Thermal insulation of plasma in the ?Tokamaks?

Art︠s︡imovich, L. A.; Bobrovskii, G. A.; Мирнов, С. В.; Razumova, K.A.; Strelkov, V. S.

doi:10.1007/bf01116249

Cited by 28 publications

(20 citation statements)

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“…From data given in Ref. 12 we attempted to estimate vd/ v th versus the anomalous resistivity, and find that their temperature anomaly is similar in magnitude and occurs in the same range oi.v^/v^ as ours. This suggests that the diamagnetic loop data may be the more reliable for the Tokamak device.…”

supporting

confidence: 51%

Normal and Anomalous Conductivity in a Toroidal Discharge from Thomson Scattering Measurements

Dimock

Mazzucato

1968

Phys. Rev. Lett.

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For many years now the electrical conductivity of plasmas has been used as a routine diagnostic tool for determining electron temperatures. This is particularly attractive for toroidal plasmas, since no electrodes need be introduced into the plasma.With the advent of Thomson-scattered laser light as a diagnostic tool, it has become possible to measure the electron distribution function as a function of position in the discharge, and from these data derive an accurate comparison with conductivity data.The necessary Thorn son-scattering measurements have now been carried out on the Model C Stellarator. 1 This is a toroidal discharge of 12 m length which was operated with a 35-kG axial confining field, plasma diameters of 7.5 to 12.5 cm, and an 1 = 3 rotational transform. The current in the plasma was 1.5 to 4 kA and the total rotational transform at the surface of the plasma was 0.6 to 1.2 rad. In this work the plasma used was an Ohmically heated discharge in hydrogen. The resulting plasmas had densities in the range 10 12 -10 13 cm"" 3 and temperatures of 20-100 eV. In this regime the Debye length is much greater than the wavelength of the ruby-laser light, and therefore we expect to see no scattering from collective modes of the plasma at our 90° scattering angle.At these low densities it is necessary to use as much energy as possible and the largest feasible collecting optics, to get signals which are not seriously limited by photon shot noise. For this reason an approximately 1-msec pulse containing 50-100 J in 5 mrad was used, along with/:3 collecting optics. In addition, multiple total internal reflections in the photomultiplier face plates were used to enhance the sensitivity. 2 The ruby laser and seven-channel monochromator were arranged to permit spatial scanning along a diameter of the discharge. The spatial resolution was 1 cm along the diameter, and 1 mm perpendicular to it.This apparatus was completely calibrated before each run. The silicon diode monitor was checked against a calorimeter, and the monochromator against a tungsten ribbon lamp.For each spatial point six sets of oscilloscope traces were taken. These consist of laser alone, plasma alone, and laser plus plasma, first with the center monochromator channel at 6942 A and then with it displaced by 25 A. This yields 14 wavelength points, of which several have to be discarded due to background or stray scattered laser radiation.In all cases, to within the experimental errors, the wavelength distribution of intensity approximates well to a Maxwell-Boltzmann distribution, and therefore the data are interpreted in terms of an electron temperature perpendicular to the magnetic field. These temperatures were obtained by least-squares fitting of the data by a Maxwell-Boltzmann distribution.By integrating the data for each spatial point over wavelength, one can obtain an electron density. When this, in turn, is integrated over the diameter of the discharge the integrated density can be compared with 4-mm microwave phase-shift measurements. This was done...

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supporting

confidence: 51%

Normal and Anomalous Conductivity in a Toroidal Discharge from Thomson Scattering Measurements

Dimock

Mazzucato

1968

Phys. Rev. Lett.

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“…The basic result of the research performed in these years on tokamaks was the conclusion that plasma thermo-isolation in toroidal systems does not worsen with the growth of plasma temperature. Experimentally measured values of plasma energy confinement time in tokamaks exceeded those predicted by the Bohm formula by an order of magnitude [11] (figure 3). This contradiction was a theme of scientific discussions within the plasma community for several years.…”

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confidence: 76%

Tokamak foundation in USSR/Russia 1950–1990

Smirnov

2009

Nucl. Fusion

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In the USSR, nuclear fusion research began in 1950 with the work of I.E. Tamm, A.D. Sakharov and colleagues. They formulated the principles of magnetic confinement of high temperature plasmas, that would allow the development of a thermonuclear reactor. Following this, experimental research on plasma initiation and heating in toroidal systems began in 1951 at the Kurchatov Institute. From the very first devices with vessels made of glass, porcelain or metal with insulating inserts, work progressed to the operation of the first tokamak, T-1, in 1958. More machines followed and the first international collaboration in nuclear fusion, on the T-3 tokamak, established the tokamak as a promising option for magnetic confinement. Experiments continued and specialized machines were developed to test separately improvements to the tokamak concept needed for the production of energy. At the same time, research into plasma physics and tokamak theory was being undertaken which provides the basis for modern theoretical work. Since then, the tokamak concept has been refined by a world-wide effort and today we look forward to the successful operation of ITER.

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“…1 The device is an axisymmetric magnetic well with only a poloidal magnetic field. The plasma, usually hydrogen, is injected from a coaxial plasma gun with an initial density of about 10 11 cm" 3 (3-cm interferometer).…”

Section: -P E =Tj K R E {K)p W {K) =E^i(k)p W (K) =P (4) -E E = -F mentioning

confidence: 99%

“…The electron trapping frequencies are calculated from our solutions of Eqs. (1) to vary between about 2oj pi and 200)^, and so anomalous electron-electron collision frequencies between foj pi and Goj pi are needed. Since turbulent-heating experiments typically excite every conceivable resonant frequency of the plasma, 13 it is not unreasonable to expect large anomalous electron-electron and ion-ion collision frequencies.…”

mentioning

confidence: 99%