Theory Of Operation - Horiba Scientific FluoroMax-4 Operation Manual

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FluoroMax -4 & FluoroMax -4P with USB rev. D (30 Jul 2012)

Theory of operation

A second source of illumination, a pulsed xenon lamp, is used for phosphorescence
measurements. Samples are excited with pulsed light; the emitted phosphorescence is
measured using an R928P photon-counting detector.
Sequence of data acquisition
The illuminator housing, or flash lamp, operates at up to 25 Hz. The control module
triggers each lamp pulse. When the start of the light output is detected, a signal is sent
to the control module for timing purposes. The control module houses the signal-gating
circuitry that intercepts the signal from the pulse-counting emission photomultiplier
tube, collects a selected, time-delimited portion of the signal, and later passes it to the
software. The maximum signal detectable per flash varies with the integration time:
Integration time Maximum signal (counts) per flash
100 μs
1 ms
10 ms
100 ms
1 s
With, for example, the counts integrated over 10 ms, the maximum detectable signal is:
(1 second/integration time) × (counts/flash) = total counts
(1 second/0.01 second) × (20 000 counts/flash) = 2 000 000 counts total
A typical sequence of data-acquisition (see below) starts with a flash from the pulsed
lamp, sensed by the control module as time t = 0. The light enters the excitation
monochromator, where it is dispersed. Monochromatic light from the monochromator
excites the sample. Luminescence emission from the sample then passes through the
emission monochromator to the photomultiplier-tube detector. The control module in-
cludes a gate-and-delay generator, allowing the signal at the detector to be integrated
only during a specific period after the flash (the Initial Delay), for a pre-determined
length of sampling time (the Sample Window). Any signal arriving before or after the
gating is ignored.
200
2000
20 000
200 000
2 000 000
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FluoroMax -4P Phosphorimeter Operation