FAQ - Radon detector for your lab

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Richard Hull
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FAQ - Radon detector for your lab

Post by Richard Hull » Mon Feb 24, 2014 4:44 pm

We all live with radiation as background. Radon is a common source of background radiation. Our labs and homes have radon in them to greater or lesser degrees based on local natural conditions or due to what we store there. If you collect a bit of uranium or thorium ore for GM check sources or have granite counter tops or any other source of uranium or radium contianing devices, (old clocks, meters, watches, etc.), you may have a slightly elevated level over your normal living environment. This is especially true if your lab, basement or shed where your fusor is located is normally sealed or shut up for long periods.

NOTE: The fusor will not create or add any radon to its environment. Radon gas only issues from radioactive decay of uranium, thorium or radium.

This FAQ lets you test for radon in your home or lab area. An ultra simple test can be made provided you have some materials common to the amateur scientist and fusioneer.


All radon gas decays to solid "daughter products" which are, themselves, radioactive. They are created as individual atoms that are positively ionized at the moment of creation. If they sense a large negative electrical field at that moment they will be accelerated towards it. In our case, that will be a needle point, where the field is the highest and they attach themselves to that point via bombardment. Note** the daughter ions will not travel far in air and we will only collect those "daughter" ions that are extremely close to the negatively charged point of our collecting needle.

List of materials.

1. Geiger counter (preferably a mica windowed pancake or tubular probe.) Some very thin walled aluminum probe tubes like the 1B85 are OK
2. A source of negative DC high voltage up to about 5kv, Though 2KV will do just fine.
3. A rod of metal about 1/4" in diameter about 6 inches long. (diameter and length not crtical.)
4. An insulating block or platform (glass or plastic only) wood not allowed.


Using a grinder or file put a definite sharp point on the metal rod. Attach the rod to the top of your insulator with its point up towards the ceiling either by drilling a hole in it to accept the blunt end of the rod or by some other suitable means. ( a very large nail is just fine)

Attach the high voltage, negative lead, of the power supply to the rod with a good insulating wire. NOTE* The supply's positive metal case must be grounded to a good electrical ground. The electrical mains ground is fine. This is very important to make this experiment work properly. This supply much not be of such a high voltage that corona can me seen in a darked room coming off the needle tip. NO CORONA ALLOWED! 1-2 kv is usually about right.

Turn the supply on and start a timer or stop watch and come back in about 45 minutes.

NOTE*** do not allow a parent, sibling, friend or pet to touch the setup while it is running. WARN THEM!

After the time is up turn OFF the supply and ground the needle and supply to discharge any capacitor in the supply.

When you are very sure the needle is grounded, turn on your GM counter and take your GM probe and approach the needle from the side. (This avoids your accidently poking the needle into the delicate mica window and destroying the probe.) It should click slightly above background when you are within 1/2 inch or 10mm of the needle. If not then you have virtually zero radon around. If it is just very slightly above backgorund, you are probably fine and have about a normal amount of radon around. If it really is clicking away double or triple background then you have a significant amount of radon around. In some few cases it might really takeoff. If so, move any radioactives out of doors to a storage shed or put them in a hermitically sealed container like an old military ammo can (can be found at some gun stores, but always at gun shows.)

This is a qualitative test and never a quantitative one, so don't go crazy if you get a high reading. Record your voltage used, photograph your setup and report your counts per minute reading as a reply to this FAQ if you do this experiment so we can compare results, if you like.

Additional experiment........Place a piece of hot uranium ore in a bell jar with an insulated high voltage connected needle in it and pump out the air. After 45 minutes, the point will be extremely radioactive as the ions from much farther away will also attach due to the increased mean free path in the vacuum. In addition, the increased radon contained in the enclosed vessel is due to the Uranium ore outgassing lots of localized radon.

Attached a simple image of the setup below.

Richard Hull
Radon Needle.jpg
Simple diagram of radon test setup. Qualitative results only!
Progress may have been a good thing once, but it just went on too long. - Yogi Berra
Fusion is the energy of the future....and it always will be
Retired now...Doing only what I want and not what I should...every day is a saturday.

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