ILC Positron Source Based on Laser Compton

Abstract

Positron generation is one of the most difficult technical challenges among the ILC (International Linear Collider) subsystems. A positron source based on Laser Compton back scattering is an attractive and advanced option for the ILC positron source. Here, the positrons are generated, via the pair creation process, from high energy gamma rays which themselves are produced by Compton scattering of laser photons off a high‐energy electron beam. Polarized positrons can be generated by employing a circularly polarized laser. The positron polarization is easily controlled and switched by changing the laser polarity. The electron beam can be unpolarized. The required electron energy is only a few GeV (in contrast, the “undulator scheme”, another advanced option, requires at least 100 GeV or more) and the system can be prototyped and tested prior to the real construction. The laser Compton technology has many other applications like advanced X‐ray sources and a good synergy is expected. In addition, this technology can be a powerful driving force for the ILC project attracting many researchers from outside the ILC community. The ILC positron source is a technical challenge and it will be realized only if the latest technologies are integrated seamlessly with the necessary R&D efforts for system specific issues. The latest technologies include high power lasers, high brightness electron beams, high finesse optical cavities for as laser‐beam interaction point, etc. We present the design status and the related experimental efforts for the ILC positron source based on Laser Compton scattering. The respective advantages of various options for the electron beam (based on Linac, storage ring, and ERL) are also compared.