In this paper, we describe the behavior of impurity transport in the HL-2A electron cyclotron resonance heating （ECRH） L-mode plasma. The neon as a trace impurity is injected by the supersonic molecular beam injection （SMBI） technique, which is used for the first time to study the impurity transport in HL-2A. The progression of neon ions is monitored by the soft X-ray camera and bolometer arrays with good temporal and spatial resolutions. The convection and diffusion process of the neon ions are investigated with the one-dimensional impurity transport code STRAHL. The results show that the diffusion coefficient D of neon ions is a factor of four larger than the neoclassical value in the central region. The value of D is larger in the outer region of the plasma （ρ 〉 0.6） than in the central region of the plasma （ρ 〈 0.6）. The convective velocity directs inwards with a value of ～-1.0 m/s in the Ohmic discharge, but it reverses to direct outwards with a value of ～ 8.0 m/s in the outer region of the plasma when ECRH is applied. The result indicates that the impurity transport is strongly enhanced with ECRH.
A normal incidence vacuum ultraviolet （VUV） and a grazing incidence extreme ultraviolet （EUV） spectrometers have been developed for the edge and core impurity measure- ments in HL-2A tokamak. The VUV and the EUV spectrometers cover wavelength ranges of 300-3200 A and 50-500A, respectively. A spatial resolution of 2 mm has been achieved for the VUV spectrometer when a space-resolved slit 50 #m in width is used. The space-resolved slit is placed between the entrance slit and the grating of the spectrometer. The spectral resolutions of 0.15/~ for the VUV spectrometer in the wavelength coverage of the concave 1200 grooves/mm grating and of 0.22A for the EUV spectrometer at λ=200A with a flat-field laminar-type holo- graphic grating are obtained. The sensitivity of the VUV spectrometer was calibrated in situ with the plasma bremsstrahlung radiation. The experimental results from both spectrometers are presented, especially the line intensity radial profiles measured by the VUV spectrometer.
One of the critical issues to be solved for HL-2M is the power exhaust.Divertor target plate geometry strongly influences the plasma profiles by controlling the neutral recycling pattern,which in turn has a strong effect on the symmetry and stability of the divertor plasma and finally on the whole edge region.The numerical simulation SOLPS5.0 package is used to design and explore the divertor target plates for HL-2M.We start with the choice of a proper target plate geometry,which has a smaller incidence angle in the permissible space,and then discuss the method of gas puffing to reduce the heat flux density on the target and the effects of gas puffing on the divertor plasma performance.
One of the critical issues to be solved for HL-2M is the power and particle exhaust. Divertor target plate geometry strongly influences the plasma profiles by controlling the neutral recycling pattern, which has in turn a strong effect on the symmetry and stability of the divertor plasma and finally on the whole edge region. The numerical simulation software SOLPS5.0 Pack- age is used to design and explore the divertor target plates for HL-2M. We choose two divertor geometries, and assess the heat flux on the target plates and first wall, then further discuss the di- vertor plasma parameters, and how private flux baffling affects both neutral recirculation pattern and pumping efficiency.
Perturbative experiments on electron heat transport have been successfully con- ducted on the HL-2A tokamak. The pulse propagation of the electron temperature is induced by the supersonic molecular beam injection （SMBI）, which has characteristics of good localization and deep deposition. A model based on the electron heat transport in cylindrical geometry has been applied to reconstruct the measured amplitude and phase profiles of the electron temperature perturbation. The results show that the heat transport is significantly reduced near the pedestal region of the H-mode plasma. In the ＂profile stiffness/resilience＂ region, similar heat diffusivities have been observed in L-mode and H-mode plasmas, which verifies the gradient-driven transport physics in tokamaks.
