9
(COINCIDENCE) COUNTING
9
(Coincidence) Counting
All single (each channel individually) and some coincidence rates (channel 1 to 4) are
directly measured in the quTAU device, leading to 19 values (8 single count rates, 6 two-
fold coincidences (1&2, 1&3, 1&4, 2&3, 2&4, 3&4), four three-fold coincidences (1&2&3,
1&2&4, 1&3&4, 2&3&4) and one four-fold coincidence (1&2&3&4)) being transferred to
the PC by USB. Additionally to the input parameter settings, the user can specify the
integration time
and the
coincidence time window
.
9.1
Integration Time
The integration (or ”exposure”) time can be set to any ms value larger than 100 ms.
All count rates will be shown according to this time window. This is also the minimum
waiting time until a count rate value can be updated.
9.2
Coincidence Time Window
The coincidence time window can be set in integer multiples of the internal time unit
(”Bins”). Two (or more) detection events will be counted as a coincident event if the
difference of their time stamps is less or equal than the specified time window.
9.3
Realizations
Count rates can be monitored by both Daisy and the quTAU GUI. The command line
interface can be used to output the last counter values.
9.3.1
Daisy
Count rate information can be accessed by switching to the Tab ”Coincidence Counters”.
At the top, the required parameters can be set. All 19 current values are displayed in a
bar plot. The plot updates once per integration time.
Additionally, the trend of a selected count rate can be displayed in a line graph.
9.3.2
quTAU GUI
A trend of all count rates is displayed in the Tab ”Count Rates”. On the right hand side,
the required parameters can be set and individual count rates can be displayed or hidden
using the check boxes.
If no device is connected, simulated data can be used to test and explore the interface.
By right clicking on the graph, the displayed data can be exported.
quTAU/quPSI Manual V4.0 Page 21
