A proposal is presented in this paper to modify the extraction line polarimeter chicane to allow the Compton backscattered electrons to be deflected further from the beam line, and to provide optics for the downstream GAMCAL detector. IntroductionThe current version of the extraction line polarimeter chicane as shown in figure 1 has four magnets located between z = 120 to 175 m [1]. We propose to run the last two polarimeter magnets BVEX3P and BVEX4P at 1½ the B-field of the first two magnets BVEX1P and BVEX2P. With the higher field the Compton electrons are deflected further away from the beam line allowing the Cherenkov detector to cover a larger range of the Compton scattered spectrum. Two additional magnets downstream of the polarimeter chicane close the orbit of the extracted beam for transport to the dump. These magnets will be used by the Gamma Calorimeter (GAMCAL) detector [2].

One of the two ILC Interaction Regions will have a large horizontal crossing angle which would allow to extract the spent beams in a separate beam line. In this paper, the extraction line design for 20 mrad crossing angle is presented. This beam line transports the primary e + /e − and beamstrahlung photon beams from the IP to a common dump, and includes diagnostic section for energy and polarization measurements. The optics is designed for a large energy acceptance to minimize losses in the low energy tail of the disrupted beam. The extraction optics, diagnostic instrumentation and particle tracking simulations are described.

A study of the beam distributions in the 2 mrad and 14/20 mrad extraction lines are presented. Beam losses, energy losses due to synchrotron radiation and spin diffusion are shown. Synchrotron radiation distributions generated by the beam as it traverses the extraction lines are studied.