MEASUREMENT OF THE ELECTRON-ENERGY AND ENERGY SPREAD AT THE ELECTRON STORAGE-RING BESSY-I

Knowledge of the electron energy with a small uncertainty is necessary for the Physikalisch-Technische Bundesanstalt (PTB) to operate the el ectron storage ring BESSY I, and the future BESSY II, as a primary rad iation source standard of calculable synchrotron radiation. At BESSY I the electron energy can now be measured either by the long-establishe d method of resonant spin depolarization or by the newly set up method of Compton backscattering (CBS) of laser photons (CO2 laser, lambda = 10.6 mu m). Results obtained at different electron energies by these two independent methods are presented. They agree within a relative un certainty of better than 10(-4). The advantages and disadvantages of t hese two complementary techniques are described and applications of CB S for the measurement of other storage-ring parameters, e.g. the elect ron energy spread, are given.