Comparison of computer predictions and magnetic field measurements for an iron spectrometer magnet

Three dimensional computer calculations using the Program TOSCA have been made for a complex-shaped iron magnet. Precision field measurements were made on this magnet in preparation for its installation in a new Low Energy Separated Beam for the post-Booster high proton intensity AGS at Brookhaven National Laboratory. Point-by-point direct comparisons for field values will be described encompassing the entire useful acceptance. The predictability of higher order multipoles will be described, including the region of the magnet ends. Computer predicted focal properties will be compared with results of experimental data analysis. The method of measurement and analysis, as well as comments on the computer calculations will be described. Conclusions will be drawn on the accuracy of calculations with respect to higher order moments and the impact on future beam optical design and execution of three dimensional computer codes