A low-background organic-type GM tube

A low-background, organic-type small GM tube with a short tungsten wire anode of 1 cm length and a cylindrical steel cathode was constructed. Reduction on the background caused by cosmic rays and contamination is achieved by using a short, small GM tube. At the same time, the problem of low counting efficiency caused by the short tube length is overcome. The drop in the field values near the ends of the short cylindrical GM tube below the values required to produce Geiger action, which in turn causes the decrease in the counter efficiency, is corrected using two metallic balls connected to both ends of the tungsten wire anode. The optimum size of these balls corresponding to the minimum capacitance of the counter is determined using a simulation technique. Plateau curves of tubes with different-sized metallic balls are reported. Then, a plateau curve of the tube with optimum ball size is compared with that of an ordinary cylindrical GM tube having the same dimensions to evaluate the effect of using the wire anode with two metallic balls at the ends in order to improve counter performance and efficiency