The Low-Level Rf Beam Control System for the Booster of the Beijing Proton Synchrotron (BPS)

A prototype of a low level RF beam control system for the BPS Booster was designed and built at Fermilab during the past year. Machine parameters are: RF Frequency range 2.76-6.31 MHz, Harmonic number h= 3, Repetition rate 12.5 Hz, Maximum synchrotron frequency 12 KHz No phase transition occurs during acceleration. We have adopted computer controlled digital curve generators for the frequency program and other programs such as the radial position offset, radial position loop gain, etc. for the operational flexibility available with such programs. The frequency mixing method was chosen for the analog beam control loops, including the phase loop and radial position loop, for improving the signal to noise ratio within the wide frequency band and for convenience in signal processing. The system is composed of a series of modules which are to be operated in several modified NIM crates. This will allow maximum flexibility during the development phase of accelerator operation. Here we give a brief description of the LLRF system and some preliminary design and test results. Study and improvement of the system will be continued. A simplified block diagram of the system is shown in Figure 1.