RADIOISOTOPES

A new GM counter was developed, which used air as counting gas, ethanol vapor as quenching gas, darning needle as anode, and plastic case with conductive paper as cathode. The characteristics of the performance of this counter were investigated by the calculation of gas gain together with equipotential curves around the needle tip and by the experimental results such as plateau curves and detection efficiencies depending on the incident position of β-rays into the counter and on the distance from the window to the needle tip. This counter is very easy to fabricate and has stable counting performance. It is therefore useful for radiation education experiments.