The requirements of Ideal pulse-type counter : 1 Every particle entering the detector should produce a pulse at the exit of the counter, which is higher than the electronic noise level of the unit that accepts it (usually this unit is the preamplifier). In such a case, every particle entering the detector will be detected

and the detector efficiency, defined as the ratio of the number of particles detected to the number of particles entering the counter, will be equal to 100 percent . 2 The duration of the pulse should be short, so that particles coming in one after the other in quick succession produce separate pulses. The duration of the pulse is a measure of the dead time of the counter and may result in loss of counts in the case of high coun ting rates. 3 If the energy of the particle is to be measured, the height of the pulse should have some known fixed relationship to the energy of the particle. To achieve this, It is important that the size of the counter is such that the particle deposits all its energy (or a known fraction) in it. with ideal energy resolution.

1.5.4 The High-Voltage Power Supply :The high-voltage power supply (HVPS) provides a positive or negative voltage necessary for the operation of the detector. Most detectors need positive high voltage (HV). Typical HVs for common detectors are given in Table 1.2. The HVPS is constructed in such a way that the HV at the output changes very little even though the input voltage (110 V, ac) may fluctuate

1.5.5 The Preamplifier provides an optimized coupling between the output of the detector and the rest of the counting system. The preamplifier is also necessary to minimize any sources of noise that may change the signal. The signal that comes out of the detector is very weak, in the millivolt (mV) range . Before it can be recorded, it will have to be amplified by a factor of a thousand or more. To achieve this, the signal will have to be transmitted through a cable to the next instrument of the counting system, which is the amplifier. Transmission of any signal through a cable attenuates it to a certain extent. If it is weak at the output of the detector, it might. be lost in the electronic noise that accompanies the transmission. This is avoided by placing the preamplifier close to the detector as possible. The preamplifier shapes the slgna1 and reduces its attenuation by matching the, impedance of ,the' detector with that of. the amplifier:? After going through the preamplifier, the signal may be safely transmitted to the amplifier, which may be located at a considerable distance away,

The discriminator (switch position: INT) The dial E (for energy) may be changed continuously from 0 to 100. The discriminator works with voltage pulses, but there is a one-to-one correspondence between a pulse height and the energy of a particle. Assume that the discriminator is set to E = 2.00 V (the 2 V may also correspond to 2 MeV of energy). Only pulses with height greater than 2 V will pass through the discriminator. Pulses lower than 2 V will be rejected. For every pulse that is larger than 2 V, the discriminator will provide at the output a rectangular pulse with height equal to 10 V (Fig. 1.12) regardless of the actual height of the input pulse. The output pulse of the discriminator is a pulse that triggers the unit (scaler), which counts individual pulses and tells it, "a pulse with height bigger than 2 V has arrived; count 1."Thus, the discriminator eliminates all pulses below E and allows only pulses that are higher than E to be counted