Control System for the Holifield Heavy Ion Research Facility Beam Buncher

A beam buncher has been developed to produce very short pulses of beam from the 25 MV accelerator for injection into ORIC. The buncher is a two-harmonic double-drift klystron-type operating over a frequency range of 4.5 to 14.5 MHz and has produced 1.1-ns pulse widths of 16O in tests on the ORNL EN tandem accelerator. Both rf voltage on, and relative phase between, the two buncher drift tubes must be accurately controlled to maintain the required narrow pulse width. A control system has been developed which accomplishes these tasks as well as automatic tuning of the buncher resonators, monitoring system parameters, and remote adjustment of various mechanical devices. Input commands and monitoring signals are CAMAC-compatible so that the system can eventually be included in the computer-based control system for the accelerator. In addition to the requirement for a very narrow beam pulse, the pulses must arrive at the ORIC dee gap with precise phasing. A closed-loop control for this task is being constructed using the beam pulse phase detector circuit developed at Argonne National Laboratory.