A Novel Idea for a CLIC 937 MHZ 50 MW Multibeam Klystron

The CLIC study is based on 937 MHz, 50 MW, 100 s Multi-Beam Klystron (MBK) with a design efficiency in excess of 65%. Unfortunately MBKs that meet the above specification are not currently available, and further design and development work will be needed to demonstrate that this specification can be achieved. An MBK is basically a parallel assembly of many low-current klystrons which use common RF structures for the interactions with the beams. Having a large number of beamlets in the klystron enables the power per beamlet to be considerably reduced leading to low current densities, low-perveance beams and hence high efficiency. A new MBK design concept is proposed, it is based on results and experience obtained from the use of Barrel-Open-Cavity (BOC) technology which was initially developed in Russia, but which has been developed further over the last few years at CERN. It is shown that this new concept leads to a multi-mode MBK design that is mechanically robust and simple to manufacture, with a possible efficiency of 80 %.