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- J.B. Murphy, J. Bengtsson, L. Berman, R. Biscardi, A. Blednykh, G.L. Carr, W.R. Casey, S.B. Dierker, E. Haas, R. Heese, S. Hulbert, E. Johnson, C.C. Kao, S.L. Kramer, S. Krinsky, I.P. Pinayev, R. Pindak, S. Pjerov, B. Podobedov, G. Rakowsky, J. Rose, T.V. Shaftan, B. Sheehy, D.P. Siddons, J. Skaritka, N. Towne, J.-M. Wang, X.J. Wang, L.-H. Yu
BNL/NSLS, Upton, Long Island, New York
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The problem of very fast higher order mode (HOM) suppression, in the order of 1ns, was investigated for a planar 30GHz accelerating structure. Both, damping and detuning were considered. A sufficient suppression could be achieved by damping waveguides in every cell in vertical and in horizontal direction. Finally, a scaled-up 10GHz model was built. It is a 35 cm long aluminum structure, which was machined by high-precision milling. In order to reduce the surface gradient on the input/output coupling irises a symmetrical RF coupler was developed. The HOM damping is accomplished by coupling six damping waveguides to each accelerating cell. The waveguides are loaded by a low resitivity RF load. The whole structure with waveguides and loads was optimized by means of the computer code GdfidL. The paper gives the design criteria and the results of s-parameter and bead-pull measurements.
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