NLC The Next Linear Collider Project Towards an

NLC - The Next Linear Collider Project Towards an Undulator Based NLC Positron Source Tuesday June 26, 2002 LCD Meeting, SLAC R. Pitthan and J. Sheppard/Pitthan 21 October 2021

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 21 October 2021 Sheppard/Pitthan 2

NLC - The Next Linear Collider Project Concepts 21 October 2021 Sheppard/Pitthan 3

NLC - The Next Linear Collider Project Change in Direction of NLC Positron Effort • 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 Ge. V 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 21 October 2021 Sheppard/Pitthan 4

NLC - The Next Linear Collider Project NLC Polarized Positron System Layout 21 October 2021 Sheppard/Pitthan 5

NLC - The Next Linear Collider Project NLC Polarized Positron Target Station Layout 21 October 2021 Sheppard/Pitthan 6

NLC - The Next Linear Collider Project What’s Going On? What’s the Status? Codes: Mat. Lab files, EGS 4 -Pol, Beam. Path Undulator: K 1, lu = 1. 4 -0. 7 cm, helical Search for Optimization: Eb, lu, 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) 21 October 2021 Sheppard/Pitthan 7

NLC - The Next Linear Collider Project Use of a Microundulator to Study Positron Production We had a discussion at LC 02 to explore the possibilities of using a microundulator and the damped, 50 Ge. V SLAC beam in the FFTB to study positron production. Expectedly warm response from all e+ folks 21 October 2021 Sheppard/Pitthan 8

NLC - The Next Linear Collider Project An Immodest Proposal Use the SLAC 50 Ge. V, 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 Do this in the next 22 -42(? ) months in the FFTB enclosure: • Proof of Principle Demonstration • Validate Codes • Develop g Spin Diagnostics • Develop e+ Spin Diagnostics • Maybe Get a Surprise (better not) 21 October 2021 Sheppard/Pitthan 9

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. 21 October 2021 Sheppard/Pitthan 10

NLC - The Next Linear Collider Project FFTB Beams Size <50 mm to thread through a narrow submm-gap undulator • Divergence < 1/g Critical parameters in red 21 October 2021 Sheppard/Pitthan 11

NLC - The Next Linear Collider Project Positron Polarization as a Function of Positron Energy 21 October 2021 Sheppard/Pitthan 12

NLC - The Next Linear Collider Project Positron Polarization as a Function of Positron Energy 21 October 2021 Sheppard/Pitthan 13

NLC - The Next Linear Collider Project Positron Spectra for Different Ti Target Lengths 21 October 2021 Sheppard/Pitthan 14

NLC - The Next Linear Collider Project Positron Polarization for Different Ti Lengths 21 October 2021 Sheppard/Pitthan 15

NLC - The Next Linear Collider Project Positron Polarization for Different Ti Lengths 21 October 2021 Sheppard/Pitthan 16

NLC - The Next Linear Collider Project What Does the Hardware Look Like? 21 October 2021 Sheppard/Pitthan 17

NLC - The Next Linear Collider Project What is Required 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 21 October 2021 Sheppard/Pitthan 18

NLC - The Next Linear Collider Project 2. 4 mm l 0 SC, bifilar helical undulator prototype: A. Mikhailichenko Cornell Univ. , 5/21/02 21 October 2021 Sheppard/Pitthan 19

NLC - The Next Linear Collider Project 2. 4 mm l 0 SC, bifilar helical undulator prototype: A. Mikhailichenko Cornell Univ. , 5/21/02 21 October 2021 Sheppard/Pitthan 20

NLC - The Next Linear Collider Project 2. 4 mm l 0 Pulsed Cu helical undulator prototype: A. Mikhailichenko Cornell Univ. , 5/29/02 21 October 2021 Sheppard/Pitthan 21

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 ebeams by different r. l. Ti targets, measure relative polarization in the E 158 Møller Spectrometer. Projected relative accuracy 1% (Chudakov). 21 October 2021 Sheppard/Pitthan 22

NLC - The Next Linear Collider Project EPOLEGS 4: Polarized e- thru Different Targets 21 October 2021 Sheppard/Pitthan 23

NLC - The Next Linear Collider Project EPOLEGS 4: Polarized e- thru Different Targets 21 October 2021 Sheppard/Pitthan 24

NLC - The Next Linear Collider Project EPOLEGS 4: Polarized e- thru Different Targets 21 October 2021 Sheppard/Pitthan 25

NLC - The Next Linear Collider Project What’s Going On? • 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+? 21 October 2021 Sheppard/Pitthan 26

NLC - The Next Linear Collider Project Summary • No Summary, Just Discussion. 21 October 2021 Sheppard/Pitthan 27