A passive scheme for ID end correction

A passive end correction scheme used on a prototype undulator is described. This scheme allows the integrated field requirements to be met at all gaps from 11.5 to 200 mm, with no active correction. The main parameters that need to be adjusted are the strength of the end magnets and the height of the next-to-last poles. The first field integral remains constant over the entire gap range, to within 25 G cm in the vertical direction and 50 G cm in the horizontal direction. The second field integral remains constant to within 10 000 G cm2. Results of magnetic measurements are presented