Induction-type laser faces critical tests

The various free electron laser (FEL) designs being tested in efforts to meet the 1 micron wavelength, 300 MeV criteria for SDI applications are described. An FEL is effected by passing an electron beam through a wiggler with a modest-power laser. Photons emitted by the electron beam pump the injected laser beam with a gain proportional to the electron beam current and inversely proportional to the beam emittance, i.e., factors which degrade electron beam quality. It is estimated that an operational FEL will function in the peak power range of gigawatts or terawatts, power levels which can be handled with induction-type devices without damaging them. The beam is to be emitted into several miles of vacuum tube to allow diffraction to spread the beam before sending it to an orbiting reflector for aiming. A magnetic modulator capable of switching rates of 2000/sec has been developed for the accelerator. A timetable is provided of the scheduled tests of various FEL apparatus under development.