Pulse-height analyzer, single channel

The detector signal is conditioned through a single channel pulse height analyzer whose output pulses are fed to a scaler-timer in the single crystal controller. 

The background of a diffraction pattern obtained with a diffractometer may be reduced by means of a single-channel pulse-height analyzer, as mentioned in Sec. 7-9. An even better method is to use a crystal monochromator in the diffracted beam. Balanced filters present still another option. 

In many tracer applications it is not necessary to measure the absolute concentration of the tracer in a sample or in a material flow. In such cases a scintillation detector accompanied by a single-channel pulse height analyzer is a sufficient device. 

Figure 1. Schematic of coincidence/noncoincidence y-ray pulse height analyzer. Key to symbols Dl, D2, Harsnaw 16MB16/5A detector FA, Ortec 113 preamplifier LA, Ortec 485 linear amplifier TSCA, Ortec 551 timing single channel analyzer FC, Ortec 414A fast coincidence DA, Ortec 489 delay amplifier LGS, Ortec 442 linear gate and stretcher PHA/RTC, nuclear data pulse hei t analyzer with segmented memory and real time clock.

Figure 2. Schematic of coincidence-limited pulse height analyzer with real time clock. Key to symbols SC A, Ortec 406A single channel analyzer T, Ortec 708 Buffered Memory Timer S1-S5, Ortec 707 buffered memory scaler others as in Figure 1.

A second technique to separate the fission activity is a so-called bias method. The counting equipment requirements now include a gamma scintillation counter, and at least a single-channel pulse-height analyzer, but preferably a multichannel analyzer. With this method, the characteristic fission activities can be measured directly from foils DU and EU. These foils must be of known weight, but only nominally equal thickness, surface area, and conditions of surface oxidation. 

Single-channel pulse-height analyzers are connected to the detectors, with the windows on the photopeak of the radioactive isotope, which was introduced into the body for investigation. 

Fig. 3.7 Pulse-height analysis (PHA) Function of the single-channel analyzer (SCA) and data recording by the multi-channel analyzer (MCA). The output (L) of the SCA yields a 5 V squareshaped pulse, a so-called TTL pulse for each y-pulse matching the voltage selection window. The SCA is set to select the Mossbauer pulses for the subsequent measurement...

The single channel analyzer has two dial settings a LEVEL dial and a WINDOW dial. For example, when the level is set at 2 volts, and the window at 0.2 volts, the analyzer will give an output pulse only when the input pulse is between 2 and 2.2 volts. The output pulse is usually a standardized height and width logic pulse, as shown in Figure 11. 

In pulse fluorometry, we take advantage of the fact that the amplitudes of the output pulses of the TAC are proportional to the times of arrival of the fluorescence photons on the photomultiplier. Selection of a given height of pulse, i.e. of a given time of arrival, is electronically possible (by means of a single-channel analyzer) and allows us to record the fluorescence spectra at a given time t after the excitation pulse. This is repeated for various times. The method described above for phase fluorometry can also be used in pulse fluorometry. 

Figure 3. Pulse height spectrum of gamma radiations. Window of single channel analyzer fixed to optimize intensity of 14.4-k,e,v, radiation...

The single-channel analyzer (switch position DIFF). Both E and AE dials operate. Only pulses with heights between E and E + AE are counted (Fig. 

The two dials form a channel hence the name single-channel analyzer. If the E dial is changed to Ej, then pulses with heights between Ej and Ej -I- AE will be counted. In other words, the width AE, or window, of the channel is always added to E. 

Figure 4.47 Definition of deadtimes in the single-channel analyzer system with the pulse-height selector operating in the integral mode. (Reprinted by courtesy of EG G ORTEC.)...

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