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Compactness and cost-effectiveness are two major concerns in the development of a Ka-band linearizer, which is a crucial accelerator component of the European CompactLight project. A higher order mode (HOM) multibeam Klystron (MBK) could accommodate a higher distributed electron current with a low operating voltage of 60 kV, thus making it competitive to deliver high RF power at high frequency compared with a single beam Klystron or a fundamental mode MBK. In this article, the modeling and design study of the 36-GHz HOM MBK is presented. The development of a double compression multibeam (MB) optics system is also elaborated in this article. The performance validation of such a device was done using sophisticated 3-D particle-in-cell (PIC) computer simulations of the entire device. PIC simulations confirmed that a power level of 2.5 MW is attainable with an efficiency of 35%. [ABSTRACT FROM AUTHOR]

High-frequency, high-power klystrons proved to be significant for application in compact particle accelerators, high-resolution radars, and fast data communication systems. As most of the linear beam devices, the performance of the klystron deteriorates progressively with an increasing operating frequency due to the reduction of individual RF cavity impedances. Coupled cell structures can alleviate such degradation by extending the beam–wave interaction region. The accurate simulation of the klystron with the coupled cell structure relies on the resources and the time-consuming particle-in-cell (PIC) codes. To speed up the klystron design process, the coupled-mode theory was carefully reviewed and extended to facilitate the calculation of the complex spectra of the arbitrarily coupled cavity system and its interaction with the bunched electron beam. These new methods were implemented in the large signal klystron simulation code KlyC. The design and optimization of the Ku-band, low-voltage klystron is explained as a demonstration of the new technique’s effectiveness. The KlyC simulations have been thoroughly benchmarked with the CST PIC code and both codes showed a good (within 1%) agreement, while KlyC is significantly (about 100 times) faster. [ABSTRACT FROM AUTHOR]

Abstract: The goal of the present CLIC Test Facility (CTF3) is to demonstrate the technical feasibility of the CLIC scheme, where the RF power extracted from the drive beam is used to accelerate the main beam. Several prototypes of the RF power extractor so-called PETS (Power Extraction and Transfer Structure) have been developed at CIEMAT for this facility. The first device was embedded in a steel vacuum tank and installed at the Test Beam Line (TBL), whose aim is to prove the beam stability during deceleration and power extraction. Presently, CERN and CIEMAT share the responsibility to build eight additional PETS for TBL. Finally, in the framework of EuCARD (European Coordination for Accelerator Research and Development) collaboration, a new PETS configuration is presently under engineering design at CIEMAT. It is based on a compact concept developed at CERN. This device will be installed in the Test Module at CTF3, in a similar configuration to that of the final two-beam scheme acceleration of CLIC. This paper describes the PETS prototype fabrication techniques used at CIEMAT, with particular attention to the production of the long copper rods which induce the RF generation and the welding and assembly procedures. The characterization of the devices with low RF power and the first tests with beam are also described. [Copyright &y& Elsevier]