EIGHT HUNDRED YEARS ago, cathedrals were the height of human achievement. It was here that humans tested the limits of ingenuity. Here that design and precision reached new heights. Here that people gathered to pray, and asked the cosmos to reveal itself.
This same quest is now carried out in monuments to modern-day physics: in accelerator tunnels holding detectors the size of churches, on the tops of mountains, and at the bottom of abandoned mines. But if you are a would-be worshipper, you needn’t work at CERN, TRIUMF or KEK to unlock the mysteries of the universe. Just construct your own private physics shrine from the comfort of your kitchen table.
While you might not be discovering new physics, you can be part of the particle club. “Doing stuff that’s very high precision, quantitative—to get all the systematic uncertainties down, to get something that you would write up and publish in a journal—costs tens or hundreds of thousands of dollars,” says Michael Kelsey, DIY enthusiast and research physicist at SLAC National Accelerator Laboratory in Menlo Park, Calif. But you don’t necessarily need optical cables, high-precision mirror mounts, and mode-locked dye lasers. “You can see the quantum effects very, very cheaply,” he says. Just how cheaply? Read on to find out.
Cloud Chambers and Fusors:
The simplest path to spying on the universe might be to build a cloud chamber. It only takes a fish tank, some felt, dry ice, and isopropyl alcohol—stuff you should be able to pick up for about $40. The felt goes into the bottom of the tank, glued in place and soaked with alcohol. When you put the metal lid on and turn the tank over on top of the dry ice, the alcohol evaporates and condenses into a thick fog. You’re done! Turn off the lights and go grab a flashlight.
In that custom-created fog, you’ll see mysterious trails appear. Those are cosmic rays, invisible bits of matter—often atomic nuclei—that collide with the atmosphere when they come crashing in from space. The smash lets loose a scatter of less massive particles: muons (an unstable subatomic particle that is a sort of sumo-version of an electron), electrons, and positrons (electron’s anti-matter partner). You may even see particle decays, in the form of tracks that suddenly fork in two.
Another class of trails will show up, too—these ones look more like short, pudgy lines. You’re seeing radon, a naturally radioactive element, heave out an alpha particle—two neutrons plus two protons. That’s pretty cool, but radon is a natural part of the atmosphere, not a cosmic ray. Sorry.
Want to embark on something even simpler? Kelsey encourages physics fans to give photon detection a try—just like Thomas Young, you can observe the wave particle dualityThose interested in stepping it up a notch (in expense and danger) can build their own fusion generator, using electric fields to contain a plasma under pressure and prompt atoms to fuse nuclei. The same thing happens in the sun, or in a fusion bomb. Two atomic nuclei join to form a heavier element, releasing a blast of energy in the process. For decades, scientists have sought to harness fusion to create clean, near-endless energy: In the south of France, an international group is building the 23,000-ton International Thermonuclear Experimental Reactor, which they hope will create hundreds of megawatts of power.
In your home, though, you can build what’s known as a Farnsworth-Hirsch fusion reactor, or fusor. Don’t expect it to help with your electricity bill, though. “You don’t get break-even [energy], you can’t use it as a power source,” Kelsey says. “But you can build this in your garage for $500 to $600.”
A homemade fusor—sometimes called a “star in a jar”—uses plywood, PVC pipe fittings, a transformer, mineral oil, and a host of other parts to generate an ionized plasma in which nuclei will fuse at low levels. But that fusion also releases gamma rays and X-rays, high energy particles that can rip your DNA to shreds. So please don’t sue us: If you build a fusor, be sure to put up steel plates or concrete blocks for shielding.
Cyclotrons:
If you’d rather accelerate particles, lend an ear to the siren song of small-scale cyclotrons. One of the first types of accelerators, these machines accelerate charged particles across a gap between two D-shaped electrodes by rapidly reversing the polarity of the electric field. The largest cyclotron (60 feet in diameter) resides in Canada, at TRIUMF (TRI University Meson Facility), where it is being modified to produce slow moving neutrons. If you want a cyclotron of your own though, it’s possible—all it takes is some determination and (cough) about $130,000. A pittance compared to TRIUMF!
For the past decade Mark Yuly, a physics professor at Houghton, has been working on a miniature cyclotron—with a lot of help from his students. In 2010, Houghton College in New York hosted the world’s first known small cyclotron conference. Only a few dozen DIY nerds attended, but what the small cyclotron community lacks in size it makes up for in commitment and verve. of light. Gather some foil, silly putty, a business card, utility knife, a laser pointer, some optical filters and a digital camera. Cut the foil into slits and shine the laser, set to a low power (or with the intensity reduced by filters), across them.
To detect the pattern formed by photons as they pass through the slits, place a camera with an “indefinite shutter” (or a piece of film) behind the foil. Set it out for a short time and you’ll see just a few pinpricks of light—indicating that light does behave like a particle. Set it out for longer and you’ll observe a distribution spread across the film. The distribution matches the patterns that occur as two waveforms create interference.
Yuly recalls reading a popular science article as a young man about a group of people who made a Van de Graaff generator. “I was surprised that you could make such a thing,” he says, “and basically use old parts to smash atoms.” He set his sights on a cyclotron and checked out the PhD thesis of M. Stanley Livingston—the graduate student who worked with Ernest Lawrence (winner of the 1939 Nobel Prize for physics) to build the first one.
That machine, which started accelerating in 1931, “was put together with old metal scraps and sealed with pieces of candle wax,” Yuly says. “I thought we could do at least as good as that.” And after about five years of construction, they did. “We were all pretty excited when we first got a beam,” says Yuly. “It was unexpected: We were just scanning the magnet and we saw the current jump up.”
About two hours later, though, a giant spark appeared in the vacuum chamber. It vaporized the glass insulators and the chamber lid, ruining the ion source, the D-shaped magnets, and the lid. “We basically had to rebuild the whole thing over the course of two years,” says Yuly. “But that’s OK, it was still pretty cool.”
Together with his students, Yuly has accelerated protons up to 100 kiloelectron volts. With their new design modifications—altering the magnetic field to better focus the beam—they should soon be able to reach 900 keV. Yes, Yuly says, the Large Hadron Collider (which is a different type of particle accelerator) has about a billion times more power, “but their accelerator is bigger than 10 inches across too.” (It’s more than 5 miles across, for a circumference of 17 miles.)
And Yuly’s mini cyclotron can do a lot of things that the LHC can’t. It teaches hands-on creativity and problem solving—skills needed in real life that are hard to pick up doing homework problems at a desk. “It’s more like what a scientist really does,” Yuly says. Sometimes his students continue to work with the machines, working for companies that make small cyclotrons for hospitals, which use the particles generated in imaging studies or cancer radiation treatments.
By and large, physics enthusiasts begin DIY projects to give their curiosity, and their desire to tinker, room to roam. Some work in public science outreach or are creating art pieces. And occasionally, they’re making something they really need.
Michael Kelsey’s favorite DIY example is creative but not exactly splashy. “For a combo of coolness and benefit to humanity,” he says, “I’d pick portable personal radiation detectors.” Following the 2011 Tōhoku earthquake and tsunami DIY sites proliferated with instructions of how to make these devices. Some included wireless data loggers allowing for crowd-sourced radiation data collection from the region. “To me that was really cool because it’s not just a project to show off,” Kelsey says. “There’s this whole group of people that really need this thing.”
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