Author/Authors :
Petrie، نويسنده , , T.W. and Greenfield، نويسنده , , C.M. and Grobener، نويسنده , , R.J. and Hyatt، نويسنده , , A.W. and La Haye، نويسنده , , R.J. and Leonard، نويسنده , , A.W. and Mahdavi، نويسنده , , M.A. and Osborne، نويسنده , , T.H. and Schaffer، نويسنده , , M.J. Cases-Thomas، نويسنده , , D.M. and West، نويسنده , , W.P. and Allen، نويسنده , , S.L. and Fenstermacher، نويسنده , , M.E. and Lasnier، نويسنده , , C.J. and P، نويسنده ,
Abstract :
We report on recent experiments for which the magnetic balance of highly triangular (δ≈0.8), unpumped H-mode plasmas was varied. Changes in divertor heat loading and particle flux were observed when the magnetic configuration was varied from a balanced double-null (DN) divertor to a slightly unbalanced DN divertor. For attached plasmas, the variation in heat flux sharing between divertors is very sensitive near balanced DN. This sensitivity can be shown to be consistent with the measured scrape-off width of the parallel divertor heat flux density, λq∥. At magnetic balance we find that the peak heat flux density at the divertor in the ∇B ion drift direction is twice that of the other divertor. Most of the heat flux go to the outboard divertor targets in a balanced double-null, where the peak heat flux density at the outer divertor targets may exceed that of the inner divertor targets by tenfold. However, the variation of the peak particle flux density between divertors is less sensitive to changes in magnetic balance. These particle and heat flux `asymmetriesʹ in DN plasmas are consistent with the presence of E×B poloidal particle drifts in the scrape-off layer and private flux region [1]. Regardless of how the divertors were magnetically balanced, D2 gas puffing always reduced energy confinement to the range τE/τE89P≈1.3–1.6. When this energy confinement range was reached, τE/τE89P remained nearly constant up to near the H-mode density limit.
