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Freeman, Stephanie

doi:10.1080/00963402.1976.11455635

Cited by 2 publications

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“…The measured energy confinement time and electron density for the circular discharge are in agreement with the scaling found by Daughney 3 and Murakami, 4 respectively. A comparison of elliptic and circular plasmas produced in Doublet IIA was reported earlier 5. This Letter reports successful control of a doublet configuration by use of an active fie Id-shaping coil system.…”

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Studies of Doublet Plasmas in Doublet IIA

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proportional to the thickness of the target.In summary, the transmittance of the laser through a laser-produced high-Z thin plasma is larger than that through a low-Z plasma, and the maximum transmittance through the Ni foil of 2.5 |im thickness is larger than that through the 1.25-/1 m foil. The transmittance is related to energy transport through the rate of a plasma expansion. These experimental results indicate that the energy transport is due not only to super thermal electrons but also to x-ray radiation in a high-Z material. The simple theoretical calculations, based on the measurements of the electron temperature and reflectivity, qualitatively agree with the experimental conclusion.Doublet IIA 1,2 is a noncircular-cross-section tokamak which allows direct comparison of various plasma configurations in the same device. The ability to compare plasmas of different cross sections in the same device and within a few shots insures the same vacuum and wall conditions which are critical in tokamak operation. Detailed diagnostic measurements of the plasma properties of doublet, elliptic, and circular cross-section discharges have been performed. The measured plasma properties of the circular discharges are characteristic of those obtained in eontem- 27, 581 (1975). 4 B. Yaakobi, I. Pelah, and J. Hoose, Phys. Rev. Lett. _37, 836 (1976) 0 5 A. W. Ehler, J. Appl. Phys. 46, 2464 (1975). 6 The measurement of the angular distribution of scattered light has been reported by R. Sigel, K. Eidmann, H 0 C 0 Pant, and P. Sachsenmaier, Phys. Rev. . Because I < \ e and \ e cc $ RA> the heating ratio, A ef has no strong dependence on <£ RA . Then the estimate of $ s does not affect the qualitative features. Assuming the total reflectivity, $ s is twice as much as the value of our experiment, the ratio A e becomes 0o5% (4-jum CH 2 ), 2% (1.25-jtim Ni), and 3% (2.5-^m Ni), and is close to the value in the text, 7 See Haas, Ref. 6. 8 K. A. Brueckner, Nucl. Fusion JL6, 387 (1976). 9 J. P. Freidberg, R. W. Mitchell, R. L. Morse, and L. I. Rudsinski, Phys. Rev. Lett. 28, 795 (1972). 10 K o A. Brueckner and S. Jorna, Rev. Mod. Phys. 46, 325 (1974). n Y. B. Zel'dovich and Y. P. Raizer, Physics of Shock Waves and High-Temperature Hydrodynamic Phenomena (Academic, New York, 1966), pp. 167, 260, and 279. 12 M. Co Marsh and P 0 C. Thompson, J. Phys. D j3, 383 (1975). porary circular-cross-section tokamaks of similar size and toroidal field strength. The measured energy confinement time and electron density for the circular discharge are in agreement with the scaling found by Daughney 3 and Murakami, 4 respectively. A comparison of elliptic and circular plasmas produced in Doublet IIA was reported earlier. 5 This Letter reports successful control of a doublet configuration by use of an active fie Id-shaping coil system. Measurements on doublet discharges are presented which show a significant increase in the electron density n e and Doublet plasmas have been produced in Doublet IIA using an active field-shaping coil system. Significan...

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“…5 To produce a doublet configuration, it is necessary to drive additional currents in selected field-shaping coils using programmed external power supplies. The two outside midplane field-shaping coils are driven by a capacitor-bank transformer supply to push inward at the plasma midplane and form the neck of the doublet.…”

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Studies of Doublet Plasmas in Doublet IIA

et al. 1977

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“…For an Ohmically-heated tokamak, the replacement time also satisfies, at least approximately, a scaling law of the form of Eq. (10). This follows provided the resistivity, 77, is neoclassical [34], as is commonly assumed [5,17].…”

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“…A < T > L eff A i e (10) where the new variables are given as follows: Bj is the toroidal magnetic field at R, Z e ff the effective charge number of ions 2 defined by (11) and A[ is the atomic mass of the working gas.…”

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Empirical scaling laws for energy confinement in Ohmically-heated tokamaks

Pfeiffer

Waltz

1979

Nucl. Fusion

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The interpretation and empirical determination of scaling laws for tokamak energy confinement are discussed. Special emphasis is given to the difficulty in determining the temperature dependence of the confinement time from Ohmically-heated data. A large collection of Ohmically-heated data is then presented. These data are analysed statistically to obtain the following temperature and confinement time scalings: ⟨Te⟩=e−9.3⟨ne⟩−0.10a−1.29R0.66I0.88≡ Π and τEe = e−43.8⟨ne⟩0.90a0.98R1.63(⟨Te⟩/Π)γ. The exponent γ; is undetermined, and the units are mks and keV. If the confinement time is assumed independent of temperature and if dimensional constraints are imposed, then the best scaling becomes τEe = e−47.5 ⟨ne⟩ a5/4 R. These scalings are compared to several previously proposed ones.

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Studies of Doublet Plasmas in Doublet IIA

Studies of Doublet Plasmas in Doublet IIA

Empirical scaling laws for energy confinement in Ohmically-heated tokamaks

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