Shape transition of the discharge ion distribution around an anode wire of a gas counter

The discharge ion density around an anode wire of a gas counter has been measured with a cylindrical counter having a rotating electrode. The azimuthal ion density has been determined from raw data of the induced signals in the rotating electrode by solving a set of linear equations with an analytical weighting function. The results are given as a function of the anode high voltage. The angular width of the discharge ion density shows a transition between the proportional- and streamer- mode operations of the counter. This fact is another evidence of the shape transition of the discharge ion density around the anode wire of the gas counter in high electric field operation