Simulation and measurement of the fringe field of the 1.5 T BABAR solenoid

In the context of the SLAG PEP-II asymmetric e(+)e(-) collider and the BABAR detector with its 1.5 T solenoid, we have calculated and measured the fringe field at the nearby beam elements and at the position of the photomultipliers external to the return iron but within a specially designed iron shield. The comparisons of these measurements with the simulations based on finite element analysis are remarkably good, within about 5 G at the most critical beam element. The field at the photomultipliers is less than 1 G, in agreement with the simulation. With a simple method of demagnetization of the shield, a maximum held of 0.6 G is obtained. (C) 1999 Elsevier Science B.V. All rights reserved.