The L-band klystron-modulator RF power system for CLIC

The long-pulse, high-power klystron-modulators are an important part of the CLIC drive-beam scheme and a number of design variations are being studied in order to improve their overall power efficiency, reliability and cost effectiveness. Because of the number needed (364 at 50 MW for the 3 TeV scheme) and their size, they will have a large impact on the capital cost of the pulsed RF power to be delivered to the beam and to the resistive losses in the drive-beam accelerating structures. Overall RF system efficiency is an important parameter for long linear colliders, and to a large extent, will be determined by the performance and efficiency of the klystron-modulators. The input AC power to output RF power efficiency of one CLIC klystron-modulator, including the klystron, power conversion, pulse transformer, auxiliary power and switching losses at 100 Hz and 100 μs pulse width, is estimated as 52%. The RF to beam efficiency is estimated at 24%, and after taking into account other RF power transmission losses within the systems the overall AC to beam efficiency will be about 10%