Extreme ultraviolet (EUV) spectra emitted from iron and copper ions in a range of 8-500 Å and molybdenum ions in a range of 8-400 Å were measured in Experimental Advanced Superconducting Tokamak (EAST) discharges accompanied with spontaneous sputtering events, by which metallic impurity influxes are suddenly increased in the discharge. Several spectral lines from L-, M-, and N-shell partially ionized ions have been successfully observed with two EUV spectrometers named EUV_Short and EUV_Long working in wavelength ranges of 8-130 Å and 20-500 Å, respectively. The wavelength position is accurately calibrated in-situ based on several well-known spectra of low-Z impurity ions. The line identification is carefully performed based on the National Institute of Standards Technology (NIST) database and previously published experimental data. As a result, it is found that B-, Be-, and Li-like iron and copper spectra Al-, Mg-, and Na-like molybdenum spectra appear in discharges with high central electron temperature (>1.8 keV). The highest ionization stages identified here are Li-like iron and copper and Na-like molybdenum, e.g. Fe XXIV at 192.028 Å (1s22p 2P3/2→1s22s 2S1/2), Cu XXVII at 153.513 Å (1s22p 2P3/2→1s22s 2S1/2) and Mo XXXII at 127.868 Å (2p63p 2P3/2→2p63s 2S1/2). Two unresolved transition arrays of molybdenum ions (Mo-UTAs) appear at wavelength ranges of 15-30 Å and 65-95 Å, and are preliminarily identified as Mo XX-Mo XXXII and Mo XVII-Mo XXXII, respectively. In addition, six spectral lines are newly found by comparing a time evolution of the line intensity from impurity ions in different ionization stages, i.e. Fe XVIII at 17.60±0.02 Å, Cu XXI at 13.15±0.02 Å, Cu XVIII at 260.32±0.07 Å, Cu XVIII at 261.00±0.06 Å, Mo XXVIII at 85.30±0.03 Å and Mo XXIX at 89.59±0.03 Å. The wavelengths of EUV spectra identified in this work are summarized in tables with transitions for each impurity species.

A visible light imaging Thomson scattering (VIS-TVTS) diagnostic system has been developed for the measurement of plasma electron temperature on the HT-7 tokamak. The system contains a Nd:YAG laser (λ = 532 nm, repetition rate 10 Hz, total pulse duration ≈ 10 ns, pulse energy > 1.0 J), a grating spectrometer, an image intensifier (I.I.) lens coupled with an electron multiplying CCD (EMCCD) and a data acquisition and analysis system. In this paper, the measurement capability of the system is analyzed. In addition to the performance of the system, the capability of measuring plasma electron temperature has been proved. The profile of electron temperature is presented with a spatial resolution of about 0.96 cm (seven points) near the center of the plasma.

The pedestal characteristic is an important basis for high confinement mode (Hmode) research. Because of the finite spatial resolution of Thomson scattering (TS) diagnostic on Experimental Advanced Superconducting Tokamak (EAST), it is necessary to characterize the pedestal with a suitable functional form. Based on simulated and experimental data of EAST, it is shown that the two-line method with a bilinear fitting has better reproducibility of pedestal parameters than hyperbolic tangent (tanh) and modified hyperbolic tangent (mtanh) methods. This method has been applied to EAST type I edge localized mode (ELM) discharges, and the electron pedestal density is found to be proportional to the line-averaged density and the edge pressure gradient is found to be proportional to the pedestal pressure. Furthermore, the ion poloidal gyro-radius has been identified as the suitable parameter to describe the pedestal pressure width.