The spinthariscope made from around the house materials demonstrates INDIVIDUAL radioactive decays.
“Continue reading” for details of this easy project and others. 8 photos and links…
For a quickie weekend project I made a spinthariscope. These date from the 1920’s and are simply a phosphor screen, a radioactive source and a lens. What you see is very faint scintillations due to individual alpha particles striking the phosphor and giving a brief flash. In days gone by radium was used for the radioactive source.
I made mine from items laying around the house. The radioactive source is americium 241 (1 micro Curie) from a smoke detector which is a small disc hot glued to a plastic rod. The phosphor is scraped from the inside of a colour TV screen delicately smashed to get good access and with a towel over it to prevent implosion and glass fragments. It was dusted over 5 minute epoxy to fix it and it fluoresces white under a UV light (see the nitrogen laser page). Heavy bolts are needed to keep those alpha particles in!
I added a small 10 X magnifying lens so it fixed the focus at a good magnification.
Your eyes need to dark adapt for 5 or preferably 15 minutes in virtually complete darkness before using this but it works with little flashes particularly closest to the americium source. Here is the Science.com site giving historical details and video representation of what you see. Here is what you see when a spinthariscope is connected to a first generation image intensifier tube from Leslie Wright. Impossible to photograph otherwise. Great pics.
I have obtained some activated Zinc sulphide and some Europium oxide to do further experiments with phosphors.
Some terms to understand:
Fluorescence is the immediate emission of light less than 10 ns after the initiating exposure.
i.e. Glows while lit (most dramatically with UV)
Phosphorescence is the delayed emission of light more than 10 ns after the initiating exposure.
i.e. Glows in the dark after being lit.
Radioluminescence Glows constantly due to radioactivity.
Here are some direct photos of radiation sources.
The top photo above shows a close up of an Americium source. The central part of the disk is 2 mm diameter. This has TV screen phosphor on sticky tape and some cross hairs over that. The right photo above shows an 8 minute exposure with the phosphor showing up blue. The red background and green lens flares are from LED’s that were on in the room.
Here are three Americium sources from household smoke detectors made visible by radioluminescence from Alpha radiation. All about 1.0 microCurie and about 1/2 inch (12 mm) in diameter. The top one has no phosphor, the left lower one has Strontium Aluminate:Europium 2% (see below) glowing red and the right lower one has activated Zinc Sulphide glowing green.
The top right photo shows the colour not restricted to the emitter, so this is due to phosphorescence from light exposure minutes before, not radioluminescence from alpha radiation. The lower photo above shows the Zinc Sulphide has a little glow not restricted to the emitter, due to phosphorescence from light exposure some hours before. The photographic exposure is about 7 minutes so this is VERY faint stuff.
Above: Alpha particles can also be seen with a phosphor screen using silver activated Zinc Sulphide as above. The central purple glow is radioluminescence from an americium sample. The needle attached to a cork is a polonium source that is only 1% as strong so doesn’t show up here.
It is still very faint. This exposure is 5 minutes long to capture enough light but it is really a spinthariscope with the same principles as the earlier on although that has magnification.
Related pages
Spark detector for alpha particles
Try something else
External links
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Photo Date:2006