Reconstructions of velocity distributions from fast-ion D-alpha (FIDA) measurements on EAST

Abstract

2D fast-ion velocity-space distributions have been reconstructed from two-view fast-ion D-alpha (FIDA) measurements on experimental advanced superconducting tokamak (EAST). To make up for the sparse data and incomplete velocity-space coverage with the dual-view, we use nonnegativity and null-measurements as prior information to reconstruct the velocity distribution in experiments with co-and counter-current neutral beam injection. An improved reconstructed fast-ion distribution is achieved by combining the existing O-and B-port FIDA measurements with the proposed A-port FIDA view. To further improve the reliability of FIDA-based reconstructions on EAST, based on real multi-view FIDA measurements on EAST in the near future, various bases will be studied further.

A new FILDSIM model for improved velocity-space sensitivity modelling and reconstructions

“…With a mapped FILD measurement and the system matrix from FILDSIM simulations, it is possible to estimate the velocity distribution of the lost fast ions by solving the inverse problem in (4), as explored in multiple studies on velocityspace tomography in fusion plasmas [25,28,32,[44][45][46][47][48][49][50][51][52][53][54][55][56]. The inverse problem is ill-posed, so regularization techniques are essential to obtain stable solutions.…”

Recent progress in Chinese fusion research based on superconducting tokamak configuration

“… 24 A fast-ion D-alpha spectrum (FIDA) has been developed to assess fast-ion behavior and energetic particle-related physics. 25 Particular attention has been paid to plasma core-edge diagnostics, such as lithium beam emission spectroscopy (Li-BES) to obtain edge electron density profiles. 26 An 11-chord, double-pass, radial viewing, and far-infrared laser-based polarimeter-interferometer (POINT) system has routinely operated for diagnosing the plasma current and electron density profiles during plasma discharge.…”

Tomographic reconstructions of the fast-ion phase space using imaging neutral particle analyser measurements

“…Using the weight functions, the FI distribution can be inferred from measurements thanks to tomographic (regression) techniques. 2D velocity-space tomography [25,[34][35][36] has been experimentally demonstrated based on various combinations of INPA, NPA, FIDA, CTS, GRS, NES and FILD at AUG, JET, MAST, EAST, DIII-D [24,[37][38][39][40][41][42][43][44][45][46][47], and is also foreseen for ITER [48].…”