New cathode design boron lined proportional counters for neutron area monitoring application

A new cathode design boron lined proportional counter of 26 mm ID × 100 mm sensitive length SS304 cathode has been developed with boron-coated baffles separated by 3 mm spacers inserted in the sensitive volume perpendicular to the axis. The baffles and the spacers were coated with indigenously available 27.7% enriched 10B. The introduction of baffles enhanced the boron coated surface area by a factor of 2.8. Tests in 120 nv thermal neutron flux show that the counter has 0.84 cps/nv thermal neutron sensitivity, which shows enhancement in the sensitivity by a factor of 2.78 due to baffle structure. For comparison standard cylindrical cathode geometry counter coated with 92% enriched 10B on its inner wall with a coating thickness of 0.8 mg / cm 2 is developed with same outer dimensions for neutron area monitoring applications. The counter has 1 cps/nv thermal neutron sensitivity. Comparative tests carried out on counters with and without baffle structure show that the baffles enhance the neutron sensitivity and in 2 kR/h gamma background the effect of gamma pile up is similar on both the counters. The variation in cathode internal diameter due to baffle structure gives higher voltage plateau slope (2.8%/10 V) as compared to conventional cylindrical geometry counter (1.2%/10 V). The usability of boron lined counters for neutron area monitoring applications for the cylindrical geometry counter has been studied.