Characterizing transverse beam dynamics at the APS storage ring using a dual-sweep streak camera

Abstract

We present a novel technique for characterizing transverse beam dynamics using a dual-sweep streak camera. The camera is used to record the front view of successive beam bunches and/or successive turns of the bunches. This extension of the dual-sweep technique makes it possible to display non-repeatable beam transverse motion in two fast and slow time scales of choice, and in a single shot. We present a study of a transverse multi-bunch instability in the APS storage ring. The positions, sizes, and shapes of 20 bunches (2.84 ns apart) in the train, in 3 to 14 successive turns (3.68 μs apart) are recorded in a single image, providing rich information about the unstable beam. These include the amplitude of the oscillation (∼0 mm at the head of the train and ∼2 mm towards the end of the train), the bunch-to-bunch phase difference, and the significant transverse size growth within the train. In the second example, the technique is used to characterize the injection kicker-induced beam motion, in support of the planned storage ring top-up operation. By adjusting the time scale of the dual sweep, it clearly shows the amplitude (±1.8 mm) and direction of the kick, and the subsequent decoherence (∼500 turns) and damping (∼20 ms) of the stored beam. Since the storage ring has an insertion device chamber with full vertical aperture of 5 mm, it is of special interest to track the vertical motion of the beam. An intensified gated camera was used for this purpose. The turn-by-turn x-y motion of a single-bunch beam was recorded and used as a diagnostic for coupling correction. Images taken with uncorrected coupling will be presented.