Detecting Alpha-induced Radioluminescence in the UVC Wavelength Range Using a UVTron Flame Sensor, and the Effect of a Gas Flow on Detection Rates as Compared to an Air Atmosphere

Alpha-induced radioluminescence provides a potential avenue for the detection of alpha-emitting materials from a distance far greater than the travel of alpha-particles themselves. This work details experiments carried out into the detection of this radioluminescence in the ultraviolet C wavelength range (180-280 nm) using an off-the-shelf flame sensor, the UVTron (Hamamatsu, Japan). There is less interference from natural and artificial background lighting in the ultraviolet C wavelength range than at other ultraviolet wavelengths. A UVTron flame sensor (R9533, Hamamatsu, Japan), which is sensitive only in the ultraviolet C wavelength range, was used to detect the presence of a 6.95 MBq 210 Po source at a distance of approximately 20 mm. The signal (0.3280 counts per second) was over 147 times that of the background, which was very low (2.224 × 10 -3 counts per second) under the general laboratory/commercial lighting conditions. The limit of detection, where the signal can be distinguished from background, can be calculated to be approximately 240 mm under these conditions, assuming a standard 1/r 2 , which is much greater than the alpha particle travel. Gas was flowed over the alpha sample to determine if this would enhance the radioluminescence and hence the detection by the UVTron. Gases of Ar, Xe, Ne, N2, Kr and P10 were tested, all of which increased the signal detected by the UVTron sensor. The greatest increase was found to be in a flow of Xe, which greater than doubled the counts per second of the detector in one instance. The ability of the UVTron to detect the radioluminescence from alpha-emitting materials and the enhancement which may be possible using a flow of gas, indicate the potential of the UVTron sensor for inclusion in an alpha-emitting materials detection system which could be operated at a distance in the field, for example for nuclear decommissioning characterisation purposes or nuclear security applications