Work has been ongoing at the NSLS to improve the orbit stability of the X-ray ring by accounting for the thermal motion of the vacuum chamber, which supports the electron beam position monitors (BPMs). In-situ contact measurements of the vacuum chamber motion have been carried out using support stands that have been designed and extensively tested to reduce errors associated with thermal changes in the stands themselves. Using this chamber motion as a correction to the orbit motion measured by the BPMs, the precise location of the radiation beam can be predicted. These predictions are compared with actual radiation beam measurements on the experimental floor, and with predictions based solely on BPM measurements of the electron beam position. This paper reviews this work including stand design and performance, chamber motion measurements, predictions based on these data, and results.
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