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 Fp which is defined as Fp=ρ/(ρiC0t)-1, where ρi 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. Fp 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 ρi (m) and the removed active layer thickness x (μm) has been determined as ρi=-0.0041+0.0011x. 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.