Author/Authors :
Wischmeier، نويسنده , , M. and Coster، نويسنده , , D. and Bonnin، نويسنده , , X. and Eich، نويسنده , , T. and Huber، نويسنده , , A. and Ingesson، نويسنده , , C. and Jachmich، نويسنده , , S. A. Kukushkin and A. V. Osipov ، نويسنده , , A. and Loarte، نويسنده , , A. and Matthews، نويسنده , , G.F. and Pitts، نويسنده , , R.A. and Rapp، نويسنده , , J. P. Reiter، نويسنده , , D. and Tsitrone، نويسنده , , E. and Contributors EFDA-JET Work Progr، نويسنده ,
Abstract :
A campaign of pure helium discharges in the JET tokamak equipped with the MarkIIGB divertor has been performed. This paper describes some of the experimental observations of divertor detachment obtained in L-mode density ramp He discharges and presents a selection of results from the application of B2.5-Eirene code modelling to a JET He plasma. Detachment is very different from that observed in equivalent D discharges. Particle fluxes remain attached up to higher densities and, with decreasing input power, particle detachment occurs earlier in density. However, in contrast to comparable D plasmas, the low measured target Te at all but the lowest ne in helium leads to an earlier decrease in power flux. Simulations show that detachment is caused by the escape of He neutrals from the target vicinity where, together with the He+ ions they radiate along the separatrix and above the X-point area, starving regions downstream of power.
Keywords :
Detachment , tokamak , Divertor , JET , Helium , B2.5-Eirene
