A 70-PERIOD HIGH-PRECISION MICROWIGGLER FOR FREE-ELECTRON LASERS

We have designed, constructed, and operated a 70-period microwiggler f or free electrons lasers (FEL's), The device is a pulsed ferromagnetic core electromagnet with a period of 8.8 mm, which generates an on-aid s peak magnetic field of 4.2 kG. The pulses, of 0.5 ms duration, are g enerated at a rate of 0.5 Hz, Each field peak is independently tunable , We employed a novel tuning regimen to reduce the RMS spread in the p eak amplitudes to 0.12%, the lowest value thus far attained in a sub c m-period periodic magnetic field.