Proposed Method to Produce a Highly Polarized e+ Beam for Future Linear Colliders

We propose a method to produce a spin-polarized e + beam using e + e - pair-creation by circularly polarized photons. Assuming Compton scattering of an unpolarized e - beam and circularly polarized laser light, scattered γ-rays at the high end of the energy spectrum are also circularly polarized. If those γ-rays are utilized to create e ± pairs on a thin target, the spin-polarization is preserved for e +'s at the high end of their energy spectrum. By using the injector linac of Accelerator Test Facility at KEK and a commercially available Nd:YAG pulse laser, we can expect about 105 polarized e +'s per second with a degree of polarization of 80% and a kinetic energy of 35–80 MeV. The apparatus for creation and measurement of polarized e +'s is being constructed. We present new idea for possible application of our method to future linear colliders by utilizing a high-power CO2 laser.