E 166 Polarized Positrons for Future Linear Colliders

E 166 “Polarized Positrons for Future Linear Colliders” John C. Sheppard E 166 Co-spokesman SLAC: August 31, 2004

Introduction • • • Overview and purpose of E 166 Experimental Setup Status & Milestones

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

Overview of E 166 • • • Demonstration experiment for production of polarized e+ FFTB at SLAC with 50 Ge. V, 1010 e-/pulse , 30 Hz 1 m long helical undulator produces circular polarized radiation 0 -10 Me. V Conversion of photons to positrons in 0. 5 rad Ti-target Measurement of polarization of positrons by Compton transmission method Idea from Alexander Michailichenko 4

Polarized positrons at linear colliders • • The >150 Ge. V electron beam itself is used for the production of polarized positrons Electron beam passes a 200 m 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/ ILC

E 166 Equipment

E 166 Undulator Area

Spectrometer Area

Beam Intensities & Energies • 1010 electrons/bunch @ 50 Ge. V into the undulator 5 x 106 ph. E 4 x 109 photons @ < 10 Me. V 5 x 104 ph. E 4 x 109 photons 2 x 107 e+ 4 x 107 photons ~ 500 Te. V 4 x 105 e+ 1 x 103 photons of total ~ 5 Ge. V (~ 5 Me. V)

The helical undulator • • 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 E 166 Length 240 m 1 m Beam 150 Ge. V Period 10 mm 2. 4 mm Strength K 1 0. 17 Cutoff ~10 Me. V 9. 6 Me. V Positrons 3 x 1010 2 x 107

Undulator radiation • Produced photons, cutoff and polarization Energy spectrum Polarization +1 5 Me. V -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 / d. N/d. E • Target: Ti or W-Re, yield 0. 5 % Energy spectrometer: spread 20% Positron energy (Me. V) 5 Me. V Extraction Counts • Pos. energy (Me. V)

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

Aerogel flux counters and Si-W calorimeter • Aerogel energy threshold: 4. 3 Me. V Ø • Photon flux measurement Si-W calorimeter Ø Ø Ø 4 x 4 Stack of 20 plates of W (1 rad. length thickness) Up to 500 Te. V 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“ Cs. I 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 „E 166“ Data Analysis

E 166 Milestones

E 166 Schedule • Now thru October 1, 2004: Ø Ø • October 1 st thru November 1 st : Ø • Develop DAQ (T 467) Develop/build equipment Install Equipment Pre. Beam Equipment Checkout, Backgrounds, Initial Data Run January 1 st thru February 1 st, 2005 : Ø Checkout, Backgrounds, Initial Data Run

E-166 Beamline Schematic 50 Ge. V, low emittance electron beam 2. 4 mm period, K=0. 17, helical undulator 10 Me. V, polarized photons 0. 5 r. l. converter target 51%-54% positron polarization Moffeit/Woods

E-166 Beam Request The SLAC FFTB: • Built to Demonstrate LC FFS: 60 -70 nm rms spot • 28 - 50 Ge. V Beam Energy • e = 1. 5 x 10 -5/ 1. 5 x 10 -6 m-rad (x/y) • sz = 50 -500 mm • Nb = 0. 1 -4 x 1010 e-/bunch • 2. 5 k. W Power Limit (1 x 1010 @ 30 Hz and 50 Ge. V) • 1 W Continuous Beam Loss Limit

SLAC FFTB

SLAC FFTB

E 166 FFTB Tunnel 1

E 166 FFTB Tunnel 2

E 166 FFTB Optics, RHI

E 166 PS: B 406

E 166 DAQ: B 407

E 166 Cs. I and Electronics, B 407

E 166 Cs. I and Electronics, B 407

SLAC FFTB, IP 1

SLAC FFTB: B 06 G, PC 7. 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 • • • E 166 is a demonstration of production of polarized positrons for future linear colliders Uses the 50 Ge. V FFTB at SLAC Approved by SLAC in June 2003 • Installation of total experiment in FFTB tunnel in August, September, October(? ) 2004 • First data taking run in October 2004 Second data taking run in January 2005 •

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