Measurement of parameters of tracks in CR-39 detector from replicas.

In determining the etched track rate in solid-state nuclear track detectors, track lengths should be determined accurately. A method based on surface profilometry is proposed to determine the track lengths in CR-39 detectors through measurements of their replicas. Tracks from alpha particles with an incident energy of 4 MeV have been chosen to demonstrate the method. After irradiation and chemical etching, resin replicas were made from the tracks, of which the heights were measured by the Form Talysurf PGI Profilometer. The results showed that the surface of the replicas were smooth and the heights of the replicas were uniform, so the replicating fluid should have filled the tracks completely and the replicas truly reflected the dimensions of the tracks. The heights of the replicas were conveniently determined from the lateral view of the replicas generated by the Form Talysurf PGI Profilometer.

Theoretical basis for long-term measurements of equilibrium factors using LR 115 detectors.

In this paper, we propose a method to determine the equilibrium factor using a bare LR 115 detector. The partial sensitivities rhoi of the LR 115 detector to 222Rn and its alpha-emitting short-lived progeny, 218Po and 214Po, were investigated. We first determined the distributions of lengths of major and minor axes of the perforated alpha tracks in the LR 115 detector produced by 222Rn, 218Po and 214Po through Monte Carlo simulations. The track parameters were calculated using a track development model with a published V function, by assuming a removed active layer of 6.54 microm. The distributions determined for different alpha emitters were found to completely overlap with one another. This implied equality of partial sensitivities for radon and its progeny, which was also confirmed through analytical considerations. Equality of partial sensitivities makes possible convenient measurements of the proxy equilibrium factor Fp, which is defined in the present work as (F1+F3) and is equal to the ratio between the sum of concentrations of the two alpha emitting radon progeny (218Po+214Po) to the concentration of radon gas (222Rn). In particular, we have found Fp = (rho/rhoitC0)-1, where rho (track/m2) is the total track density on the detector, rhoi = 0.288 x 10(-2) m, t is the exposure time and C0 (Bq/m3) is the concentration of 222Rn. If C0 is known (e.g. from a separate measurement), we can obtain Fp. The proxy equilibrium factor Fp is also found to be well correlated with the equilibrium factor between radon gas and its progeny through the Jacobi room model. This leads to a novel method for long-term determination of the equilibrium factor.