Multichannel pulse height analyzer, and

The output from the coincidence electronics passes to a multichannel pulse height analyzer and thence to a computer. The computer can also take data from other detectors that are in line with the column eluent in addition to instrument control. Data is processed and then presented on a monitor or printer. Cells for both homogeneous and heterogeneous counting are available. Homogeneous counting cells provide efficiencies of 55% for tritium and at least 95% for " carbon, whereas the heterogeneous cells provide about 10% for tritium and about 90% for " carbon. 

Figure 1. Block diagram of single-photon time-correlation apparatus from Barker and Weston 11 HV, high-voltage supplies L, lamp PI, photomultiplier M, monochromator FURN, furnace C, sample cell LP, light pipe F, interference filter P2, photomultiplier AMP, amplifier DISCI, discriminator D1SC2, discriminator T-S, timer scaler DL, delay line TAC, time-to-amplitude converter BA, biased amplifier MCPHA, multichannel pulse-height analyzer TTY, teletype printer and paper-tape punch REC, strip-chart recorder.

The counting rate varies linearly with x-ray intensity up to rates of about 5,000-10,000 cps. Counting losses in the counter-electronics system occur in the electronics rather than the counter. The electronics are more complex than usual and include, besides the usual pulse amplifiers and shapers, a multichannel pulse-height analyzer (Sec. 7-9). 

Figure 4.6 Pulse shapes encountered with a NaI(Tl) detector and spectrometer electronics. The detector is responding to the 22-keV silver K lines from a radioactive ° Cd source and the 6-keV Mn K lines from a radioactive Fe source, (a) The preamplifier output pulses, (b) Output pulses from a delay-line clipped pulse-shaping amplifier with a 1-/Ltsec delay line clip and a l/4-)US integration time constant, (c) Output pulses from the alternative semigaussian shaping amplifier with a 0.5-fxs time constant, (a), (b), and (c) are multiple traces on an oscilloscope, (d) The energy (pulse height) spectrum obtained by analyzing the delay line amplifier output on a multichannel pulse height analyzer. (Reprinted by courtesy of EG G ORTEC.)...

If -emitting substances are thought to be present in water, then these substances are to be analyzed with a scintillation crystal, for example in the geometrical configuration of a well-type crystal, and using a multichannel pulse height analyzer. Concentration of the radionuclides in the water is usually necessary for this measurement as well if a sensitivity level of, for example, 1 Bq/1 is to be attained. 

Excitation by high-energy electrons, radioactive particles or X-rays may be used. Analysis of the emitted X-rays using crystal analyzers is followed by detection using gas ionization detectors or scintillation counters. Nondispersive semiconductor detectors and multichannel pulse height analyzers are often used in conjunction with scanning electron microscopes. 

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