See the Radioactive World with This Peltier Cloud Chamber

Remember when a homemade cloud chamber was a science fair staple? We haven’t participated for decades, but it seemed like every year someone would put a hunk of dry ice in a fish tank, add a little alcohol, and with the lighting just right – which it never was in the gymnasium – you might be lucky enough to see a few contrails in the supersaturated vapor as the occasional stray bit of background radiation whizzed through the apparatus.

Done right, the classic cloud chamber is a great demonstration, but stocking enough dry ice to keep the fun going is a bit of a drag. That’s where this Peltier-cooled cloud chamber comes into its own. [mosivers] spares no expense at making a more permanent, turn-key cloud chamber, which is perched atop a laser-cut acrylic case. Inside that is an ATX power supply which runs a Peltier thermoelectric cooling module. Coupled with a CPU cooler, the TEC is able to drive the chamber temperature down to a chilly -42°C, with a strip of white LEDs providing the required side-lighting. The video below gives a tour of the machine and shows a few traces from a chunk of pitchblende; it’s all pretty tame until [mosivers] turns on his special modification – a high-voltage grid powered by a scrapped electronic fly swatter. That really kicks up the action, and even lets thoriated TIG welding electrodes be used as a decent source of alpha particles.

It’s been a while since we’ve seen a Peltier cloud chamber build around here, which is too bad because they’re great tools for engaging young minds as well as for discovery. And if you use one right, it just might make you as famous as your mother.

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Irène Joliot-Curie and Artificial Radioactivity

When Marie and Pierre Curie discovered the natural radioactive elements polonium and radium, they did something truly remarkable– they uncovered an entirely new property of matter. The Curies’ work was the key to unlocking the mysteries of the atom, which was previously thought to be indivisible. Their research opened the door to nuclear medicine and clean energy, and it also led to the development of nuclear weapons.

Irène Joliot-Curie, her husband Frédéric, and many of their contemporaries were completely against the use of nuclear science as a weapon. They risked their lives to guard their work from governments hell-bent on destruction, and most of them, Irène included, ultimately sacrificed their health and longevity for the good of society. Continue reading “Irène Joliot-Curie and Artificial Radioactivity”

Uncertainty – The Key to Quantum Weirdness

All these fifty years of conscious brooding have brought me no nearer to the answer to the question, ‘What are light quanta?’ Nowadays every Tom, Dick and Harry thinks he knows it, but he is mistaken.

                       Albert Einstein, 1954

As 1926 was coming to a close, the physics world lauded Erwin Schrodinger and his wave mechanics. Schrodinger’s purely mathematical tool was being used to probe the internal structure of the atom and to provide predictable experimental outcomes. However, some deep questions still remained – primarily with the idea of discontinuous movements of the electron within a hydrogen atom. Niels Bohr, champion of and chief spokesperson for quantum theory, had developed a model of the atom that explained spectral lines. This model required an electron to move to a higher energy level when absorbing a photon, and releasing a photon when it moved to a lower energy level. The point of contention is how the electron was moving. This quantum jumping, as Bohr called it was said to be instantaneous. And this did not sit well with classical minded physicists, including Schrodinger.

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Open Source Cloud Chamber

If you are a certain age, there were certain science toys you either had, or more likely wanted. A chemistry set, a microscope, a transparent human body, and (one of several nuclear toys) a cloud chamber. Technically, a Wilson cloud chamber (named after inventor Charles Wilson) isn’t a toy. For decades it was a serious scientific tool responsible for the discovery of the positron and the muon.

The principle is simple. You fill a sealed chamber with a supersaturated water or alcohol vapor. Ionizing radiation will cause trails in the vapor. With a magnetic field, the trails will curve depending on their charge.

If you didn’t have a cloud chamber, you can build your own thanks to the open source plans from [M. Bindhammer]. The chamber uses alcohol, a high voltage supply, and a line laser. It isn’t quite the dry ice chamber you might have seen in the Sears Christmas catalog. A petri dish provides a clear observation port.

We’ve covered cloud chamber builds before, ranging from the simple to ones that use thermoelectric coolers.

An actively cooled cloud chamber

This cloud chamber is designed to keep the environment friendly for observing ionizing radiation. The group over at the LVL1 Hackerspace put it together and posted everything you need to know to try it out for yourself.

A cloud chamber uses a layer of alcohol vapor as a visual indicator of ionizing particles. As the name suggests, this vapor looks much like a cloud and the particles rip though it like tiny bullets. You can’t see the particles, but the turbulence they cause in the vapor is quite visible. Check out the .GIF example linked at the very bottom of their writeup.

The chamber itself uses a Peltier cooler and a CPU heat sink. The mounting and insulation system is brilliant and we think it’s the most reliable way we’ve seen of putting one of these together. Just remember that you need a radioactive source inside the chamber or you’ll be waiting a long time to see any particles. They’re using a test source here, but we saw a cloud chamber at our own local Hackerspace that used thoriated tungsten welding rods which are slightly radioactive.

[Thanks JAC_101]

Researching cosmic rays with cloud chambers

In the late 1940s, the US Naval Research Laboratory used a few German-built V2 rockets to study cosmic rays from above Earth’s atmosphere. To do this, a nitrogen-powered cloud chamber was fitted inside the nose cone of these former missiles, sent aloft, and photographed every 25 seconds during flight. When [Markus] read about these experiments, he thought it would be an excellent way to study cosmic rays from a high altitude balloon and set about building his own Wilson cloud chamber.

Cloud chambers work by supersaturating the atmosphere with water or alcohol vapor. This creates a smoky cloud inside the chamber, allowing for the visualization of radiation inside the cloud. Usually the clouds in these chambers are made in a very cold environment using dry ice, but rapidly decreasing the air pressure in the chamber will work just as well, as [Markus] discovered.

[Markus]’s small cloud chamber uses a CO2 cartridge to provide the pressure in the cloud chamber before dumping the CO2 out of the chamber with the help of a solenoid valve.

In the video after the break, [Markus] demonstrates his cloud chamber by illuminating the cloud with a laser pointer and introducing a few alpha particles with a sample of Americium 241. It looks very cool, and seems to be useful enough to count cosmic rays aboard a balloon or amateur rocket.

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Your very own cloud chamber

 

[Kenneth] and [Jeff] spent a weekend building a cloud chamber. This is a detection device for radiation particles that are constantly bombarding the earth. It works by creating an environment of supersaturated alcohol vapor which condenses when struck by a particle travelling through the container, leaving a wispy trail behind. This was done on the cheap, using isopropyl alcohol and dry ice. They already had a beaker, and after a few tries figured out that the dry ice worked best when serving as a bed for the flask. A black piece of paper was added inside the base of the container to help raise the contrast when looking for condensate. They experimented with a couple of different methods for warming the alcohol, including an immersion heater built from power resistors.

There’s a video explaining the apparatus which we’ve embedded after the break. It’s a bit hard to see evidence of particle travel in the video but that’s all the more reason you should give this a try yourself.

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