CHEREN2, the Cherenkov counting efficiency by an anisotropy detection model

Abstract

The commercially available liquid-scintillation spectrometers are also feasible for the detection of the Cherenkov light emitted by β-rays in transparent liquids, when the maximum-point energy of the Fermi distribution is greater than the Cherenkov threshold energy. We present a second version of the program CHEREN, which applies Poisson statistics to compute the two photomultipliers counting efficiency. We redefine previous version free parameters, including two new different coefficients into the counting efficiency equation. The Frank and Tamm theory of Cherenkov radiation is applied to compute the total number of Cherenkov light photons emitted by the β-particles along their pathways. Program summary Title of program:CHEREN2 Catalogue identifier:ADWJ Program summary URL: http://cpc.cs.qub.ac.uk/summaries/ADWJ Program obtainable from: CPC Program Library, Queen's University of Belfast, N. Ireland Licensing provisions:none Computers: any IBM PC compatible with 80386 or higher Intel processors Operating systems under which the program has been tested:MS-DOS and higher systems Programming language used:FORTRAN 77 Memory required to execute with typical data:45 kword No. of bits in a word:32 No. of lines in distributed program, including test data, etc.:966 No. of bytes in distributed program, including test data, etc.:7356 Distribution format:tar.gz Nature of the physical problem:Although a liquid-scintillation spectrometer can be applied to count Cherenkov light photons free of noise interference, the non-isotropic character of the Cherenkov light emission reduces the counting efficiency of the two-phototube system working in coincidence, and makes the Cherenkov light measurements comparatively much less efficient than with scintillators. However, the application of standardization techniques based on Cherenkov counting is recommend when the radioactive sample cannot be dissolved into the liquid scintillator cocktail. Also the ability to recover the radioactive sample unaltered and the possibility of eliminating low-energy contributions below the Cherenkov threshold energy are interesting aspects to be considered. Method of solution:The directional character of Cherenkov light and the amount of energy Cherenkov light needs to create one photoelectron at the photocathode are defined as two new free parameters into the counting efficiency expression. The number of photons emitted by the β-particle is computed according to Frank and Tamm theory. Additionally, the application of a range to energy relationship, which takes into account the strong deceleration of the β-particle in the medium, is required. To determine the free parameter values, the program needs the measured efficiencies for at least two radionuclides of well-known shape factors (e.g., 36Cl and 32P). Restrictions on the complexity of the problem:Computations are restricted to pure β and β- γ-emitters for which the contribution of the Compton electrons to the total Cherenkov counting efficiency is less than 2%. The comparison between the computed and experimental counting efficiencies requires one to maintain unaltered the vial material, the sample volume and the acid concentration throughout the experiments.