Geiger Muller counter recomendations

[shed9]

Appreciate it is a bit of an odd one. Can anyone recommend a useful low budget Geiger Muller counter for infrequent non-critical use?

I need to check some old vintage camera lenses, the likes of Super Takumar, some Zeiss and OM lenses mostly so it doesn't need to be or warrants being too advanced or expensive for that matter. Any advice or recommendations?

 

[Spectric]

You are not mentioning the sensitivity required or levels, background will be much lower than if there was a nuke landing up the road. Why do think these lenses are contaminated?

 

[shed9]

You are not mentioning the sensitivity required or levels, background will be much lower than if there was a nuke landing up the road.

Good point, very unlikely to peak beyond 100 uSv/h in what I want to measure so anything that measures within that range relative to background levels, i.e. an ability to get a base line.

Why do think these lenses are contaminated?

A fair few vintage lenses from the 1940's through to the 70's (and I suspect possibly the 80's) are contaminated with Thorium oxide, typically 30% by weight. It has a crystalline structure similar to Fluorite which is used in mid-high end optics to reduce chromatic aberration. The Thorium oxide is cheaper than the Fluorite option so it got used instead in some models within some manufacturer's ranges. I have lot of lenses and whilst there is some info on some of the usual suspects (like the Takumar's listed up there ^), the list is not exhaustive and I want to double check in order to take measures when storing, using or indeed selling on.

In reality I don't need a very accurate reading, just need to know how high it is (or not) relative to background radiation (and bananas ).

 

[MusicMan]

You might check a nearby university department that does Xray work (engineering, physics, materials or chemistry departments). The person to ask for is the Radiation Protection Officer. They will quite likely do you a favour and do a quick check if you can bring the lenses in. And their dosimeters will be calibrated.

A local hospital will have the facilities but they are a tad busy at the moment.

Quick search online shows that most proper instruments run at the £400ish mark. Be wary of the cheap 'radiation meters' as these seem to be mostly for electric fields not Xray/beta/gamma fields. See also hps.org.

Keith (a former RPO)

 

[shed9]

You might check a nearby university department that does Xray work (engineering, physics, materials or chemistry departments). The person to ask for is the Radiation Protection Officer. They will quite likely do you a favour and do a quick check if you can bring the lenses in. And their dosimeters will be calibrated.

A local hospital will have the facilities but they are a tad busy at the moment.

Quick search online shows that most proper instruments run at the £400ish mark. Be wary of the cheap 'radiation meters' as these seem to be mostly for electric fields not Xray/beta/gamma fields. See also hps.org.

Keith (a former RPO)

Thanks for the comments and response, I've worked with organisations with radioactive materials and NDT X-ray imaging in the past (albeit many years ago now). If someone had turned up with a box of potentially active components, I think I'd have called the police. I'd expect the NHS to call the CNC on me in those circumstances in the very least.

Looking on line, the GQ models seem to get a fair review which are typically sub £100 but not sure if there any members who can recommend that or something similar. I appreciate that low end counters will be only gamma and beta (and x-ray) with alpha detection being much higher cost but even cheap tubes will give a reading to give an idea of emitted radioactivity relative to background. Just would rather get something someone can apply some real world experience to it if possible before I push the buy button is all. I knew it was an odd one but given the breadth of experience on here, just wanted to double check.

 

[Nic Rhodes]

Coatings an also be radioactive. The levels i have generally seen have not been significant however. Is the information going to change what you do? Microscopes are similarly effected, some very old. The 'postal people' often detect these lenses on international shipments but levels are tiny and explained but items are returned to sender or more normally just confiscated. I would not be taking potentially contaminated equipment to hospitals / university etc ( heap on pain coming if you do) so plan to buy your own tube is a good one. Requests in the past 20 years to test similar stuff have been gently batted back politely by these organisations but prior to that many may have helped. I would look secondhand / military surplus but am afraid I don't have any specific recommendations.

 

[shed9]

Coatings an also be radioactive. The levels i have generally seen have not been significant however. Is the information going to change what you do? Microscopes are similarly effected, some very old. The 'postal people' often detect these lenses on international shipments but levels are tiny and explained but items are returned to sender or more normally just confiscated. I would not be taking potentially contaminated equipment to hospitals / university etc ( heap on pain coming if you do) so plan to buy your own tube is a good one. Requests in the past 20 years to test similar stuff have been gently batted back politely by these organisations but prior to that many may have helped. I would look secondhand / military surplus but am afraid I don't have any specific recommendations.

I'd not heard of coatings being radioactive, just assumed it was only the glass itself. I was aware that microscope eyepieces sometimes used Thorium which is incredibly disturbing given the ability for the radiation to penetrate the eye so much more easily than skin, that and the proximity of it.
I know there is mixed info out there ranging from laughing it off to it being quite serious but I'm erring on the side of caution so I'm selling the ones I know are radioactive and going to check the ones I'm unsure of which is why I want a counter. I'll be quite clear in the sale listings as people need to know either way and I'm also aware these lenses are sometimes sought after. I know the general consensus is that if used appropriately they pose little risk but that position is totally thrown out of the window if the optics become damaged. I'm a little cautious of buying secondhand mostly because of unknown provenance and calibration. I'm leaning towards this unit at the moment. Not too expensive and I'm sure I've seen it come up on the photography forums in the past (just can't remember those links or find them anymore).

 

[shed9]

Okay quick update, I purchased a GQ GMC320+. Not too expensive and gets lots of positive online reviews from users with access to much higher end equipment. Arrived yesterday and I did a check of my lenses. Thankfully the majority of them are fine with no discernible reading beyond background levels which for my area is about 15 CPM (0.1 uSv/h). The biggest reading was an Olympus Zuiko 50mm 1.4 which topped out at 330+ CPM which clearly sounds high but that's having the Geiger Muller tube directly over the lens glass. Moving the detector away drops that reading significantly as radiation dispersion is a squared function relative to distance. The detector only picks up beta, gamma and x-ray but I only wanted to reference the difference against the base background so whilst I'm not picking up alpha particles this is sufficient info to ascertain safety.

If any of you have old lenses from the 35mm film days that you still use either with film of DSLR's, mirrorless, etc, I'd recommend doing a quick online check if I were you. Better to know now IMO.