The AGS main magnet power supply upgrade

The AGS is a strong focusing, combined function magnet, particle accelerator. The main parameters of the accelerator are a peak operating energy of 29.4 Gev, a peak magnetic field of 11.5 kG, a typical injection field of 0.9 kg, an injection energy of 1.5 Gev, and a maximum pulse repetition rate of 0.6 Hz. The injection is from a rapid cycling Booster synchrotron, which receives either a proton beam from a 200 Mev Linac, or a Heavy Ion beam from a 15 MV Tandem Van de Graaf Accelerator. Flattops of up to 2 seconds can be added to the AGS cycle for slow extracted beam applications. Particles accelerated include protons (mass=1), both polarized and non-polarized, and fully stripped ions up to gold (mass=197). The maximum proton intensity attained thus far is 60×10ˆ13 particles per pulse. Modes of operation for the AGS are full-turn extraction (2.5 usec), slow extraction (1-2 sec), and bunch-by-bunch extraction. These modes are applicable for both protons and heavy ions. The peak apparent power required during acceleration is approximately 70 MVA while the maximum average power needed is less than 7 MW. In order to isolate this large power swing from the local power grid, a motor-generator (MG) set is used as a buffering source. The MG set stores approximately 315 Kilojoules of energy in its rotating mass. As energy is drawn to charge or discharge the ring magnets, the speed of the rotating mass changes in such a manner as to supply the required load power demand. The input to the motor is controlled by a power regulator that forces the input power to be equal to the average losses during each cycle. The line sees nearly a constant load equal to the system losses. The peak power requirements are met by changes in the stored energy of the rotating mass that translates directly into speed variations. Thus, for a fixed operating cycle, the losses during each cycle are reproducible, and the speed oscillates around an average value and is returned to the same value at the beginning of each supercycle