Lasers Provide Antimatter Bonanza
Hui Chen and Scott Wilks of the Lawrence Livermore National Laboratory in California and their colleagues now report that they have generated copious amounts of positrons with intermediate energies–in the range of a million electron-volts. They fired picosecond pulses with intensities of around 1020 watts per square centimeter from the Titan laser at Livermore’s Jupiter laser facility onto millimeter-thick gold targets. Positrons were produced via the “Bethe-Heitler” process, in which part of each laser pulse creates a plasma on the surface of the target, and the remaining part of the pulse then blasts electrons from the plasma into the solid. Next, the electrons are slowed down by gold nuclei, an interaction that generates gamma-ray photons. The gamma rays then interact with more gold nuclei and transform into electron-positron pairs.