Imaging: Inside the x-ray tube, a high-voltage current sends electrons to a tungsten target. The electrons slam into atoms inside the target, lose energy, and emit x-rays. The x-rays then flash ahead and create a shadow image of the subject. Most machines use flat-panel radiation detectors to get these pictures, but they cost about $65,000. Instead Munich bought a scintillation screen, a plastic sheet that turns fluorescent green when it’s hit with ionizing radiation.
Safety: Munich built his own Geiger counter to measure the radiation. The volume of x-rays coming out of the tube was in line with his estimates, and he found that the backscatter, or amount of radiation elsewhere, was very low. Still, he only uses it outside, aiming it at the woods behind his house. Otherwise some of the x-rays could bounce off an interior wall. He also added a speaker that emits a warning buzz when the machine is generating x-rays.
Design: Matching art suitcases, linked by cable, enclose the two pieces of the machine. Munich cut holes in the lid for an on/off switch, meters that monitor current and voltage, dials to set the exposure time, and a Nixie-tube display from a Ukrainian supplier that counts the exposure time down to the tenth of a second.
Five amazing, clean technologies that will set us free, in this month's energy-focused issue. Also: how to build a better bomb detector, the robotic toys that are raising your children, a human catapult, the world's smallest arcade, and much more.