The conceptual design of CLARA, a novel fel test facility for ultra-short pulse generation

CLARA will be a novel FEL test facility focussed on the generation of ultra-short photon pulses with extreme levels of stability and synchronisation. The principal aim is to experimentally demonstrate that sub-cooperation length pulse generation with FELs is viable, and to compare the various schemes being championed. The results will translate directly to existing and future X-ray FELs, enabling them to generate attosecond pulses, thereby extending their science capabilities. This paper gives an overview of the motivation for CLARA, describes the facility design (reported in detail in the recently published Conceptual Design Report [1]) and proposed operating modes and summarises the proposed areas of FEL research

Design of the ILC Crab Cavity System

Abstract The International Linear Collider (ILC

Dynamical aspects of multipacting induced discharge in a rectangular waveguide.

Multipacting induced discharge in a rectangular waveguide is studied experimentally at a RF frequency of 500 MHz. The waveguide has a cross-section of 457 mm by 102 mm. The maximum forward RF power is 600 and 300 kW in traveling and standing wave mode, respectively. A continuous multipacting band structure is observed. Electron pick-up probes of antenna-type are used to measure the multipacting current and its longitudinal as well as horizontal distributions. The electron energy spectrum is measured with the retarding field method. The end-point energy of the spectra taken in traveling wave mode is in the range of 100-1000eV and agrees well with the impact energy calculated by the classical multipacting theory. However, a large fraction of electrons has energies lower than 100eV. Electron stimulated gas desorption is found to play a critical role in the dynamics of multipacting induced breakdown. It is concluded that the ionization discharge of desorbed gases is the immediate cause for RF breakdown. (C) 2004 Elsevier B.V. All rights reserved

Suppression of multipacting in rectangular coupler waveguides.

Although a rectangular waveguide coupler has the conceptual advantages of simplicity and capability of withstanding higher power, builders of modern superconducting accelerators are routinely choosing instead a coaxial coupler for its proven performance. Multipacting induced discharge has been found to be an operating mechanism that prevents a rectangular waveguide coupler from reaching its full potential. Earlier calculations predicted the existence of two-sided multipacting in a rectangular waveguide geometry. In the present study, special waveguide sections of CESR type were built and tested. Multipacting characteristics of the waveguide were identified. Two multipacting suppression methods. the slotted waveguide method and the DC magnetic bias method, were experimentally evaluated. The multipacting current is suppressed by a factor of more than 2 by opening a slot on the broad wall. Complete multipacting suppression can be realized by using the DC magnetic bias method. (C) 2003 Elsevier Science B.V. All rights reserved