Increased Intensity Performance of the Brookhaven AGS

With the advent of H^- injection into the Brookhaven AGS, circulating beams of up to 3 × 10¹³ protons at 200 MeV have been obtained. Rf capture of 2.2 × 10¹³ and acceleration of 1.73 × 10¹³ up to the transition energy (≈ 8 GeV) and 1.64 × 10¹³ to full energy (≈ 29 GeV) has been achieved. This represents a 50% increase over the best performance obtained with H⁺ injection. The increase in circulation beam current is obtained without filling the horizontal aperture. This allows the rf capture process to utilize a larger longitudinal phase space area (≈ 1 eV sec/bunch vs ≤ 0.6 eV sec with H⁺ operation). The resulting reduction in relative longitudinal density partially offsets the increase in space charge effects at higher currents. In order to make the capture process independent of injected beam current, a dynamic beam loading compensation loop was installed on the AGS rf system. This is the only addition to the synchrotron itself that was required to reach the new intensity records. A discussion of injection, the rf capture process, and space charge effects is presented.