Energy calibration of SPEAR by g-2 precession

We have checked the absolute energy calibration of SPEAR near 3.6 GeV to an accuracy of +- 0.02% by measuring the g-2 precession frequency of a stored positron beam at a fixed machine energy. This is considerably more accurate than the +- 0.01% systematic uncertainty assigned to the energy calibration on the basis field measurements of the SPEAR magnets. Alternatively, these results can be interpreted as a large-..gamma.. (..gamma.. /approximately/ 7055) measurement of the positron magnetic anomaly a/sub e+/ = (1.1599 +- 0.0012) /times/ 10/sup /minus/3/. 6 refs., 2 figs., 1 tab.