JCS e + /e - Source Development and E166 J. C. Sheppard, SLAC June 15, 2005

JCS Parameters/Specifications ILC e- and e+ Sources Bunch trains at 5 Hz 2820 bunches per train (upgrade to 5600) ns bunch spacing in(?) and out of the DR’s (850  s) 2x10 10 e + per bunch out of the DR’s (upgrade to 1x10 10 ) e- Polarization > 80% (upgrade to e+ Polarization)

JCS Laser System generates Pulse Train -Unique laser system to generate the ILC pulse train and charge -Electron gun R&D - Main goal: Improve HV performance to reduce Space Charge Limit - Electrode Materials (Ti, Mo) and design - Improved Vacuum Performance beyond Torr to eliminated ion and electron backbombradment of cathode - Photocathode R&D -Further increase polarization above 90 % -Measurement of physics increases with square of polarization! -Improve Quantum Efficiency, Lifetime and robustness -Explore other potential cathode materials - Bunching and preacceleration is closely related to source performance - Polarization control through-out machine Polarized e- Source R&D based on polarized DC – Gun A. Brachmann, SLAC

JCS Polarized e- Source Polarized RF – Gun R&D RF gun advantages: –High gradient results in an e - beam of several MeV at the source (compared to several 100’s of keV for a DC gun) –Initial acceleration by RF fields allows shorter bunches and reduces requirements for subharmonic bunching and pre-acceleration as well as damping ring design Present RF Gun technology does not allow the use of GaAs cathodes Main challenge is the required vacuum to eliminate ion back-bombardment So far, all experimental evaluations of GaAs cathodes in RF guns have been conducted with equipment not designed to provide the UHV needed! We propose the development of an RF gun that meets the necessary vacuum requirements –Extensive simulations and design –Experimental program using the L-band RF in ESB A. Brachmann, SLAC

JCS POSITRON PRODUCTION SCHEMES EM Shower e + to damping rings Conventional Undulator-based (from USLCTOS) W-Re Target 6 GeV e -

JCS Generic Positron Source, polarized, photon or conventional From last ½ radiation length of target and downstream, the issues are the same with a few differences related to beam spray and corresponding power levels (details are important) ---Will always run design to Damage Threshold of the Target--- target e -, γ flux concentrator or SC coil ~5T Solenoid, ~1T Solenoid, 0.5T  L-band NC capture section e-e- e+e+ SC pre-accelerator “Adiabatic matching device: capture optics” 6-D aperture

JCS e+ Design Issues Capture into DR phase space Target Station Design for undulator based system and for conventional system Capture Optics: SC coil pair and pulsed flux concentrator Downstream Heat Load and Activation Undulator optimization studies e- Drive Linac specifications Keep Alive Source Layout Development

JCS

TDR R&D Topics Undulator Prototype AMD Engineering and Prototype: SC dc coils and pulsed flux concentrator Rotating Shaft: vacuum:water:radiation environment Remote Handling

JCS E166 Collaboration About 45+2 members from 16+1 institutions from all three regions (Asia, Europe, the Americas, and Daresbury) John Sheppard, Kirk McDonald (co- spokesmen) E166: Polarized Positrons for Future Linear Colliders Kirk T. McDonald & John C. Sheppard, Co-spokespeople

JCS Overview of E166 Demonstration experiment for production of polarized positrons In the FFTB at SLAC with 50 GeV, e - /pulse, 30 Hz 1 m long helical undulator produces circular polarized  ‘s 0-10 MeV Conversion of photons to positrons in 0.5 rad Ti-target Measurement of polarization of positrons by Compton transmission method

JCS Status of E166 Run June and September, 2005 in the FFTB Tuning up 46.6 GeV beam thru undulator Working on Undulator/Beam/Detector Alignment Good progress to date; 2 more weeks of running in June

JCS Summary: e-/e+ Sources Draft Design Description for Snowmass Selection of ILC Baseline Design Baseline Technical Description by End of 2005 CDR Text and Cost in late 2006 TDR Work to Start in 2006 E166 Running

JCS Snowmass: WG3A e-/e+ Sources