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Manuscript Title: CHEREN2, the Cherenkov counting efficiency by an anisotropy detection model
Authors: A. Grau Carles, A. Grau Malonda
Program title: CHEREN2
Catalogue identifier: ADIE_v2_0
Distribution format: tar.gz
Journal reference: Comput. Phys. Commun. 174(2006)30
Programming language: FORTRAN 77.
Computer: any IBM PC compatible with 80386 or higher Intel processors.
Operating system: MS-DOS and higher systems.
RAM: 45 kword
Word size: 32
Keywords: Radioactivity, Cherenkov counting, beta-decay, shape factor, liquid-scintillation counting.
PACS: 07.57.Kp, 29.30.Dn.
Classification: 17.4.

Nature of 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 recommended 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.

Solution method:
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:
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.

Running time:
A few seconds.