Design of a thin quadrupole to be used in the ags synchrotron

Abstract

The alternating gradient synchrotron (AGS) employs two partial helical snakes[1] to preserve the polarization of the proton beam during acceleration. In order to compensate for the focusing effect of the partial helical snakes on the beam optics in the AGS during acceleration of the beam,we introduced eight quadrupoles in straight sections of the AGS at the proximity of the partial snakes. At injection energies, the strength of each quad is set at a high value,and is ramped down to zero as the effect of the snakes diminishes by the square of beam's rigidity. Four of the eight compensation quadrupoles had to be placed in very short straight sections ~30 cm in length,therefore the quadupoles had be thin with an overall length of less than 30 cm. In this paper we will discuss: a. the mechanical and magnetic specifications of the "thin" quadrupole. b. the method to minimize the strength of the dodecapole harmonic,c. the method to optimize the thickness of the laminations that the magnet iron is made,d. mechanical tolerances of the magnet,e. comparison of the measured and calculated magnetic multipoles of the quadrupole.