Studies of the Time Response of Electronic Radon Detectors

Studies of the Time Response of Electronic Radon Detectors S. Georgieva, I. Dimitrovaa, V. Todorova, B. Krasteva,b, K. Miteva,* a) Sofia Universtiry ‘St. Kliment Ohridski’, Faculty of Physics, Bulgaria b) Department of Radiotherapy, University Oncology Hospital “Prof. Ivan Chernozemski”, 1756 Sofia, Bulgaria * Presenting author. Email: [email protected] Session: NSS-16 ID: N-16-228 Why is time-response important? Model function of time-response based on the Bateman equations for 222Rn, 218Po and 214Po activities: + Radon concentrations can vary quickly within few hours Analytical solutions Experimental system to study the time-response Time-response can be characterized: Time-response of different detectors to rectangular pulses Objectives In this work we have explored experimental and theoretical methods to determine the time-response function of the detectors. We have developed an experimental setup and experimental procedures to expose the detectors to delta-like spikes of radon and to evaluate the timeresponse function. In parallel, we have created an analytical model based on the Bateman equations to describe the time-response of the detectors. The results of the experimental studies show that the developed approach is feasible, and the model accurately represents the measured time series. This allows to deduce the response of the electronic radon detectors to arbitrary change of the ambient radon concentrations. Motivation A new generation of electronic radon (222Rn) detectors has emerged over the past decade. These are inexpensive devices that use passive 222Rn sampling and are based on ionization chambers or diode detectors to detect the alpha particles emitted by 222Rn and its short-lived progeny. Combined with appropriate data collection and storage protocols, these detectors have proven to be very effective for generating reliable time-series data of 222Rn concentrations in dwellings and workplaces. Challenges Metrological testing of these devices has demonstrated their reliable performance and they have been shown to provide accurate long-term radon exposure estimates such as the yearly average radon concentration in dwellings and workplaces. One of the most promising applications of electronic radon detectors is real-time monitoring of 222Rn in workplaces and the estimation of working time correction factors. The main challenge in these applications is the delayed response of these detectors, which stems from two factors: the passive sampling of radon from the environment via diffusion, and the behavior (buildup and decay) of radon progeny within the active volume of the detectors. Conclusions and future work We have developed an experimental setup and procedures to evaluate the time-response function of electronic radon detectors. In parallel, we have created an analytical model based on the Bateman equation to describe the time response. The results from the experimental studies demonstrate that the developed approach is feasible, and the model accurately represents the measured time series. Acknowledgement: This work is supported by the project RadonNET (23IND07), which received funding from the European Partnership on Metrology (ID: 10.13039/100019599), co-financed from the European Union’s Horizon Europe Research and Innovation Programme and by the Participating States. 𝐶𝑀= 𝑖=1,2,4𝜀𝑖𝐶𝑖 𝐶𝑀𝑡 =𝐶0𝑟𝑒𝑓 1−𝑒−𝜆𝑑𝑡 𝑖=1,2,4𝜀𝑖𝐹0𝑖 𝐹01 =𝑒−𝜆1𝑡𝐹02 =𝜆2𝑒−𝜆1𝑡−𝑒−𝜆2𝑡 𝜆2−𝜆1 𝐹03 = 𝑙=1 3𝑒−𝜆𝑙𝑡 𝑞=2 3𝜆𝑞 𝑘=1,𝑘≠𝑙 3𝜆𝑘−𝜆𝑙𝐹04 = 𝑙=1 4𝑒−𝜆𝑙𝑡 𝑞=2 4𝜆𝑞 𝑘=1,𝑘≠𝑙 4𝜆𝑘−𝜆𝑙 𝐶𝑀(𝑡+𝑇)=𝐶0𝑟𝑒𝑓 1−𝑒−𝜆𝑑𝑇𝑒−𝜆1𝑇 𝑖=1,2,4𝜀𝑖𝐹𝑇𝑖 𝐹𝑇1 =𝐹01(𝑇)𝑒−𝜆1 ∗𝑡 𝐹𝑇2 =𝜆2𝑒−𝜆1 ∗𝑡−𝑒−𝜆2𝑡𝐹01(𝑇) 𝜆2−𝜆1 ∗+𝐹02(𝑇)𝑒−𝜆2𝑡 𝐹𝑇4 =𝐹0𝑖(𝑇)𝑒−𝜆𝑖𝑡+ 𝑗=1 𝑖−1 𝐹0𝑗 𝑙=𝑗 𝑖𝑒−𝜆𝑙𝑡 𝑞=𝑗+1 𝑖𝜆𝑞 𝑘=𝑗,𝑘≠𝑙 𝑖(𝜆𝑘−𝜆𝑙) 𝜆1 ∗=𝜆1+𝜆𝑑 In the expression for 𝐹𝑇4 , 𝜆1is replaced by 𝜆1 ∗ 𝐶𝑖(𝑡)=𝐶0𝑖 𝑒−𝜆𝑖𝑡+ 𝑗=1 𝑖−1𝐶0𝑗 𝑙=𝑗 𝑖𝑒−𝜆𝑙𝑡 𝑞=𝑗+1 𝑖𝜆𝑞 𝑘=𝑗,𝑘≠𝑙 𝑖(𝜆𝑘−𝜆𝑙) Parameters of the model functions Parameter RadonEye T=60 min RadonEye T=180 min AlphaE T=60 min λd (min-1) 0.0472(40) 0.0440(47) 0.1141(59) ε1 0.321(76) 0.310(96) 0.142(17) ε2= ε4 0.248(41) 0.351(48) 0.486(10)