A Radial Signal Process Method for the BPS Booster LLRF Control System

The function of the Radial Position Processor is to convert rf fundamental frequency components induced by circulating bunches in a Position Pick-up Unit into an analog voltage proportional to the average beam transverse deviation from the synchronous orbit position. Because of the relatively large frequency swing, (2.76-6.31 MHz), some second harmonic components of lower frequencies would be passed by a broad-band system capable of covering the entire frequency range. Because of this, and because of the relatively high signal to noise ratio inherent in swept narrow-band channels, the superheterodyne principle has been chosen for this system. Position error discrimination is developed by amplitude to phase conversion following frequency conversion to 10 MHz. This technique results in high precision radial position error discrimination over a 52 db dynamic range of input signals. The system can, therefore, operate without readjustment over a large range of beam intensity and bunching factor. Detailed system design and test results are described. Since the BPS booster synchrotron is not yet completed, no actual performance details are available.