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ILD-TECH-PUB-2017-001, 12 June 2017, "Impact of Beam-Gas Interactions of the IP region of ILD", Robert Karl and Jenny List.
Abstract: Due to two changes in the ILC baseline design which reduce the focal length of the final doublet and introduce an additional beam position monitor, the forward region of ILD has to be redesigned. Within this context, the option of removing the vacuum pump from the forward region of ILD is under consideration. This removal would imply a degradation of the vacuum resulting in a higher background of beam-gas interactions. Therefore, the interactions between the electron bunch of the ILC and the residual gas atoms in the interaction region of ILD, their pressure dependency and their impact on the detector was studied with Geant4-based simulations. It has been shown that beam-gas collisions constitute a non-negligible, but minor source of background even if the pump is removed.