Magnetic Measurement of the Pi Bend Dipole Magnets for the Ir-fel at the Thomas Jefferson National Accelerator Facility*

A family of large bending dipoles has been successfully magnetically measured, installed and is operational in the high power IR-FEL. These magnets are unique in that they bend the beam 180 degrees on a 1 meter radius. The optics requirements for the magnets include low fields, large horizontal apertures, tight field homogeneity, high repeatability of core field & integrated field, and control of the horizontal & vertical focusing terms that are designed into the magnets. Quantifying the optics requirements proved to be a difficult task, due to the magnet’s mechanical construction and sharp bending radius. The process involved in measuring and achieving the results are discussed.