A thin 4 pi beta-counter operating by negative high voltage for the 4 pi beta-gamma coincidence measurement....

A thin 4 pi beta-counter with five anode wires was operated by supplying negative high voltage to the inner wall and showed good plateau characteristics in the case of using only the center anode to take out signals in the previous experiments. This counter, as the 4 pi beta-counter and both 2 pi beta-counters, showed good plateau characteristics in these detailed experiments and no dependency on the disintegration rates examined up to 6000 dps. Then a 4 pi beta-gamma coincidence equipment was set up using this 4 pi beta-counter and one NaI(T1) scintillation detector with size of 76 mmphi x 76 mm. The radioactivities that were measured for beta-gamma and electron capture-gamma decay nuclides by this coincidence equipment were coincided with those measured by the other one. The improvement of the gamma-ray detection efficiency to aim was achieved by that the efficiency obtained by this system was the same as one by the other system having two NaI(T1) detectors with the same size.