1. NLC - The Next Linear Collider Project Sheppard/Pitthan June 26, 2015 Towards an Undulator Based NLC Positron Source Towards an Undulator Based NLC Positron Source Tuesday June 26, 2002 LCD Meeting, SLAC R. Pitthan and J. Sheppard

2. Sheppard/PitthanJune 26, 2015 2 NLC - The Next Linear Collider Project Contacts Roger Carr, SSRL Max Cornacchia, SSRL Ralph Nelson, SLAC RP Roman Tatchyn, SSRL Helmut Wiedemann, SSRL Klaus Flöttmann, DESY Alexander Mikhailichenko, Cornell Yuri Batygin, SLAC NLC Vinod Bharadwaj, SLAC LCLS/NLC Artem Kulikov, SLAC PEPII David Schultz, SLAC NLC Maria Caturla, LLNL Werner Stein, LLNL

3. Sheppard/PitthanJune 26, 2015 3 NLC - The Next Linear Collider Project Concepts

4. Sheppard/PitthanJune 26, 2015 4 NLC - The Next Linear Collider Project Put development of NLC conventional e+ source on hold Use resources to investigate the feasibility of a polarized positron source for the NLC Look into the use of a K  1 helical undulator and 150 GeV NLC primary electron beam for polarized positron production Because of drawback of coupling e + production to primary e -, investigate other options: back scattered laser (Compton) short-period novel undulator on dedicated beam Change in Direction of NLC Positron Effort

5. Sheppard/PitthanJune 26, 2015 5 NLC - The Next Linear Collider Project NLC Polarized Positron System Layout

6. Sheppard/PitthanJune 26, 2015 6 NLC - The Next Linear Collider Project NLC Polarized Positron Target Station Layout

7. Sheppard/PitthanJune 26, 2015 7 NLC - The Next Linear Collider Project Codes: MatLab files, EGS4-Pol, BeamPath Undulator: K  1, u = 1.4-0.7 cm, helical Search for Optimization: E b, u, K, target material and thickness, collection scheme Photon Beam Specification Target Studies: Ti-alloy: hydro and radiation damage study launched at LLNL Effect on primary electron beam, studies begun; commissioning and operating scenarios Open also to Compton based photon sources (lasers and FELs) What’s Going On? What’s the Status?

8. Sheppard/PitthanJune 26, 2015 8 NLC - The Next Linear Collider Project We had a discussion at LC02 to explore the possibilities of using a microundulator and the damped, 50 GeV SLAC beam in the FFTB to study positron production. Expectedly warm response from all e+ folks Use of a Microundulator to Study Positron Production

9. Sheppard/PitthanJune 26, 2015 9 NLC - The Next Linear Collider Project Use the SLAC 50 GeV, low emittance beam in conjunction with a  1-2 mm period helical undulator to demonstrate undulator based production of polarized positrons for linear colliders Measure the yield, spectrum, and polarization of both the photons and positrons An Immodest Proposal Do this in the next 22-42(?) months in the FFTB enclosure: Proof of Principle Demonstration Validate Codes Develop  Spin Diagnostics Develop e+ Spin Diagnostics Maybe Get a Surprise (better not)

10. Sheppard/PitthanJune 26, 2015 10 NLC - The Next Linear Collider Project What’s the Big Idea? Goals: demonstrate the viability of undulator based positron production, both polarized and unpolarized measure the yield, spectrum, and polarization gammas and positrons. design (steal, borrow) conversion, collection, and detection systems validate the microundulator-photon production codes Many opportunities for collaboration amongst collider laboratories, and including experimenters from both the colliding physics and the fixed target physics communities who are experts in polarimetry. Efforts for the development of such a collaboration underway.

11. Sheppard/PitthanJune 26, 2015 11 NLC - The Next Linear Collider Project FFTB Beams Size <50  m to thread through a narrow sub- mm-gap undulator Divergence < 1/  Critical parameters in red

12. Sheppard/PitthanJune 26, 2015 12 NLC - The Next Linear Collider Project Positron Polarization as a Function of Positron Energy

13. Sheppard/PitthanJune 26, 2015 13 NLC - The Next Linear Collider Project Positron Polarization as a Function of Positron Energy

14. Sheppard/PitthanJune 26, 2015 14 NLC - The Next Linear Collider Project Positron Spectra for Different Ti Target Lengths

15. Sheppard/PitthanJune 26, 2015 15 NLC - The Next Linear Collider Project Positron Polarization for Different Ti Lengths

16. Sheppard/PitthanJune 26, 2015 16 NLC - The Next Linear Collider Project Positron Polarization for Different Ti Lengths

17. Sheppard/PitthanJune 26, 2015 17 NLC - The Next Linear Collider Project What Does the Hardware Look Like?

18. Sheppard/PitthanJune 26, 2015 18 NLC - The Next Linear Collider Project A fully modeled experiment which simulates results and identifies hardware requirements Beam line design to determine accelerator hardware specifications Cost and schedule development Acceptance of proposal and release of funds Construction, Installation, Checkout, and Commissioning Do experiment and compare with simulations What is Required

19. Sheppard/PitthanJune 26, 2015 19 NLC - The Next Linear Collider Project 2.4 mm l 0 SC, bifilar helical undulator prototype: A. Mikhailichenko Cornell Univ., 5/21/02

20. Sheppard/PitthanJune 26, 2015 20 NLC - The Next Linear Collider Project 2.4 mm l 0 SC, bifilar helical undulator prototype: A. Mikhailichenko Cornell Univ., 5/21/02

21. Sheppard/PitthanJune 26, 2015 21 NLC - The Next Linear Collider Project 2.4 mm l 0 Pulsed Cu helical undulator prototype: A. Mikhailichenko Cornell Univ., 5/29/02

22. Sheppard/PitthanJune 26, 2015 22 NLC - The Next Linear Collider Project Experimental Anchor Point Needed Since there is no experimental data on polarization (or loss) in scattering, propose a Testbeam Experiment in Sector 0 (the “Ladder” Experiment): Scatter the SLAC polarized electron e - beams by different r.l. Ti targets, measure relative polarization in the E- 158 Møller Spectrometer. Projected relative accuracy 1% (Chudakov).

23. Sheppard/PitthanJune 26, 2015 23 NLC - The Next Linear Collider Project EPOLEGS4: Polarized e- thru Different Targets

24. Sheppard/PitthanJune 26, 2015 24 NLC - The Next Linear Collider Project EPOLEGS4: Polarized e- thru Different Targets

25. Sheppard/PitthanJune 26, 2015 25 NLC - The Next Linear Collider Project EPOLEGS4: Polarized e- thru Different Targets

26. Sheppard/PitthanJune 26, 2015 26 NLC - The Next Linear Collider Project Need viable polarimetry for demonstration Proposal by Summer’s End (2002) Thoughts on Depolarization via ionization loss? (Multiple scatter does not look to be a problem) Is electron experiment useful? Is demonstration required? What if NLC produces partially polarized e+? What’s Going On?

27. Sheppard/PitthanJune 26, 2015 27 NLC - The Next Linear Collider Project Summary No Summary, Just Discussion.