Data Transmission across High Voltage Interfaces via Light Links

Computer control/monitoring of the LAMPF injector requires data to be transmitted to and from the ion source in the high voltage head. These data must be digitized for computer use as is done throughout the rest of the accelerator. The A/D converter, interfacing instrumentation equipment, and control logic are placed in the head. Signals are transmitted across the 750 kV interface to and from the high voltage head through 5 light links. Four are used to replace insulated rods and strings for data and control. One transmits the pulse signal to the ion source. The system should operate at computer speeds; therefore, rise and fall times for pulse transmission of data must be less than 200 ns. The pulse width is 800 ns with a 50% duty cycle. The ion source pulse requires the same rise time but the pulse width must extend to 1.5 ms. This paper describes the system and reports the test results on a system designed to meet these specifications. The modification of the system to provide linear transmission of fast waveforms is discussed.