| The 4πβ-γanticoincidence method for radioactivity measurements is described andthe 4πβ(PPC)-γ(HPGe) anticoincidence apparatus is constructed. The measurements of133Ba and 131I are described and the results are compared with those obtained by othermethods.The principle of the 4πβ-γanticoincidence method is correlated with the4πβ-γcoincidence method, and their apparatus are similar, but the 4πβ-γanticoincidencemethod records the signals of anti-coincident channels other than coincident ones. The keyof the 4πβ-γanticoincidence method is to measure theβ-efficiency with proper selectionofγrays rather than the efficiency extrapolation technique, and this approach suits4πβ-γcoincidence method too.A HPGe detector is taken to replace the NaI (TI) detector in the conventional 4πβ-γcoincidence system, which can detectγrays more accurately. Furthermore, a 4πβhighpressurized proportional counter (PPC) is designed to measure the nuclides of EC decay.The radioactivities of 133Ba and 131I were measured by the 4πβ(PPC)-γ(HPGe)Anticoincidence apparatus and compared with those obtained by the conventionalcoincidence counting method or the DCC method. It is shown that the results from the4πβ-γanticoincidence method are in good agreements with those obtained by the othermethods within the uncertainties.From this study, it is concluded that the 4πβ(PPC)-γ(HPGe) anticoincidence methodis a very simple method for radioactivity measurements of nuclides that have complexdecay schemes, though this method has its own disadvantages. It is shown that the4πβ(PPC)-γ(HPGe) anticoincidence method can be widely used as one of the standardmethods to measure radioactivity. |
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