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To optimize the operation parameters of the beam line of NBI on HL-2A, features of the beam line, including the beam profile and the power deposited on components and injected into the tokamak plasma, were measured. The operational parameters of the four sources on the beam line were optimized with the monitor of the beam profile and beam power, and the transmission efficiency of the NBI injected power was therefore increased. A beam diagnostic system for the beam line of the NBI system on HL-2A as well as the diagnosed results was also presented.

The pellet injection experiments for fuelling and diagnostics have been carried out on the HL-1M tokamak. The eight-pellet injector was installed on HL-1M. A reliable monitor-detector and camera system was set up to take initial pellet photographs and measure the initial pellet speed and size. High fuelling efficiency of 60%-100% and a density profile with a peaking factor of 1.8-2.0 were obtained. The maximum density close to 1014/cm3 in HL-1M was achieved with newly optimized combined fuelling techniques. Two typical models of pellet ablation have been utilized for simulative calculation of the ablation rates in HL-1M. In comparison with the distribution of the measured Hα emission intensity from the digital data of the CCD camera, the experimental result seems more optimistic for core fuelling than theoretical predictions by the two models. The safety factor profile q(r) has been extracted from the information provided by the CCD camera during the pellet injection. The reliability of the measured results depends mainly on the calibration of the imaging space position. Based on the calibration, the measured q-profile becomes more reasonable than those published previously for the same shot number and same photograph.

The measurement on radial profile of electrostatic Reynolds stress, plasma poloidal rotations, radial and poloidal electric field have been performed in the plasma boundary region of the HL-1M Tokamak using a multi-array of Mach/Langmuir probes. In the experiments of Lower Hybrid Current Drive (LHCD), Supersonic Molecular Beam Injection (SMBI), Multi-shot Pellet Injection (MPI) and Neutral Beam Injection (NBI), the correlation between the Reynolds stress and poloidal flow in the edge plasma is presented. The results indicate that a sheared poloidal flow can be generated in Tokamak plasma due to radially varying Reynolds stress.

In this paper, the principle and method of the electron temperature measurement by means of electron cyclotron emission (ECE) have been discribed. Several results under different conditions on HL-1M tokamak have been given. The hollow profile of electron temperature appears in some stages, such as current rising, pellet injection and impurity concentration in the plasma centre. When the bias voltage is applied, the electron temperature profile become steeper. All of the phenomena are related with the transport in plasma centre.

The radial profile of electrostatic Reynolds stress, plasma poloidal rotations, radial and poloidal electric fields have been measured in the plasma boundary region of the HL-1M tokamak using a multiarray of Mach/Langmuir probes. In the experiments of ohmic discharge, lower hybrid current drive, supersonic molecular beam injection (SMBI) and multi-shot pellet injection, the correlation between the Reynolds stress and poloidal flow in the edge plasma is presented. The radial profile changes of the Reynolds stress and poloidal flow velocity Vpol with lower hybrid wave injection power and SMBI injection are obtained. The results indicate that the sheared poloidal flow can be generated in tokamak plasma due to the radially varying Reynolds stress.

During pellet injection and supersonic molecular beam injection, we have observed the increase of electron density and the enhancement of hard x-ray radiation, but the runaway electrons normally decrease without additional fuelling when the density of plasma increases. This phenomenon may come from the synergetic effects of Dreicer and avalanche runaway electrons. The experimental results are consistent with the calculation based on the theory of avalanche runaway in the HL-1M tokamak.

Using a floating double probe, we have determined values for the cross-field diffusion coefficient D⊥(a) (0.2–1.0 m2/s), the gross particle confinement time τp (10–100 ms) and the radial particle flux Γ(a) (1019–1020 m−2 s−1), near the limiter radius for Ip = 100 kA, ne = (1.0–4.5) × 1019/m3 and BT = 1.4–2.5 T. The parametric dependence of the edge plasma parameters on BT and line averaged density, n¯e, has been found to be non-linear. The turbulence characteristics have been studied using spectroscopy, microwave reflectometry, magnetic coils and an array of Langmuir probes. The experimental results indicate that turbulent diffusion plays a key role in the particle transport.

HL-2A plasmas heated by neutral beam injection (NBI) regularly exhibit n = 1 long-lived saturated magnetohydrodynamic instabilities. A reduction in the electron density and plasma stored energy and an increase in fast ion losses are usually observed in the presence of such perturbations. The observed long-lived saturated internal mode (LLM) occurs when the safety factor profile has a weak shear in a broad range of the plasma centre with qmin around unity. It is found that the ideal interchange mode can become marginally stable due to the weak magnetic shear reaching a critical value. The LLM, due to its pressure-driven feature, is destabilized by the strong interaction with fast ions in the low-shear region during the NBI. Furthermore, for the first time it is clearly observed that the LLMs can be suppressed by electron cyclotron resonant heating (ECRH), or by supersonic molecular beam injection in HL-2A plasmas. Low-n sidebands observed during the LLM are also suppressed by increasing the ECRH power. The control of LLMs is due to the change in the magnetic shear or in the pressure profile induced by the local heating or fuelling.

Arc efficiency is a critical criterion for assessing the performance of the ion source. High arc efficiency is necessary for a high power ion source, because it can decrease the load of the arc power supply. Thus the relationship between the discharge parameters (gas pressure, arc voltage, filament current, bias resistance connecting between the anode and plasma grid) and the arc efficiency is investigated in experiment especially. It is found that with increasing pressure, the arc efficiency increases fast if the pressure is below 0.4 Pa, but when it is above 0.4 Pa, the arc efficiency remains unchanged or increases slowly. If we increase the arc voltage or filament current, the arc efficiency decreases. The bias resistance also influences the arc efficiency, at the same pressure the arc efficiency increases with resistance.

For heating the tokamak plasma effectively, the ion source must be capable of producing ions with high proton ratio. The proton ratio, which is found to be more than 65.6% at the ion current of 19.6 A with the extraction voltage of 39.6 kV, is measured with an image spectrograph by Doppler shift effect of Balmer-α-radiation spectrum emitted from fast hydrogen particles. The tendency of proton ratio with the ion density in experiment is almost the same as the mode devised by Zhang et al. Okumura et al. only gave the affection of the plasma volume and ion loss area on the proton ratio, but the relationship between the ion density in chamber and the proton ratio was not presented. We give the relationship.

A circular magnetic multi-pole line-cusp ion source with a nominal 45 keV 25 A hydrogen ion beam is developed for the neutral beam injector of the HL-2A tokomak. At present, this bucket ion source can produce a 40 keV 20 A hydrogen ion beam for less than 100 ms on a test bed, and a 35 keV 13 A ion beam for 300 ms on the injector of the HL-2A tokomak. The 1/e half-width of the ion beam power profile is about 6.0 ± 0.2 cm at the position of 3.26m downstream from ion source, and the corresponding divergence degree is nearly 1.1. The optimum perveance matched conditions were obtained experimentally, and were in good agreement with the values from experiential equation of Uhlemann et al. The maximum of optimum perveance reached 2.2 × 10−6 A/V1.5 for 38 keV beam energy. An ion beam with above 60% H+ species fraction can be achieved, which was measured by Hα light Doppler shift spectroscopy. According to research results, a neutral beam with a total power of more than 0.6 MW was successfully injected into the plasma of the HL-2A Tokomak in 2008.