Investigation of proportional counter action with application in the study of low energy radiations

The method of measuring the energy of a charged particle by means of the total amount of ionisation it produces in a gas, through which it passes, is well established. Gas filled devices may be subdivided into (a) current ionisation chambers and (b) pulse ionisation chambers, proportional counters and Geiger counters. Proportional counters in a very crude form were used by Rutherford and Geiger in 1908. Soon afterwards the Geiger counter was developed, which after considerable improvement by Geiger and Müller in 1928, became the well known Geiger-Müller counter. In fact the three gas filled devices mentioned in (b) can be achieved with the same counter by using it with different applied voltages. If the applied voltage on a typical cylindrical counter is varied and the output pulse height is measured for a fixed number of ion pairs liberated in the gas, a characteristic curve of the form shown in Fig.(1) will be obtained. With voltages between say v₁ and v₂, the field strength is just sufficient to collect all the ion-pairs and no new ion-pairs are liberated, so the pulse height will remain constant. This is the region of pulse ionization chambers where the gas gain is unity. As the voltage is further increased to between v₂ and v₃ both elastic and inelastic collisions take place and the pulse height increases exponentially..