engleski

Interpolation of gamma-ray buildup factors for arbitrary source energies in the vicinity of the K-edge

Recently, a new buildup factors approximation formula based on the expanded polynomial set (E-P function) was successfully introduced (Michieli 1994.) with the maximum approximation error below 4 % throughout the standard data domain. Buildup factors interpolation in E-P function parameters for arbitrary source energies, near the K-edge in lead, was satisfactory. Maximum interpolation error, for lead, lays within 12% what appears to be acceptable for most Point Kernel applications. 1991. Harima at. al. , showed that, near the K-edge, fluctuation in energy of exposure rate attenuation factors i.e.:D(E)B(E,ľr)exp(-ľr), given as a function of penetration depth (r) in ordinary length units (not mfps.), is not nearly as great as that of buildup factors. That phenomenon leads to the recommendation (ANSI/ANS-6.4.3) that interpolations in that energy range should be made in the attenuation factors B(E,ľr)exp(-ľr) rather then in the buildup factors alone. In present article, such interpolation approach is investigated by applying it to the attenuation factors in lead with E-P function representation of exposure buildup factors. Simple form of the E-P function leads to straight calculation of new function parameters, and thus allowing the same representation form of buildup factors, as in the standard interpolation procedure, for arbitrary source energy near the K-edge. Results of the interpolation are discussed and compared with those from standard approach.

buildup; approximation; expanded polynomials; interpolation

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