Shaped Excitation Current for Synchrotron Magnets

A 500 MeV synchrotron at Argonne National Laboratory (ANL) operates at 30 Hz with its beam spill locked to neutron choppers with a precision of ± 0.5 ¿s. The average beam will be increased by running the magnets at 45 Hz. Three 45 Hz circuits are discussed which differ greatly in overall cost and complexity. The first is a conventional 45 Hz sine wave circuit. The reduction in time for beam acceleration results in a costly increase in peak RF power. This problem is avoided in the other two circuits by making the field rise slowly and fall rapidly. The second circuit discussed is resonant at 45 Hz and 90 Hz. Exciting this circuit with a mixture of dc, 45 Hz, and 90 Hz can produce a magnetic field with the same maximum dB/dt as the present 30 Hz field. A third, and possibly least expensive, solution is a novel circuit which produces 30 Hz during acceleration and 90Hz when the magnets are reset. The RF requirements are, of course, identical to present requirements during acceleration. Circuit details are given.