Performance of the New AGS (Alternating Gradient Synchrotron) RFQ Preinjector.

摘要

In the fall of 1988, the 750 keV Cockcroft-Walton (C-W) preinjector for the AGS 200 MeV H(-) linac was replaced by an RFQ, in what has proved to be a very successful upgrade. The motivations for the upgrade included improved reliability, simpler maintenance, and the added convenience of having the ion source located at nearly ground potential. At the same time, the controls and instrumentation in the preinjector area were modernized. The linac has been operating full time with this RFQ preinjector since January 1, 1989, and the reliability has been excellent. The source, RFQ, and linac operate at a 5 Hz repetition rate, and the beam pulse width is approximately 450 mu s. At this time, the H(-) current at 200 MeV is typically 23-25 mA, the same as previous operation with the C-W, although the capability is there to reach higher currents in the future. The layout of the new preinjector is shown in Figure 1. An important consideration in the layout of this line was the decision to leave the final 2.4 m section before the linac intact, so the optics of a second C-W injector line and polarized H(-) injection from another RFQ remained the same. The resulting line has a distance of almost 6 m from the RFQ to the linac, and there are three ''rebuncher'' cavities to maintain the bunching of the beam from the RFQ. The following sections will describe some details of the preinjector line, and then discuss the installation and performance. (ERA citation 14:029206)