Simulation of a microstrip proportional detector for radon and daughter detection by MCNPX Code

Many detection methods have been applied to detect radon gas. Due to the low noise and high resolution of gas detectors compared to semiconductor detectors or scintillation detectors, using them to detect alpha radiation is very considerable. Microstrip proportional detector is also included in this group and it has not been used for the detection of radon. In this article, response of the microstrip gas detector to alpha particles from radon and its daughters has been investigated in low radiation fields in the range of 1-103Bq/m3 using MCNPX code. First the radon volumetric source above the Mylar is transferred to surface source. For an alpha particle that enters the active volume from the Mylar lower surface, the loss of energy has been achieved as a function of distance along the track. To scrutinize this detector, the energy loss above the anode strips is also calculated as a function of angle and energy. The findings show that increase in the incident angle of the particle result in the increase in the maximum amount of energy loss. Moreover, because of the proportionality of detector, by increasing the energy, energy loss per unit length is reduced and as a result, pulse height is decreased with increasing particle energy. With the increase of the alpha incident angle, the number of anode strips producing pulse is increased but the pulse duration is reduced. Therefore, due to the sensitivity of the microstrip detector to the angle and the energy of alpha particles of radon and its daughters at low activities, the detector can be considered as a good choice for radon detection, as studied in this paper.