Development of manufacturing procedure for stainless-steel prototype quarter wave resonator

The superconducting accelerating structure which is a Nb Quarter Wave Resonator cavity is used for the LINAC Booster to boost the energy of heavy ion beams delivered by the Pelletron accelerator at the Pelletron LINAC Facility, TIFR. The operational frequency of LINAC is 150 MHz. The LINAC booster consists of seven modules, each module is a liquid helium cryostat housing four QWRs. QWR is a coaxial type structure with central conductor and outer conductor and it is jacketed with Outer jacket where liquid Helium flows. The development of QWR is planned in three stages using Stainless steel in the first stage, copper in the second stage and Niobium in the third stage. A prototype Stainless Steel Quarter Wave Resonator (QWR) has been developed to test the design, fabrication and feasibility of the manufacturing technique. This study will serve as a reference for further manufacturing of Superconducting Niobium QWR, which is to be used in LINAC Booster at TIFR. Electron Beam Welding (EBW) is crucial in manufacturing Nb QWR, ensuring smooth top and under bead weld surfaces in order to minimize the disruption of very high electric and magnetic fields during operation. Preserving the RRR value in EB weld joints is paramount. Leveraging this analogy, EB Welding parameters were optimized for Stainless Steel SS 304L. This paper delves into the manufacturing challenges encountered and the corresponding solutions implemented. The prototype resonator underwent performance testing and field application assessments using Helium leak tests and RF measurements. The paper presents the results of these tests, including the RF performance of the prototype, also data collected from the fabrication, processing, and preparation of the cavities is presented, and potential improvements for better alternatives are highlighted. (author)