Cloud chambers are an exciting and highly visual science experiment. They’re fascinating to watch as you can see the passage of subatomic particles from radioactive decay with your very own eyes. Many elect to build small chambers based on thermoelectric Peltier elements, but [Cloudylabs] decided to do something on a grander scale.
[Cloudylabs] started building cloud chambers after first seeing one in a museum back in 2010. The first prototype was an air-cooled Peltier device, with a cooled area of just 4x4cm. Over the years, and after building many more Peltier-based chambers, it became apparent that the thermoelectric modules were somewhat less than robust, often failing after many thermal cycles. Wanting to take things up a notch, [Cloudylabs] elected to build a much larger unit based on phase-change technology, akin to the way a refrigerator works.
The final product is astounding, consisting of a 32x18cm actively cooled area mounted within a large glass viewing case. A magnet is mounted underneath which causes certain particles to curve in relation to the field, as well as an electrically charged grid up top. The chamber is capable of operating for up to 12 hours without requiring any user intervention.
By stacking several Peltier coolers in a cascade, it’s possible to increase the temperature differential generated. In this design, the copper plate of the chamber is cooled down to -33 degrees Fahrenheit (-36.11 Celcius), more than cold enough for the experiment to work. Alcohol is added to the glass chamber, and when it reaches the cold plate, it creates a super-saturated vapor. When disturbed by charged particles zipping out of a radioactive source, the vapor condenses, leaving a visible trail.
Cloud chambers are a popular experiment to try at home. It’s a great science fair project, and one that can be easily constructed with old computer parts and a couple of cheap modules from eBay. Just be careful when experimenting with radioactive sources. Video after the break.
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.
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”→
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.
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.
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.