Design of radiation hard spare units for the orbit corrector dipoles of LHC

Due to the High Luminosity upgrade of the Large Hadron Collider (HL-LHC), the orbit corrector dipoles located just before the interaction points of the accelerator will receive significantly increased gamma radiation doses, i.e., up to 20 MGy over the HL-LHC lifetime. Since these magnets were not designed to withstand such high gamma doses, new MCBC and MCBY magnets have to be designed and produced using radiation hard impregnation insulation and materials. In this paper, we describe both the gamma radiation campaign we are performing to determine the radiation hardness of the present MCBC and MCBY magnets and the new design and technologies that we have selected for the manufacturing of radiation hard spare units. We also discuss the impact of failing MCBC and MCBY magnets on the LHC and the foreseen alternative solutions.