E166
“Polarized Positrons for Future Linear Colliders”
John C. SheppardJohn C. Sheppard
E166 Co-spokesmanE166 Co-spokesman
SLAC: August 31, 2004SLAC: August 31, 2004
Introduction
• Overview and purpose of E166Overview and purpose of E166• Experimental SetupExperimental Setup• Status & MilestonesStatus & Milestones
Collaboration
• About About 45+2 45+2 membersmembers from from 16+1 16+1 institutionsinstitutions from from all three regionsall three regions(Asia, Europe, (Asia, Europe, the Americas, the Americas, and Daresbury)and Daresbury)
• John Sheppard, John Sheppard, Kirk McDonald Kirk McDonald (co-spokesmen)(co-spokesmen)
4
Overview of E166
• Demonstration experimentDemonstration experiment for production of polarized e for production of polarized e++
• FFTB at SLAC with FFTB at SLAC with 50 GeV, 1050 GeV, 101010 e e--/pulse , 30 Hz/pulse , 30 Hz• 1 m long1 m long helical undulator produces helical undulator produces circular polarizedcircular polarized
radiation radiation 0-10 MeV0-10 MeV• Conversion of photons to Conversion of photons to positrons positrons in 0.5 rad Ti-targetin 0.5 rad Ti-target• MeasurementMeasurement of polarization of positrons by of polarization of positrons by Compton Compton
transmission methodtransmission method
Idea fromAlexander Michailichenko
Polarized positrons at linear colliders
• The >150 GeV electron beam The >150 GeV electron beam itselfitself is used for the is used for the production of polarized positronsproduction of polarized positrons
• Electron beam passes a Electron beam passes a 200m helical undulator200m helical undulator (50% (50% surplus)surplus)
• After conversion, the positrons are capturedAfter conversion, the positrons are captured and and acceleratedaccelerated
• They collide with a subsequent bunch train They collide with a subsequent bunch train
E-166 ExperimentE-166 is a demonstration of undulator-based E-166 is a demonstration of undulator-based production of polarized positrons for linear colliders:production of polarized positrons for linear colliders:- Photons are produced in the same energy range and - Photons are produced in the same energy range and polarization characteristics as for a linear collider;polarization characteristics as for a linear collider;
-The same target thickness and material are used as -The same target thickness and material are used as in the linear collider;in the linear collider;
-The polarization of the produced positrons is -The polarization of the produced positrons is expected to be in the same range as in a linear expected to be in the same range as in a linear collider.collider.
-The simulation tools are the same as those being -The simulation tools are the same as those being used to design the polarized positron system for a used to design the polarized positron system for a linear collider.linear collider.
- However, the intensity per pulse is low by a factor of - However, the intensity per pulse is low by a factor of 2000.2000.
TESLA, NLC/USLCSG, and E-166 Positron Production Table 1: TESLA, NLC/USLCSG, E-166 Polarized Positron Parameters
Parameter Units TESLA* NLC E-166 Beam Energy, Ee GeV 150-250 150 50 Ne/bunch - 3x1010 8x109 1x1010
Nbunch/pulse - 2820 190 1 Pulses/s Hz 5 120 30 Undulator Type - planar helical helical Undulator Parameter, K - 1 1 0.17 Undulator Periodu cm 1.4 1.0 0.24 1st Harmonic Cutoff, Ec10 MeV 9-25 11 9.6 dN/dL photons/m/e- 1 2.6 0.37 Undulator Length, L m 135 132 1 Target Material - Ti-alloy Ti-alloy Ti-alloy, W Target Thickness r.l. 0.4 0.5 0.5 Yield % 1-5 1.8† 0.5 Capture Efficiency % 25 20 - N+/pulse - 8.5x1012 1.5x1012 2x107
N+/bunch - 3x1010 8x109 2x107
Positron Polarization % - 40-70 40-70 *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.
