Number 421 (Story #1), March 31, 1999 by Phillip F. Schewe and Ben Stein|
CREATING ANTIMATTER WITH LASER LIGHT. Intense light from the Petawatt laser at Livermore, the world's most powerful laser, has been directed onto a thin gold film where it creates a plasma plume which acts as a sort of messy wakefield accelerator. In particular the laser electric fields rip electrons from the gold atoms and send the electrons shooting off with energies as high as 100 MeV. Some of these electrons radiate gamma rays which in turn can create electron-positron pairs (the first antimatter made in laser-solid interactions) and can also induce fission. Thus laser photons at the electron-volt level can, by teaming up, initiate the sort of million-electron-volt nuclear reactions that normally take place only at an accelerator. Moreover, the femtosecond laser pulses can be focused to a much smaller spot size than is possible with any conventional particle beam. Tom Cowan (925-422-9678, email@example.com) reported these results at last week's APS Centennial Meeting in Atlanta (see figure at Physics News Graphics).