Acta Chimica 21. (1959)
1. szám - PHYSIKALISCHE CHEMIE - T. Lengyel: Energy Dependence of the Back-scattering Factor of Absolute Beta Counting
ENERGY DEPENDENCE OF THE BACK-SCATTERING FACTOR OF ABSOLUTE BETA COUNTING T. Lengyel (Central Research Institute for Chemistry, Hungarian Academy of Sciences, Budapest) Received February 14, 1959 Introduction The determination of the activity and radiation energy of beta radiating isotopes is one of the most important parts of radioactive measurements. With exact measurements and an application of radioactive samples, a possibility is given to carry out besides comparative measurements also an absolute counting. For the determination of the absolute activity of solid beta-radiating preparations, the following relation proved to be suitable according to Zumwalt and others [1, 2, 3, 4, 5]. fa -ft ■f/3 ■fw -fn ■fs •fn'/м(1) where / = number of radioactive decompositions per minute [tpm] 1' — number of decompositions per minute registered by a measuring instrument [cpm] fa = geometrical factor fr = dead time factor /в = back-scattering factor fw = factor for window and air absorption fH = scattering factor caused by the measuring instrument fs = self-absorption factor /ч = sensitivity of the measuring instrument (GM tube) /м = correction factor for pseudo-counting The experimental work described in the present paper was carried out with the purpose of determining the magnitude of the back-scattering factor (f,j) and the energy dependence of this factor under conventional experimental conditions. Data in connection with this subject are only sparsely given and are often contradictory to each other [5, 6, 7, 8, 9]. Therefore, new systematic measurements appeared to be necessary. To vary the back-scattering conditions only during the experiments, whilst all other factors should remain unchanged, was regarded as the main point. Acta Chim. Hung. Tomua 21. 1959 4*