Pulse-height selectors

When a proportional counter is. used in conjunction with a pulse-height selector, the occurrence of an escape peak may vitiate the results. Assume that the counter filling contains argon, whose K edge is at 3.87 A, and suppose that the pulse-height selector is set to select an x-ray line 3f shorter wavelength the intensity of which is to be measured. This line will excite the K lines of argon. To the extent that these lines are... 

Were these spreads not so likely to remain large, one could look forward to a replacement of crystals by pulse-height selectors as a means... 

Dispersive instruments are often equipped with pulse-height selectors to reject noise and to supplement the monochromator in separating the analyte line from higher-order, more energetic radiation that is diffracted at the same crystal setting. 

Fach transducer in a multichannel instrument has its own amplifier, pulse-height selector, scaler, and counter or integrator. These instruments are equipped with a computer for instrument control, data processing, and display of analytical results. A determination of twenty or more elements can be completed in a few seconds to a few minutes. 

The operating voltage range for a flow proportional counter is 1-3 kV. As seen in Fig. 8.22, the amplification factor, which is the number of ion pairs discharged at the electrodes divided by the number of primary ion pairs formed, is 10 -10 . The current pulse is converted to a voltage pulse, is processed through a pulse height selector or discriminator and counted. Maximum count rate for a flow proportional counter is on the order of 2 X 10 cps. 

This effect of increasing the order of the background with increasing Bragg angle is the reason why the use of the pulse height selector for removal of background... 

Although the basic function of the pulse height selector is simple to comprehend, proper techniques for its use are much more subtle and often misunderstood. In this section the response of the pulse height selector to idealized spectra is described in order to demonstrate the various methods of use. 

Figure 4.13 Pulse responses with the pulse height selector in the integral discriminator mode (a) Pulses from the delay-line amplifier output, (b) The output logic pulses from the pulse height selector. (Reprinted by courtesy of EG G ORTEC.)...

A second discriminator level Vu has been added to the lower-level discriminator Vl normally used in the integral mode. In the window mode the pulse height selector produces a standard output logic pulse only if the amplifier pulse amplitude... 

Frequently, it is desirable to use the window mode in conjunction with a pulse-height-selector scanner in order to measure the spectrum of Fig. 4.16(a) on a strip-chart recorder. If the resolution of Fig. 4.16(a) is to be faithfully reproduced in Fig. 4.16(b), the window width must be small compared to the peak width in Fig. 4.16(a). That is, the window width must be small compared to the pulse height resolution inherent in the amplifier pulse height spectrum. A good practical choice is to make the window width less than one-fourth of the width of the narrowest peak in the amplifier pulse height spectrum—the width being taken as the width of the peak at half the peak amplitude above background. 

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