"Directed" Geiger counter for gamma radiation

[MareTranquil]

Hello.

For a personal project, I'd like to know if its possible to modify a tiny geiger mueller tube like this one in a way so that it only detects gamma radiation from a small arc of only a few degrees, while ignoring other gamma radiation sources. The obvious Idea would be to attach something like a long lead tube around the instrument which simply blocks all unwanted sources. My question is: would it be possible to do this and end up with something thats still somewhat small (not larger than a cigar would be perfect), or would this be rather impossible because of the massive required shielding?

[Cycoticpenguin]

gamma shielding... difficult.

The only way Id see this being possible is by using 2 detectors.

have one with an certain amount of lead around it, and have the other free. Calculate the difference and extrapolate the shielded difference to get what you want. Tenth thickness of lead is 2 inches, so Unless you want a 300 pound detector....

[MareTranquil]

Thanks, thats a nice idea.

One more short question: Would it help to use a low energy gamma source, like I-123 with its ~30keV?

[RDTroja]

Thanks, thats a nice idea.

One more short question: Would it help to use a low energy gamma source, like I-123 with its ~30keV?

If that is the isotope you are looking for, then yes. It would be less useful (or even useless) for other isotopes of higher energies.

Many years ago (1976, to be exact) I saw a directional gamma meter -- not discriminating to a single direction, but indicating direction to the source. It was pocket sized and had an array of very small detectors around the periphery of the case. The gentleman that owned it had brought it with him from Eastern Europe -- I never saw another one. Very cool, but probably not what you are looking for.

[OldHP]

(not larger than a cigar would be perfect

Most of the instrument manufacturers have available a good shielded GM or NaI detector; however, cigar sized (and I assume you also mean weight) - unless your looking for a very specific very low energy gamma with no other isotopes or other potential sources present, the answer is a very simple NO!

I saw the same instrument RDT described along about the same time, but here again, what you are asking for it is not a fit.

[namlive]

Instead of an arc, I would use a sphere with shielding at the center. That way I could get an area profile. Instead of using GM tube, use  TLD type material. Take your read out. Divide by the period of time it was placed in the area to get a dose profile.