Abstract
We present the results of an experimental study of the longitudinal beam dynamics at injection in the Advanced Light Source (ALS), an electron storage ring. By measuring the longitudinal bunch distribution following injection using a streak camera, we were able to study several useful and interesting e.ects as well as improve overall injection efficiency. These include measurement and correction of the phase and energy offsets at injection, measurement of the injected bunch length and energy spread, direct observation of phase space filamentation due to the spread in synchrotron frequencies, and measurement of the effective damping rate of the bunch shape including radiation damping and decoherence. We have also made some initial studies of the decay of an uncaptured beam at injection which may provide a novel means of measuring the radiation loss per turn.
Highlights
Injection is a crucial process in any storage ring, the details of the longitudinal beam dynamics at injection in electron storage rings are usually ignored as long as there is adequate capture of the injected beam
We present the results of an experimental study of the longitudinal beam dynamics at injection in the advanced light source, an electron storage ring
We have made some initial studies of the decay of an uncaptured beam at injection which may provide a novel means of measuring the radiation loss per turn
Summary
Injection is a crucial process in any storage ring, the details of the longitudinal beam dynamics at injection in electron storage rings are usually ignored as long as there is adequate capture of the injected beam. We can directly observe the transient due to a longitudinal phase mismatch of the injected bunch and the subsequent phase filamentation through the spread in synchrotron frequencies within the bunch induced by the nonlinear rf voltage In addition to these studies of a stored beam, we have recorded the injection transient of an uncaptured beam (i.e., no rf voltage) and have used this as a novel technique for measuring the radiation loss per turn. Moshammer [6 –8] studied the injection process both theoretically and via computer simulation and developed several useful expressions for the time evolution of the bunch moments with arbitrary injection conditions in the case of a quadratic tune dependence on oscillation amplitude This was applied to both betatron and synchrotron transients.
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