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[en] A method is described for estimating the finite gyroradius stabilization of m> or =2 magnetohydrodynamic modes in diffuse high-β stellarators. The procedure combines both analysis and numerical computation. In particular, the difficult trajectory integrals which arise in the formulation are evaluated by plasma simulation techniques. The method is successfully applied to the m=2 modes in the high-β, l=1 stellarator configuration. It is found that the stability criterion for diffuse profiles is somewhat more optimistic than earlier estimates based on the sharp boundary model

[en] The start up of advanced fuel tokamaks is analyzed to determine if there are any specific challenges related to the start-up of these tokamaks (Cat. D, D³He) that are not found in a DT tokamak. High neutral particle power and neutral beam penetration have been envisioned as such challenges. The results indicate that using an advanced fuel enriched with tritium the plasma can first achieve D-T ignition and runaway to high temperature. Thus using this ''match head'' technique and low initial density and size ignition of the advanced fuel tokamak can be achieved with about the same external neutral beam energy and power requirements as a D-T device. However unless care is taken in the refueling sequence very high transient neutron wall loadings may result

[en] When a high-power Nd/glass laser pulse is incident on a polyethylene target, a bright plasma plume is created. Subsequently, a cloud of un-ionized gas is formed which contains 10--100 times the amount of material in the plasma plume. This gas cloud is cold (expansion velocity approx.10⁵ cm/sec) and dense (n> or approx. =10¹⁹). It is shown to contain diatomic molecules of carbon C₂ by heating the core of the cloud with the pulse from a 1-kJ TEA CO₂ laser. Then, the C₂ molecules in the cold outer regions of the cloud are seen in absorption on the light emitted by the hot core

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[en] The radial density and temperature profiles of ignited plasmas utilizing non-DT fuels can be optimized to maximize fusion power density and minimize required anti n tau/sub E/ under the constraint of a maximum average plasma pressure. Strong axial temperature peaking or strong density peaking is advantageous, according to whether the fusion reactivity increases faster or more slowly than quadratically with temperature, respectively. For tokamak plasmas with maximum beta limited to 10% or less by MHD instability, optimal profile tailoring allows ignition of catalyzed D-D or D-³He fuels in devices of reasonable size (R₀ approximately less than 8 m), and with first-wall power loadings exceeding 1 MW/m²

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[en] A simplified theoretical model for laser-produced spherical plasma during the laser heating period is proposed mainly from the application viewpoints. Attentions are paid to the time variation of the cut-off density surface, the plasma temperature and the transparency time for laser light, and these quantities are obtained in analytical forms for given parameters. The analytical results are compared with those obtained from numerical analyses based upon a spherically symmetric, one-dimensional Lagrangian hydrodynamic code (one-fluid, two-temperature). These two are found to be in good agreement, irrespective of the rather crude assumptions made in the analytical treatments. Thus, our simple theoretical model appears to serve to explain the approximate gross properties of laser-produced plasma during the laser heating phase. (auth.)