Deterioration and recovery of BF 3 counters due to operation in intense radiation fields

Abstract

A number of BF 3 counters was irradiated under operating conditions in a neutron field 1.2×10 4 n v and gamma ray fields of various fluxes between 15 and 64000 R/h. The counters underwent a degradation common to all regardless of the kind and flux of the external radiation. The degradation speed was slower for the operation at a lower gas multiplication and at a higher temperature, 40°C. Many of the counters exhibited a recovery at a certain amount of irradiation (∼ 10 4 R and ∼ 10 10 n vt) and were stable for further irradiation. The degradation was characterized by the signal pulse height reduction. The cathode inner surface analysis was conducted after the irradiation. More fluorine was found on the cathode surface of a recovered counter than on that of a non-recovered one. The deterioration-recovery mechanism is discussed.