Heterogeneous scintillator geometries to maximise energy deposition for waterborne beta particle detection. (April 2018)

• Record Type: Journal Article
• Authors: Alton, Tilly; Monk, Stephen; Cheneler, David
• Is Part Of: Radiation measurements. Volume 111(2018:Apr.)
• Page Start: 6
• Page End: 12
• Publication Date: 2018-04
• Subjects: Tritium -- Beta particles -- CaF2:Eu -- Scintillator -- Flow cell; Nuclear emulsions -- Periodicals; Particle tracks (Nuclear physics) -- Periodicals; Thermoluminescence -- Periodicals; Cosmic rays -- Periodicals; Radiation -- Measurement -- Periodicals; Radiometry -- Periodicals; Radiation Monitoring -- Periodicals; Émulsions nucléaires -- Périodiques; Particules (Physique nucléaire) -- Traces -- Périodiques; Thermoluminescence -- Périodiques; Rayonnement cosmique -- Périodiques; Radiométrie -- Périodiques; 539.77
• DOI: 10.1016/j.radmeas.2018.02.004
• Languages: English
• ISSNs: 1350-4487

Abstract

Abstract: Here the geometries that maximise detection efficiency of heterogeneous scintillators used to detect beta particles in aqueous solutions by maximising energy deposition are described. The determination of the geometry was achieved with the Monte Carlo code Geant4 using CaF2 :Eu scintillator as a pertinent case study, and validated with experimental data using single crystal CaF2 :Eu and heterogeneous CaF2 :Eu scintillators. Both 2D and 3D structures composed of arrays of primitive unit cells of packed spheres were examined to find the optimal geometry to maximise detection of volumetric sources of tritium and aqueous Carbon 14 and Lead 210. The 2D structures were evaluated relative to a single crystal scintillator and results show the detection efficiency of the 2D structures is maximised when the sphere radius is c.a. 0.46x the maximum track length of the beta particle in the scintillator. Data for the 3D structures show that the efficiency is maximised when the sphere radius is minimised, but it is further shown that practical issues limit the minimum radius that can be used for transient radiological contamination monitoring. Highlights: Simulation results show that a heterogeneous scintillator comprising of a single layer of scintillator spheres (2D) has a higher energy deposition efficiency from distributed beta radiation sources as compared with an equivalent single crystal scintillator. Experimental data is provided to validate these results. The data implies general heterogeneous scintillator design rules exist as scintillator behaviour results can be normalised using the radioisotopes Maximum Track Length and Maximum Geometric Track Length to yield comparable results for different radioisotopes. 3D heterogeneous scintillator simulations show an optimal geometry when considering the detection of transient beta radiation sources, such as contamination of environmental water sources. Simulation data shows that for simulating large periodic structures of heterogeneous scintillators, an optimal number of unit cells exist and are equivalent to infinite arrays. A quantified example of how the practicalities of detecting a transient source of beta radiation affects flow cell design is provided.