T. HIGO, Y. FUNAHASHI, Y. HIGASHI, N. HITOMI, T. SUZUKI, T. TAKATOMI, N. TOGE, Y. WATANABE (KEK), Z. LI, R. MILLER, J. WANG (SLAC)
Following the successful design and fabrication of damped detuned structures (DDS), the NLC/JLC linear collider project advanced to rounding the cavity shape to obtain a better shunt impedance. The structure is named as rounded damped detuned structure (RDDS). It is essentially important to make the constituent disks with a high accuracy for the accelerating mode frequency and with a smooth distribution of higher order mode frequencies along the design distribution. The fabrication technologies for those disks were established with a periphery error of 2 microns. The accelerating mode frequencies were controlled with an integrated phase advance error of a few degrees along almost full length of the structure with the application of feed forward technique. The random error of higher order mode frequencies were within 0.6MHz rms, which was much better than the requirement. This paper describes the techniques from the RF point of view to reach such a high precision and the results of the first prototype of RDDS.
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