Inverse Cerenkov accelerator results

Laser acceleration experiments of relativistic electrons utilizing the inverse Cerenkov effect, whereby a gas slows the phase velocity of the laser light to match the electron velocity, have recently demonstrated >30 MeV/m acceleration gradients over a 12-cm interaction length using a /spl sim/580-MW CO/sub 2/ laser beam. These experiments were performed at the Brookhaven National Laboratory Accelerator Test Facility (ATF). With a 5-GW laser pulse, an energy gain of >12 MeV is predicted over a 20-cm interaction length corresponding to >60 MeV/m acceleration gradient. Future experiments will examine prebunching the electrons to optical wavelengths and staging the acceleration process. The CO/sub 2/ laser is also being upgraded to produce higher peak power. With 250-GW peak power, the goal is to eventually demonstrate 100 MeV net energy gain and an acceleration gradient of >300 MeV/m.