Pulse shape issue in PRA 24

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GeoSteve
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Pulse shape issue in PRA 24

Post by GeoSteve » 30 Sep 2019, 07:10

The issue I'm having is simple: if I uncheck boxes in the pulse shape settings window, the checked boxes are automatically set to other values.
I'm following the instructions from this post by Steven: viewtopic.php?f=7&t=495#p2334
No issues if I leave all boxes checked.
First, I acquire a few thousand pulses to obtain this
First, I acquire a few thousand pulses to obtain this
pulse_shape_1.PNG (27.08 KiB) Viewed 3527 times
Then, I uncheck some boxes to make the pulse shorter, and save
Then, I uncheck some boxes to make the pulse shorter, and save
pulse_shape_2.PNG (26.16 KiB) Viewed 3527 times
However, when I open the pulse shape settings, all values have been modified to something completely different
However, when I open the pulse shape settings, all values have been modified to something completely different
pulse_shape_3.PNG (24.49 KiB) Viewed 3527 times
The same happens if I do a copy-paste of the original values and save. Am I doing something wrong, or is it a bug? Anyone else having the same issue?
Right now this is not a problem for me because I don't have any sample with high count rates, but I may have to use shorter pulses in the future.
Steve N.

Scionix 38B57 NaI(Tl), ~3 cm lead shield, GS-USB-PRO

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Sesselmann
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Re: Pulse shape issue in PRA 24

Post by Sesselmann » 30 Sep 2019, 09:35

Steve,

The software centres the peak on or around sample #30, so to narrow the sample window you should un-tick the same number of samples at either end, i.e. 1-10 and 40-50.

The important thing here is to understand the relationship between sample rate and number of samples so that your window is a reasonable size with respect to your pulse. So for the GS this is in the order 90 - 150 µs.

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GeoSteve
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Re: Pulse shape issue in PRA 24

Post by GeoSteve » 30 Sep 2019, 09:54

I tried to uncheck boxes both before and after (i.e., 5 before and 5 after), but the same issue comes up anyway. I have tried with different sampling rates too.
Again, this is not an real problem for me at the moment, I can easily use the full pulse width, but it has been puzzling me for a while now.
Steve N.

Scionix 38B57 NaI(Tl), ~3 cm lead shield, GS-USB-PRO

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Cosmic
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Re: Pulse shape issue in PRA 24

Post by Cosmic » 23 Oct 2019, 17:44

Hi Steve,

this isn't a bug, this is a feature of PRA, bacause the pulse shape is normalized, see manual->pulse shape editor.
If you plot the different pulse shapes (original and shortened) i.e. with Excel you can see that they are quite similar.

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