Adiabatic damping of the bunch length in the induction synchrotron

We observed that the bunch length decreases with acceleration in an induction synchrotron (IS) experiment, where a single proton bunch injected from a 500 MeV booster ring was accelerated to 6 GeV in the KEK proton synchrotron (KEK-PS). A novel technique that can be used to quantitatively predict the adiabatic phenomenon in barrier–bucket acceleration has been newly developed on the basis of a hypothesis that the particle oscillation amplitude varies inversely proportional to the square root of its oscillation frequency. This approach was verified by comparing the analytic prediction with experimental results which indicates that the bunch length in barrier–bucket acceleration does not continue to shrink, but reaches a constant value depending on the time duration between barrier voltages. It turns out that the experimental result and analytical prediction are in good agreement.