Gamma Spectrometry Forum

Hi All,

Does anyone here have experience with Liquid scintillation counting?

[broken link removed - Steven]

Looks simple enough and should work with PRA, just not sure about how to rig up the PMT's. Would the scintillation liquid and sample be in direct contact with the PMT's or is it normally in a separate glass tube?

I have never seen one in the flesh.

Steven

A late reply...

The sample is mixed in with the scintillation fluid, in a "standard" scintillation vial that is opaque. The PMTs are not in contact with the sample.

I don't really know what kind of "resolution" one can get with these kinds of detectors. My experience is only of gross counting in the lab, when labelling cells with radionuclides, or to analyze swabs.

Thanks Karl,

Wouldn't it be better if one had some kind of coupling liquid between the PMT and the vial?

I'm thinking in terms of silicone oil or something like that, into which one could plunge the whole vial.

Steven

Hello Steven,

We are using clear glass vials with low content of potassium to lower the background, and 2 inches PMT for liquid scintillation counting. The method is most effected for beta and alpha radiation. Spectrometry is possible for both aforementioned types of radiation. The glass vial should be as close to PMT photocathode as possible without special connection with the PMT screen.

Sincerely,

Vit

Hi Steven,

Long time no chat, I do have a crystal housing, with nothing inside (see att), the scintllator: BoDiPy in ethanol, no clue what it was used for.

Cheers, Boris.

Boris,

Thanks for posting, I have no clue what that is either...

Might be cool to make a container with a glass window that could be filled with various liquids and tested.

Tonic water, ink from fluorescent pens etc..

Steven

I have used liquid scintillation in the past when I was a graduate student back in the 1990s. It was used for measuring beta activity in liquid samples. The sample would be intimately mixed with the scintillator then placed in a square-section glass vial (approximate dimensions 1cm x 1cm x 4cm). The vial was then inserted in a slot in the machine. The slot had a window behind which I assume the PMT was located. There was no use of a coupling compound between the glass vial and the window, just close mechanical proximity (close fit of the vial in the slot).
The isotope I used it most with was 32P.
I don't recall what the scintillator liquid was, but it had an eerie purplish fluorescence under fluorescent light; I assume it might have been a water-soluble anthracene derivative or similar.