Time-to-pulse height converter

In a third method for lifetime measurements, the levels to be investigated are excited by a short pulse and subsequently the number of fluorescence quanta is counted as a function of the delay time (e.g. with a multichannel analyzer and a time-to-pulse height converter). The experimental procedure is described by Bennet 2 and has been perfected by several authors using light pulses 22) or electron pulses 23) for excitation. 

A typical PEPICO apparatus is shown in Figure 1, where an acceleration region followed by a drift tube is used to determine the ionic species. The coincidence condition is achieved by using electron and ion signals as start and stop inputs, respectively, to a time-to-pulse height converter whose output is sent to a multichannel pulse height analyser. 

Another advantage of these detectors is the fact that the detector output pulses rise rapidly, and hence they are well suited for fast ( 1 ns) timing with coincidence circuitry in time-to-pulse-height converters. The efficiency of the active volume of these detectors is essentially 100%, and AE/AC is linear over a rather broad range. Compared to scintillation counters, gas proportional counters or ionization... 

A single photon gives rise to an electric pulse, which in good photomultipliers has a length of only a few nanoseconds. A Time-to-Amplitude pulse height Converter (TAC) is a critical component when using this technique. A clock is started when the excitation pulse is fired. The clock runs... 

Figure Bl.10.7. Electron impact ionization coincidence experiment. The experiment consists of a source of incident electrons, a target gas sample and two electron detectors, one for the scattered electron, the other for the ejected electron. The detectors are coimected tlirough preamplifiers to the inputs (start and stop) of a time-to-amplitiide converter (TAC). The output of the TAC goes to a pulse-height-analyser (PHA) and then to a nuiltichaimel analyser (MCA) or computer.

The y-detector of a Mossbauer spectrometer converts the incident y-photons into electric output pulses of defined charge (see Sect. 3.1.6). The detector signals are electronically amplified and shaped by an amplifier network to obtain strong needle pulses with well-defined rise time, so that the pulse height is proportional to the energy of the incident photon. The amplifiers are usually adjusted to obtain... 

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.

Fig. 5. The schematic diagram of the pulsing system and the ion beam pulse radiolysis system with an optical emission spectroscopy. PMT denotes photomultiplier tube HV, high voltage supply CFD, constant fraction discriminator TAC, time to amplitude converter and PH A, pulse height analyzer. From Ref. 36...

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