#### P. G. Carolan A. C. Selden C. A. Bunting P. Nielson

The superior etendu available from a Fabry-Perot spectrometer is also accessible when used in reflective mode in producing a narrow bandwidth rejection, or “notch,” filter. We consider the instrumental defects and the practical effects involved in realizing a useful device. A simple figure of merit is obtained which allows the Fabry-Perot chara…

Published#### 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…

Published#### K. 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…

Published#### A. W. Morris P. G. Carolan Fl Fitzpatrick T. C. Hender T. N. Todd

The question of the influence of nonaxisymmetric field perturbations on tokamaks is investigated. Recent experiments in the COMPASS-C tokamak [in Proceedings of the 15th Symposium on Fusion Technology, Utrecht (North-Holland, Amsterdam, 1989), Vol. 1, p. 3611 with externally applied helical fields reveal that magnetic islands do not appear until th…

Published#### C. N. Lashmoredavies R. O. Dendy

The gyrokinetic theory of ion cyclotron resonance is extended to include propagation at arbitrary angles to a straight equilibrium magnetic field with a linear perpendicular gradient in strength. The case of the compressional Alfvén wave propagating in a D(3He) plasma is analyzed in detail. A self-consistent local dispersion relation is obtained u…

Published#### J. 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…

Published#### J. 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…

Published#### S. 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…

Published#### R. 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…

Published#### F. 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…

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