Development of a High-Resolution Digital Beam Position Processor for the Hefei Advanced Light Facility Preresearch Project

A digital beam position processor (DBPP) with high resolution is required and developed for the Hefei Advanced Light Facility Preresearch Project to measure the orbit information and control the beam orbit jitter within one-tenth of the beam size. In this article, the design of the developed processor is presented in detail. Special attention is given to the analog part of the processor for a small noise figure and the calibration method for acceptable long-term stability. Different from the traditional calibration method using only the quasi-crossbar switch, our method combines temperature compensation attenuators, static digital attenuators, and the quasi-crossbar switch to a compound dynamic calibration method. In addition, a design of a switchable amplification stage is adopted to reduce the noise figure. A test stand, specially designed for the calibration and tests of the processor, is described. The initial laboratory tests show that the DBPP has a resolution of ~500 nm for turn-by-turn position, ~90 nm for fast acquisition at 5.03 kS/s rate, and ~30 nm for slow acquisition at 9.83-S/s rate, at a simulated beam current of about 500 mA. The alternative tests of the processor at Hefei light source-II verify the performance.