MEETING XIII -- BEVATRON RESEARCH CONFERENCE -- TARGET AREA MODIFICATIONS

Abstract

The following modifications are planned to facilitate greater usefulness of available target space in the west tangent tank: (1) A 3/32-inch x 6-inch x 106-inch aluminum window is to be added to the outer radius tank wall. (2) One 12-inch x 6-inch air lock is to be added on the inside centerline of the reentrant section on the west tangent tank. (3) Two 24-inch x 30-inch openings are to be cut on the beam centerline in the top of the west tangent tank, one at each end. These openings will accommodate photographic plate wells of various kinds and also a large air lock that is being designed. It is suggested that any other modifications to the target area be presented to E. Lofgren as soon as possible so that the modifications can be programmed with respect to operations. The same general policy holds for target location, viz: (a) Small targets - allocations in west tangent tank; and (b) Large targets - allocations in south tangent tank. The design of two general purpose magnets is in the final stages. Copper for the coils will be ordered soon. The characteristics of these magnets are given. Results of magnetic field measurements on the Bevatron are reported, Some of the details and compromises in design of the magnet are discussed. The pole tip confiscation in the 1 x 4-foot aperture nominally n = 0.6 has been cut to a mechanical slope of 0.63. The laminated pole tips have protruding ears which modify the fringing field at low magnet currents to provide the widest possible aperture at injection. These ears are slotted so that they saturate and at intermediate field values become ineffective. This design represents a compromise between maximum useful field width and maximum obtainable field at peak current. The pole tips contain 21 pairs of pole face windings which can be separately energized to allow small local field perturbations. Some of these windings are self-excited to shape the field at injection. Others are available for increasing the high field aperture. The presence of fringing fields in the straight sections between quadrants is considered in defining for these regions an effective length given by: Effective magnetic length = 1/{bar B} at mid-quadrant Bdl at constant radius According to this definition, the magnetic length of a quadrant may vary with field strength. To compensate for the amount that the effective magnetic length of the quadrant is different from the 90{sup o} mechanical length, the particle orbit center is displaced from the quadrant center and some loss of useful aperture results. The end sector pole tips of each quadrant have been cut back 5 1/2 inches as an attempt to bring the magnetic length more nearly in agreement with the quadrants mechanical length. To insure that iron samples would not introduce an azimuthal harmonic perturbation in the magnetic field, a random mixing schedule was followed in the assembly of magnet iron.