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Abstract <p>In the DIII-D tokamak, the central electron temperature <i>T</i><sub><i>e</i></sub>(0) was in a factor of 3–4 higher than the temperature <i>T</i><sub><i>e</i></sub>(<i>r</i><sub>res</sub>) in discharges with off-axis heating at the second harmonic of electron cyclotron resonance (ECRH), when the resonance <i>r</i><sub>res</sub> is located at the middle of the minor radius. Also the safety factor <i>q</i> at the edge was high and the plasma densities were moderate, At the T-10 tokamak, the high central temperatures <i>T</i><sub><i>e</i></sub>(0) ≈ 1.3<i>T</i><sub><i>e</i></sub>(<i>r</i><sub>res</sub>) were also observed in high-current, low-density discharges with off-axis ECRH. The canonical profile transport model (CPTM) is used to describe the steady-state phase of these experiments. In this model, the radial heat flux is proportional to the deviation of the temperature profile <i>T</i><sub><i>e</i></sub>(<i>r</i>) from the canonical <i>T</i><sub><i>ce</i></sub>(<i>r</i>). Using the CPTM, it was shown that in the plasma core (0 &lt; <i>r</i> &lt; <i>r</i><sub>res</sub>) under nonzeroth boundary and initial conditions, the stationary solutions with the high central electron temperature exist even without the deposition of the ECRH power in this region, and we call them ‘the special solutions’. Analysis of the DIII-D experiments shows that in the radial range (0, <i>r</i><sub>res</sub>), practically the whole ohmic power <i>Q</i><sub><i>j</i></sub> is transferred to the ions due to the large electron–ion exchange term, while the radial heat flux in the electron channel, directed outward, is very small. As a result, in this radial range, the solution of the transport equation for <i>T</i><sub><i>e</i></sub> practically coincides with the canonical profile <i>T</i><sub><i>ce</i></sub>, therefore the central electron temperature at the several times higher than in the power deposition zone. The different peaking of the canonical profiles in DIII-D and T-10 is largely determined by the difference in the radial distribution of the safety factor <i>q</i>(<i>r</i>).</p>

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Analysis of Off-Axis ECRH in Tokamaks Using a Canonical Profile Transport Model

  • 期刊论文

  • 发表日期：

    2026年3月1日

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  • Yu. N. Dnestrovskij,
  • A. V. Melnikov,
  • N. V. Kasyanova,
  • V. F. Andreev,
  • S. E. Lysenko,
  • S. V. Cherkasov

摘要

Abstract

In the DIII-D tokamak, the central electron temperature Te(0) was in a factor of 3–4 higher than the temperature Te(rres) in discharges with off-axis heating at the second harmonic of electron cyclotron resonance (ECRH), when the resonance rres is located at the middle of the minor radius. Also the safety factor q at the edge was high and the plasma densities were moderate, At the T-10 tokamak, the high central temperatures Te(0) ≈ 1.3Te(rres) were also observed in high-current, low-density discharges with off-axis ECRH. The canonical profile transport model (CPTM) is used to describe the steady-state phase of these experiments. In this model, the radial heat flux is proportional to the deviation of the temperature profile Te(r) from the canonical Tce(r). Using the CPTM, it was shown that in the plasma core (0 < r < rres) under nonzeroth boundary and initial conditions, the stationary solutions with the high central electron temperature exist even without the deposition of the ECRH power in this region, and we call them ‘the special solutions’. Analysis of the DIII-D experiments shows that in the radial range (0, rres), practically the whole ohmic power Qj is transferred to the ions due to the large electron–ion exchange term, while the radial heat flux in the electron channel, directed outward, is very small. As a result, in this radial range, the solution of the transport equation for Te practically coincides with the canonical profile Tce, therefore the central electron temperature at the several times higher than in the power deposition zone. The different peaking of the canonical profiles in DIII-D and T-10 is largely determined by the difference in the radial distribution of the safety factor q(r).