Energy Deposition due to Secondary Particles in The Helical Undulator\n Wall at ILC-250GeV

In the future, International Linear Collider (ILC), a helical undulator based\npolarized positron source is expected to be chosen. A high energy electron beam\npasses through a superconducting helical undulator in order to create\ncircularly polarized photons which will be directed to a conversion target, the\nresult of which, will be electron-positron pairs. The resulting positron beam\nis longitudinally polarized. In order to produce the required number of\npositrons in ILC250 the full undulator length is needed. Since the photons are\ncreated with an opening angle and traveling through a 320 m long undulator, it\nis expected that the superconducting undulator vacuum will be hit by the\nphotons. Photon masks are needed to be inserted in the undulator line to keep\nthe power deposition in the vacuum below the acceptable limit which is 1W/m. A\ndetailed study of the power deposition in the vacuum and masks is needed in\norder to design the photon masks. This paper describes the power deposition in\nthe undulator vacuum due to secondary particles assuming an ideal undulator. In\naddition, the mask model is proposed.\n