Final construction of the CREOL 8 millimeter period hybrid undulator

The construction of an 8 millimeter period hybrid undulator for the CREOL high power far-infrared free electron laser has just been completed. This FEL is expected to come on-line in the spring of 1995 and produce close to a kilowatt of continuous power at wavelengths of 225–800 μm. The undulator has precise mechanical tolerances and high field uniformity allowing for high electron beam recovery rates. Almost complete beam recovery is required for DC operation at high currents. A simple method for measuring the magnetic properties of individual magnets and sorting the magnets to reduce the peak field errors and the phase errors will be reported. These errors are further reduced by inserting and tuning adjustable pole pieces. The reduction of magnetic field errors through these two techniques will be presented.