Heating of a Toroidal Plasma by Skin Current

Kalfsbeek, H. W.

doi:10.1016/b978-1-4832-8384-5.50025-9

Cited by 2 publications

(6 citation statements)

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“…The set of TORTUR equilibria are found to be Mercier-unstable in the region around the magnetic axis where the pressure profile is hollow. This is in agreement with experimental observations because such profiles disappear in a few microseconds [14].…”

Section: Discussionsupporting

confidence: 93%

“…The plasma is stable up to betas of 18% and, when in an experiment the beta decreases owing to loss of energy, the plasma does not enter into an unstable region. The turbulently heated tokamak plasma is Mercierunstable in the centre of the discharge even for small values of beta, in agreement with the experimentally observed disappearance of the hollow pressure profile [14].…”

Section: Introductionsupporting

confidence: 87%

“…This gives rise to a q-profile that in general decreases with radius. The plasma in a turbulently heated tokamak (TORTUR) is in the initial stage of the discharge characterized by a hollow pressure profile in combination with a skin-like current [14]. In a diagram of shear versus pressure gradient the equilibria of the three types of plasma (screw-pinch, flux-conserving, and turbulently heated tokamak) lie each in a different quadrant.…”

Section: Introductionmentioning

confidence: 99%

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Ballooning stability of tokamak, screw-pinch, and turbulently heated tokamak plasmas

Rem¹,

Galvão²

1982

Nucl. Fusion

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The plasma ballooning stability of three sets of equilibria characteristic of tokamak, screw pinch, and turbulently heated tokamak has been investigated. Already at low beta, the tokamak becomes ballooning-unstable and enters at higher betas again a stable region when q on axis is larger than unity. The screw pinch remains stable up to high betas and no second stable region can be found. The third equilibrium is always Mercier-unstable in the centre of the plasma.

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Section: Discussionsupporting

confidence: 93%

Section: Introductionsupporting

confidence: 87%

Section: Introductionmentioning

confidence: 99%

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Ballooning stability of tokamak, screw-pinch, and turbulently heated tokamak plasmas

Rem¹,

Galvão²

1982

Nucl. Fusion

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“…As examples: an initial skin current layer of a few centimeters thickness with enhanced dissipation is found from radial electron temperature measurements as a function of time with Thomson scattering (KOLFSCHOTEN, 1982). The rate of electron heating during the current ramp is anomalously high, concurring with calculations on heating by ion acoustic turbulence (KALFSBEEK, 1978). Also electron cyclotron radiation observatiohs with an ECE spectrometer as well as X-ray measurements indicate the quenching and scattering of initially freely accelerated electron tails.…”

Section: Stage I: Heating During the Current Rampsupporting

confidence: 81%

“…The TORTUR Tokamak was originally designed to study the turbulent heating with an l/e-width of about 2 cm (KALFSBEEK et al, 1975(KALFSBEEK et al, , 1978. Furthermore, the dissipated energy in the skin, W,, is almost exactly equal to the poloidal magnetic skin energy?…”

Section: Stage Iii: the Turbulent Heating Pulsementioning

confidence: 99%

Current driven turbulence and microturbulent spectra in the TORTUR Tokamak

Kluiver

Barth

Donné

1988

Plasma Phys. Control. Fusion

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In the TORTUR Tokamak ( R = 0.46 m, a = 0.085 m. B, = 2.9 T, I, < 55 kAl T, P T, < 1 keV, IZ < IOzo m--3, Z,,,(imp) < 2) plasmas are heated by current driven turbulence in the build-up phase to high beta values and electron temperatures a factor of two above values retrieved from scaling law studies reported in literature for ohmically heated Tokamaks. A stationary state of current driven turbulence with the same fl value can be maintained during the plateau state by virtue of relatively high loop voltages ( 2 4 times the classical value) giving proportionally enhanced resistive dissipation.The turbulent fluctuations of the plateau state have been observed at r,'a = 0.7 by collective scattering of microwaves in a wide spectral region for I,, P 30 kA corresponding with plasmas in the safe q range: y(u) = 7. Three frequency domains of turbulence have been distinguished with rather arbitrary separation, interpreted as follows: (a) A low-frequency region (0 -0.7 MHz) containing the frequently reported electrostatic drift modes and low-frequency electromagnetic modes, which may account for a considerable fraction of the electron heat diffusivity xe(r); (b) Unstable magnetic microtearing modes driven by a supercritical electron temperature gradient characterized by real frequencies in the interval 0.7-3 MHz.Indirect ebidence for the presence of this magnetic tearing exists by the observation of distinct satellites in the Thomson scattering spectrum: (c) A magnetic fluctuation spectrum in the high-frequency region (5-55 MHz) which can be ascribed to current driven modes from non-thermal electron tails around 50 keV. All spectral domains exhibit slow time periodicities synchronous with the development of high-energy tails of the ions and with the Mirnov-type small sawteeth found on the loop voltage, electron cyclotron emission signals and soft X-rays.

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Heating of a Toroidal Plasma by Skin Current

Cited by 2 publications

References 0 publications

Ballooning stability of tokamak, screw-pinch, and turbulently heated tokamak plasmas

Ballooning stability of tokamak, screw-pinch, and turbulently heated tokamak plasmas

Current driven turbulence and microturbulent spectra in the TORTUR Tokamak

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