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

Introduction Overview and purpose of E166 Overview and purpose of E166 Experimental Setup Experimental Setup Status & Milestones Status & Milestones

Collaboration About 45+2 members from 16+1 institutions from all three regions (Asia, Europe, the Americas, and Daresbury) About 45+2 members from 16+1 institutions from all three regions (Asia, Europe, the Americas, and Daresbury) John Sheppard, Kirk McDonald (co-spokesmen) John Sheppard, Kirk McDonald (co-spokesmen)

4 Overview of E166 Demonstration experiment for production of polarized e + Demonstration experiment for production of polarized e + FFTB at SLAC with 50 GeV, e - /pulse, 30 Hz FFTB at SLAC with 50 GeV, e - /pulse, 30 Hz 1 m long helical undulator produces circular polarized radiation 0-10 MeV 1 m long helical undulator produces circular polarized radiation 0-10 MeV Conversion of photons to positrons in 0.5 rad Ti-target Conversion of photons to positrons in 0.5 rad Ti-target Measurement of polarization of positrons by Compton transmission method Measurement of polarization of positrons by Compton transmission method Idea from Alexander Michailichenko

Polarized positrons at linear colliders The >150 GeV electron beam itself is used for the production of polarized positrons The >150 GeV electron beam itself is used for the production of polarized positrons Electron beam passes a 200m helical undulator (50% surplus) Electron beam passes a 200m helical undulator (50% surplus) After conversion, the positrons are captured and accelerated After conversion, the positrons are captured and accelerated They collide with a subsequent bunch train 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 ILC/

E166 Equipment

E166 Undulator Area

Spectrometer Area

Beam Intensities & Energies GeV into the undulator 4 x 10 9 < 10 MeV 4 x 10 5 e + 4 x 10 9 photons 4 x 10 7 photons ~ 500 TeV 5 x 10 4 phE 5x10 6 phE 1 x 10 3 photons of total ~ 5 GeV (~ 5 MeV) 2 x 10 7 e +

The helical undulator Rotating magnetic field Rotating magnetic field Wire winded helically Wire winded helically Inner diameter 0.89 mm Inner diameter 0.89 mm Magnetic field: 0.76 T Magnetic field: 0.76 T Pulsed current: 2300 A Pulsed current: 2300 A Rate 30 Hz Rate 30 Hz e - /pulse incident e - /pulse incidentParameterNLCE166Length 240 m 1 m Beam 150 GeV 50 GeV Period 10 mm 2.4 mm Strength K Cutoff ~10 MeV 9.6 MeV Positrons 3 x x 10 7

Undulator radiation Produced photons, cutoff and polarization Produced photons, cutoff and polarization 5 MeV +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 Polarization / dN/dE Positron energy (MeV) MaterialPolarization Ti 0.25 rad. 52 % Ti 0.5 rad. 53 % W-Re 0.5 rad. 49 % Pos. energy (MeV) Counts 5 MeV Extraction

CsI Calorimeter „DESY Zeuthen and Humboldt University Berlin“ „DESY Zeuthen and Humboldt University Berlin“ Pack 3 x 3 crystals in a stack Pack 3 x 3 crystals in a stack CsI crystals: ~ 6 cm X 6 cm X 28 cm from DESY CsI crystals: ~ 6 cm X 6 cm X 28 cm from DESY ~1000 Re-converted photons -> Max 5 GeV ~1000 Re-converted photons -> Max 5 GeV Readout by PIN diodes (large linear dynamic range) Readout by PIN diodes (large linear dynamic range) 14 degrees aparture 14 degrees aparture Magnet W-Target  e+e+

Aerogel flux counters and Si-W calorimeter Aerogel energy threshold: 4.3 MeV Aerogel energy threshold: 4.3 MeV  Photon flux measurement Si-W calorimeter Si-W calorimeter  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 ComponentStatusInstitution Helical undulator 1.0 m prototype „Cornell University“ Positron transport system In design „Princeton University“ Analyzer magnets In construction „DESY Hamburg“ CsI calorimeter Prototype, In construction „DESY Zeuthen/ Humboldt Unversity Berlin Si-W calorimeter Ready „University Tenessee“ Aerogel counters Ready „Princeton University“ DAQ and Readout Ready„SLAC“ Data Analysis In Discussion „E166“

E166 Milestones

E166 Schedule Now thru October 1, 2004: Now thru October 1, 2004:  Develop DAQ (T467)  Develop/build equipment  Install Equipment  PreBeam Equipment Check October 1 st thru November 1st : October 1 st thru November 1st :  Checkout, Backgrounds, Initial Data Run January 1 st thru February 1 st, 2005 : January 1 st thru February 1 st, 2005 :  Checkout, 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: nm rms spot GeV Beam Energy  = 1.5x10 -5 / 1.5x10 -6 m-rad (x/y)  z =  m N b = 0.1-4x10 10 e - /bunch 2.5 kW Power Limit (1x10 30 Hz and 50 GeV) 1 W Continuous Beam Loss Limit

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

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 demonstration of production of polarized positrons for future linear colliders E166 is a demonstration of production of polarized positrons for future linear colliders Uses the 50 GeV FFTB at SLAC Uses the 50 GeV FFTB at SLAC Approved by SLAC in June 2003 Approved by SLAC in June 2003 Installation of total experiment in FFTB tunnel in August, September, October(?) 2004 Installation of total experiment in FFTB tunnel in August, September, October(?) 2004 First data taking run in October 2004 First data taking run in October 2004 Second data taking run in January 2005 Second data taking run in January 2005

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