Test results of the LEDA beam-position/intensity measurement module

This paper describes progress in the design and testing of the log-ratio-based beam- position/intensity measurement module being built for the Low Energy Demonstration Accelerator (LEDA) and Accelerator Production of Tritium (APT) projects at Los Alamos National Laboratory. The VU-based module uses four, 2 MHz if inputs to perform two-axis position measurements and one intensity measurement. To compensate for systematic errors, real-time error-correction is performed on the four input signals after they are digitized and before calculating beam position and intensity. Beam intensity is computed by using the average of the four log-amplifier outputs. This method provides a better off-axis intensity response than the traditional method of summing the rf power from the four lobes. Several types of test data are presented including results of the real-time error correction technique, a working dynamic range of over 80 dB, and achievable resolution and accuracy information.