Precise fabrication of X-band detuned accelerating structure for linear colliders

The precise frequency control of the dipole modes in all of the cells in a structure in addition to the control of the accelerating mode is one of the key issue to realize a detuned structure for the main linac of the linear collider. The present approach is to machine the accelerating cell precisely with the use of the ultra-precision machines and keep the precision through the following fabrication processes such as the diffusion bonding aiming at the precision of the dipole-mode frequency better than 0.01%. In addition to this frequency control, the cell alignment should be a few micro meters and this criteria will be accomplished by the precise machining of the outer surfaces of the cells followed by the alignment along a good vee block. In the present paper are presented some of experimental results on the fabrication of 30 cm-long structures. The bonding at the temperature above 800°C was found reliable to obtain the vacuum tight junction. The change of the accelerating mode frequency was found to be less than 1 MHz out of 11.4 GHz but it seems to have a pressure dependence. The study of 132-cell bonding test was also performed and the alignment of 40 microns along 1.2 m stacking was obtained though a severe trouble happened to the jiggings. Based on these experiences, the possibility of a precise fabrication method for the detuned structure in full size is discussed