An experimental study of microwave stability near transition in the PSR

We have undertaken a study of microwave stability in the PSR storage ring under a variety of beam conditions near transition, including variable intensity and machine impedance, which can be independently controlled in the PSR. Results indicate that the general features of a linear stability model are valid, namely that the instability threshold becomes very small sufficiently close to transition. In addition, many nonlinear features are apparent and the results suggest an extended operating regime is possible with saturated, but otherwise benign, longitudinal fluctuations. Details of the linear model experimental results and corresponding simulations will be presented