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Volume 68, Issue 1
Displaying 1-5 of 5 articles from this issue
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Takeo Nishitani1992 Volume 68 Issue 1 Pages 6-17
Published: July 25, 1992
Released on J-STAGE: October 22, 2010
JOURNAL FREE ACCESSAbsolutely calibrated measurements of the neutron yield are important for the evaluation of the plasma performance such as the fusion gain Q in D-D operating tokamaks. Time-resolved neutron yield is measured with neutron detectors using fission chamber in large tokamaks. The neutron detectors are calibrated by moving the 252Cf neutron source toroidal ly through the vacuum vessel. In JT-60U, the detection efficiencies were measured by the toroidal scan of the neutron point source resulting the uncertainty of ±11%. The maximum neutron yield of 1.3×1016n/s and the fusion gain QDT of 0.2were obtained in the initial D-D experiment of JT-60U.View full abstractDownload PDF (1252K) -
Akio Komori1992 Volume 68 Issue 1 Pages 18-27
Published: July 25, 1992
Released on J-STAGE: October 22, 2010
JOURNAL FREE ACCESSRecent experiments on chaos in plasma systems are reviewed.Universal aspects of chaotic behavior obtained in these experiments are described, and a theory is briefly presented, which explains cascading bifurcations to chaos observed in a current-carrying ion sheath.View full abstractDownload PDF (1009K) -
Noriyoshi Sato1992 Volume 68 Issue 1 Pages 28-33
Published: July 25, 1992
Released on J-STAGE: October 22, 2010
JOURNAL FREE ACCESSA brief review is presented of measurements of electric double layers in laboratory collisionless plasmas. A emphasis is on formation of electric field along magnetic field lines in magnetoplasmas, which is closely related with field-aligned particle acceleration.View full abstractDownload PDF (655K) -
Shinji Sakurai, Shuichi Takamura1992 Volume 68 Issue 1 Pages 34-45
Published: July 25, 1992
Released on J-STAGE: October 22, 2010
JOURNAL FREE ACCESSIn order to diverge the enormous heat flux on the divertor plate in tokamak fusion reactor, new methods by using kinds of perturbed magnetic field made by either periodically deformed divertor coil or a set of in-vessel coils are proposed. By tracing magnetic field lines in JT-60 configuration, we confirmed that the nonaxisymmetric perturbed magnetic field can make a stochastic edge field, and that a toroidally rotating perturbed field can sweep a separatrix on the plate by about 10cm in width. In the latter case, a penetration of rapidly changing A. C. perturbation field into the confiment region can be avoided by a plasma skin effect.View full abstractDownload PDF (1240K) -
Noriyoshi Nakajima, Masao Okamoto1992 Volume 68 Issue 1 Pages 46-57
Published: July 25, 1992
Released on J-STAGE: October 22, 2010
JOURNAL FREE ACCESSEffects of external momentum sources, i.e., fast ions produced by the neutral beam injection and an external inductive electric field, on the neoclassical ion parallel flow, current, and rotation are analytically investigated for a simple plasma in general toroidal systems. It is shown that the contribution of the external sources to the ion parallel flow becomes large as the collision frequency of thermal ions increases because of the momentum conservation of Coulomb collisions and sharply decreasing viscosity coefficients with collision frequency. As a result, the beam-driven parallel flow of thermal ions becomes comparable to that of electrons in the Pfirsh-Schlüter collisionality regime, whereas in the 1/ν or banana regime it is smaller than that of electrons by the order of √me/mi (me and mi are electron and ion masses). This beam-driven ion parallel flow can not produce a large beam-driven current because of the cancellation with electron parallel flow, but produces a large toroidal rotation of ions.As both electron and ions approach the Pfirsh-Schluter collisionality regime the contribution of thermodynamical forces becomes negligibly small and the large toroidal rotation of ions is predominated by the beam-driven component in the non-axisymmetric configuration with large helical ripples.View full abstractDownload PDF (1350K)
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