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  • David Aceituno commented on David Aceituno's instructable How to build a Cloud Chamber2 years ago
    How to build a Cloud Chamber

    Hi! I believe you need to use a weaker top-peltier than 12710, as a 12715 may have a hard time transporting all the heat. Perhaps try feeding the 12710 around 5-6 V, or running it in series together with a second 12710. As for the heat source, it's not a good idea when using peltiers as any excess heat has to be dealt with by your peltiers and thus affect its minimum temperature at some point. With dry-ice (or compression cooling) you have plenty of cooling capacity to spare, so you can afford to have a heater for your alcohol. Personally I don't really think its necessary, as the heat that leaks in through the glass dome is enough to maintain a supersaturation above the cold plate (due to a sufficiently large temperature gradient).Also you can read a lot more on the youtube comments of...

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    Hi! I believe you need to use a weaker top-peltier than 12710, as a 12715 may have a hard time transporting all the heat. Perhaps try feeding the 12710 around 5-6 V, or running it in series together with a second 12710. As for the heat source, it's not a good idea when using peltiers as any excess heat has to be dealt with by your peltiers and thus affect its minimum temperature at some point. With dry-ice (or compression cooling) you have plenty of cooling capacity to spare, so you can afford to have a heater for your alcohol. Personally I don't really think its necessary, as the heat that leaks in through the glass dome is enough to maintain a supersaturation above the cold plate (due to a sufficiently large temperature gradient).Also you can read a lot more on the youtube comments of that video, where I've answered many questions, and the reddit thread I made for it here: https://www.reddit.com/r/Physics/comments/2vuzwb/how_to_build_a_cloud_chamber_with_peltiers/I am not entirely sure how the diffusion process works, but in my experience reaching the -25 C mark is a must; its not just about having a proper gradient. Also, I believe that the sole purpose of the ion scrubber is not only to remove naturally ocurring heavy ions suspended in the gas, that may deflect incomming radioactive particles. My best guess is the following model: Alcohol molecules, being dipolar, can spontaneously build droplets with some surface tension if the temperature is high enough, because then the kinetic energy is enough to overcome some potential energy barrier related to the surface tension. These droplets look like a constantly moving cloud or mist, on top of the cold plate, and the few radiation trails that are not deflected by ions, mostly drown in that mess. However, below a certain temperature, lets call it T_critical, alcohol molecules need a condensation core or a small perturbation to make droplets. If this is somewhat correct we can draw some conclusions: 1) Naturally occurring free ions may provide condensation cores for making undesired droplets even below T_critical, which means that 2) an ion scrubber, upon removing these ions, leaves a volume of (desired) supersaturated gas ready to condense around a trail of ions left by alpha/beta/muons. 3) An ion scrubber may also align the (dipolar) alcohol molecules making it even harder for them to condense into droplets on their own. 4) Last, but perhaps most relevant to your question, is that if any of this is accurate it suggests that reaching a low enough temperature is a prerequisite more important than the gradient. In other words, no temperature gradient would allow a working cloud chamber if the temperature isn't low enough, since you simply need to get the mean kinetic energy down below some threshold value for the process to occur.I mostly like this idea due to my experience playing around with the machine and the ion scrubber, but I don't have anything solid to support it.

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