If you watch Star Trek, you will know one way to get rid of pesky aliens is to vent antimatter. The truth is, antimatter is a little less exotic than it appears on TV, but for a variety of reasons there hasn’t been nearly as much practical research done with it. There are well over 200 electron accelerators in labs around the world, but only a handful that work with positrons, the electron’s anti-counterpart. [Dr. Aakash Sahai] would like to change that. He’s got a new design that could bring antimatter beams out of the lab and onto the desktop. He hasn’t built a prototype, but he did publish some proof-of-concept simulation work in Physical Review Accelerators and Beams.
Today, generating high-energy positron beams requires an RF accelerator — miles of track with powerful electromagnets, klystrons, and microwave cavities. Not something you are going to build in your garage this year. [Sahai] is borrowing ideas from electron laser-plasma accelerators (ELPA) — a technology that has allowed electron accelerators to shrink to mere inches — and turned it around to create positrons instead.
There are two stages. One creates a high-energy electron flux using the conventional a conventional ELPA process. This stage creates a shower or flux of electrons. The second stage is where things get interesting. The electron flux bounces off a metal target which causes them to decelerate. However, that additional energy has to go somewhere, so it creates a gamma ray. The gamma ray however is unstable and converts into a low-energy positron/electron pair. Those low-energy positrons can be formed into a high-energy beam.
Unlike conventional methods, the only large part of this accelerator design is the laser system which currently takes about 25 square meters of space. However, as the laser designs get better, it should eventually be possible to build such a device on the desktop. If that seems crazy, look at what’s happened with electron beam generation. SLAC using conventional methods can produce a 1 GeV beam in a 64 meter-long track. The record for ELPA is 4.25 GeV over 9 centimeters and a 2 GeV beam has been produced in equipment measuring 2 centimeters!
Does this mean we are going to finally get our Space Ranger antimatter pistol we always wanted? Maybe. Meanwhile, you might have to settle for just the laser. It seems like most of the big lasers we see anymore are relegated to cutting.