Determination of a source in a box with two detectors. I. non-absorbing media

Radioactive point source localization in a bulky volume

“…The results described so far refer to aqueous absorption media, but in practice, the need of data for lower absorption media may arise (as for waste containers where most of the volume is air). In order to check if the proposed method is applicable also to this case, we used the data obtained in a previous work where non-absorbing media were investigated [1]. First, we obtained the A 0 and A 1 values for air.…”

“…Thus, the function fitting method can be used for a great range of densities and gamma energies, covering the range from m ¼ 0:0001 cm À1 ( 137 Cs gamma rays in air) to at least m ¼ 0:2 cm À1 (the highest value checked experimentally). The previously suggested method for lowabsorption media [1] seems to be preferable as it does not require any adjustable parameter. However, as the parameters used in the present method are obtained solely by calculations and do not require any calibration measurements, both methods are about the same, and the method proposed in the present work has the advantage that it is general and applicable to all gamma energy values.…”

“…It was shown elsewhere [1], that in the case of non-absorbing media (neglecting the absorption effect), the location of the source point can be determined from the count rate ratio of the two detectors by the simple analytical expression:…”

“…a low value of linear attenuation coefficient (due to either low dense material or high-energy photons). The results of this study [1] have shown that the activity of the point source can be determined accurately, independent of its location in the box, using a special algorithm based on the square of the harmonic mean of the square roots of the two count rates, M SH . The absorption factor was studied in a system measuring only parallel photons, and in this case, it was shown that the activity of the point source can also be determined accurately, independent of its location in the box, by using an algorithm based on the geometrical means of the two count rates.…”

“…The ratio between the count rates of two detectors, placed at opposite sides of the bulky sample, will be dependent on the location of the source in the sample, and this information can be used to evaluate correction factors. In previous studies [1,2] we dealt separately with the geometrical and absorption factors to develop appropriate correction algorithms. We considered the extreme case of non-homogeneity of a point source located on the line connecting the centers of the two detectors, within a box of known external dimensions.…”