Microwave start-up of tokamak plasmas near electron cyclotron and upper hybrid resonances

Peng, Yueng Kay Martin; Borowski, Stanley K.; Kammash, T.

doi:10.1088/0029-5515/18/11/002

Cited by 63 publications

(36 citation statements)

References 18 publications

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“…Here ℓ is the length along the field line. Then the ambi-polar potential in the plasma is estimated as [19]. Then the perpendicular electrostatic filed is estimated as E ⊥ ∼ T e /ae and the E × B drift velocity is u E×B ∼ T e /aeB ϕ .…”

Section: Pressure Driven Equilibrium Current In Open Fieldsmentioning

confidence: 99%

Open field equilibrium current and cross-field passing electrons as an initiator of a closed flux surface in EC-heated toroidal plasmas

Maekawa¹,

Yoshinaga²,

Uchida³

et al. 2012

Nucl. Fusion

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A modeling for the non-inductive initiation of a closed flux surface observed in electron cyclotron (EC) heated toroidal plasmas is presented. First, a pressure driven equilibrium toroidal current develops under a weak external vertical field so as to counter balance the pressure-ballooning and current-hoop forces. When the self field from the current almost cancels out the external vertical field, a forward energetic part of electrons in the velocity space begin to make cross field passing (CFP) orbits. The CFP electrons are generated by the EC heating of bulk electrons and subsequent pitch angle scattering, which is analyzed using the Fokker Planck equation. They provide an additional current that closes the filed lines. The model is examined for experiments in the small low aspect ratio device of LATE and in the large conventional device of JT-60U with a search for appropriate modes of EC heating. Simultaneous coincidence of the model with these two experiments is obtained in terms of microwave power and driven current. The results predict that initiation of closed flux surface requires more and more EC power as the plasma major radius increases. Especially, careful injection of high N ∥ EC waves are needed for large devices, both for initiation of a closed flux surface and for subsequent enlargement of the flux surface by usual EC current drive (ECCD) onto the closed flux area.

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Section: Pressure Driven Equilibrium Current In Open Fieldsmentioning

confidence: 99%

Open field equilibrium current and cross-field passing electrons as an initiator of a closed flux surface in EC-heated toroidal plasmas

Maekawa¹,

Yoshinaga²,

Uchida³

et al. 2012

Nucl. Fusion

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“…Electron cyclotron resonance (ECR) assisted pre-ionization is a common technique used in tokamaks [1][2][3][4][5][6][7][8][9][10][11][12], stellerators [13,14] and other plasma devices such as tokapole [15] for start-up and to assist plasma formation in the initial stage of the discharge. In ohmic discharge, high loop voltage is required to initiate the discharge when plasma density, temperature and conductivity are low and the line radiation from impurities are the dominating losses.…”

Section: Introductionmentioning

confidence: 99%

Electron cyclotron resonance breakdown studies in a linear plasma system

2008

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Electron cyclotron resonance (ECR) plasma breakdown is studied in a small linear cylindrical system with four different gases -hydrogen, helium, argon and nitrogen. Microwave power in the experimental system is delivered by a magnetron at 2.45 ± 0.02 GHz in TE10 mode and launched radially to have extra-ordinary (X) wave in plasma. The axial magnetic field required for ECR in the system is such that the fundamental ECR surface (B = 875.0 G) resides at the geometrical centre of the plasma system. ECR breakdown parameters such as plasma delay time and plasma decay time from plasma density measurements are carried out at the centre using a Langmuir probe. The operating parameters such as working gas pressure (1 × 10 −5 -1 × 10 −2 mbar) and input microwave power (160-800 W) are varied and the corresponding effect on the breakdown parameters is studied. The experimental results obtained are presented in this paper.

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“…Although ways of maintaining a currentless plasma in equilibrium have been discussed in several papers and realised in some experiments (22)(23)(24), the objective of the Varennes experiment is to bring the current to as low a value as possible (i.e., a value as low as MHD would allow for an equilibrium to exist) and to maintain the current at this value. For the Varennes experiment parameters, this should correspond to a total current of about 20 kA.…”

Section: The Ramp Down Of the Currentmentioning

confidence: 99%

The equilibrium and time evolution of the parameters of the Tokamak de Varennes

Shoucri¹,

Shkarofsky²,

Fuchs³

et al. 1985

Can. J. Phys.

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The equilibrium and time evolution of the density, current, and temperature profiles for a tokamak are numerically analyzed using the one-dimensional transport code VARTOKl. The numerical model contains the full neoclassical transport, with coefficients covering transitions between regimes, and includes the Ware pinch and bootstrap currents, empirical anomalous particle and electron heat transports based on Alcator scaling, neutral particle transport, oxygen impurity, and diffusion of the poloidal magnetic field. The solution uses a time-and space-centered Crank-Nicolson scheme. The equilibrium profiles are first determined for a constant current of 200 kA by running the code at constant current. Then the current is ramped down to zero in 20 ms, and the time evolution of the different parameters are followed.

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Microwave start-up of tokamak plasmas near electron cyclotron and upper hybrid resonances

Cited by 63 publications

References 18 publications

Open field equilibrium current and cross-field passing electrons as an initiator of a closed flux surface in EC-heated toroidal plasmas

Open field equilibrium current and cross-field passing electrons as an initiator of a closed flux surface in EC-heated toroidal plasmas

Electron cyclotron resonance breakdown studies in a linear plasma system

The equilibrium and time evolution of the parameters of the Tokamak de Varennes

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