[en] Several arrays of soft X-ray diagnostic are developed on the HT-7 tokamak and used to study the sawtooth oscillations. The occurrence and characteristics of the sawtooth are related closely with the discharge conditions such as electron density N_e, electron temperature T_e, safety factor q_α on the plasma edge, as well as the wall condition, etc. In lower hybrid current drive (LHCD) plasmas, an m/n=1/1 mid-mode oscillation can be observed, which appears during sawtooth ramps, rapidly-develops, saturates, damps and disappears before the sawtooth collapse. The sawtooth behaviors in ohmically heated plasma and LHCD plasma are discussed and summarized. (authors)

[en] The metal foil resistive bolometer signals are found to be interfered by low hybrid wave in EAST experiment. The performance of microwave transmission and shielding are studied using the simulation software HFSS (High Frequency Structure Simulator). It is possible for microwave stray in the vacuum vessel to reach the sensors through the front collimating aperture which is bared without any shielding at present. Shielding properties of Circle holes with different diameter are compared for low hybrid wave at 2.45GHz and 4.6GHz. The result shows that a hole with diameter less than λ/30 can shield the microwave well to ensure the coupled E field bellow 4V/m near the sensor which is evaluated as the equivalent power of sensor background noise. The parameter of shielding metal mesh is chosen for EAST bolometer according the simulation results. (author)

[en] This paper introduces the bolometer system on EAST. The system mainly consists of 48 metal foil detectors and the electronics. The system has been used to measure the temporal and spatial distribution of plasma radiation power in the whole plasma poloidal cross-section on EAST. Classical Wheatstone bridge structure was adopted in the detector and the carrier amplifier technique was applied in the electronics. This radiation bolometer system is suitable for weak signal measurement in strong electromagnetic interference environment. Calibration result and typical measurement result on EAST are given in the paper. (authors)

[en] It designs a kind of current amplifier of practical photoelectric weak signal for the detection of weak diagnosis signal of the Plasma physics experimental in EAST, with the high noise environment in EAST experimental and the basic principles of photoelectric detection circuit. The circuit is made up of pre-amplifier, active filter and behind voltage amplifier, combined with EMC technology to get a low-noise signal which has enough gain and bandwidth. Experimental show that the circuit could effectively measure weak current signal, and it has preferably SNR and stability. (authors)

[en] The Bolometer diagnostic system at the superconducting Tokamak EAST is introduced briefly. The shielding and grounding method of Bolometer diagnostic system is studied. Measures of shielded cabinet, low noise double-shielding cables and single point grounding are adopted to insure the long distance transmission of weak voltage signals in complex electromagnetic environment. The method can avoid grounding loop and resonance among the 4-channel model. The testing result shows that it can protect effectively weak signal from electromagnetic interference. (authors)

[en] The diagnostic system of soft X-ray spectra is introduced, and the electron temperature on HT-7 tokamak has been measured by this system. Remarkable increase of the electron temperatures has been observed in the experiments of plasma heating by ion Bernstein waves in collaboration with lower hybrid waves. (authors)

[en] The metal foil resistive bolometer was successfully applied on EAST device for measurement of radiation power. Classical Wheatstone bridge circuit is adopted in the detector and the carrier amplifier technique inspired by sine wave is applied in the electronics. Thus, it is suitable for weak signal measurement in strong electromagnetic interference environment. The measurement system on EAST mainly consists of 48 detectors and corresponding electronics to measure the temporal and spatial distribution of plasma radiation power in the whole plasma poloidal cross-section. Calibration result and typical measurement result on EAST are given in the paper. (authors)

[en] The relative calibration method of AXUV photodiodes used on the nuclear fusion Tokamak EAST and HT-7 was given. These photodiodes were used for absolute radiated power measurement. The changes of the detector surface were usually observed after one experiment campaign. Five sensors suffered different plasma discharge irradiations were compared by relative calibration. The X-ray tube and standard light source were chosen as the calibration source. The results show that the detector response can decrease 15% after 25000 discharge irradiation accumulations. The response changes between channels in one photodiode array were observed. The cumulative irradiation doses were evaluated according to the geometry parameter of the detector in radiation field. (authors)

[en] The fast bolometer diagnostic system for absolute radiated power measurement on EAST tokamak is introduced, which is based on the absolute extreme ultraviolet (AXUV) photodiodes. The relative calibration of AXUV detectors is carried out using X-ray tube and standard luminance source in order to evaluate the sensitivity degradation caused by cumulative radiation damage during experiments. The calibration result shows a 23% sensitivity decrease in the X-ray range for the detector suffering ∼27000 discharges, but the sensitivity for the visible light changes little. The radiated power measured by AXUV photodiodes is compared with that measured by resistive bolometer. The total radiated power in main plasma deduced from AXUV detector is lower a factor of 1∼4 than that deduced from resistive bolometer. Some typical measurement results are also shown in this article. (author)

[en] Plasma disruption on the Tokamak device often generates a lot of runaway electrons. Primary (Dreicer) acceleration and secondary avalanching are two mechanisms responsible for the generation of runaway electrons during disruptions. The behavior of runaway electrons generation was investigated at different phases of discharges on Experiment Advanced Superconducting Tokamak. It is found that primary acceleration is the main mechanism in current ramp-up phase while avalanching played an important role in current quench. In the paper, the diagnostics system is described, and the mechanisms of runaway electrons generation in different phases of discharges are presented by hard X-ray measurement. (authors)