N. Hitomi, Y. Funahashi, Y. Higashi, T. Higo, S. Koike, T. Suzuki, K. Takata, T. Takatomi, T. Toge, Y. Watanabe, (KEK, Tsukuba)
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 better shunt impedance. The structure is named as rounded damped detuned structure (RDDS). Various advanced techniques comparing to those for DDS for fabrication of constituent disks were needed to make RDDS disks to meet the requirements on the frequencies of the lowest dipole modes in addition to the accelerating mode. We established the machining technology satisfying the peripheral tolerance of 2 microns for the prototype production. In the present paper we describe those techniques and the results for the first prototype of RDDS. These disks were stacked on a precision V block. The inclination of disks with respect to the tangential line to the curve connecting their center points became much smaller than the previous DDS. These stacked disks were joined to make a 1.8m long main body through a pre-bonding process at less than 200 degrees centigrade followed by a high-temperature diffusion bonding. The main features related to these stacking and bonding are also described briefly.
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