The capacitor charging power supply for the next-generation linear collider

The klystrons for the next-generation linear collider (NLC) are designed to operate at 500 kV, and have a microperveance of 0.75×10^-6 AV^3/2, or 265 A of beam current. Two klystrons are planned to be driven in parallel by one pulse modulator with a 1:14 step up transformer. The impedance of the pulse forming network (PFN) for the modulator is therefore 4.8 Ω, while the charge voltage is 71.5 kV. The pulse width is 1.5 μs, so the total capacitance to be charged is 0.156 μF. The maximum repetition frequency is 180 Hz. The power supply required to charge the PFN is thus an 80 kV, 100 kW capacitor charging power supply. Because of the large number of klystrons used in the NLC, up to approximately 10,000, there are several additional requirements which the capacitor charging supply must meet. The most important of these requirements is efficiency, which must be approximately 95% or better. Next is cost, followed by reliability (greater than 50,000 hour MTBF), maintainability, ease of connection, disconnection and transport. Several circuit topologies designed to meet the charger requirements have been studied. Detailed analysis has been performed on a flyback power converter, a series resonant power converter, and a command resonant power converter. Advantages and disadvantages of each are discussed