Permanent Magnet for a Beam Profile Monitor

The ionization beam profile monitor system for the Main Injector ring is under construction at Fermilab. The beam profile detector unit is installed inside the main magnet gap. The magnet has a novel configuration previously used for this type of application in the Main Injector. However, this magnet is far more compact with a higher quality field. Most flux from the main gap returns symmetrically along the beam pipe through two side gaps. It provides nearly full compensation to yield integrated magnetic field close to zero, and helps eliminate distortions of the circulating proton beam. The permanent magnet poles are assembled from SmCo5 bricks (0.5^´´×1^´´×2^´´), which have good thermal stability and reasonable cost. Further integrated field reduction is obtained by the use of a ferromagnetic plate that shunts the main gap. The plate position and flux shunting are adjusted in conjunction with magnetic measurements. Three permanent magnets were successfully fabricated and measured. Results of the magnet design, 3-D FEA analysis, and magnetic measurements by the rotational coil and the 3-D Hall probe will be presented.