Zang, L. and Bailey, I. and Woski, A. (2008) Studies on the role of a photon collimator for the ILC positron source. Working Paper. UNSPECIFIED.
Full text not available from this repository.Abstract
A positron source based on a helical undulator provides the capability of producing a beam of polarised positrons. The degree of polarisation of the positrons depends upon the polarisation of the photons produced from the undulator; the polarisation of the photons in turn depends on the photon energy and production angle. We calculate the photon energy spectrum and polarisation for one design of the helical undulator for the International Linear Collider (ILC), investigate approximations commonly made in calculating these quantities, and explore the role of a photon collimator in improving the positron polarisation.