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11 HISTOGRAMS
11 Histograms
All of our histograms are time difference histograms. They differ only in their usage of
events as a start or stop signal.
11.1 Start-Stop Histograms
Start-Stop histograms use each detection event in one channel (e.g. channel A) as the
start signal and only the first following detection event in another channel (e.g. channel
B) as a stop signal. It is possible that A and B is the same channel, and, additionally,
there is a channel independent Start-Stop histogram, where each event triggers a start or
stop signal. In total, there are 8
·
8 + 1 = 65 Start-Stop histograms, with the 8 possibilities
of channel A and B.
Example As an example, consider the events x
i
, ordered by their timestamp, in the
channels A and B depicted in Figure 20 . The arrows show the considered time differences
for the different histogram types.
For the A-A Start-Stop histogram, the time differences x
2
−
x
1
, x
6
−
x
2
, x
8
−
x
6
and
x
9
−
x
8
would be recorded. In the A-B case, it would be x
3
−
x
2
, x
7
−
x
6
and x
10
−
x
9
.
For the channel independent case, all x
n +1
−
x
n
result.
Figure 20: Example of the determination of time differences for different start-stop
histograms. Three possibilities are shown: Start and stop event in the same channel (A-
A), start and stop events in different channels (A-B) and channel independent (ind.). Each
arrow starts on a STOP-event and points towards the respective START-event. Please note
that, by convention, time differences of events happening in different channels but the same
time bin are recorded as
x
A
−
x
B
= 0 for the (A-B) histogram with A < B.
11.1.1 Realization in the quTAU GUI
Start-Stop Histograms can be easily obtained by the quTAU GUI by switching to the
”Start-Stop Histograms” tab, see Figure
21 . Settings can be accessed on the right hand
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