Tunable Microwiggler Free Electron Experiment

Microwigglers with tunable field amplitude profiles can be tuned for optimal electron beam matching, and highly uniform (or precisely tapered) field profiles. We have constructed a 70-period, tunable amplitude, pulsed-electromagnet microwiggler with an 8.8 mm period and 4.2 mm gap, which produces a wiggler magnetic field of 5 kG. The wiggler field is uniform to ˜ 0.5% RMS, with the ends tapered for displacement-free and steering-free e-beam propagation. Shot-to- shot variations in the wiggler field amplitude have been reduced to ˜0.2% RMS. In operation, the wiggler produces 0.5 msec pulses at a rate of about 0.25 Hz. The wiggler will be used initially to produce visible light from a 50 MV electron beam at the Accelerator Test Facility, Brookhaven National Laboratory.