Overview of recent experimental results from the Aditya tokamak

Abstract

Several experiments, related to controlled thermonuclear fusion research and highly relevant for large size tokamaks, including ITER, have been carried out in ADITYA, an ohmically heated circular limiter tokamak. Repeatable plasma discharges of a maximum plasma current of ~160 kA and discharge duration beyond ~250 ms with a plasma current flattop duration of ~140 ms have been obtained for the first time in ADITYA. The reproducibility of the discharge reproducibility has been improved considerably with lithium wall conditioning, and improved plasma discharges are obtained by precisely controlling the position of the plasma. In these discharges, chord-averaged electron density ~3.0–4.0 × 1019 m−3 using multiple hydrogen gas puffs, with a temperature of the order of ~500–700 eV, have been achieved. Novel experiments related to disruption control are carried out and disruptions, induced by hydrogen gas puffing, are successfully mitigated using the biased electrode and ion cyclotron resonance pulse techniques. Runaway electrons are successfully mitigated by applying a short local vertical field (LVF) pulse. A thorough disruption database has been generated by identifying the different categories of disruption. Detailed analysis of several hundred disrupted discharges showed that the current quench time is inversely proportional to the q edge. Apart from this, for volt–sec recovery during the plasma formation phase, low loop voltage start-up and current ramp-up experiments have been carried out using electron cyclotron resonance heating (ECRH). Successful recovery of volt–sec leads to the achievement of longer plasma discharge durations. In addition, the neon gas puff assisted radiative improved confinement mode has also been achieved in ADITYA. All of the above mentioned experiments will be discussed in this paper.

Overview of operation and experiments in the ADITYA-U tokamak

“…Recently, the first medium sized tokamak facility of India named ADITYA (R0 = 75 cm, a = 25 cm) [4], operated over 2 decades with circular poloidal limiter [5] has been upgraded to a tokamak named ADITYA Upgrade (ADITYA-U) for the purpose having shaped plasma operation with an open divertor geometry with divertor plates without any baffle, to support the future Indian Fusion program. The foremost objective of ADITYA-U is to prepare the physics and technological base for future ITER and DEMO machine [6 -7] by performing the dedicated experiments, such as generation and control of RE, disruption prediction and mitigation studies, along with plasma position control and confinement improvement studies with shaped plasmas.…”

Evaluation of an Oxygen Transport Coefficient in the Aditya Tokamak Using the Radial Profile of O4+ Emissivity and the Importance of Atomic Data Used Therein

“…The edge electron density and temperature were measured using Langmuir probes. Standard magnetic diagnostics were used to measure the plasma current, loop voltage, plasma position, and magneto-hydrodynamic (MHD) activities [12].…”

“…The edge electron density and temperature were measured using Langmuir probes. Standard magnetic diagnostics were used to measure the plasma current, loop voltage, plasma position, and magneto-hydrodynamic (MHD) activities [12]. The spatial profile of 650.024 nm spectral line emitted by the O 4+ ion was measured using a space resolved visible spectroscopic system [13].…”

“…In the Aditya tokamak [12], an intense visible line from Be-like oxygen at 650.024 nm (2p3p 3 D 3 -2p3d 3 F 4 ) is routinely observed [13]. Therefore, this emission was used to study the impurity transport in the Aditya tokamak by utilizing the advantage of visible spectroscopy, which is the use of optical fiber for the space resolved measurement.…”

Modeling of the Hα Emission from ADITYA Tokamak Plasmas

“…ADITYA tokamak is a mid-sized air-core tokamak with a major radius (R) of 0.75 m and a minor (a) radius of 0.25 m. It has a circular poloidal ring limiter made of graphite material at one particular toroidal location. The typical discharges of ADITYA have the plasma current of 80-140 kA and plasma duration of 100-200 ms with a toroidal magnetic field in the range of 0.75-1.2 T [14]. The fueling gas is hydrogen and pre-filled at a pressure of 4-6 × 10 −5 mbar using a gas feed system.…”