Manipulation of the ZGS Beam for Targeting

Abstract

The feeding of as many as four experimental areas from a single ZGS pulse calls for a flexible system for controlling the spill of the beam. The beam is displaced radially into as many as four targets plunged into position after radial damping of the beam has occurred. Beam spills have been adjusted in time duration from 5 microseconds to 500 milliseconds during a flat-top period of the main magnet cycle. Spills shorter than about 0.5 millisecond are accomplished by a pulsed magnetic bump which displaces the orbit center. Spills longer than about 0.2 milliseconds are accomplished by programmed adjustment of the accelerating rf so as to expand or contract the orbit radius. Radiation level monitors in the vicinity of the targets or in the experimental beam lines are used to feedback a signal into the rf program which results in the reduction of spill irregularities due to main magnet ripple and other noises. Such a spill has rf structure and is on from 25% to 50% of the time. The repeatability for placing the beam into a given position for targeting is about 0.01 inch without employing feedback from radiation level monitors. A description of the equipment and instrumentation is given along with the performance.