## Confusing paper about a PMT

Scintillation crystals, PMTs, voltage dividers etc...
tim.hbn
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Joined: 04 Aug 2021, 00:19
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### Confusing paper about a PMT

Hi Everyone

I would be very grateful if any of you could make sense of something for me:

Please have a look at Figure 4 of the following paper:

https://cds.cern.ch/record/2278277/file ... ciency.pdf

It shows that at four different temperatures, the pulse height distributions are identical (apart from small random variations). All of the units and numbers on both axes are the same. However, the paper claims the following:

"The only notable difference between the plots is that the total signal frequency, found by summing over all bins, is decreasing as the temperature decreases which is consistent with the results presented in Figure 3."

There seems to be a contradiction here. Can anyone therefore help me to understand this?

Thank you very much

Kind regards

Tim

GigaBecquerel
Posts: 163
Joined: 04 Jul 2020, 07:34
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### Re: Confusing paper about a PMT

You answered your own question.
The paper says that the frequency decreases with temperature and represents that in Figure 3.

Figure 4 displays pulse height, and not frequency.
Figure 4 shows the measured pulse height distribution at varying PMT temperature. It
can be seen that the distribution shape is almost identical in every plot and therefore, it
can be said the the pulse height distribution is independent of temperature, at least within
the temperature range investigated.
Lukas

tim.hbn
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Joined: 04 Aug 2021, 00:19
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### Re: Confusing paper about a PMT

Hi Lukas

Thank you very much for your reply.

If you look at Y axes of the four charts in Figure 4, you will see that they all say "Frequency per bin (Hz/10mV)" (and the numbers are the same in all four chrarts) so how is this not about frequency?

Thank you very much.

GigaBecquerel
Posts: 163
Joined: 04 Jul 2020, 07:34
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### Re: Confusing paper about a PMT

Fig 3 is Signal / (Signal + Dark counts), which is more or less the SNR, while Fig 3 is absolute counts, or rather their frequency

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