Requirement for the LCLS Undulator Magnetic Measurement Bench

The magnetic measurements for the LCLS undulators will be done using a measurement bench which transports probes through the undulator under test. Errors in the bench construction cause errors in the probe motion through the undulator. This in turn causes measurement errors. In this note, limits are placed on the bench construction errors such that the measurements remain within tolerance. Secondary requirements for the bench are also discussed