Commercially Bought Expansion Type Cloud Chamber

About a month ago, I finally completed the construction of a cloud chamber. To be honest, it is actually less of "building", and more like "assembling" because the main part is available commercially. It started in 2014, when I bought a Wilson's Cloud Chamber from an Australian scientific instrument supplier for education: Industrial Equipment and Control Pte. Ltd, or (IEC).

The exact catalog link is here and screenshot are as below:

Here is the list of materials inside the package when it arrived:

1. Cloud Chamber (presumably the most expensive part)
2. A reverse bicycle pump, (sucks air when you pull the piston)
3. A plastic bottle for collection of radon gas
4. Some silicone tubing to connect the pump to the chamber, d = 6 mm
5. A Mohr clip, act as a valve to prevent turbulence if you use the plastic bottle to feed radon gas into the chamber. (as shown in photo)
6. An aluminum vertical stand
7. An instruction on how to use them is available on their website, here. 

It costs a whopping 400 AUD then (I was a postgraduate student then) so I guess I was really desperate to try out the technology. Yet, despite the cost, I didn't make full use of it since purchase. I tested it yes, it worked perfectly fine, but suffers some minor drawbacks.

For a simple operation test, you will need:

1. The chamber
2. The pump
3. The silicone tubing
4. 2-propanol (isopropanol) or ethanol (ethyl alcohol)
5. A high voltage source (this is absolutely necessary)
6. A strong source of light, actually a cellphone flash in continuous operation will do.
7. An alpha radiation source. Easiest to get is Am-241 from smoke detectors.  

METHOD

1. Connect the pump to the chamber through the silicone tube.
2. Clean all internal surfaces with damp, lens paper. (so it doesn't leave paper fibers) 
3. Place the Am-241 inside the chamber. 
4. Wet the bottom of the chamber with said alcohol. (use a dropper)
5. Seal the chamber. 
6. Connect a high voltage source. You can literally use the voltage generated by an electric mosquito swatter (tested, OK). I used a small dedicated 1.5 kV lab power supply then.
7. Pull the valve of the pump. 

This was what I got.

It works well even when the chamber was dusty. The banana plug on 5 o'clock position was annoying. It reduces observation space but the plug is necessary because it connects the high voltage supply to the circular wire on top of the chamber to provide an ion sweep electric-field. 

The alpha tracks were crisp clear if you give an appropriate voltage to sweep away "old" ions, and running the experiment in an environment not exceeding 25 C°. In fact I find the tracks were much clearer and sharper than diffusion type cloud chambers seen so often in YouTube. This is one and perhaps the best advantage of the expansion type cloud chamber.

Absolutely amazed by the result; but like I said, this configuration suffered some serious setbacks:

• The set up is extremely "mobile", it is nigh impossible to take photos without blurring due to all the vigorous motion. The silicone tube was too short so whenever I pulled the valve, the chamber will most certainly move or shake.
• The lighting has to be aligned to the area where the tracks appear. It has to be very bright and "point like" with respect to the chamber. The issue above makes this difficult.
• More importantly, your hands get tired after the 20-th pull. It is difficult to focus on keeping the setup stable and observe the tracks simultaneously. Besides, you only get to see a glimpse of the tracks during each pull, and it never lasts more than a fraction of a second.
• You can, use a video camera to record your findings during each pull, but the FPS of my camera was low then, and I would need to review the videos frame-by-frame. Rather tedious. 

The conclusion was: if I want to take quality photos of whatever tracks emerging in this chamber, I need to put it on a steady box, inside the box contains all the systems needed to keep the chamber working. In the end, I would be operating the chamber by pressing a button instead of pulling the piston. 

This chamber was kept for a long while until mid 2019, when I had the chance to use my father's workshop; and finally completed during peak COVID pandemic in 2020 when I had the time to work out the installations.