Figure 2. Beam-based feedback for accelerator stabilization.

The width of the arrival time distribution for each bunch within the macro-pulse is evaluated over 600 consecutive single shots. As shown in a, the jitter is considerably reduced for bunches at the end of the macro-pulse where the accelerating fields have been corrected using the arrival time of the first bunches. The ‘latency’ period of this feedback spans the first 5 μs (5 bunches). During the ‘feedback adaptation’ period, the effect of the corrections reduces the observed jitter to the final steady-state value. The distribution of arrival times of the last bunch in the macro-pulse is shown in b and has a width of (19±2) fs r.m.s., with accuracy given by the numerical fit.