Passive monitoring of the equilibrium factor inside a radon exposure chamber using bare LR 115 SSNTDs

In this paper, we propose and study a method using bare LR 115 SSNTDs for passive monitoring of the equilibrium factor F inside a radon exposure chamber. The method is based on the proxy equilibrium factor F_p which is defined as F_p = ρ / (ρ_i C₀ t) - 1, where ρ_i is the partial sensitivity (i.e., the number of tracks per unit area per unit exposure), C₀ is the radon gas concentration and t is the exposure time. F_p was found to be well correlated with F. LR 115 detectors were exposed in a huge exposure chamber with a volume of 43 m³, with integrated radon exposure and equilibrium factor as 100 kBq m^-3 h and 0.680, respectively. The relationship between ρ_i (m) and the removed active layer thickness x (μm) has been determined as ρ_i = - 0.0041 + 0.0011 x. The method has also been verified through determination of the equilibrium factor from the track densities on the LR 115 detectors. The mean of the mid points of the determined ranges of F for a few LR 115 SSNTDs can give a very good estimate of the true equilibrium factor. © 2006 Elsevier B.V. All rights reserved.