345 research outputs found

    Analytical model of fast ion behavior in current hole tokamak plasmas

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    A qualitative theoretical approach is proposed for the study of fast ion behavior in tokamak plasmas with a current hole. For the equilibrium magnetic configuration in a current hole tokamak we employ a simplified model based on an analytical approximation of the poloidal flux function shape. For that the radial extent of the plasma core area with zero rotational transform is used as a characteristic parameter. The modification of the fast ion orbit topology, as caused by the current hole, is studied. The model yields manageable analytical expressions describing completely the current hole effect on the confinement domains as well as on the boundaries separating the regions of different-type orbits in the constants-of-motion space. Subject of investigation is the current hole effect, both on the convective transport of fast ions induced by their slowing down as well as on the diffusive transport caused by pitch angle scattering. The influence of slowing down on the distribution functions of energetic particles (charged fusion products, NBI ions) in current hole tokamak plasmas is calculated and illustrated. The approach proposed is tested for a specific JET current hole scenario and the results are compared with numerical Fokker-Planck predictions.Comment: 12th International Congress on Plasma Physics, 25-29 October 2004, Nice (France

    Measurements of DT alpha particle loss near the outer midplane of TFTR

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    Measurements of DT alpha particle loss to the outer midplane region of TFTR have been made using a radially movable scintillator detector. The conclusion from this data is that mechanisms determining the DT alpha loss to the outer midplane are not substantially different from those for DD fusion products. Some of these results are compared with a simplified theoretical model for TF ripple-induced alpha loss, which is expected to be the dominant classical alpha loss mechanism near the outer midplane. An example of plasma-driven MHD-induced alpha particle loss is shown, but no signs of any ``collective`` alpha instability-induced alpha loss have yet been observed

    Overview of the JET ITER-like wall divertor

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    Measuring fast ions in fusion plasmas with neutron diagnostics at JET

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    Power exhaust by SOL and pedestal radiation at ASDEX Upgrade and JET

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    Multi-machine scaling of the main SOL parallel heat flux width in tokamak limiter plasmas

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    ELM divertor peak energy fluence scaling to ITER with data from JET, MAST and ASDEX upgrade

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