A tire comprising a rubber composition based on at least one diene elastomer, a reinforcing filler predominantly comprising silica, a crosslinking system, and an alkali metal hydroxide or alkaline earth metal hydroxide. A sensor in the tube utilizes opposing C and I shaped magnetic cores attached to opposing ends of the support tube. 5\xd71014 neutrons cm\u22122 s\u22121 and more preferably greater than 1\xd71015 neutrons cm\u22122 s\u22121 for a predetermined period of time preferably from 20 days to 30 days and more preferably approximately 25 days to convert a substantial fraction of the Am-241 to Cm-242, e.