A Synchrotron Light Fast Camera for EROS*
Vertical mismatching or mis-steering of the beam at the injection point of the pulse stretcher ring leads to an emittance growth of the extracted beam with respect to the injected beam. A mismatched beam shows up as a modulation of the vertical size of the beam from turn to turn, while a mis-steered beam results in a modulation of the vertical position of the beam centroid. Simulations indicate that a fast beam profile monitor would be useful to detect and diagnose the conditions of beam mismatching and mis-steering. The spatial resolution of the monitor must be about 100 µm to detect beam mis-steering and about 200 µm to detect beam mismatching in order to keep the emittance growth below 20%. The monitor must be capable of observing the first four turns of the beam in the ring to allow detection of non-optimal conditions at injection. The fast beam profile monitor is a high speed, high resolution SIT Vidicon camera. The fast camera is triggered by a solid state modulator to meet space restrictions, as well as gate pulse requirements, of the monitoring system. The camera utilizes optics which give it a field of view of 1 cm2 at a distance of 2.84 meters. Theoretical limitations on the resolution of the fast camera are discussed, as are expected beam behavior for various conditions of beam mismatching prior to, and mis-steering in, the injection line. The synchrotron light fast camera works well; the resolution attained is near the theoretical limits calculated. While the resolution limits were not measured rigorously, tests with the camera indicated the 100 µm resolution requirement was achieved.