The basic idea is to get the beam excited at the tune frequency. For large enough beam currents this happens naturally. For smaller currents, it is done with the tune measurement system. Synchronized data for 1024 turns are collected. Typical measurement errors on the phase advances are about a degree.
Betas are determined to a few percent.
By measuring how the phase advances change when the RF frequency is changed, one can see how the chromaticity is distributed around the ring. By measuring how the phase advances change when the beam current is changed, one can measure the distribution of the reactive transverse impedance. The BPM phase advance and beta function package gives one the ability to make all of these measurements online. It also allows data to be saved for further off-line analysis. Setup Note that measurements can be taken for x or y, but not both at the same time.