Investigations toward the development of polarized and unpolarized high intensity positron sources for linear colliders

In the present work possibilities for a high intensity, polarized or unpolarized positron source for linear colliders are investigated. We consider a source, based on the conversion of high energy photons in a thin target. The photons are generated in a wiggler or undulator. Beside the possibility of generating polarized positrons, a source based on the conversion of photons offers also important advantages with respect to the maximum obtainable intensities. Future linear colliders require positron sources, able to deliver intensities up to two orders of magnitude higher than existing sources. The first part of this paper deals with the intensity problem. After optimizing all components of the source (i.e. photon source, target and capture optics), parameters of a high intensity positron source (up to 4.1014 e+/s) are summarized. Problems of the source operation are discussed. The second part of the paper concerns the possibilities of a polarized source. In order to take care of the processes in the shower, the calculation of polarization states has been introduced into the already existing Monte-Carlo program EGS 4, so that a complete simulation of the polarized source is possible