Design and fabrication of UHV compatible RF-shielded bellow assembly for Indus-2

Full text: Indus-2, a 2.5 GeV electron storage ring is a dedicated source of synchrotron radiation (SR). The required base pressure of the ring is of the order of 2x10-10 mbar. In order to take care of thermal expansion and manufacturing tolerances of vacuum chambers the stainless steel bellows are installed in the ring. But ordinary bellows give rise to RF power dissipation as the corrugations may function as RF cavities. This may even result in puncturing of bellows. Therefore an ultra high vacuum (UHV) compatible RF-shield has been developed for INDUS-2 storage ring. The RF-shield keeps good electrical while absorbing the thermal expansion during beam operation or baking. It reduces the excitation of higher order modes (HOM) and ensures smooth flow of wall current. The RF-shield sub-assembly is made of beryllium copper material. Being toxic material it requires careful consideration for their fabrication and heat treatment. Precipitation heat treatment has been done in vacuum furnace with nitrogen purging for fast cooling. This paper describes the design and fabrication aspects of UHV compatible RF-shielded bellow assemblies