1. E166 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) E166: Polarized Positrons for Future Linear Colliders Kirk T. McDonald & John C. Sheppard, Co-spokespeople

2. 2 Overview of E166 Demonstration experiment for production of polarized positron beams Demonstration experiment for production of polarized positron beams 1 m long helical undulator produces 0-10 MeV circularly polarized  ‘s from 50 GeV e - (10 10 e - /pulse, 30 Hz) in the FFTB at SLAC 1 m long helical undulator produces 0-10 MeV circularly polarized  ‘s from 50 GeV e - (10 10 e - /pulse, 30 Hz) in the FFTB at SLAC Conversion of polarized  ‘s to polarized positrons in 0.5 rad Ti-target Conversion of polarized  ‘s to polarized positrons in 0.5 rad Ti-target Expected positron polarization of 50-60% to be measured by the Compton transmission method after reconversion of e +‘s to  ‘s Expected positron polarization of 50-60% to be measured by the Compton transmission method after reconversion of e +‘s to  ‘s

3. 3 Status of E166 Negotiating for runs in June and September, 2005 in the FFTB Negotiating for runs in June and September, 2005 in the FFTB All equipment is at SLAC and installed in FFTB tunnel All equipment is at SLAC and installed in FFTB tunnel except the Undulator, which is in final alignment at SLAC (800  m id bore aligned to 700  m id protection collimator) except the Undulator, which is in final alignment at SLAC (800  m id bore aligned to 700  m id protection collimator) Ready for power system tests and beam Ready for power system tests and beam