Gamma Spectroscopy Data upload

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2 years 11 months ago #4704 by Simomax
I like your setup RHStation! Not the best looker with the PVC tape but looks like you are getting some mighty nice results! The pulse shape looks pretty perfect! That's the bit I'm currently struggling with by modifying my Mini Instruments 5.40. Whilst I get the amplitude to the sound card input mine is ringing like crazy so I have to make some kind of inverting amp and conditioner to smooth things out a bit.

I have a couple of scintillation probes. A Mini Instruments 44A which uses a sodium iodide crystal and some old alpha scintillation probe that I picked up from ebay. Both use photomultiplier tubes. I think the 44A is 32mm and the old alpha probe is about 25mm. I'm yet to get the alpha probe working/tested as the rate meter that came with the probe needs completely re-cap'ing before I can go further with it, and I inadvertently broke the aluminium window on the alpha probe by stabbing it with a screwdriver :( That's one of those rainy weekend projects when I have time. I also think I might have another alpha scintillation probe that is part of an old British Army Contamination Meter No 2 set (has 3 probes and the rate meter) but I haven't even looked at that yet. I picked it up from an antique place, brought it home and haven't touched it since! Another rainy day project!

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2 years 11 months ago #4708 by RHStation
I use to turn aluminum tubes for probe enclosure, as done in one of my previous project here:
rhelectronics.net/store/diy-multi-channe...pectroscopy-detector

it also require to add mu-metal magnetic shield inside around the PMT.

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2 years 11 months ago #4714 by Simomax
Wow! That project looks fantastic! Very nice work.

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2 years 11 months ago #4753 by RHStation
Do you have a link to Mini Instruments 5-44A? What I was able to find is here:
stratecservices.nl/wp-content/uploads/20...900Scintillation.pdf

If it correct link, it say the 44A probe has crystal NaI(Tl) 32mm dia by 2.5mm thick, that fits only low energy range like 15keV to 250keV
For gamma spectroscopy in range 26keV-3000keV it better to use crystal with equal DxH, at least 25x25mm or 30x50mm, or bigger size.

The probe divider resistance is 55 Mega ohm. But I'm not sure that 5-44A and 44A are same things.

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2 years 11 months ago #4756 by Simomax
I have some info on the 5-44A probe, but not a lot. It is an old probe from ~1985. I'm sort of starting to think from what you say that my probe isn't really made for spectroscopy?

This is the manual for the meter and probe. The details about the probe are on pages 14-17: ia600900.us.archive.org/23/items/MiniIns...%20manuals%20etc.pdf
This is the data sheet for the PMT in that probe: et-enterprises.com/images/data_sheets/9902B.pdf

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2 years 11 months ago #4759 by RHStation
Simon, 32x2.5mm crystal will not be good for spectroscopy in range of 26keV-3000keV. 5-44A probe made rather for low energy detection of medical isotopes or some XRF
For gamma spectroscopy you need crystal geometry like 25x25mm, 30x30mm, 40x40mm, 30x50mm, 63x63mm or similar ratio. Equal ratio 1:1 works better. And PMT photocathode diameter should be equal or larger than crystal window.
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