Thermal-Photon and Residual-Gas Scattering in the NLC Beam Delivery

Without collisions, the largest contribution to the beam lifetime in LEP is Compton scattering off thermal photons. Even if only a few particles are scattered in a single pass, the potential background generated could make this effect important for the NLC as well. We used a modified version of the tracking program DIMAD, which includes a Monte Carlo simulation for the Compton scattering on thermal photons, to calculate the fraction of scattered particles that are intercepted by downstream aperture restrictions and to determine the loss locations. We also studied particle losses due to other scattering processes. For all processes, the effect of additional collimators in the final focus was investigated.