Systematic Selection of Undulator Magnets Using the Techniques of Simulated Annealing,
STANFORD UNIV CA STANFORD SYNCHROTRON RADIATION LAB
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The problem of sorting and placement of permanent magnets in undulators is considered. First, the constraints on the electron trajectory imposed by orbital stability and optimal synchrotron radiation output are used to construct a simple cost function. This function describes the deviation of the magnetic field in the device from an ideal, and is dependent upon magnet placement. The cost function is then minimized using a Simulated Annealing algorithm until the optimal arrangement of elements is found. The results of optimization of magnet placement are presented for the particular case of the SSRL Beam Line V Multiundulator 15 period devices. The electron path through the device is calculated and compared with a simpler optimization strategy, and with a random unoptimized magnet arrangement. The simulated annealing optimization strategy is found to offer significant advantages resulting in a predicted electron trajectory that is close to ideal.