Micro-stepping motor control for tuner and coupler

In the superconducting linear accelerator at PLF, Mumbai each RF cavity is fitted with a coupler for feeding RF power and a tuner for frequency adjustment, The coupler/tuner are controlled using a stepper motor coupled to a suitable mechanical arrangement. Presently, bipolar stepper motors are used with a single channel motor controller. Thus any dynamic adjustment on multiple cavities during the beam operation requires interruption in beam. Further, this bipolar motor doesn't have the micro-stepping control and hence operations in cold condition are not always smooth. Therefore, an improved control module for multichannel control with communication to PC is designed. The design is based on Leadshine make EM503 micro-stepping module and uses Silicon lab make C8051F020 microcontroller. The module can control upto 16 couplers/tuners. The multiplexing is done using high current four pole relays. The design also has additional features like motor selection, start/stop, speed change, limit control and remote operation. (author)