103 research outputs found
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TAE modes and MHD activity in TFTR DT plasmas
The high power deuterium and tritium experiments on TFTR have produced fusion a parameters similar to those expected on ITER. The achieved {beta}{sub {alpha}}/{beta} and the R{triangledown}{beta}{sub {alpha}} in TFRR D-T shots are 1/2 to 1/3 those predicted in the ITER EDA. Studies of the initial TFTR D-T plasmas find no evidence that the presence of the fast fusion {alpha} population has affected the stability of MHD, with the possible exception of Toroidal Alfven Eigenmodes (TAE`s). The initial TFTR DT plasmas had MHD activity similar to that commonly seen in deuterium plasmas. Operation of TFTR at plasma currents of 2.0--2.5 MA has greatly reduced the deleterious effects of MHD commonly observed at lower currents. Even at these higher currents, the performance of TFTR is limited by {beta}-limit disruptions. The effects of MHD on D-T fusion {alpha}`s was similar to effects observed on other fusion products in D only plasmas
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The Roles of Electric Field Shear and Shafranov Shift in Sustaining High Confinement in Enhanced Reversed Shear Plasmas on the Tftr Tokamak
The relaxation of core transport barriers in TFTR Enhanced Reversed Shear plasmas has been studied by varying the radial electric field using different applied torques from neutral beam injection. Transport rates and fluctuations remain low over a wide range of radial electric field shear, but increase when the local E x B shearing rates are driven below a threshold comparable to the fastest linear growth rates of the dominant instabilities. Shafranov-shift-induced stabilization alone is not able to sustain enhanced confinement
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RAGE simulations of single-mode Richtmyer-Meshkov growth in a convergent geometry
The Richtmyer-Meshkov (RM) instability is initiated by a shock accelerating an interface between two materials. Small perturbations of the interface grow into bubble and spike structures causing mixing of the materials that lie on either side of the interface. Recent Los Alamos National Laboratory experiments have focused on RM initiated mix in a compressible, miscible, convergent geometry. Motivated by the lack of a generally accepted model for this physical regime, cylindrical implosion experiments of single-mode, nonlinear RM growth and saturation are undeway at the OMEGA laser facility. Initial targets consist of an m=28 perturbation with an initial amplitude of 2.5 microns machined onto an aluminum marker layer embedded 55 {micro}m from the target surface. Initial perturbations of varying amplitudes and wavelengths are being studied using the RAGE code
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Calculations of double cylinder implosions at OMEGA
Foam-filled double cylinder targets have been imploded by the OMEGA laser at the University of Rochester. A marker layer of heavier material is placed between the foam and the outside ablator. The marker layer is hydrodynamically unstable when a strong shock passes through both these interfaces and the marker layer material mixes into the foam and the ablator. These experiments thus measure mix in the compressible, convergent, miscible, strong-shock regime. With double cylinder targets, the initial shock converges on the central cylinder and then rebounds and expands. The shock is predicted to create even more mixing of the marker layer as it traverses the previously mixed region. The strength of the reflected shock can be varied by changing the materials in the inner cylinder. Calculations of these implosions using the AMR code, RAGE, are presented for the several target designs. The 2-d calculations give the hydrodynamic evolution of the implosion, shock timings, and the growth of the mix width. The calculations include the effects of surface roughness in the marker layer. Simulated radiographs of the cylindrical implosions are also shown
The influence of foreign direct investment on accommodation patterns in Vietnam as a result of the open-door policy
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