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The thermionic RF cavity gun for the Stanford FIR-FEL functions satisfactorily as an FEL accelerator, at high peak gradients from 100-140 MV/m, where the electron beam is obtained from 1.5 cell. The electron beam from the 1.5 cell cavity gun in a parameter range has been analyzed as a far infrared FEL's accelerator.

The design and construction of a free electron laser (FEL) at a cost of $300,000 is discussed. The project, which was carried out at Stanford University, reduced the cost due to the innovative design of its components. These concerned the accelerator's microwave cavity gun, the staggered-array wiggler magnet and the on-axis hole in the upstream cavity resonator for electron ingress and radiation egress. To date, the FEL has lased at far infrared wavelengths with a micropulse duration of about 12 ps.

A staggered-array wiggler confers rapid wavelength tuning, high wiggler field, electron beam confinement and tolerance with respect to fabrication errors for a far-infrared free-electron laser. A 1. 2% wiggler field fluctuation does not influence small-signal gain. The wiggler comprises a staggered iron array situated along the solenoid center.