ILC
ILC/
E166 Equipment
E166 Undulator Area
Spectrometer Area
Beam Intensities & Beam Intensities & EnergiesEnergies
• 1010 electrons/bunch @ 50GeV into the undulator
4 x 109 photons @ < 10 MeV
4 x 105 e+
4 x 109 photons
4 x 107 photons ~ 500 TeV
5 x 104 phE5x106 phE
1 x 103 photons of total ~ 5 GeV(~ 5 MeV)
2 x 107 e+
The helical undulator
• RotatingRotating magnetic field magnetic field• Wire winded Wire winded helicallyhelically• Inner diameter Inner diameter 0.89 mm0.89 mm• Magnetic field: Magnetic field: 0.76 T0.76 T• Pulsed current: Pulsed current: 2300 A2300 A• Rate Rate 30 Hz30 Hz• 10101010 e e--/pulse incident/pulse incident
ParameterParameter NLCNLC E166E166
LengthLength 240 m240 m 1 m1 m
BeamBeam 150 GeV150 GeV 50 GeV50 GeV
PeriodPeriod 10 mm10 mm 2.4 mm2.4 mm
Strength KStrength K 11 0.170.17
CutoffCutoff ~10 MeV~10 MeV 9.6 MeV9.6 MeV
PositronsPositrons 3 x 103 x 101010 2 x 102 x 1077
Undulator radiation
• Produced photons, cutoff and polarizationProduced photons, cutoff and polarization
em
phot
em
phot
K
K
mmdL
dN37.0
1
6.302
2
MeV
Kmm
GeVEMeVE e
C 6.91
50/24
2
2
5 MeV
-1
+1
PolarizationEnergy spectrum
5 MeV
Target and spectrometer
• Target: Ti or W-Re, yield 0.5 %Target: Ti or W-Re, yield 0.5 %• Energy spectrometer: spread 20%Energy spectrometer: spread 20%
With Photons from Undulator
Po
lari
zati
on
/ d
N/d
E
Positron energy (MeV)
MaterialMaterial PolarizatioPolarizationn
Ti 0.25 rad.Ti 0.25 rad. 52 %52 %
Ti 0.5 rad.Ti 0.5 rad. 53 %53 %
W-Re 0.5 rad. W-Re 0.5 rad. 49 %49 %
Pos. energy (MeV)
Co
un
ts
5 MeV Extraction
CsI Calorimeter
• „„DESY Zeuthen and Humboldt University Berlin“DESY Zeuthen and Humboldt University Berlin“• Pack Pack 3 x 3 crystals3 x 3 crystals in a stack in a stack• CsI crystals: ~ 6 cm X 6 cm X 28 cm from CsI crystals: ~ 6 cm X 6 cm X 28 cm from DESYDESY• ~1000 Re-converted photons~1000 Re-converted photons -> Max 5 GeV -> Max 5 GeV• Readout by Readout by PIN diodesPIN diodes (large linear dynamic range) (large linear dynamic range)• 14 degrees aparture14 degrees aparture
Magnet
W-Target
e+
Aerogel flux countersAerogel flux countersand Si-W calorimeterand Si-W calorimeter
• Aerogel energy threshold: 4.3 MeVAerogel energy threshold: 4.3 MeV Photon flux measurementPhoton flux measurement
• Si-W calorimeterSi-W calorimeter 4 x 4 Stack of 4 x 4 Stack of 20 plates of W20 plates of W
((1 rad. length1 rad. length thickness) thickness) Up to Up to 500 TeV500 TeV signal signal Total Total energy energy of of undulator photonsundulator photons
Status of Subcomponents
ComponentComponent StatusStatus InstitutionInstitutionHelical undulatorHelical undulator 1.0 m 1.0 m
prototypeprototype„„Cornell University“Cornell University“
Positron transport Positron transport systemsystem
In designIn design „„Princeton Princeton University“University“
Analyzer magnetsAnalyzer magnets In constructionIn construction „„DESY Hamburg“DESY Hamburg“
CsI calorimeterCsI calorimeter Prototype,Prototype,
In constructionIn construction„„DESY Zeuthen/ DESY Zeuthen/ Humboldt Unversity Humboldt Unversity BerlinBerlin
Si-W calorimeterSi-W calorimeter ReadyReady „„University University Tenessee“Tenessee“
Aerogel countersAerogel counters ReadyReady „„Princeton Princeton University“University“
DAQ and ReadoutDAQ and Readout ReadyReady „„SLAC“SLAC“
Data AnalysisData Analysis In DiscussionIn Discussion „„E166“E166“
E166 Milestones
E166 Schedule
• Now thru October 1, 2004: Now thru October 1, 2004: Develop DAQ (T467)Develop DAQ (T467) Develop/build equipmentDevelop/build equipment Install EquipmentInstall Equipment PreBeam Equipment CheckPreBeam Equipment Check
• October 1October 1stst thru November 1st : thru November 1st : Checkout, Backgrounds, Initial Data RunCheckout, Backgrounds, Initial Data Run
• January 1January 1stst thru February 1 thru February 1stst, 2005 : , 2005 : Checkout, Backgrounds, Initial Data RunCheckout, Backgrounds, Initial Data Run
E-166 Beamline Schematic
Moffeit/Woods
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
E-166 Beam Request
The SLAC FFTB:•Built to Demonstrate LC FFS: 60-70 nm rms spot•28- 50 GeV Beam Energy• = 1.5x10-5/ 1.5x10-6 m-rad (x/y)• z = 50-500 m• 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
• E166 is a E166 is a demonstrationdemonstration of production of of production ofpolarized positrons for future linear colliderspolarized positrons for future linear colliders
• Uses the Uses the 50 GeV50 GeV FFTB at SLAC FFTB at SLAC• ApprovedApproved by SLAC in June 2003 by SLAC in June 2003
• Installation of total experiment in FFTB tunnel Installation of total experiment in FFTB tunnel in August, September, October(?) 2004in August, September, October(?) 2004
• First data taking run in October 2004First data taking run in October 2004• Second data taking run in January 2005Second data taking run in January 2005
The endThe end
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