The chirped-pulse inverse free-electron laser: A high-gradient vacuum laser accelerator

The inverse free-electron laser (IFEL) interaction is studied theoretically and computationally in the case where the drive laser intensity approaches the relativistic regime, and the pulse duration is only a few optical cycl es long. The IFEL concept has been demonstrated as a viable vacuum laser ac celeration process; it is shown here that by using an ultrashort, ultrahigh -intensity drive laser pulse, the IFEL interaction bandwidth and accelerati ng gradient are increased considerably, thus yielding large energy gains. U sing a chirped pulse and negative dispersion focusing optics allows one to take further advantage of the laser optical bandwidth and produce a chromat ic line focus maximizing the gradient. The combination of these novel ideas results in a compact vacuum laser accelerator capable of accelerating pico second electron bunches with a high gradient (GeV/m) and very low energy sp read. (C) 1999 American Institute of Physics. [S1070-664X(99)04110-5].