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Quadrupole Focusing Lenses for Charged Particles

Description: A set of four strong focusing magnetic quadrupole lenses has been constructed and operated. Each lens consists of four air cooled electromagnets with pole tips having a hyperbolic cross section. Each lens is 4 in. long and has an aperture 2 in. in diameter. Measurements of the magnetic field demonstrate that the hyperbolic cross section satisfies the requirements of a constant magnetic field gradient very well. The technique of deflecting a current carrying flexible wire has been used to measure the trajectory of charged particles through the system of lenses. It has been observed that the strong focusing requirements are satisfied. The system of lenses was then used to focus 0.5 Mev protons, 20 Mev deuterons, and 40 Mev alpha particles. The parallel beam of 0.5 Mev protons was detected by observing the incandescence of a quartz plate while the protons were bombarding it. The focused beam was less than 1 mm in diameter. The astigmatic 20 Mev deuteron beam from the 60 in. cyclotron was increased in current density by a factor greater than 30.
Date: April 15, 1953
Creator: Cork, Bruce & Zajec, Emery
Partner: UNT Libraries Government Documents Department


Description: The targets and probes will be introduced 6-inches below the median plane so that adequate mechanical support can be effectively utilized without reducing the aperture. Probe heads will be of such configuration as to allow monitoring of any desired vertical strip of the aperture. It is probable that some space will be available in the quadrants after first performance tests have been on the machine. No targets or probes will be located in that 1-foot x 4-foot aperture initially. Provision will be made for driving the inner radius targets on the west tangent tank into the aperture during acceleration. The drive mechanism will locate the target (within an adjustable radius) in 1/2 a second. Because of the asymmetry in geometry of pole tip magnets with respect to the magnet yokes and the curvature of the quadrants, it will be difficult to remove positive charged meson beams. A re-entrant side plate on the inside radius of the west tangent tank is under study. While such a plate would provide a location for bending magnets and collimators for positive particles and would simplify the construction of some beam monitoring probes, its presence may introduce a first harmonic distortion in the magnet field of a prohibitive amplitude.
Date: October 27, 1953
Creator: Chupp, Warren
Partner: UNT Libraries Government Documents Department


Description: 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 ...
Date: March 23, 1954
Creator: Chupp, Warren
Partner: UNT Libraries Government Documents Department