Leica TCS SP8 SMD, User Manual

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Summarized manual for FLIM experiments
Figure 148: Online monitoring of the photon count rate in the SymPhoTime preview window. Left: Display
of the count rate over time. Right: FLIM image preview specifying the maximum count rate (red
rectangle).
3. Make sure that the maximum Peak Count Rate is below the values given in the table
below Table 21 .
Table 21: Upper count rate limit for FLIM detection with different detectors
The reason for limiting the detection count rate lies in the Pile-up effect that causes an
apparently shorter lifetime at high detection count rates.
For example, using a laser repetition frequency of 40 MHz and a detection count rate of 1
MHz leads to an error of below 1 % for the calculated lifetime. At a 3 MHz count rate, the
obtained lifetime will be 2 % too low. The error induced by the pile-up effect is proportional
to the ratio between the detection count rate and the laser repetition frequency. The
maximum measurement count rate is calculated from the maximum of the
time trace
displayed on the tab of the same name (see Figure 148 , left ). The binning ( resolution ) should
be set to 1 ms. This allows you to see the changes of the count rate over time.
Laser pulse frequency
(repetition rate) Upper count rate limit for different detectors, in [kcounts/s]
PMA photomultiplier or MPD
APD (MPD)
PE AQR APD
PE APD (AQR)
40 MHz 1000 700
20 MHz 1000 700
10 MHz 500 500
5.0 MHz 250 250
2.5 MHz 125 125