Beam size versus intensity for resonant extracted beam at the Brookhaven AGS

Transverse beam sizes were measured in the AGS prior to the initiation of the third order resonance (ν_H=8 2/3; driven by sextupoles) used for the slow extraction and again in the external beam lines. The measurements were made using the AGS ionization profile monitor (IPM) and an external profile monitor (EPM). Both of these monitors use the ionized residual gas to image the beam on arrays of wires that are aligned parallel to the direction of the beam. The effects of space charge on the IPM are significant at the intensities measured, but the EPM measurements are not affected by space charge. Two measurements are reported. First is the intensity dependence of the resonant beam size, and secondly, an indirect measure of the space charge effect on the IPM. A differential comparison of the two monitors in the vertical plane allows unfolding the effect of the space charge on the measurements. These measurements were made over an intensity range between 15×10¹² and 36×10¹² protons per AGS pulse