A new 4πβ counter operated at atmospheric pressure of CF4 gas for the computer discrimination method

4πβ-γ coincidence counting using a 4πβ pressurized proportional counter combined with the computer discrimination method has made it possible to determine the disintegration rate precisely and rapidly. Recently, measurement of short half-life nuclide requires further shortening of the gas replacement time, and we proposed to use atmospheric CF4 gas instead of pressurized Ar 90%-CH4 10% mixture. However, a conventional 4πβ counter with CF4 gas at atmospheric pressure gave unsatisfactory results; small slopes of coincidence efficiency functions and low detection efficiencies for electron-capture decay nuclides. In order to resolve these problems, we constructed a new 4πβ counter with large volume and multianodes. Good plateau characteristics and good time relation between β and γ pulses were obtained in spite of large volume, and the slopes of coincidence efficiency functions and the detection efficiencies were improved. Use of this counter made it possible to measure short half-life nuclides and also easy to measure usual nuclides. (author)