Spectroscopic Measurements of Impurity Ion Toroidal and Poloidal Flow Velocities and Their Dependence on Vertical Magnetic Field in QUEST Toroidal ECR Plasmas
Abstract:Toroidal electron cyclotron resonance (ECR) plasma is an ECR heated plasma in an open toroidal magnetic field. The plasma contains no toroidal current and is used for the pre-ionization and non-inductive startup of a tokamak plasma. To obtain a deeper understanding of the basic properties of the plasmas produced in the spherical tokamak QUEST (Q-shu University Experiment with steady-state Spherical Tokamak), we have developed an optical emission spectroscopy system with multiple viewing chords and have used it… Show more
“…In the ST discharge produced with ECH, a cylindrical plasma in an open field equilibrium is initially produced around the resonance layer [2,4,5]. Then, by ramping up the plasma current, an ST plasma sustained only with ECH is formed [2,4,6].…”
The spatial distribution of the hydrogen atom density was evaluated in a spherical tokamak (ST) plasma sustained only with 28 GHz electron cyclotron heating (ECH). The radially resolved Hδ emissivity was measured using multiple viewing chord spectroscopy and Abel inversion. A collisional-radiative (CR) model analysis of the emissivity resulted in a ground-state hydrogen atom density of 1015–1016 m−3 and an ionization degree of 1–0.85 in the plasma.
“…In the ST discharge produced with ECH, a cylindrical plasma in an open field equilibrium is initially produced around the resonance layer [2,4,5]. Then, by ramping up the plasma current, an ST plasma sustained only with ECH is formed [2,4,6].…”
The spatial distribution of the hydrogen atom density was evaluated in a spherical tokamak (ST) plasma sustained only with 28 GHz electron cyclotron heating (ECH). The radially resolved Hδ emissivity was measured using multiple viewing chord spectroscopy and Abel inversion. A collisional-radiative (CR) model analysis of the emissivity resulted in a ground-state hydrogen atom density of 1015–1016 m−3 and an ionization degree of 1–0.85 in the plasma.
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