Estimation of extra dose contribution in the LHC arcs arising from proton losses far downstream of the high luminosity interaction points IP1 & IP5

This work continues the study of expected doses in the LHC arc sections, previously reported for the beam-gas interaction case. Further contributions to the annual dose arise due to the off-momentum proton losses downstream of the high luminosity interaction points IP1 and IP5. To determine whether these losses are an important consideration, this report presents updated dose maps for the LHC arc sections taking into account proton point loss distributions in the region of QF13 and beyond (specifically QF15, QF17 and QF19) for the arcs downstream of IP1 and IP5. Typical doses of ~5-10Gy/y will be observed in the vicinity of the arc quadrupoles and alongside the first downstream dipole for QF13 and QF15, reaching a maximum dose of ~35Gy/y close to the quadrupole magnet of QF13. Dose distributions beyond QF19 are essentially unmodified by the extra point loss contributions and the annual dose maps for arc sections downstream of Q19 will be given by those reported in the publications of dose due to beam-gas interactions alone. A good estimation of the radiation resistance of equipment to be placed in the arc sections of the LHC machine will thus be given by the study of dose due to beam-gas interactions alone (i.e. few tens Gy/y multiplied by the lifetime of the LHC machine and any relevant safety margins). This value is not significantly altered for the regions of estimated maximum dose in the LHC arcs of a few tens Gy/y alongside the arc quadrupole and the adjacent downstream dipole when we include the extra dose contribution from point losses