Relationship Between High Voltage and Charge Collected

2 RELATIONSHIP BETWEEN HIGH VOLTAGE AND CHARGE COLLECTED 

Assume that the following experiment is performed (Fig. 5.2). A radioactive source of constant intensity is placed at a fixed distance from a gas counter. The high voltage (HV) applied to the counter may be varied with the help of a potentiometer. An appropriate meter measures the charge collected per unit time. If the HV applied to the counter is steadily increased, the charge collected per unit time changes as shown in Fig. 5.3. The curve of Fig. 5.3 is divided into five regions, which are explained as follows. 

Region II. In region II, the charge collected stays constant despite a change in the voltage because the recombination rate is zero and no new charge is produced. This is called the ionization region. 

Region V. If the applied voltage is raised beyond the value iv. a single ionizing event initiates a continuous discharge in the gas, and the device is not a particle detector anymore. No gas counter should operate with voltage V Viv 

If the graph discussed above is obtained using an a, j8, or y source, the results will be as shown in Fig. 5.4. 

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