Influence of the plasma density and heating power on the intensity of electron cyclotron emission in the L-2M stellarator

Akulina, D. K.; Batanov, G. M.; Berezhetskiǐ, M. S.; Voronov, G. S.; Gladkov, G. A.; Grebenshchikov, S. E.; Danilkin, I. S.; Larionova, N. F.; Meshcheryakov, A. I.; Sarksyan, K. A.; Fedyanin, O.I.; Kharchev, N. K.; Khol'nov, Yu.V.; Shchepetov, S. V.

doi:10.1134/1.1633622

“…The electron temperature profile in the L-2M stellarator is measured by four methods: soft x-ray intensity measurements by the foil technique [2], ECE intensity measurements [3], visible and near UV spectroscopy and Langmuir probes. Each of these methods measures its individual segment of the plasma profile: the ECE and soft x-ray measurements are used for the plasma core (0 < r/a < 0.6), the spectroscopy is used for the outer part of the plasma column (0.5 < r/a < 1) and the probes measure the temperature near the last closed magnetic surface, where T e < 30 eV.…”

mentioning

confidence: 99%

Edge transport barrier modification in the L-2M stellarator depending on the heating power and plasma parameters

Voronov

¹

,

Воронова

²

,

Akulina

³

et al. 2006

Plasma Phys. Control. Fusion

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Boronization of the vacuum chamber of the L-2M stellarator has resulted in modification of the electron temperature profile. In particular, a welldefined jump in the electron temperature to T e ∼ 100 eV in a narrow region r/r ∼ 0.05 is observed in the temperature profile at the plasma edge. In the present paper, the value and shape of the jump in T e are studied at different values of plasma parameters and ECR heating power. A jump in T e is absent at a power of P ∼ 100 kW, whereas at P ∼ 200 kW the electron temperature drops from 150 eV to zero within r ∼ 0.5 cm. The value of threshold power for the formation of a jump in T e at n e ∼ 1.7 × 10 19 m −3 lies within the range P ∼100-160 kW. In terms of power per particle this power threshold is P /V /N e ∼ 0.2-0.3 Mw/m 3 /10 19 m −3 , the value of which coincides with threshold power for ETB formation found recently in the CHS stellarator. When the helical-field strength is 25% or 50% below its standard value, a jump in T e at the plasma edge in L-2M is absent.

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“…It is pertinent to note that the ECE signal at the frequency 74 GHz corresponds to the region that is located near the vacuum magnetic axis. During the initial phase of discharge, the plasma is non-Maxwellian that cause a steep pulse of radiative temperature [18]. However, at the stationary phase of discharge with sufficiently high plasma density, this signal well reproduces the electron temperature [19].…”

Section: Resultsmentioning

confidence: 98%

“…The basic set consists in the use of H a photon emission detectors and electron cyclotron emission (ECE) channels, measuring the radiative temperature T e [5,7]. The peculiarities of ECE system of L-2M were presented in [18]. The Langmuir probe for measuring the value of floating potential V f is also in use.…”

Section: Resultsmentioning

confidence: 99%

Second harmonic ECRH breakdown: a theoretical insight and comparison to experimental results from L-2M

Shchepetov

¹

,

Tereshchenko

²

,

Vasilkov

³

et al. 2018

Plasma Phys. Control. Fusion

3

0

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The breakdown by the 2nd electron cyclotron harmonic microwaves is studied theoretically, with a particular regard to the geometry and experimental set-up of the L-2M stellarator. The collisionless time-averaged electron dynamics in a microwave field is re-examined. There is a widespread opinion that breakdown in stellarators and tokamaks is governed by deeply trapped electrons that undergo nonlinear regime of energy oscillation. Our analysis has shown that there exist four groups of electrons differing by the scale of energy oscillation, and that all these groups participate in the breakdown, although with different roles. We have determined the boundaries of all groups in the 2D parametric space, their relative population and the rate of energy gain. This allowed us to find out which of the groups is actually responsible for the electron avalanche onset near the magnetic axis and how the breakdown expands then across the magnetic surfaces. Theoretical estimates show good agreement with the L-2M experimental results.

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“…The aim of the present paper is to examine how the value and shape of the jump in T e vary depending on the plasma parameters and ECR heating power. The electron temperature profile in the L-2M stellarator is measured by four methods: soft x-ray intensity measurements by the foil technique [2], ECE intensity measurements [3], visible and near UV spectroscopy and Langmuir probes. Each of these methods measures its individual segment of the plasma profile: the ECE and soft x-ray measurements are used for the plasma core (0 < r/a < 0.6), the spectroscopy is used for the outer part of the plasma column (0.5 < r/a < 1) and the probes measure the temperature near the last closed magnetic surface, where T e < 30 eV.…”

mentioning

confidence: 99%

Theoretical Study of Exposure Latitude of Chemically Amplified Resists Used for Extreme Ultraviolet Lithography

Kozawa¹,

Tagawa²

2011

Jpn. J. Appl. Phys.

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Boronization of the vacuum chamber of the L-2M stellarator has resulted in modification of the electron temperature profile. In particular, a welldefined jump in the electron temperature to T e ∼ 100 eV in a narrow region r/r ∼ 0.05 is observed in the temperature profile at the plasma edge. In the present paper, the value and shape of the jump in T e are studied at different values of plasma parameters and ECR heating power. A jump in T e is absent at a power of P ∼ 100 kW, whereas at P ∼ 200 kW the electron temperature drops from 150 eV to zero within r ∼ 0.5 cm. The value of threshold power for the formation of a jump in T e at n e ∼ 1.7 × 10 19 m −3 lies within the range P ∼100-160 kW. In terms of power per particle this power threshold is P /V /N e ∼ 0.2-0.3 Mw/m 3 /10 19 m −3 , the value of which coincides with threshold power for ETB formation found recently in the CHS stellarator. When the helical-field strength is 25% or 50% below its standard value, a jump in T e at the plasma edge in L-2M is absent.

show abstract

Influence of the plasma density and heating power on the intensity of electron cyclotron emission in the L-2M stellarator

Cited by 6 publications

References 9 publications

Edge transport barrier modification in the L-2M stellarator depending on the heating power and plasma parameters

Edge transport barrier modification in the L-2M stellarator depending on the heating power and plasma parameters

Second harmonic ECRH breakdown: a theoretical insight and comparison to experimental results from L-2M

Theoretical Study of Exposure Latitude of Chemically Amplified Resists Used for Extreme Ultraviolet Lithography

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