One of the major concerns in the development of Dielectric-Loaded Accelerating (DLA) structures is the destructive breakdown at dielectric joints caused by a local electric field enhancement induced by the discontinuity of the dielectric constant at the surface of the joint gap. Our previous X-band traveling wave DLA structure design [1], for example, incorporated two separate impedance matching sections with at least two dielectric joints. In this paper, we present a new design to avoid this problem. This scheme is based on a coaxial type coupler which is able to implement mode conversion and impedance matching at the same time and therefore to eliminate joint gap induced breakdown. The new structure is under construction; bench test results will be presented.

No abstract

1This paper presents a progress report on a joint project by the Naval Research Laboratory (NRL) and Argonne National Laboratory (ANL), in collaboration with the Stanford Linear Accelerator Center (SLAC) and Euclid Techlabs, LLC, to develop an X-band dielectric-loaded test accelerator in the NRL Magnicon Facility. The magnicon is a high-power 11.4-GHz amplifier tube that can produce up to 25 MW of power in 200-ns pulses at up to 10 Hz. The dielectric accelerating structures are developed by ANL and Euclid Techlabs, and tested at NRL and SLAC. The accelerator will include a 5-MeV electron injector developed by the Accelerator Laboratory of Tsinghua University, Beijing, China. SLAC has developed a means to combine the two magnicon output arms, in order to drive an injector and accelerator with separate control of the power ratio and relative phase. The initial operation of the injector should take place later this year, and the first test with a DLA structure, and a spectrometer should take place within the next year.

We report on the most recent results from a series of high power tests being carried out on rf-driven dielectricloaded accelerating (DLA) structures. The purpose of these tests is to determine the viability of the DLA as a traveling-wave accelerator and is a collaborative effort between Argonne National Laboratory (ANL), Naval Research Laboratory (NRL), and Stanford Linear Accelerator Center (SLAC). In this paper, we report on the recent high power tests of a fused quartz-based DLA structure that was carried out at incident powers of up to 12 MW at NRL and 37 MW at SLAC. We also report on test results of a TiN coated quartz structure, that exhibits good multipactor suppression.