The neutral beam injection (NBI) system was developed on the Experimental Advanced Superconducting Tokamak (EAST) for plasma heating and current driving. This paper presents the brief history, design, development, and the main experimental results of the RD (2) the design of the EAST-NBI system including the high power ion source, main vacuum chamber, inner components, beam diagnostic system and sub-system; (3) the experimental results of beamline-1 on the summer campaign of EAST in 2014 and, (4) the status of beamline-2 and the future plan of EAST-NBIs.

Overview of Development Status for EAST-NBI System

Plasma-facing components damage and its effects on plasma performance in EAST tokamak

The neutral beam injection (NBI) system is one of the most important auxiliary plasma heating and current driving methods for fusion device. A high power ion beam of 3 MW with 80 keV beam energy in 0.5 s beam duration and a long pulse ion beam of 4 s with 50 keV beam energy ion beam extraction were achieved on the EAST neutral beam injector on the test- stand. The preliminary results show that the EAST-NBI system was developed successfully on schedule.

Preliminary Results of Ion Beam Extraction Tests on EAST Neutral

Neutral beam injection has been recognized as one of the most effective means for plasma heating. According to the research plan of the EAST physics experiment, two sets of neutral beam injectors (4–8 MW, 10–100 s) were built and operated in 2014. We present the development of the EAST neutral beam injector (NBI) and the latest experiment results obtained on the test-stand about operation of ion source, beam extraction, and measurement of key parameters. Those results show that all targets reach or almost reach the design targets. All these lay a solid foundation for the achievement of plasma heating and current drive for EAST in 2014.

The Recent Development of the EAST Neutral Beam Injector

Arcing on the plasma-facing components (PFCs) is one of the mechanisms of material erosion and impurity production in the magnetic-confinement fusion devices. EAST tokamak has been upgraded to almost full metal PFCs. The arcing phenomena in EAST has special features due to the lithium coating and the RF heating. Post-mortem analysis of arc traces is performed on both plasma-wetted components and PFCs in sub-limiter remote areas. The arcs in sub-limiter remote areas nearly have no influence on the normal discharges as most of them were produced during the glow discharge cleaning. But some arcs on the first mirrors of infrared and visible tangential wide-angle viewing systems in EAST can form patterned traces in the videos, which affects the precision of temperature measurements and visible imaging quality. The arcs on plasma-wetted components were mainly observed at two locations: the tungsten upper divertor and the lower hybrid current drive (LHCD) antennas. The random-walk arc traces on the surface of the upper tungsten divertor are limited to a very small area and most probably formed without magnetic field during glow discharge, unable to influence plasma discharges so far, and still need long-term tracking. The arcs on the LHCD antenna surface can be sustained for more than hundreds of milliseconds, and produce large numbers of impurity particles and molten droplets, which can result in plasma current quench and disruption, and the effects of arcing on LHCD heating mode and power should be further studied. 

Observations on arcing on the metal plasma-facing components in EAST

Neutral beam injection is recognized as one of the most effective means of plasma heating. The preliminary data of beam power deposition in different electrodes during beam extraction are obtained on the EAST neutral beam injector test stand. The measurement of the cooling water temperature rise of accelerating electrodes is reported. The data given can guide the optimization of beam extraction parameters and decrease the damage to the accelerating electrodes following long pulse beam extraction.

Analysis of the Cooling Water Temperature Rise of Accelerating Electrodes in EAST Neutral Beam Injector Beam Extraction

High-energy neutral beam injection(NBI) is one of the four Tokamak auxiliary heating methods(The four methods are the neutral beam injection, lower hybrid, ion cyclotron waves paragraph, and the section electron cyclotron waves). Due to the highest heating efficiency, and the clearly physical mechanism, NBI is regarded as the most effective heating method by international fusion community. In order to explore shine through of EAST（Experimental Advanced Superconducting Tokamak）-NBI, specific hardware circuit block diagram and experimental scheme are designed based on the theoretical analysis of the principle of shine through, and the correctness of the theoretical deduction is verified by experiments. The method of quantitative calibration of the thermocouple in the center point of the ion source beam spot is the standard for the calculation of the shine-through. The value of shine-through is calculated by the ratio of the armor tile thermocouple unit energy of temperature rise to that of calibrated one. The experimental results show that, in a certain range, the shine through increases linearly with the increase of the injection beam energy, and decreases exponentially with the increase of the plasma density.

Analysis of shine-through of EAST neutral beam

Analysis of the Effect of Beam Divergence Angle on Back-Streaming Electron Region in Ion Source for EAST-Neutral Beam Injection

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Analysis of the Cooling Water Temperature Rise of Accelerating Electrodes in EAST Neutral Beam Injector Beam Extraction

Analysis of shine-through of EAST neutral beam

Analysis of the Effect of Beam Divergence Angle on Back-Streaming Electron Region in Ion Source for EAST-Neutral Beam Injection