Precision alignment of the Advanced Light Source U5.0 and U8.0 undulators
The U5.0 and U8.0 undulators for the Advanced Light Source (ALS) incorporate 4.6-m-long, hybrid-configuration magnetic structures. The structures consist of modules with half-period pole assemblies mounted on 0.8-m-long aluminum mounts, which are in turn attached to continuous steel backing beams. The vertical and longitudinal alignment tolerances for the poles of these structures are 25 microns and 50 microns, respectively, over the entire 4.6-m length of the devices. To meet these tolerances, the modules were first aligned individually using an automated coordinate measurement machine and shimming techniques. Several adjustment iterations were required for each module. Averaging and three-dimensional linear least-squares fitting techniques were employed to establish statistically based error reference planes. Graphical spread sheets were used to create representations of vertical and longitudinal pole position errors for alignment. The adjusted modules were installed on the backing beams and aligned relative to each other using laser interferometer techniques. The longitudinal positions of all poles of each module were measured using a simple linear interferometer and associated optics. Because of the differential expansion coefficient between the aluminum modules and steel backing beam, a bilinear temperature-compensation function was applied to the position data to predict periodicity errors at a predetermined operating temperature, which is generally higher than temperatures in assembly and measurement areas. Vertical alignment of the periodic modules was performed by generating vertical pole position error profiles of the full 4.6-m structures. Least-squares-fit planes for each module were calculated and used in making differential vertical and angular adjustments. Repeatability error for these measurements was typically less than 3 microns. In addition, by using difference techniques, systematic profile variations of 1 micron have been resolved.
- Research Organization:
- Lawrence Berkeley Lab., CA (United States)
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 10186849
- Report Number(s):
- LBL-33237; CONF-930722-45; ON: DE94001260; TRN: 93:023058
- Resource Relation:
- Conference: Annual meeting of the Society of Photo-Optical Instrumentation Engineers (SPIE),San Diego, CA (United States),11-16 Jul 1993; Other Information: PBD: Jul 1993
- Country of Publication:
- United States
- Language:
- English
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