ADITYA upgrade vacuum vessel: Design, construction, testing, installation and operation

Abstract

Limiter based ADITYA tokamak has been upgraded in the divertor configured ADITYA-U tokamak. The ADITYA tokamak upgradation includes the replacement of rectangular cross section vacuum vessel by circular cross section vacuum vessel to accommodate additional poloidal (divertor) coils in space between the new vessel and toroidal field coils. The major radius (0.75 m) and minor radius (0.25 m) has been kept same as of old torus so as to accommodate the new torus inside the toroidal field coils. In order to accommodate as many numbers of diagnostics as possible, the ADITYA-U vessel is designed to have 111 port openings directly on the vessel. The leak proof, UHV condition, precise dimensions and lots of weld and demountable joints in the new vessel made the fabrication job very challenging. The ADITYA-U vacuum vessel of SS304L has been precisely fabricated as per IPR design by Godrej & Boyce Mfg. Co. Ltd. under the supervision of IPR scientists. The factory and IPR site acceptance tests of new vessel had been completed successfully, such as dimensional measurement, leak test, pressure, baking. The final acceptable tests had been carried out successfully as results of local leak rate <5 × 10−10 mbar l/s and global leak rate <5 × 10−8 mbar.l/s, UHV test as <10−9 mbar, vessel baking >150 °C. After external testing, the vessel has been installed successfully in ADITYA-U tokamak structure. In this paper, we present the all details of ADITYA-U vacuum vessel like design, analysis, fabrication, acceptance, installation and operation to ascertain its suitability for the plasma experiments.