Studies, Jobs and the likes

Hang up the labcoat, relax and chat about anything
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Posts: 33
Joined: 18 Oct 2019, 08:27
Location: Colorado, USA

Re: Studies, Jobs and the likes

Post by ColoRad-o » 03 Jun 2024, 10:12

I am a retired theoretical physicist, spent 8 years at a US federal lab predicting from first principles the properties of new materials for photovoltaic applications, then 28 years in academics doing some research and teaching mostly graduate physics courses across a wide spectrum of topics. My wife and I bought a house near the Rocky Flats National Wildlife Refuge in Colorado (once the site of a plutonium processing DOE facility) and I was horrified at the extent to which misinformation pervaded public discussion and social media. When I retired I vowed to provide clear, thoroughly documented radiation information of all sorts, from measurement through long-term cancer risk estimates. (More below.)

My favorite of two GM counters is a bGeigie Nano (now no longer available, but with a successor) I built from a kit, a data-logging GPS-enabled pancake with mica window model, a very nice survey meter which can detect alphas and betas as well. As a theoretical physicist, I'm a sucker for taking and analyzing my own data, so got a 50x50 mm NaI:Tl gamma system from Steven.

If you're curious what a theoretical physicist brings to a problem such as radon abatement, take a look at ... -basement/. The docs on radon take you from the diffusion equation through its analytic solution for a leaky-floor radon geometry, and fits to experimental data from other people. There's a cute method for collecting radon daughters using a charged balloon, which I carried far enough that I could easily see gammas from some of them (but nothing from 'thoron' (the radon isotope from the 232Th decay series) daughters). I taught myself a great deal about the ICRP radiation protection and the health physics business and maintain , devoted to reliable science about Rocky Flats. No one gives a rat's ass [as we say in English], however, so entrenched is the misinformation. Still I try to fight the good fight.
D. M. Wood, retired physics professor
Arvada, Colorado (USA)
SAFECAST member (bGeigie Nano)

Rob Tayloe
Posts: 110
Joined: 10 Nov 2020, 12:00

Re: Studies, Jobs and the likes

Post by Rob Tayloe » 03 Jun 2024, 22:32

In the introductory section I summarized my relevant work experience.

With respect to "thoron" measurements - when I was teaching a radiation detection lab at Ohio State Univ or sometimes as part of a lecture to a larger group of students, I would perform (or have students perform) a simple measurement of "thoron" decay. The "thoron" is Radon 220 which has a 55 sec half-life. My measurement experiment is summarized below -

Place a thorium laden lantern mantle (the old Coleman ones seem to work best) in a quart-size zip lock bag.
Open the upright zip lock bag
Using a large (e.g. 200 ml) syringe, draw an air / radon mixture from the bottom of the zip lock bag (radon is more dense than air and will collect at the bottom)
Inject the air / radon mix from the syringe into an upright DIY ion chamber (typically powered by a 9 volt battery) and output to a digital volt meter (or ADC if getting fancy with graphical display)
Record ion chamber "readings" (i.e., voltage) at periodic intervals (in the class or lecture room, we used 10 or 15 sec intervals with data being entered into a spread sheet)
After about 3 min the spread sheet results will yield a pretty straight line (with a semi-log scale). The slope is close to 55 sec. Usually there is also some "leakage" from the imperfectly sealed DIY ion chamber and I would often have students calculate the leakage rate.

Details on construction of an inexpensive DIY ion chamber can be found at the links below -

Note: the newer Coleman lantern mantles no longer contain thorium. I was able to source some of the older items from a Coleman Museum some years ago. Following is a link about the thorium laden lantern mantles - ... ntles.html

In the YouTube video below a fellow searches antique shops for radioactive lantern mantles (finds some about 9 min into vid) -

Additional YouTube videos on a DIY ion chamber are linked below. Note: there was a "kit" sold by the Mad Scientist Hut, this appears to now be a defunct webpage. However schematics for a similar device are given on the techlib webpage.

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