Energy measurements from betatron oscillations

In the Stanford Linear Collider the electron beam is accelerated from 1 to 50 GeV in a distance of 3 km. The energy is measured and corrected at the end with an energy feedback loop. There are no bends within the linear accelerator, so no intermediate energy measurements are made. Errors in the energy profile due to misphasing of the RF, or to calibration errors in the klystrons RF outputs are difficult to detect. Since the total betatron phase advance down the accelerator is about 30 X 2 π, an energy error of a few percent can cause a large error in the total phase advance. This will degrade the performance of autosteering programs. A diagnostic program which generates and measures several betatron oscillations in the accelerator has been developed