After 25 years of successful operation of ADITYA tokamak (~ 30,000 discharges) in a circular poloidal ring limiter configuration, it has been upgraded to a tokamak named ADITYA Upgrade (ADITYA-U) to realize the shaped-plasma operations in an open diverter configurations. The upgradation was conceptualized in the year 2014 and the ADITYA tokamak had been dismantled to its base level in the year 2015. The ADITYA-U tokamak construction was completed in the year 2016 and the first plasma was achieved in December 2016.
The ADITYA-U tokamak is a medium-size air-core tokamak with a major radius of 0.75me and a minor radius (limiter radius) of 0.25 m and maximum toroidal magnetic field of 1.5 T. It has a toroidal belt limiters and two quarter poloidal limiters at two toroidal locations made up of graphite. The ADITYA-U is designed to produce circular plasmas with plasma current ~ 150 – 250 kA, plasma duration of ~ 250 – 350 ms with a chord average electron density in the range of 1 – 5 x 10^19 per meter cube and electron temperature ~ 300 eV – 1000 eV. In addition, it is designed to achieve shaped plasmas with plasma current ~ 100 – 150 kA, elongation (k) ~ 1.1 - 1.2 and triangularity ~ 0.45.
Since 2017, ADITYA-U is routinely being operated and maximum plasma current of ~ 200 kA and longest plasma duration of ~ 350 ms has been achieved in circular plasmas of ADITYA-U tokamak with toroidal belt limiter. Several novel experiments such as electromagnetic particle injection for disruption studies, rotation reversal and saturated Ohmic confinement modes, runaway electron dynamics with gas-puffs etc. are being carried out mainly in circular plasmas. The divertor coils are charged and shaping of the plasma current has been attempted recently obtaining some very encouraging results.