Sunday, April 12, 2020

Diffusion Cloud Chamber (Conclusion)

The Diffusion Cloud Chamber in operation! 

The clips bellows are from the very first test of the completed Cloud Chamber (best viewed in a full-screen mode).
The Cloud Chamber is capable of displaying only charged particles such as α-particles (Helium nuclei), β- particles (electron), β+ particles (positron), μ (muon), Cosmic Rays / proton clusters, etc..
It will not display neutrons, neutrinos and any other sub-atomic particles without a charge.
When I say "display", you don't see and you cannot see the actual particle but rather the ionized path and the resulting  condensation trails left behind a charged particle going thru the volume. 

I injected the Cloud Chamber with "Thoron" which is a short-lived isotop of Radon - Rn-220 has a half-life of only 55.6 sec and it is an α-emitter (6405 keV). It is a daughter product of Ra-224, which on the other hand is down the decay chain of Thorium.
My son's reaction to this α-particle fireworks display was pretty rewarding!

Here is another example of Radon-220 in the Cloud Chamber. To obtain the "Thoron", I placed a Thorium Gas Mantle (Thorium Dioxide) inside a large syringe and capped it for a couple of days - no point of waiting more than that as it is a very short-lived isotop (55.6 sec) and it will decay quickly after it is produced by Radium-224 (one of the Thorium series decay daughter products) so no substantial accumulation will occur. (In a couple of days, inside the syringe, an equilibrium state will take place - the concentration of Rn-220 will become stable as new Rn-220 will be generated to replace the one which is decaying at that moment.)
I lifted the edge of cover and gently injected the air and radon mixture from the syringe into the Cloud Chamber.
Similar experiment can be done with another isotop - Rn-222 and Radium Watch hands but then it is worth waiting at least 3-4 days longer for more Radon-222 to accumulate in the syringe - Rn-222 has a half-life of 3.82 days.

The clip shows some high energy β-particles and some low energy β are also visible. Around 0:08 there is nice Y-trace showing an interaction with an atom by a high-energy β. One leg of the Y is sort of zigzagging probably from the knocked off electron, the other leg of the Y is straighter, created by the original particle. There is also a nicely deflected low-energy β at around 0:07.

An α-particle, then a low-energy β-particle and at the very end a high-energy β or a muon (μ).

Some really nice particle interactions!

This is the equivalent of a Sub-Atomic Particles Disco-Club. On the left is a Uranium doped glass marble emitting mainly alpha particles and some beta. In the center is a pellet of Am-241 (a very strong alpha emitter) and on the right is a vial filled with Tritium (H³) emitting very-low-energy betas.
This video is from an early test before the Light bars were fully constructed.


I must say, this was a real fun project to work on! (And a true kitchen table / garage project) My son and I had great time designing and working on the Cloud Chamber and the results absolutely exceeded my expectations. It is a nice portable setup and I have the feeling my son will be bringing it to school more than once.
Unfortunately, the Science Fair, we built the Cloud Chamber for was postponed due to the COVID-19 Pandemic but this will give him time to prepare all of the supporting materials and diagrams.
On the bright side, besides being a Cloud Chamber, this instrument is a good platform to demonstrate, study and experiment with multi-stage Thermo-Electric Coolers.
The High-Voltage Power supply and adjustable electric field strength is also useful for experimentation with electric fields.
The Liquid Cooling Plant is quite useful too for various physics, chemistry or electronics experimentation.
Just as with a Telescope - now I wish the Cloud Chamber was a bit bigger tho :-)
Next on the table - Gamma Spectroscopy!

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