A Diffusion Cloud Chamber

How can we "see" ionizing radiation? A diffusion cloud chamber makes ionizing radiation visible. Here we demonstrate our design that uses air-cooled thermoelectric plates to reach the required low temperature. We show alpha, beta, and gamma radiation from several sources, including Pb-210, Sr-90, Na-22, and U-238. We also show a nice example of Rutherford scattering. Best viewed full screen at high resolution.

[@Name-js5uq]

I would love to say thank you so much for making this video I'm in the middle of making my own and I cannot believe how helpful this is going to be so thank you from the bottom of my heart I just can't thank you enough I really really and truly want to be successful in this endeavor

[@KarbineKyle]

Excellent build and demonstration! I _really_ need to build my own! I have a lot of relatively strong sources! Basically a collection! I have several Geiger-Müller counters, and I did have an alpha particle spark detector, but I'd love to "see" what my sources could produce! Great job! Thank you for sharing this!

[@samwesemael7923]

Best cloud chamber video on KZbin, will try to make my own.

[@prashantjoshi1180]

Would love to try it at home some day! Thanks for making my day today!

[@ReinhardSchumacher1]

I am glad to see that you liked it.

[@ghfreakwierdo123]

This was an extremely helpful supplement to my chemistry class. Thanks so much for taking the time to make this!!

[@ReinhardSchumacher1]

Indeed, it was a fun project, and we are happy to offer an instructive and useful tutorial.

[@johnkeo358]

Pretty sweet video!

[@MohammadFaisal-rv8ku]

Amazing demo!!! Thanks mate!!!

[@Noah-ek8hp]

Big question: how many Peltier devices should I use?

[@ReinhardSchumacher1]

Look closely at the video: we used two identical devices stacked on top of each other to reach the necessary temperature. It is important to have thermal paste between the two plates and also between the plates and the heat sink and the top aluminum plate. That is needed to get the heat conductivity up high enough. Again, check the video for a diagram, and also for experimental data showing how fast the devices cooled the top surface.

[@Noah-ek8hp]

@@ReinhardSchumacher1 thanks a lot! I just have a bunch of them, and figured too many would produce too much heat, because these things are crazy inefficient.

[@ReinhardSchumacher1]

@@Noah-ek8hp Keep in mind that the lowest one in the stack has to take ALL the heat from the ones above to the heat sink at the bottom. The temperature across the last one can get big. We found that this became an issue. We tried three but got no better performance than with two.

[@joecooksey4331]

Maybe you have an answer for this. I can't find anything on it. Last night and early this morning after watching "action lab", I built a cloud chamber using dry ice and 91% isopropyl. Shining a flashlight inside I didn't really observe any cloud like trails, but what I did see were flashes/streaks of RED light. I repeated it again this morning and got the same red flashes/streaks with no additional light source and a big coat over my head and chamber to block any extraneous light even though the room was dark. I had my wife viewed it and she saw the same thing. I'm going to repeat the setup in a box with my Nikon and see if I can photograph the red flashes/streaks. Are these flashes in red expected? Signed a former high school science teacher.

[@railsnothandles]

Did you figure out what is the red light?

[@joecooksey4331]

@@railsnothandles No.

[@railsnothandles]

@@joecooksey4331 Thx.

[@stuart9768]

I have used stacked peltier cells (top at 5V and bottom at 12 V) and the lowest I can get is -20 degrees C. I have used a 4" diameter 1/4" thick aluminum disc and a 3" diameter 1/16 aluminum disc and oddly the 4" disc more consistently attains -20. Any tips to get to -30? I am using the same peltier cells that you use here, and I have tried air cooling and water cooling and both reach -20.

[@ReinhardSchumacher1]

We used stacked Peltier plates with 5V on top and 12V on bottom, like you. It was important to put conduction paste (for electronics) between the plates and between the top plate and the aluminum plate. It is a little gooey, and it is messy to disassemble once it is constructed: that is why on the video I did not just pick off the top plate to show the Peltier plates underneath. It was important to have a felt insulating ring around the heat sink and the Peltier/aluminum plate assembly. When we measured the temperature at the center of the top aluminum plate it was covered with a 1/4" felt insulator to mimic the presence of the cloud chamber. At the edges of the aluminum plate we found that the temperature was closer to -28 C while at the center it was close to -34 C. We were somewhat surprised that the 1/16" aluminum top worked better that a 1/14" aluminum top. Not only did the thinner plate reach the low temperature faster, but the low temperature was lower by a few degrees. Good luck.

[@jinojohnson9653]

I thought beta particles were much more penetrating than alpha particles . But here it is shorter . How?

[@ReinhardSchumacher1]

Good question. Beta particles (electrons) are indeed more penetrating than alpha particles (helium nuclei) when they have the same kinetic energy. However, in these sources the beta particles come from decays that leave them with much less kinetic energy that the alphas. They don't have as much energy to give away, on the average, as the alpha particles do. On top of that, since they are so much lighter, the beta particles easily get deflected by the massive gas molecules and ricochet around to leave spidery jagged tracks. The alpha particles blast through the gas, ionizing it, but leave strong straight tracks.

[@weeFILM]

HI Reinhard - I am hoping to build a cloud chamber as part of an art installation and have come by an ultra low temperature freezer (a new Brunswick model capable of cooling to -86 degrees Celcius) . i imagined installing a kind of porthole on the front but i wonder if i might just be better starting from scratch? - a friend thought that the freezer might not work as a cloud chamber as he said that there needs to be a thermal gradient (in order to create the right conditions with the alcohol vapour. do you know if he is correct? thanks very much for the fascinating post :)

[@ReinhardSchumacher1]

Hello Russell, A big cold box like that would be a great start for such a project: colder than you really need, but adjustable, and plenty of volume. You'll get the necessary thermal gradient assuming you feed in room temperature isopropanol that vaporizes enough before it cools. You need the thermal gradient because you need not just a cold vapor, you need a supersaturated cold vapor. That means you start out with a saturated vapor at some higher temperature, which then cools so there is more alcohol in the gas than it really can hold at the lower temperature. Expect to do a lot of experimentation.

[@thebends6580]

@@ReinhardSchumacher1 does the enthalpy of ethanol alcohol (96%) do the trick? or it has to be isopropanol? Cheers

[@remcobooy9837]

How many Peltiers are you using? How many stages?

[@ReinhardSchumacher1]

Two of them are used, in series. See the diagram in the video.

[@thebends6580]

will common alcohol (96%) work?

[@ReinhardSchumacher1]

The "common" alcohol we used is isopropanol, or "rubbing" alcohol. No need to get high purity stuff, just use the 70% product sold in drug stores. Alternatively, you can try methanol or "denatured" alcohol, but that worked slightly less well for us. We tried several other alcohols just because we could: glacial butanol and ethanol. They did not work any better than isopropanol in our setup.

[@hydrostaticshocker3048]

Red HEET is available at any Walmart or auto parts stores and is 99.9% IPA.