Abstract
In a previous paper a hybrid chamber was proposed to improve non-uniformity of sensitivity and instability of operation of normal self-triggering spark chambers. It was composed of an ionization chamber (IC), a proportional chamber (PC) and a spark chamber (SC) . The method of the improvements was based on the decrease of the sparking voltage, the starting voltage of sparks, by increasing the number of initial electrons which trigger a spark. In this paper two subjects about the performance of the chamber are described. One is the dependency of the sparking voltage on the number of initial electrons at the cathode of the SC. Another is the property of the sparks in the PC induced by the sparks in the SC. To begin with, gas multiplication factor of electrons in the PC and transmission coefficient of electrons through the gauze, the electrode between the IC and the PC, were determined experimentally. Then the relation between sparking voltage Va and average number of initial electrons N was examined. As the result, it was found that Va was decreased with increase of N, more than 20% at N=106. The dependency of Va on N was roughly understood from the model of streamer formation. When the electric field strength in the PC was increased to increase the number of initial electrons and exceeded the critical value (-5kV/cm) sparks were induced in the PC by the sparks in the SC. As the occurrence of induced sparks was not desirable for the improvement of the instability of the operation the properties were examined. The delay time of the induced spark appeared after the spark in the SC was nearly 0.1-1μsec and depended on the field strength in the PC not depending on that in the SC. The occurrence of the induced sparks are considered as the following. The positive ions produced by a spark in the SC pass through the gauze electrode and form space charge field in the PC. By increasing the field strength near the anode of the PC a streamer will be formed and a spark induced.
