A tokamak, which is the most successful device now on the road to controlled fusion, has the major disadvantage of pulsed operation because of a need to induce a toroidal current in the plasma. The application of rf to drive the current in steady-state tokamak reactors has been considered by a number of authors. 1 " 5 A method of producing continuous current carried by electrons in the tail of distribution function via quasilinear Landau damping of high-phase-velocity rf waves near the lower hybrid (LH) frequency has been proposed. 4,5 The linear and quasilinear Landau damping of slow electrostatic waves near LH frequency has been confirmed in a linear test device 6 and in the LH electron heating experiment on the tokamak (Doublet IL4). 7 These experiments provide a physical base for understanding the quasilinear Landau damping in the toroidal plasma with a relatively high electron temperature. Recently, the current generated by the unidirectional electron plasma waves has been observed in linear devices 8 * 9 and a toroidal device. 10 These experiments have been carried out in a plasma with a lower electron temperature, in which a transfer of momentum from LH waves to electrons via collisional absorption is significant.In order to make effective coupling between the LH waves and electrons, it is necessary to avoid the deposition of the rf energy into ions resulting ^. Mandelbrot, Fractals: Form, Chance, and Dimension (Freeman, San Francisco, 1977). e from the linear mode conversion and the excitation of parametric instabilities. The previous experiments on the rf ion heating indicated that i-for w Q /w lh {$) ^ l c 6 the ions did not interact with i the rf waves and the parametric decay instabilities almost disappeared, 11,12 where ou 0 is the frequency of the applied rf field and oo lh (0) is the LH QS frequency at the center of the plasma column. In this Letter, we report the experimental study on s the coupling between the rf waves and electrons under the conditions of oo 0 /uo lh (0) < 2 and the relatively high electron temperature in a tokamak. J-The experiment, with a 750-MHz rf source, e 6 was performed in the J FT-2 (JAERI Fusion Torus) i tokamak, which was a conventional tokamak with a major radius of JR 0 = 90 cm and a minor radius of a = 25 cm. The experimental setup and the discharges were reported in detail, 13 and hence will be described only briefly here. In the present l-experiment, the following discharge was used as a magnetohydrodynamically stable operation; toroidal magnetic field B t = 14 kG, plasma current I p = 3Q kA, mean line-of-sight electron density n ^3xl0 12 cm -3 , central electron temperature T^ -(250 eV)/k and effective ionic charge Z e ff of 2-5. The working gas was deuterium. The wave-3 guide array employed here consists of four indei pendently driven waveguides mounted 1.5 cm 5 away from the plasma edge, which is defined by It is observed that the waves launched from a phased array antenna of four waveguides couple effectively with electrons under the condition of oo 0 /oo lh (...
The helium ash exhaust function of a divertor has been experimentally demonstrated. Helium atoms accumulate in the divertor region as the electron density of the main plasma increases. With a helium concentration of ~ 1.6% of electron density in the main plasma, neutral helium pressure at the divertor region is as high as 1.0 x 10" 4 Torr. This experiment indicates the possibility of helium ash exhaust in an a-particleheated diverted tokamak with use of pumping ducts of a practical size.
This paper deals with the structural mechanism of traditional wood frames to evaluate the seismic performance of wooden buildings like Japanese temples. The outline of shaking table tests and static tests using several scale models is described and typical experimental results are discussed. From experiments, it is found that the horizontal restoring force of wooden frame without walls depends mainly on the bending moment resistance from tie beams and the restoring force due to column rocking. The equilibrium relationship between the total restoring force and all the bending moments involved is established and verified. Using this equilibrium relationship, it is possible to evaluate the restoring force due to column rocking. The restoring force due to column rocking is the major part of the total restoring force when the frame deformation is small. The bending moments from tie beams become dominant as the deformation increases. The traditional wooden frame has the large flexibility and deformability. It is essential to take advantage of the structural mechanisms found from this study in the seismic and enhancement design of traditional wooden buildings.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.