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1991
This paper compares the form of f(v||) arising from the warm-ion, kinetic models of Emmert et al. [ Phys. Fluids 23, 803 ( 1980) ] and Bissel and Johnson [ Phys. Fluids 30,779 ( 1987) ] with experimentally measured distributions from the DITE tokamak obtained with a retarding field analyzer (RFA). The results show that the commonl…
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1991
The inclusion of the variation of the equilibrium magnetic field across the Larmor orbits of the resonant particles is crucial for a self-consistent treatment of cyclotron resonance in plasmas. Two contrasting nonrelativistic self-consistent calculations [T. M. Antonsen and W. M. Manheimer, Phys. Fluids 21,2295 (1978); C. N. Lashmore-Davies and R. …
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1991
The purpose of this paper is to investigate the possible relationships between transport properties such as thermal diffusivity and resistivity on the one hand, and the magnetic properties such as q profile and toroidal flux change on the other, in tokamaks that exist under macroscopically quasistationary conditions. It is experimentally well estab…
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1990
Experiments performed in a volume production negative ion source show that the use of a tent or supercusp magnetic filter leads to a more uniform plasma at the normal extraction plane than that obtained with a dipole filter. For the tent filter geometry the extracted negative ion current density, increased as the accelerator was moved into the sour…
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1990
Local extrema in the equilibrium magnetic field strength can occur in tokamak plasmas when the plasma beta is increased. Furthermore, the magnetic field strength experienced by an electromagnetic wave propagating along a vertical chord in lower-beta tokamak plasmas may also pass through an extremum. For both these reasons, it is of interest to calc…
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1990
This paper presents the results of experimental studies on a number of different ' current carrying wire' type first grid electron suppressors: or ' inserts', as they shall be called throughout this paper. Extracted negative ion currents are compared for the different inserts over a range of field strengths. Currents are also compared to those extr…
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1990
The series of experiments carried out in recent years on the HBTX reversed field pinch [Plasma Phys. Controlled Fusion 30, 843 ( 1988)] have highlighted the importance of minimizing the flux that penetrates the plasma-wall boundary. This flux penetration, whether from equilibrium field errors, the presence of limiters, or plasma magnetic activity f…
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1990
This paper reports tests of an electron suppressor, for volume negative ion sources with variable electric and magnetic fields. The experiments have been carried out with a source and accelerator operating d.c. and with an extraction aperture of 16 mm diameter. The results are compared to those obtained with a permanent magnet suppressor and to a t…
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1990
The set of semicollisional layer equations derived by Fitzpatrick [Phys. Fluids B 1, 2381 (1989)] is used to investigate the effect of trapped particles on the linear stability of long wavelength resistive modes in a large-aspect-ratio tokamak. At 0( 1) shear, destabilization by trapped particles is found to significantly modify previous cylindrica…
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1990
Showing 2561 - 2570 of 2581 UKAEA Paper Results