New Light Link System for High Voltage Terminal

A new light link system has been running to control the ion source more than 2,500 hours without trouble at the 750 kV preinjector. It has two optical fiber cables and two microprocessors (CPU´s). Triggering pulses and control signals are sent serially through one optical fiber cable to the high voltage terminal. Analog parameters of the ion sources are converted to digital data and sent through the other cable from the high voltage terminal. Pre-arc pulses, which synchronize with the booster synchrotron of 20 pps, start cycles of data transfer. To avoid jitter, the arc trigger pulses are not processed in the CPU´s, which only regulate gates for the pulses. A word of the control signal consists of 10 bits, a start bit, 8 bit data and a stop bit. The light link is checked in every cycle. When error is detected, then the control signals are not delivered to the ion source and the error is indicated at the control desk. Since the error is mainly caused by noise due to breakdown in the accelerating column, the program does not stall and the next pre-arc pulse starts the data transfer again.