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 is considered evidence of a shape transition of the discharge-ion density around the anode wire of the gas counter in high-electric-field operation.<>