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Mirror theory applied to toroidal systems

Description: Central features of a mirror plasma are strong departures from Maxwellian distribution functions, ambipolar potentials and densities which vary along a field line, and losses, and the mirror field itself. To examine these features, mirror theorists have developed analytical and numerical techniques to solve the Fokker-Planck equation, evaluate the potentials consistent with the resulting distribution functions, and assess the microstability of these distributions. Various combinations of mirror-plasma fetures are present and important in toroidal plasmas as well, particularly in the edge region and in plasmas with strong r.f. heating. In this paper we survey problems in toroidal plasmas where mirror theory and computational techniques are applicable, and discuss in more detail three specific examples: calculation of the toroidal generalization of the Spitzer-Haerm distribution function (from which trapped-particle effects on current drive can be calculated), evaluation of the nonuniform potential and density set up by pulsed electron-cyclotron heating, and calculation of steady-state distribution functions in the presence of strong r.f. heating and collisions. 37 refs., 3 figs.
Date: August 25, 1987
Creator: Cohen, R.H.
Partner: UNT Libraries Government Documents Department

Mirror theory applied to toroidal systems

Description: Central features of a mirror plasma are strong departures from Maxwellian distribution functions, ambipolar potentials and densities which vary along a field line, end losses, and the mirror field itself. To examine these features, mirror theorists have developed analytical and numerical techniques to solve the Fokker-Planck equation, evaluate the potentials consistent with the resulting distribution functions, and assess the microstability of these distributions. Various combinations of mirror-plasma features are present and important in toroidal plasmas as well, particularly in the edge region and in plasmas with strong rf heating. In this paper we survey problems in toroidal plasmas where mirror theory and computational techniques are applicable, and discuss in more detail three specific examples: calculation of the toroidal generalization of the Spitzer-Haerm distribution function (from which trapped-particle effects on current drive can be calculated), evaluation of the nonuniform potential and density set up by pulsed electron-cyclotron heating, and calculation of steady-state distribution functions in the presence of strong rf heating and collisions. 37 refs.
Date: August 25, 1987
Creator: Cohen, R.H.
Partner: UNT Libraries Government Documents Department

Review of the Advanced Toroidal Facility program

Description: This report summarizes the history and design goals of the Advanced Toroidal Facility (ATF). The ATF is nearing completion at ORNL with device completion expected in May 1987 and first useful plasma operation in June/July 1987. ATF is a moderate-aspect-ratio torsatron, the world's largest stellarator facility with R = 2.1 m, ..cap alpha.. bar = 0.3 m and B = 2 T (5-s pulse) or 1 T (steady-state capability). It has been specifically designed to support the US tokamak program by studying important toroidal confinement issues in a similar magnetic geometry that allows external control of the magnetic configuration properties and their radial profiles: transform, shear, well depth, shaping, axis topology, etc. ATF will operate in a current-free model which allows separation of current-driven and pressure-driven plasma behavior. It also complements the world stellarator program in its magnetic configuration (between Heliotron-E and W VII-AS) and its capabilities (large size, good access, steady state capability, second stability access, etc.). For both roles ATF will require high-power long-pulse heating to carry out its physics goals since the high power NBI pulse is limited to 0.3 s. The ATF program focuses on demonstrating the principles of high-beta, steady-state operation in toroidal geometry through its study of: (1) scaling of beta limits with magnetic configuration properties and the plasma behavior in the second stability regime; (2) transport scaling at low collisionality and the role/control of electric field; (3) control of plasma density and impurities using divertors; (4) plasma heating with NBI, ECH, ICH, and plasma fueling with gas puffing and pellet injection; and (5) optimization of the magnetic configuration.
Date: February 25, 1987
Creator: Lyon, J.F. & Murakami, M.
Partner: UNT Libraries Government Documents Department

The potential for reducing the cost of a heavy ion accelerator for ICF: Final report

Description: This study was initiated to identify the high leverage areas for reducing the cost of a 10 MJ heavy ion beam driver for a high gain target development facility. Our efforts to innovate to reach affordable cost have been mostly successful, in that it looks like the $500 M range may indeed be possible. We conclude that heavy ion beams do have substantial promise for an inertial fusion driver. However, the pace of R and D would have to be substantially increased to realize this promise on a timescale necessary for a High Gain Test Facility.
Date: February 25, 1987
Creator: Monsler, M.J.
Partner: UNT Libraries Government Documents Department

A technique for production glass macro-shells for ICF targets. Final report, 1 November 1986--31 October 1987

Description: A study of bubble formation, movement and distortion in viscous glass is described. A glass rod containing an irregularly shaped hole is heated to a temperature at where the glass viscosity is low enough to let the hole form a spherical bubble. Spheration occurs as the bubble moves upward in the glass rod. At the proper time, the rising bubble is decelerated and brought to a stop by increasing the glass viscosity by slowly reducing the temperature. The entrapped bubble is then cut from the glass rod and heated again, if necessary, to a lower temperature, to reduce distortion of the bubble. Conditions distorting the bubble and ways to reduce the distortion have been investigated. With the present technique, bubbles have been produced in Corning 7740 and Schott BK-7 glasses with a nominal diameter of 3 and 6 mm that have a distortion of 0.3%. Glass macro shells can be formed from the bubbles trapped in the glass by grinding the outside surface concentric with the perfectly spherical inside surface. These high quality glass shells, with a high degree of geometrical perfection, should be adequate for inertial confinement fusion targets.
Date: November 25, 1987
Creator: Day, D. E. & Wang, S. C. P.
Partner: UNT Libraries Government Documents Department

Spatially resolved x-ray laser spectra and demonstration of gain in nickel-like systems

Description: A recent series of experiments have provided spatially resolved near field images of several candidate x-ray lasing transition in neon-like, nickel-like, and hydrogen-like ions from laser-produced plasmas. From these time-gated, spatially, and spectrally resolved measurements the source size for the J = 0 - 1 and the J = 2 - 1 transitions in Ne-like selenium have been determined. Source regions as small as 50 ..mu..m have been observed on transitions with gain-length products >9. In addition, we have obtained the first experimental evidence for the amplification of spontaneous emission in the nickel-like ions of europium and ytterbium. Gains of order 1 cm/sup -1/ and gain-length products of up to 3.8 are observed on the J = 0 - 1, 4d-4p transitions in Eu + 35 at 65.26 and 71.00 A. Analogous transitions in Yb = +42 have been identified and some evidence for ASE has been observed. 7 refs., 11 figs.
Date: September 25, 1987
Creator: Whelan, D.A.; Keane, C.J.; MacGowan, B.J.; Matthews, D.L.; Trebes, J.E. & Eckart, M.J.
Partner: UNT Libraries Government Documents Department