Infrastructure development for 650 MHz SCRF cavity fabrication by laser welding

After successful development of world's first laser welded 1.3 GHz single cell SCRF cavity, effort has been initiated at CDCA Section, RRCAT to develop 650 MHz single cell and multi-cell cavity. However, the existing welding rig, which was originally developed for proving and establishing this innovative technology of fabrication of SCRF cavities by Laser welding, is limited by its capacity to accommodate 650 MHz cavities. Therefore, a new bell jar type welding rig has been developed along with motion manipulating system satisfying precise alignment requirement and clean environment for fabricating multi-cell 650 MHz SCRF cavities (maximum overall size 408 mm dia. X 1390 mm long). The system builds upon the experience gained in fabricating 1.3 GHz single cell and multi-cell cavities. The gas flow system as well as the target maneuvering system has been improvised. The top bell jar of the rig can be moved by hydraulic cylinder based lifting mechanism to facilitate the assembly of fixtures and cavity components on the fixed bottom part. The rig can accommodate precisely aligned rotary bed and linear bed mounted on industry made motorized stages for job holding where motion is controlled externally by in-house developed motion controller. The rig is attached to a fibre coupled 1 kW average power pulsed Nd:YAG laser beam delivery system to take care of higher thicknesses of 650MHz SCRF cavities. An improvised ultra-high purity argon gas delivery system for driving out the weld muck has been provided. The rig can conveniently handle 650 MHz 5-cell cavity and has an overall size of 1216 mm outer diameter X 1970 mm height. (author)