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Caver451

Starbucks Cloud Chamber

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I've always wanted to make a cloud chamber. They look like simple devices, and seemed pretty easy to make. As I usually do when a project like this pops into my cluttered brain, I started making a shopping list. Plexiglass sheets, epoxy, metal plate, ... hold on a second! Why am I making this so complex? This are simple devices. How simple can I make one?

 

At that moment, I decided I was going to make a cloud chamber in a Starbuck's cup. For the uninitiated--and I can't imagine there are many--Starbuck's is a mega-coffee shop chain. Think $5 "gourmet" coffee. Unfortunately, I'm addicted to their black iced tea, and I usually have three or four a week. The iced tea comes in three sizes of cups, the largest 16cm tall with a 9.5cm diameter mouth. They are clear plastic. Could I actually make a cloud chamber in a Starbuck's cup?

 

I stopped by Starbuck's on the way home, bought the largest iced tea, and then ducked into the grocery store to buy a few pounds of dry ice. As I was with my wife, it started the typical conversation:

 

Wife: "Errr, what are you going to do with the dry ice?"

Me: "Cloud chamber."

Wife: "Oh." *shakes head*

 

After consuming the iced tea, I rinsed the cup and dried it thoroughly. I then folded a small paper towel into a square just large enough to stuff into the bottom of the cup. I taped it in place and then poured in some 99.9% pure anhydrous isopropyl alcohol. The paper towel now saturated, I turned the cup upside down. Was pleasantly surprised that the tape held it in place.

 

Next I cut a circle of aluminum foil slightly larger than the opening of the cup. I folded the edges against the cup and taped it in place, making sure the seal was airtight.

 

Next I crushed some of the dry ice and placed the resulting snow into a small dish. The cup was then placed on the dry ice, aluminum foil side down. I turned off the lights and used a small flashlight to illuminate the bottom of the cup.

 

After a few minutes, I started to get a little discouraged. There WAS a fine mist, but... BANG! A trail, plain as day, zipped along about a centimeter from the foil! A half minute later, another, and then another. You can imagine my excitement.

 

I decided I needed a little more "umph", so I removed the foil, added a bit more alcohol to the paper towel. I then sealed a small sample of uranium ore in the cup, and sealed the foil back up. The effect was almost immediate, and absolutely dramatic. Dozens of small trails sped away from the sample. This continued for over 20 minutes, until the dry ice completely sublimed.

 

I attempted to take pictures, but these trails are really tough to photograph! I did manage to get a few trails to photograph. Please find two attachments enclosed. One is of the completed cloud chamber, and the other is a close up of a few trails.

 

I can't imagine a more simple cloud chamber. It's just a plastic starbucks cup, a paper towel, some aluminum foil, tape, dry ice and isopropyl alcohol. Took about two minutes to make, and worked like a charm!

 

This must put me in the running for some sort of geek award. ;-)

 

-Caver

starbucks-cloud-small.jpg

cloud-tracks-small.jpg

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Cool. Now you need to add a webcam :)

 

Actually, that was my thought a few months back when I visited TRIUMF, and saw the cloud chamber they have in the lobby. I did a brief Google search but couldn't find anyone who had done this. Anybody know of such a setup already in place?

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Cool. Now you need to add a webcam :)

 

Actually' date=' that was my thought a few months back when I visited TRIUMF, and saw the cloud chamber they have in the lobby. I did a brief Google search but couldn't find anyone who had done this. Anybody know of such a setup already in place?[/quote']

 

The problem with adding a webcam, which would be super cool, is that the chambers only work for about 20-30 minutes, until all the dry ice sublimes. You would need to cool the bottom of the chamber some other way, such as mechanical refrigeration. I was considering the possibility of using a peltier cooler, but I don't think you can get enough cooling that way.

 

Eventually, a considerable amount of the alcohol condenses on the bottom of the chamber. I imagine, eventually, the majority of it would puddle at the bottom. I'm sure you would need to figure out how to get the alcohol back to the top of the chamber where it can warm again.

 

I might experiment with different alcohols and configurations. I tried a larger chamber, with a small 2.5 gallon glass tank, but my results were mixed. Oddly, the Starbuck's cup really makes an awesome chamber!

 

-Caver

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I must admit I am having difficulty seeing any tracks in that picture. I suppose if they are moving you can see them more easily.

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You meet one geek and 'bang' you meet another one. Would isopropyl alcohol from a spray can be okay to use? I've just sourced out two companies that supply both the dry ice (Global ice UK) and isopropyl alchohol (MAPLIN UK), The cost to make a home made cloud chamber for the average UK geek would set him or her back at around about £46 ($82).

Caver451, I can see in your photographs a rock on the base of the cup, what type of rock did you use?

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Er, anhydrous? Does it have to be anhydrous isopropyl alcohol?

Caver mentioned it but I don't see why isopropyl alcohol cannot be used.

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Er' date=' anhydrous? Does it have to be anhydrous isopropyl alcohol?

Caver mentioned it but I don't see why isopropyl alcohol cannot be used.[/quote']

 

Just a guess, but supercooling the alcohol may be a problem if you have ice crystals forming from the water.

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You meet one geek and 'bang' you meet another one. Would isopropyl alcohol from a spray can be okay to use? I've just sourced out two companies that supply both the dry ice (Global ice UK) and isopropyl alchohol (MAPLIN UK)' date=' The cost to make a home made cloud chamber for the average UK geek would set him or her back at around about £46 ($82).

Caver451, I can see in your photographs a rock on the base of the cup, what type of rock did you use?[/quote']

 

he used uranium ore...

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The rock is a small piece of Uranium ore, which is approximately 2.5 cm long, 1.9 cm wide and 1.0 cm tall. I read around 900cpm at a distance of approximately 1cm. You don't really need the ore--but with such a small chamber, I was only catching one or two cosmic rays a minute, which was like watching paint dry. ;)

 

The 99.953% pure anhydrous isopropyl alcohol was purchased at "Fry's Electronics" in California. They don't ship, as far as I am aware. The manufacturer is MG Chemicals. Catalogue number 824-1 Litre. $7.99/liter. They appear to be a Canadian company. http://www.mgchemicals.com/

 

My research indicated that pure anhydrous isopropyl alcohol would work the best, and that the typical supermarket 70% "rubbing alcohol" would not. I assume it is because the water would interfere. I also heard that pure ethanol would work, but that is harder to get here. I do have some denatured ethyl alcohol which I am going to try.

 

The dry ice I bought at the local grocery store. It was $1.00/pound. Pengiun brand.

 

Over the next few days, I am going to try a few different configurations, though I admit I won't be using the Starbuck's cup. It was just to see if I could do it. I am going to try store bought 70% rubbing alcohol and denatured alcohol as well.

 

As far as the tracks go, I admit in the pictures it is hard to see anything. It is also hard to pick out the tracks from reflections off the aluminum foil. It is much easier to see them as they happen. I will try to do a short video when I can borrow a video camera. I put arrows near them in the enclosed photo. They collapse pretty fast, so are very difficult to capture with the camera!

 

-Caver

Copy of cloud-tracks-small.jpg

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