Tuff (Volcanic Rock)

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Go-Figure
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Tuff (Volcanic Rock)

Post by Go-Figure » 03 Jun 2019, 07:48

Hi folks,
This weekend I recorded two interesting spectra (interesting for me at least, hopefully for you too).
This is the first one: tuff blocks. Tuff is a volcanic rock and here in Italy is a common building material, albeit it is less used now than say 20 or 30 years ago.
As far as I know tuff is the most radioactive building material in my area. As an engineer who works a lot on builidings I have easy access to this sort of material. The blocks I tested are from the 1970s and come from a buillding site where I am currently working.
Tuff contains U238, Th232 (and their progenies of course) and K40 so basically all the "natural" peaks are there even if they are not all visible since some are too weak and some are on top of each other.
Here I identified only the ones which were clearly there without assuming the presence of what I didn't see just because I knew was there. The spectrum is so crowded that I didn't labeled the single and the double escape peak, which seem to be both there (the double escape peak is so close to Ac228 peak at 1588 keV which is hard to tell one from the other).

Calibration was done using the backgrouns, since I knew I was going to find many of them in what I was going to analise and I have to say it holds pretty well all the way to Tl218 peak at 2.6 MeV which in my case is usually off by more than 50 keV.

There's a peak around 135 keV (it's not the first time it shows up in my spectra) which I didn't label because it's not clear to me what it is. It could be a back scatter peak (it's just an hypothesis), and its energy is campatible with a back scatter peak of a gamma around 300 keV, which I have from Lead 214 (295 keV), but for now I decided not to "call" it.

I also attach some quantitative analysis of the result. The activity is spread out across many different peaks but in the end the energy per unit time of the samples on the crystal is less than that coming from the background.

Again this is an unshielded measurement and I used background subtraction. As you can see the samples measurements was done by buiding a small tuff castle around the detector.
The spectrum is shown both in counts per bin and energy per bin.
The dead time for this measuremenet was 140 µs, a further improvement thanks to Steven's help.

In the future I plan to test also granite and porphyry.

Nice start of the week to everyone!

Massimo
Attachments
Tufo - ID - 01-06-19 - Counts x Bin - BG Subtraction - Stanza Fondo - 15 Hours - Clean-0.062.png
Tufo - ID - 01-06-19 - Energy x Bin - BG Subtraction - Stanza Fondo - 15 Hours - Clean-0.062.png
Spectrum Analysis-001.jpg

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pilgrim
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Re: Tuff (Volcanic Rock)

Post by pilgrim » 04 Jun 2019, 04:04

As usual, excellent work Massimo!
This, https://ibb.co/cYgpLm, is an old attempt I made with a single block.
Daniel, Italy

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Go-Figure
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Re: Tuff (Volcanic Rock)

Post by Go-Figure » 04 Jun 2019, 06:50

pilgrim wrote:
04 Jun 2019, 04:04
As usual, excellent work Massimo!
This, https://ibb.co/cYgpLm, is an old attempt I made with a single block.
Thank you Daniel,
I see you have two distinct peaks in the X-rays region, is the higher one from the lead shield?

Ironically today I was at a building site and I came across a few old tuff blocks which game me 40% more counts on the geiger counter than the one I just tested!
I already asked to borrow them for a couple of days.
I am currently waiting for a sample of Trinitite and one of Tornernite, if they don't make it for the weekend I will go for the Tuff again on saturday. Not that I expect to see different peaks, I just want to see how much more gamma radiation comes out from it, if any.

Massimo

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pilgrim
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Re: Tuff (Volcanic Rock)

Post by pilgrim » 06 Jun 2019, 13:40

Honestly I don't remember, I only remember I recorded the spectrum outside the Lead shield because of the dimensions of the block.
Daniel, Italy

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Go-Figure
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Re: Tuff (Volcanic Rock)

Post by Go-Figure » 07 Jun 2019, 06:55

pilgrim wrote:
06 Jun 2019, 13:40
Honestly I don't remember, I only remember I recorded the spectrum outside the Lead shield because of the dimensions of the block.
So no lead shield fluorescence.

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