[en] Highlights: • A stray light analysis model of baffle was built. • Stray light suppression effect of installed double edged baffle was analyzed. • A new corrugation baffle with 33.3% less stray light than the old one was designed. • An EAST TS diagnostic system simulation model was built. • Stray light suppression effect of the system with the two type baffles was analyzed. - Abstract: Baffle is a critical technique to suppress stray light. In order to reduce stray light of EAST Thomson scattering (TS) diagnostic system, a 60° cone angle double edged baffle array was installed for the system. Recently the 45° cone angle corrugation baffle was designed based on double edged baffle and simulation results indicate that the new design can reject 33.3% more stray light than the old one. Based on the mechanical structure and surface property of EAST TS diagnostic system, a stray light analysis model has been built, and using the model, stray light of the system was simulated with the two types of baffles added to the system respectively. Results show that the installation of 60° cone angle double edged baffle array in input tube can cut 92.1% of the stray light to the system, while using 45° cone angle corrugation baffle array in input tube and three 45° cone angle corrugation baffles in exit tube, additional 74.1% of the stray light will be removed.

[en] The first neutral beam injector (NBI) system of the Experimental Advanced Superconducting Tokamak (EAST) was installed in the spring of 2014, and the NBI initial experiments were carried out during the EAST operation campaign with its partial design capability. The maximum designed deuterium NB power and energy are 4 MW and 80 keV, respectively; an extracted beam full energy is mostly below 60 keV under the current EAST experimental conditions. The target plasma temperature is obviously increased with the NBI. L–H mode transitions are conducted by only NBI auxiliary heating. The pedestal formation in temperature profiles is observed through Thomson Scattering (TS) diagnostics. The NBI power can be modulated with different frequency and duty ratio has been also well checked.

[en] In order to get high signal-to-noise ratio, silicon avalanche photodiode (APD) is used to measure Thomson scattered spectrum. A charge-sensitive preamplifier has been developed for minimizing the noise contribution from detector electronics. Many measures are taken, including a new design electronic amplification circuit and a series of anti-interference technique. Therefore the Thomson scattering diagnostic system is successful to measure the plasma electron temperature on HT-7 tokamak. (authors)

[en] A multipulse Nd:YAG (Neodym-yttrium aluminium garnet) laser Thomson scattering diagnostic system developed was recently applied on HT-7 tokamak to obtain more accurate electron temperatures. A CAMAC-based real-time computer system for laser control, data acquisition, analysis and calibration was investigated in detail. Furthermore, the reliability and accuracy of this diagnostic system were demonstrated by comparing the results with those of a soft-X ray diagnostic system.

[en] The pedestal characteristic is an important basis for high confinement mode (H-mode) 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. (paper)

[en] Thomson scattering diagnostic is important for measuring electron temperature and density profiles. To improve the signal-to-noise ratio, a silicon avalanche photodiode (APD) with high quantum efficiency, high sensitivity, and high gain up to 100 was adopted to measure the Thomson scattering spectrum. A preamplifier, which has low noise, high bandwidth, and high sensitivity, was designed with suitable transimpedance. Using AD8367 as the post-amplifier, good performance of the APD readout electronics have been obtained. A discussion is presented on the performance of the amplifier using a laser diode to simulate the Thomson scattering light. The test results indicate that the designed circuit has a high amplifying factor and fast rising edge. So reduction of the integral gate of the CAMAC ADC converter can improve the signal-to-noise ratio. (brief communication and research note)

[en] Primary physical design of the Thomson scattering system for EAST, including the configuration of the system and the design considerations of different sections of the system, is presented. The expected measurability of this design, namely an electron temperature of 50 eV to 5 keV and a plasma density beyond 0.5 x 10¹⁹ m^-3, fulfills the requirements of the EAST operation.

[en] 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

[en] A multipulse neodym doped yttrium aluminum garnet laser Thomson scattering system calibrated by the anti-Stokes rotational Raman scattering from nitrogen gas had been developed in the HT-7 superconducting Tokmak. By virtue of this system, measured electron density results of the plasma were obtained. The results showed good repeatability and its total uncertainty was estimated to be ±18%

[en] A multipulse and multipoint Nd:YAG (neodymium-yttrium aluminum garnet) laser Thomson scattering diagnostic system was developed on EAST to obtain more accurate electron temperature T_e and electron density n_e profiles. In this paper, the optical system, the VME (versa module eurocard)-based real-time computer system for laser control, data acquisition, analysis and calibration are discussed in detail. Furthermore, a developed data processing method is presented.