HV Training as a Cure for the Ageing in the Outer Tracker

The straw-tubes modules of the Outer Tracker detector suffer from gain loss under irradiation at moderate intensities. High voltage training beyond the proportional regime, producing large dark currents, has been shown to repair the gain loss in most cases, and even prevent future radiation damage until certain irradiation doses. This note summarizes the HV training studies and their results and proposes a recipe for application in situ at LHCb.