Monte Carlo simulation experiments on box-type radon dosimeter Khalid Jamil n , Muhammad Kamran, Ahsan Illahi, Shahid Manzoor Research in Modeling and Simulation (RIMS) Group, Physics Department, COMSATS Institute of Information Technology (CIIT), Park Road, Chak Shahzad, Islamabad, Pakistan article info Article history: Received 27 May 2014 Received in revised form 24 June 2014 Accepted 4 July 2014 Available online 14 July 2014 Keywords: Monte Carlo simulation Radon Carcinogenic Box-type dosimeter SSNTD Track registration efficiency abstract Epidemiological studies show that inhalation of radon gas ( 222 Rn) may be carcinogenic especially to mine workers, people living in closed indoor energy conserved environments and underground dwellers. It is, therefore, of paramount importance to measure the 222 Rn concentrations (Bq/m 3 ) in indoors environments. For this purpose, box-type passive radon dosimeters employing ion track detector like CR-39 are widely used. Fraction of the number of radon alphas emitted in the volume of the box type dosimeter resulting in latent track formation on CR-39 is the latent track registration efficiency. Latent track registration efficiency is ultimately required to evaluate the radon concentration which consequently determines the effective dose and the radiological hazards. In this research, Monte Carlo simulation experiments were carried out to study the alpha latent track registration efficiency for box type radon dosimeter as a function of dosimeter’s dimensions and range of alpha particles in air. Two different self developed Monte Carlo simulation techniques were employed namely: (a) Surface ratio (SURA) method and (b) Ray hitting (RAHI) method. Monte Carlo simulation experiments revealed that there are two types of efficiencies i.e. intrinsic efficiency (η int ) and alpha hit efficiency (η hit ). The η int depends upon only on the dimensions of the dosimeter and η hit depends both upon dimensions of the dosimeter and range of the alpha particles. The total latent track registration efficiency is the product of both intrinsic and hit efficiencies. It has been concluded that if diagonal length of box type dosimeter is kept smaller than the range of alpha particle then hit efficiency is achieved as 100%. Nevertheless the intrinsic efficiency keeps playing its role. The Monte Carlo simulation experimental results have been found helpful to understand the intricate track registration mechanisms in the box type dosimeter. This paper explains that how radon concentration from the experimentally obtained etched track density can be obtained. The program based on RAHI method is also given in this paper. & 2014 Elsevier B.V. All rights reserved. 1. Introduction Radon ( 222 Rn) is an alpha emitting radioactive inert gas pro- duced by traces of radium ( 226 Ra) present in indoors and outdoors environments [1]. Epidemiological studies show that inhalation of radon gas may cause cancer especially among the people living in closed indoor energy conserved environments, underground dwell- ings and uranium mine workers [2]. It is, therefore, of paramount importance to measure the 222 Ra concentrations in indoors envir- onments. Ion track detectors such as CR-39 have been widely employed for environmental radon measurements and dosimetry [1,3,4]. Modeling and Simulation has become an alternate of doing experiments in science, engineering and in particular to determine the efficiency of radiation detectors including ion track detectors [5–8]. Since alpha decay from radon is a stochastic phenomenon, the application of Monte Carlo technique is the most pertinent to model and simulate a box type dosimeter [9,10]. Monte Carlo simulation gives the results just like doing the real experiments. The response of any radon dosimeter is usually given as the calibration factor in track density rate per unit integrating radon concentration (tracks/cm 2 -h/Bq/m 3 ) [11–13]. In this research, latent track registration efficiency is the fraction of the number of radon alphas reaching the ion track detector surface out of the total radon alphas emitted within the volume of the box type dosimeter. If latent track density is determined by modeling and simulation then one can find the radon concentration (Bq/m 3 ) and eventually the radiological hazards. This research is purporting to understand the intricate radon latent alpha track registration mechanisms through the use of Monte Carlo simulation experiments. Two self developed Monte Carlo simulation models have been developed to simulate box type radon dosimeter. Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/nima Nuclear Instruments and Methods in Physics Research A http://dx.doi.org/10.1016/j.nima.2014.07.015 0168-9002/& 2014 Elsevier B.V. All rights reserved. n Corresponding author. E-mail address: kjamil@comsats.edu.pk (K. Jamil). Nuclear Instruments and Methods in Physics Research A 764 (2014) 18–23