1010 @ 30 Hz and 50 GeV)
• 1 W Continuous Beam Loss Limit
SLAC FFTB
SLAC FFTB
E166 FFTB Tunnel 1
E166 FFTB Tunnel 2
E166 FFTB Optics, RHI
E166 PS: B406
E166 DAQ: B407
E166 CsI and Electronics,
B407
E166 CsI and Electronics,
B407
SLAC FFTB, IP1
SLAC FFTB:B06G, PC7.5
SLAC FFTB: Det. Tables
SLAC FFTB  Table
Cornell: Undulators
DESY-HH: Analyzer Magnets
E-166 Beam Measurements
•Photon flux and polarization as a function of K.
•Positron flux and polarization for K=0.17, 0.5 r.l. of Ti vs.
energy.
•Positron flux and polarization for 0.1 r.l. and 0.25 r.l. Ti and
0.1, 0.25, and 0.5 r.l. W targets.
•Each measurement is expected to take about 20 minutes.
•A relative polarization measurement of 10% is sufficient to
validate the polarized positron production processes
Conclusions
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E166 is a demonstration of production of
polarized positrons for future linear colliders
Uses the 50 GeV FFTB at SLAC
Approved by SLAC in June 2003
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Installation of total experiment in FFTB tunnel in
August, September, October(?) 2004
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First data taking run in October 2004
Second data taking run in January 2005
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The end
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