Stanford Linear Accelerator Center Alignment Engineering Alignment Engineering

SSRL Pre-SPEAR3 Leveling History



The following poster provides a comprehensive analysis of pre-SPEAR3 leveling data for the remaining ring monuments. The earliest on-file data that reasonably encompasses the entire ring was from September 1998, thus the data begins at this point. Subsequent surveys were made regularly every year after although the most extensive survey was completed in September 2000. For this reason, this 2000 data set was chosen as the reference from which all other surveys are compared. A combination wall and floor graph at the bottom of the poster represents these height comparisons starting at quadrant 1 through quadrants 2, 3 and 4. The middle plot shows only floor data while the other two represent either wall.

All data was re-processed using the free-network adjustment method. This ensures proper weighting of the measurements allowing for a reasonable comparison of height changes over the years. Monument SP4S3D which happens to be located in quadrant 4 was found to be most common in all surveys and was therefore chosen as the reference height for all other data sets.

In general, the data and graphs clearly indicate that the west side of the ring (near and not quite so near the old “west pit”) shows the most significant changes in height. Variations are as large as about 1 mm for SP5N (located in quadrant 1 but near quadrant 2). For the remainder of the ring, the floor and walls seem much more stable with an average of less than 0.3 mm in variation.


Leveling Data Poster