Stop signal delay

The residence time was determined for our neutron counter by measuring the time intervals between beta start signals and neutron stop signals. With a residence half-time of 11 ms and a coincidence resolving time of 40 ms. 92 of the true coincidence events were included. The fraction of true events not detected does not influence the present results because we normalize the Pn measurements to a known Pn value measured under identical conditions. The coincidence rate was measured by a simple overlap coincidence module where the beta pulse Input was stretched to 40 ms by a gate and delay generator. To measure the accidental coincidence rate, the same beta pulse was sent to a second coincidence module and overlapped with neutron pulses which had been delayed 45 ms. After correcting each coincidence rate for deadtime effects, the difference was the true coincidence rate. 

The signal shape shown right was reeorded with 10 m delay cable in the stop signal path. A TAG range of 50 ns, a TAG gain of 1, and display zoom factor of 5 were used. The FWHM of the initial peak of the signal is redueed to 87 ns. 

The location of the source of the ionization is obtained by making use of a delay wire. The delay wire is a very thin wire that is wound over the cathode, and pulses pass along the delay wire in both directions. The pulses are detected by ampliflers at each end of the wire. The arrival of a pulse at one end starts the time-to-amplitude (TA) circuit, while the other pulse is delayed and provides a stop signal in the circuit. The difference between the time of arrival at the two ends of the wire can thus be measured and is proponional to the position of the initial ionization. An analog-to-digital converter (ADC) converts the TA-signal to a digital position value that is processed by the data system. 

The time resolution of the instrument is governed not only by the pulse width but also by the electronics and the detector. The linear time response of the TAC is most critical for obtaining accurate fluorescence decays. The response is more linear when the time during which the TAC is in operation and unable to respond to another signal (dead time) is minimized. For this reason, it is better to collect the data in the reverse configuration the fluorescence pulse acts as the start pulse and the corresponding excitation pulse (delayed by an appropriate delay line) as the stop pulse. In this way, only a small fraction of start pulses result in stop pulses and the collection statistics are better. 

Figure 7.2.8 shows the contour plot of one constituent of the phthalate separation. Here the dead volume between the UV detector and the SFC flow cell was determined before the separation. After an adequate delay after the occurrence of the UV signal of bcnzyl-n-butylphthalate in the UV detector, the SFC separation was stopped and the two-dimensional acquisition was started. The pressure proved to be stable for several hours, which was sufficient for the acquisition of the two-dimensional COSY spectrum. Despite the intense... 

Figure 4.47 Typical electronic circuit for the measurement of electron-electron coincidences with two spectrometers (SP1, SP2) placed at the positions 0 , and 5, , respectively. The pre- and main amplifiers are together represented by a triangle. The delay retards the signal from SP1, thus providing a STOP of the time-to-digital converter (TDC) if this time measuring device has been initiated by a START signal from a time-correlated event registered in SP2. The output of the TDC, i.e., the number of time-correlated events as function of the correlation time is stored in a histogramming memory (HIS. MEM.) which then is read out by a computer (COMP.).

Fig. 10. Photon arrival time statistics of single emitters, (a) Schematic description of the temporal structure of single-emitter emission, (b) Simulated timetraces for different intersystem crossing rates as indicated, (c) Start-stop measurement yielding and anticorrelation, so called antibunching, at zero delay (the offset is due to different lengths of cables for both detectors), (d) Same measurement for pulsed excitation. Thick line Single emitter with missing peak at zero time delay. Thin line scattered laser light signal for comparison.

The compressors are automatically started and stopped as the load varies. When the total flow can be handled by a single compressor or when any of the surge valves open, FSL-03 triggers the shutdown logic interlock circuit 1 after a time delay. Automatic starting of an additional compressor is also initiated by interlock 1 when PSH-04 signals that one of the compressors has reached full speed. The ratio flow controllers (FFIC-01 and... 

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