Design And Fabrication Of A Surface-Wave Accelerator Based On Silicon Carbide
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The principles and electromagnetic simulations of a novel accelerating structure are described. The structure is planar, consisting of two plates of silicon carbide (SiC) separated by a vacuum gap. Charged particle bunches are accelerated in the vacuum gap by the surface electromagnetic waves (phonon polaritons) localized near the vacuum/SiC interface. The structure can be powered by a carbon dioxide (CO2) laser with the wavelength lambda(0) approximate to 10.6mum. The operating wavelength is dictated by the frequency-dependent dielectric permittivity epsilon(omega) of SiC which is negative for the frequencies in the CO2 tunability range. The resulting accelerator can support accelerating fields well in excess of 1 GeV/m without breakdown, and provide the path to compact and inexpensive particle accelerators. The challenge of coupling radiation into a very narrow (a few microns) vacuum gap is resolved by designing a coupling grating on the top surface of a Si wafer, and attaching a thin SiC film to the bottom of the wafer. Preliminary fabrication results are reported.