C. N. Lashmoredavies R. O. Dendy
09The thin beam model of an axis-encircling relativistic electron beam in a uniform, constant, external magnetic field in a cylindrical waveguide is used to develop a unified theory of the various interactions of such a beam with the electromagnetic field. The model includes the gyrotron interaction (longitudinal displacement of the beam) and the p…
PublishedK. Avinash F. A. Haas A. Thyagaraja
This Brief Communication investigates the influence of toroidal effects (due to the coupling of various poloidal harmonics) on the nonlinear saturation of the m = 1 island. Bounds are obtained relating the aspect ratio, the shear at the q= 1 surface, and the saturated island width. Provided these bounds are satisfied, it is then found that the cyli…
PublishedR. O. Dendy C. N. Lashmoredavies K. F. Kam
Intense superthermal ion cyclotron emission (ICE) has been observed from tokamak plasmas. The power spectrum displays narrow peaks at multiple harmonics of the background ion cyclotron frequency [Cottrell and Dendy, Phys. Rev. Lett. 60, 33 (1988)] in Ohmic deuterium plasmas, and the radiation appears to be driven by the fusion ion population in the…
PublishedJ. W. Connor R. J. Hastie J. B. Taylor
In a cylindrical plasma, tearing modes can be calculated by asymptotic matching of ideal magnetohydrodynamic (MHD) solutions across a critical layer. This requires a quantity that represents the “discontinuity*’ in the ideal solution across the layer. In a torus, poloidal harmonics are coupled and there are many critical surfaces for each toroi…
PublishedJ. W. Connor R. J. Hastie J. B. Taylor
This is Part II of a study of resonant perturbations, such as resistive tearing and ballooning modes, in a torus. These are described by marginal ideal magnetohydrodynamic (MHD) equations in the regions between resonant surfaces; matching across these surfaces provides the dispersion relation. Part I [Phys. Fluids B3, 1532 (1991)] described how all…
PublishedS. B. Wells Y. Takeiri A. F. Newman R. Mcadams A. J. T. Holmes
A rf ion source with a large extraction area suitable for fusion applications is considered. The source is a metallic magnetic multipole bucket with an internal antenna to couple the rf (at a frequency of 2 MHz) to the plasma. The source is diagnosed by an array of Langmuir probes to measure uniformity, density, and temperature and a small probe ac…
PublishedR. O. Dendy C. N. Lashmoredavies K. F. Kam
The Euler-Lagrange equations for a charged particle in a tokamak magnetic fieid, in the limit of large aspect ratio, are obtained in terms of toroidal coordinates from the exact Lagrangian, which is expressed in terms of the toroidal and poloidal magnetic fluxes. It differs fundamentally from the standard guiding-center approach, where the local ma…
PublishedF. P. Keenan S. M. Mccann et al.
Electron-impact excitation rates for transitions in heliumlike Mg xI, calculated with the R-matrix code, are used to derive the electron-density-sensitive emission line ratio R (= f/i) and temperature sensitive ratio G [ = (f+i)/r]. A comparison of these with R and G ratios determined from x-ray…
PublishedNathan Mattor
In this paper, a theory of toroidal ion temperature gradient-driven weak turbulence near the threshold is presented. The model considers gyrokinetic ions and adiabatic electrons in toroidal geometry. The linear theory considers modes generally not considered in toroidal theories. The instability is saturated via nonlinear ion resonance, andit is sh…
PublishedR. A. Pitts
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…
Published