Radiation Environment in the Dispersion Suppressor regions of IR1 and IR5 of the LHC

This report presents the expected annual dose and high energy particle fluences due to point losses and beam-gas interactions in the dispersion suppressor regions (covering the magnet string Q8-Q11 and the dipoles) downstream of the high luminosity interaction points IP1 and IP5. Results show that some areas in the dispersion suppressors will be found with doses comparable to the arc annual levels (i.e. several Gy/y to several tens Gy/y), although positioning of the more radiation sensitive equipment will be important due to the non-uniformity of the dose distribution. Hot-spot region with doses per year > 100 Gy are observed in the vicinity of MB9A, MB9B, the empty cryostat and Q11. Details of dose to the quench diodes are also provided. An indication of the minimum dose value required for the radiation hardness of equipment to be placed in the dispersion suppressors of IR1 and IR5 is given. In addition, discussion will be extended to the expected dose in the dispersion suppressor regions of Point 3 & 7 in the light of predicted proton loss distributions for these sections of the LHC ring. In comparison to the expected dose in DS1 and DS5, the maximum annual dose in DS3 and DS7 is expected to be much lower. To enable investigation of possible electronics problems due to Single Event Effects, details of the expected particle fluences in the LHC tunnel of the dispersion suppressors are presented in the form of fluence : dose ratio maps. These are given for a range of particle energy cuts (100 keV - 100 MeV). It is found that the radiation environment (R=fluence/dose) is the same for both DS1 and DS5 regions.