Clean ¹³⁸La

[GigaBecquerel]

Hello guys!

Lanthanum often tends to be contaminated with actinium, as you can see here:
viewtopic.php?f=5&t=900

I got my hands on ~150 g of LaCl3 (at least that's what it's labled as, but one of the powders is not hygroscopic at all, so I have no idea what I actually got), and so I took a spectrum of it.
The samples were left in their containes and just propped up on my NaI, inside the lead castle.

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photo_2021-11-04_21-12-36 (2).jpg (70.16 KiB) Viewed 2735 times

After around 13 hours I took the samples out of my lead castle and proceeded to take around 5 hours of background.
Subtracting the background (scaled accordingly) from the actual spectrum showed all three ¹³⁸La peaks nicely and was clear of any actinium contamination!

Raw Spectrum with background included

Clean Spectrum

Please note that the total activity was 30-50 Bq, so a longer sample time would have improved the spectrum a lot.
Lanthanum is a nice sample to test the low end of your detectors sensitivity, the metal is ~0.8 Bq/g, and you'll end up with a gamma every two seconds or thereabout.

Lukas

[Peter-1]

I also measured La138 a few months ago. It was 100 grams of La oxide. I could only see the 2 lines of La138.

Peter