Some rules to improve the energy resolution in alpha liquid scintillation with beta rejection

Abstract

Abstract Two common scintillating mixtures dedicated to alpha measurements by means of alpha liquid scintillation with pulse shape discrimination were tested: the di-isopropylnaphthalene — based and the toluene-based solvents containing the commercial cocktails Ultima Gold AB® and Alphaex®. We show the possibility to enhance the resolution up to 200% by using no-water miscible cocktails and by reducing the optical path. Under these conditions, the resolution of about 200 keV can be obtained either by the Tri CarbTM or by the PeralsTM spectrometers. The time responses, e.g., the time required for a complete energy transfer between the initial interaction alpha particle-solvent and the final fluorescence of the organic scintillator, have been compared. Both cocktails present similar behavior. According to the Förster theory, about 6-10 ns are required to complete the energy transfer. For both apparatus, the detection limits were determined for α emitters. The sensitivity of the Tri Carb was improved by 300% but remains 40% lower than that of Perals, due to a higher α/β discrimination and the use of vials with lower optical path.