engleski

Improvements of 60 keV gamma-ray spectrum by reducing scattering effects

A considerable reduction of background and an improvement of spectra of low-energy gamma-rays, measured with a planar high-purity Ge detector, has been achieved by a small source and a careful design of collimators and shielding. The aim of the design was to reduce strongly the detection of scattered radiation. The design of the shielding was based on previous study by the present authors of effects of near-source scattering on photon spectra. That work has shown the effects of different distribution of mass around the gamma-ray emitting atoms, seen as continuous distributions adjacent to the full-energy peaks (the "shoulders"). In the present measurement, reduction of intensity of the shoulders by as much as a factor of 10 has been achieved. The calculated shoulder spectra reproduce well the measured ones. Since a much lower background was achieved (peak-to-shoulder height ratio of about 2500), the shape of the full-energy peak could be analyzed in a broader range. Deviations from the Gaussian shape have not been observed in the range +-3.4sigma about the midpoint of the peak. The calculated shoulder spectrum, which was dominated by scattering in the source, and the Gaussian peak represent the measured spectrum in their energy range very well, so that only 0.1% of counts are not accounted for. Present arrangement offer improved searches for lines of weak intensity and more accurate determination of peak intensities in x-ray and low-energy gamma-ray spectra.

germanium detector ; response function ; shoulder ; Compton scattering ; shape of full-energy peak

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