Studies on recoil proton tracks in NTA films with the [formula omitted] reaction

Abstract

Recoil proton tracks in nuclear emulsion are counted by scanning them using strip, square or circular field of view of optical microscope. In this paper, the overestimate due to the edge effects in counting recoil proton tracks at different neutron energies produced from the T( d, n) 4 He reaction has been determined by measuring the true track density in NTA film. The overestimate has also been calculated using the measured value of the mean projected track length ( L) in the film. The percentage of measured overestimates has been compared with those obtained by calculation and the results agree reasonably well. Fading effect in NTA film has been studied and found to be 22% more in the summer than in the winter season. A great reduction in fading rate could be achieved if the films are desiccated and sealed in highly pure dry nitrogen maintained at an over-pressure of 1000 Pa to reduce water vapour ingress. After the edge effect correction, the sensitivity of NTA film has been calculated from (1.72±0.08)×10 −3 tracks n −1 to (1.97±0.16)×10 −3 tracks n −1 in the neutron energy ranges from 15.91 to 18.88 MeV . The response was found to be from 0.24±0.02 tracks cm −2 per mSv to 0.26±0.01 tracks cm −2 per mSv in the same energy range.