Long radial coherence of electron temperature fluctuations in non-local transport in HL-2A plasmas

The dynamics of long-wavelength (kθ < 1.4 cm⁻¹), broadband (20 kHz-200 kHz) electron temperature fluctuations ( T ∼ e / T e ) of plasmas in gas-puff experiments are observed for the first time in HL-2A tokamak. In a relatively low density (n e(0) ≃ 0.91 × 10¹⁹m⁻³-1.20 × 10¹⁹m⁻³) scenario, after gas-puffing the core temperature increases and the edge temperature drops. On the contrary, temperature fluctuation drops at the core and increases at the edge. Analyses show the non-local emergence is accompanied with a long radial coherent length of turbulent fluctuations. While in a higher density (n e(0) ≃ 1.83 × 10¹⁹ m⁻³-2.02 × 10¹⁹ m⁻³) scenario, the phenomena are not observed. Furthermore, compelling evidence indicates that E × B shear serves as a substantial contributor to this extensive radial interaction. This finding offers a direct explanatory link to the intriguing core-heating phenomenon witnessed within the realm of non-local transport.