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The ELMy H-mode plasmas realized with the supersonic molecular beam injection(SMBI) are studied in relation to the energy confinement and the heating power for the L–H transition(P_(L-H) ) in the HL-2A tokamak. A database is assembled for this study based on the ELMy H-mode discharges during the experimental campaigns in the period 2009–2013at the HL-2A tokamak. The statistical results show that the SMBI is favourable for reaching the H-mode by reducing the heating power at the L–H transition and for the H-mode performance by improving the energy confinement compared with the ordinary gas puffing(GP). The reduction of P_(L-H) is about 20% when the density is low, and the energy confinement enhancement factor of H_(H98y2)= τ_E/τ_(th,98y2) ≈ 1.5 is achieved with the SMBI. Note that in the database the density dependence of P_(L-H) is non-monotonic with the ˉne,min≈ 3×10~(19) m~(-3) at which the P_(L-H) is minimum. Most of P_(L-H) data are on the low density branch where the P_(L-H) increases with the decrease in density. The minimum of the P_(L-H) in HL-2A is comparable to the ITPA multi-machine threshold power scaling P_(thr■scal08). The physics behind the reduction of the P_(L-H) with the SMBI is also investigated in relation to the change of the density gradient at the plasma edge, the gas fuelling efficiency, and the recycling.
The ELMy H-mode plasmas realized with the supersonic molecular beam injection (SMBI) are studied in relation to the energy confinement and the heating power for the L-H transition (P_ (LH)) in the HL-2A tokamak. A database is assembled for this study based on the ELMy H-mode discharges during the experimental campaigns in the period 2009-2013 at the HL-2A tokamak. The statistical results show that the SMBI is favourable for reaching the H-mode by reducing the heating power at the L-H transition and for the H-mode performance by improving the energy confinement compared with the ordinary gas puffing (GP). The reduction of P_ (LH) is about 20% when the density is low, and the energy confinement enhancement factor of H_ (H98y2) = τ_E / τ_ (th, 98y2) ≈ 1.5 is achieved with the SMBI. Note that in the database the density dependence of P_ (LH) is non-monotonic with the ˉne, min≈3 × 10 ~ ) m ~ (-3) at which the P_ (LH) is minimum. Most of P_ (LH) data are on the low density branch where the P_ (LH) increases with the decrease in density. The minimum of the P_ (LH) in HL-2A is comparable to the ITPA multi-machine threshold power scaling P_ (thr_scal08). The physics behind the reduction of the P_ ( LH) with the SMBI is also investigated in relation to the change of the density gradient at the plasma edge, the gas fuelling efficiency, and the recycling.