LIGA-FABRICATED COMPACT MM-WAVE LINEAR-ACCELERATOR CAVITIES

Millimeter-wave rf cavities for use in linear accelerators, free-elect ron lasers, and mm-wave undulators are under development at Argonne Na tional Laboratory. Typical cavity dimensions are in the 1000 mu m rang e, and the overall length of the accelerator structure, which consists of 30-100 cavities, is about 50-100 mm. An accuracy of 0.2% in the ca vity dimensions is necessary in order to achieve a high Q-factor of th e cavity. To achieve this, these structures are being fabricated using deep X-ray lithography, electroforming, and assembly (LIGA). The firs t prototype cavity structures are designed for 108 GHz and 2 pi/3-mode operation. Input and output couplers are integrated with the cavity s tructures. The cavities are fabricated on copper substrates by electro forming copper into 1 mm-thick PMMA resists patterned by deep x-ray li thography and polishing the copper down to the desired thickness. Thes e are fabricated separately and subsequently assembled with precision spacing and alignment using microspheres, optical fibers, or microfabr icated spacers/alignment pieces. Details of the fabrication process, a lignment, and assembly work are presented in here.