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

Abstract

Oxygen impurity transport in the typical discharges of the Aditya tokamak was investigated using emissivity radial profile of emissivity of the spectral line (2p3p 3D3–2p3d 3F4) at 650.024 nm from the Be-like oxygen ion. This O4+ spectral line was recorded using a 1.0 m multi-track spectrometer capable of simultaneous measurements from eight lines of sight passing through the plasma. The oxygen transport coefficients were determined by reproducing the experimentally measured emissivity profiles of O4+, using a one-dimensional impurity transport code, STRAHL, and photon emissivity coefficient (PEC) belonging to that transition. The PEC values were obtained from both ADAS and NIFS atomic databases. Using both the databases, much higher values of diffusion coefficients compared to the neo-classical values were observed in both high and low magnetic field edge regions of typical Aditya tokamak Ohmic plasma. Although, almost similar profiles of diffusion coefficients were obtained using PEC values from both databases, the magnitude differs considerably. The maximum values of diffusion coefficients in the plasma edge at low field side of tokamak were ~45 and ~25 m2·s−1 when modeling was done using the ADAS and NIFS databases, respectively. Further analysis on the atomic data used in the calculation indicates that the difference in diffusion coefficients is mainly related to the variation in the values of atomic data of the two databases.

Physics studies of ADITYA & ADITYA-U tokamak plasmas using spectroscopic diagnostics

“…Large value of the oxygen impurity diffusion coefficient at the plasma edge, ∼45 m 2 s −1 , has been obtained as compared neo-classical transport and is explained using fluctuation-induced transport [25], which is mainly ion temperature gradient driven transport. Not only that it is found that obtained diffusion coefficient depends on the atomic data and the atomic processes included in the code [24]. The results from newly developed code have been also compared with the study done using STRAHL for benchmarking of the newly developed code.…”

“…Various studies on the impurities behaviour and plasma properties, such as impurity influx, reduction of plasma Z eff after Li coating of wall, etc, have been regularly carried out using diagnostics based on PMT (photomultiplier tube), PMT array, and the multiple PMT modules in the visible range. The plasma ion temperature, rotation and spatial profile of brightness measurement have been done routinely using a high-resolution spectrometer having 1 m focal length and equipped with a CCD (charge coupled device) camera [22] to understand the physical mechanism behind intrinsic rotation [23] and to study the impurity transport [24][25][26], respectively. A fast visible imaging camera coupled with a fiber bundle has been also used to measure the plasma shape and size and also to study the plasma disruption.…”

Study of increment of emission intensity in a cold atmospheric pressure helium plasma jet using the ADAS

“…The collisional-radiative (CR) model is used to study in various types of plasmas [19][20][21][22][23]. The CR model works well in the intermediate density regime i.e., ∼ 10 10 -10 15 cm −3 .…”

“…The CR model of the ADAS code and database has been used for the study of the laser plasma, the tokamak plasma, etc. [19][20][21][22][23]. The ADAS is an interconnected set of computer codes and data collections for modelling the radiating properties of ions and atoms in plasmas.…”