Puzzling N.O.R.M. Spectra

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Posts: 14
Joined: 21 Jan 2019, 10:43
Location: Willunga South, South Australia

Puzzling N.O.R.M. Spectra

Post by elemental » 22 May 2019, 13:46

Greetings all,
I have recently collected a few spectra of N.O.R.M specimens collected within South Australia.
Some of the results are for me very puzzling so I have posted them with the hope that somebody
can provide an answer.

Firstly, the spectra were collected using a Bicron NaI probe, a GS-1100 driver, a Digitech XC-4905
external USB sound card and a Windows Surface Pro. They are displayed using the InterSpec software.

The spectra were calibrated using a Thorium mantle, which, due to the results, was used to check the probe and calibrations at the end of the experiment.

The N.O.R.M. samples used, in order of the following pictures, were:
1. Fergusonite, Arkaroola, SA
2. a reddish- brown opaque specimen - type and locality unkown.
3. Torbenite, South Alligator Gorge, NT

The second and third specimens are VERY active on a geiger counter.

The first Picture shows the pre (black) and post (green) calibration checks.

The next picture is the spectra obtained from the Fergusonite.

The next spectra was obtained from the sample of unknown type and locality.

This last Spectra was obtained from the torbenite sample.

Looking at the previous two sectra, I think it is apparent why I immediately rechecked the calibration and equiptment, fearing that something had broken down.
If anyone can offer an explanation as to the cause of the last two spectra, it would be greatly appreciated.

Gary Reed
Willunga South

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Joined: 27 Apr 2015, 11:40
Location: Sydney

Re: Puzzling N.O.R.M. Spectra

Post by Sesselmann » 22 May 2019, 16:12


Your Thorium spectrum looks pretty normal, it appears you have had a bit of temperature drift between the first and second run, plausible for South Australia.

The second spectrum also looks like a typical rock containing tome Uranium, also plausible for South Australia :)

The two last spectra make no sense, what was the count rate during collection of these?

Are you sure it was the Pulse Height Histogram you exported.

PS: Give your images some descriptions and insert them inline with your text, makes it easier to identify.


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