A calibration methodology for the novel radioluminescence detector systems
Creators: name: Krasniqi, Faton S.
name: Taubert, Richard Dieter
name: Röttger, Stefan
name: Luchkov, Maksym
name: Mertes, Florian
name: Honig, Anja
name: Baltruschat, Christoph
name: Dangendorf, Volker
name: Giesen, Ulrich
Publisher: name: Physikalisch-Technische Bundesanstalt
Year: 2023
Subjects: Alpha particles
Optical detection
Radioluminescence
Activity standard
Radiance standard
Emergency management

description: Radioluminescence mapping using well-characterized and optimized optical systems is an effective method for localizing contaminations with alpha-emitting radionuclides. To apply this novel approach to radiological emergency management, nuclear safeguards, nuclear decommissioning, and nuclear forensics, an established traceability chain is required. Within the EMPIR project 19ENV02 RemoteALPHA, SI-traceable calibration standards and procedures have been developed to provide the metrological basis for optical detection of alpha-emitting radionuclides. This work presents the development and implementation of a novel calibration methodology to provide valuable information about, and confidence in, the performance of radioluminescence detection systems. The proposed calibration methodology is based on two complementary approaches: (a) application of well-characterized activity standards to establish a traceable relationship between radioluminescence intensity and alpha activity, and (b) use of all-optical radiation-based devices that, when calibrated against an alpha activity standard, simulate the radioluminescence induced in nitrogen (N2) and nitric oxide (NO) gases by alpha particles in specific spectral regions. A dedicated 210Po alpha activity standard with a sharp peak of less than 32 keV FWHM at 5:3MeV and a surface activity of 648 kBq has been developed and used to characterize a lens-based radioluminescence detection system in terms of its sensitivity to alpha-induced radioluminescence in different atmospheres (air, N2, N2 + NO mixture) in the UV-A and UV-C (solar blind) spectral regions. This detection system was used as an intermediary transfer device to cross-calibrate two portable integrating sphere-based radiance standards designed to simulate radioluminescence in the UV-A and UV-C spectral regions. The UV-A radiance standard simulates alpha source activities from 3:6 104 Bq to 5:1 108 Bq (340nm central wavelength, 12nm bandwidth), whereas the UV-C one from 4:4 105 Bq to 8:7 104 Bq (260nm central wavelength, 16nm bandwidth). These radiance standards substantially simplify routine quality control of radioluminescence detection systems by eliminating the need for open alpha sources, which are always associated with strict radiation safety precautions. Furthermore, since their intensity is adjustable over a very wide range, linearity and detection limits of radioluminescence detectors can be readily determined. The design, construction, radiometric characterization, and calibration of dedicated transfer standards, as well as the development of new calibration procedures for radiometric traceability of radioluminescence detection systems, will enable appropriate accident and post-accident radiation measurements that will lead to more effective countermeasures and better protection of people, wildlife, and the environment.