While the choice of the more modern hybrid permanent magnet undulator configuration for the UCSB FEL undulators seemed obvious, it was equally obvious that application of the techniques used by others to achieve high quality were beyond our resources. This lead to adoption of a different philosophy; rather than impose stringent and expensive mechanical tolerances or apply sophisticated sorting strategies to a large number of the highest quality magnets available, the idea of adjusting away inhomogeneities was explored. In our "university" environment labor is generally cheaper, so a strategy of trading material cost for labor cost made sense. Ironically, the adoption of a robotic adjustor eventually reduced labor as well as material cost.
This early illustration of the FIR-FEL's adjustor has been rotated 90° to reflect the configuration as actually used.