ar X iv : 0 70 9 . 28 59 v 1 [ ph ys ic s . in s - de t ] 1 8 Se p 20 07 Simulation Studies and Detector Scenarios for an ILC Polarimeter

Electron polarimetry at the International Linear Collider (ILC) will be based on Compton scattering using a laser colliding head-on with the incident lepton beam in the beam delivery system. The shape of the differential Compton cross section depends strongly on the helicity states of electron beam and laser. Asymmetries can then be determined from different helicity configurations, which scale with the longitudinal polarization of the electron bunches [2]. At ILC energies of 250 GeV or more, the angular distributions of both the scattered photons and the recoil electrons are constrained to within a few μrad for all but the most highly energetic photons. The polarimeter, therefore, will be placed in a magnet chicane serving as a spectrometer for the recoil electrons (see figure 1). The setup consists of four sets of dipoles in such a way that the emittance of the incident electron beam should not be impaired by more than 1%. The electrons are first displaced parallel to their original direction by about 2 cm to the side by two sets of dipoles. After that, a pulsed laser (10 ps with 35 μJ) hits the bunches head-on and deflects about 10 out of the 20 · 10 electrons.