MIT microwiggler for free electron laser applications

A microwiggler-based FEL permits operation at shorter wavelengths with a reduction in the size and cost of the device. The MIT microwiggler is a pulsed ferromagnetic-core electromagnet with 70 periods of 8.8 mm each which generates an on-axis peak magnetic field of 4.2 kG. The pulse repetition rate is 0.5 Hz with FWHM 0.5 msec. The microwiggler is characterized by extensive tunability. We employed a novel tuning regimen through which the rms spread in peak amplitudes was reduced to 0.08%, the lowest ever achieved in a sub-cm period magnetic field, The microwiggler is a serviceable scientific apparatus: spontaneous emission has been observed for wavelengths of 700-800 nm using a 40 MeV beam from the Accelerator Test Facility LINAC at BNL.