Beam Position Monitor Using a Single Cavity

Beam tests have been carried out with a cylindrical cavity tuned to 2.415 GHz which is the third harmonic of the accelerator frequency. The beam excites a TM110-like mode when the centroid is displaced horizontally and an orthogonal mode when the beam is displaced vertically. The phase reversal detected when the beam crosses the plane of symmetry identifies the cartesian quadrant occupied by the beam. The signals are proportional to beam current and displacement with average slope 0.35 mW1/2.mm-1. mA-1.