Xie Yuanlai

Charge Exchange Recombination Spectroscopy Based on Diagnostic Neutral Beam in HT-7 Tokamak

Charge exchange recombination spectroscopy (CXRS) based on a diagnostic neutral beam (DNB) installed in the HT-7 tokamak is introduced. DNB can provide a 6 A extracted current at 50 kV for 0.1 s in hydrogen. It can penetrate into the core plasma in HT-7. The CXRS system is designed to observe charge exchange (CX) transitions in the visible spectrum. CX light from the beam is focused onto 10 optical fibers, which view the plasma from −5 cm to 20 cm. The CXRS system can measure the ion temperature as low as 0.1 keV. With CXRS, the local ion temperature profile in HT-7 was obtained for the first time.

Modeling process of the neutral beam re-ionization loss

The basic process of re-ionization loss was studied. In the drift duct there are three processes leading to re-ionization loss: the collision of neutral beam particles with the molecules of background gas, similar collisions with released molecules from the inner wall of the drift duct and the ferret-collisions among particles with different energy of the neutral beam. Mathematical models have been developed and taking EAST-NBI parameters as an example, the re-ionization loss was obtained within these models. The result indicated that in the early stage of the neutral beam injector operation the released gas was quite abundant. The amount of re-ionization loss owing to the released gas can be as high as 60%. In the case of a long-time operation of the neutral beam injector, the total re-ionization loss decreases from 13.7% to 5.7%. Then the reionization loss originating mainly from the collisions between particles of the neutral beam and the background molecules is dominant, covering about 92% of the total re-ionization loss. The drift duct pressure was the decisive factor for neutral beam re-ionization loss.

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

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.

The Recent Development of the EAST Neutral Beam Injector

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 Arc Regulation Characteristics of the High-Current Ion Source for the EAST Neutral Beam Injector

The arc regulation method is applied to the high-current ion source for high-power hydrogen ion beam extraction for the first time. The characteristics of the arc and beam, including the probe ion saturation current, the arc power and the beam current, are studied with feedback control. The results show that the arc regulation method can be successfully applied to ion beam extraction. This lays a sound foundation for the testing of a new ion source and the operation of a conditioned ion source for neutral beam injector devices.

Thermal Analysis and Optimization for Cryopanel of NBI Cryocondensation Pump

Excellent vacuum performance ensures a high beam transmission efficiency of the neutral beam injector (NBI). The vacuum performance is mainly determined by the cryoperformance of the cryopanel of the cryocondensation pumps which are the main vacuum pumps of NBI. In order to optimize the cryoperformance, the requirements for the temperature distribution and the heat load of the cryopanel are analysed and the factors that affect the cryopanels temperature distribution are studied. The results indicate that the temperature difference of the cryopanel can be reduced by fabricating the cryopanel with high thermal conductivity material, increasing its thickness and cutting the distance between the two upward cooling pipes. The results may be applied to a cryopanel cooled by forced flow liquid helium.

Engineering of Cryopump for Neutral Beam Injection

Neutrals beam injection (NBI) has proven to be a very effective method for plasma heating. A set of positive-ion-based NBI system is being designed, manufactured and tested at ASIPP. The aim of this study was to ascertain the most effective cryocondensation pump structure for the hydrogen NBI system. The parameter design and mechanical design were made to determine the optimum parameters and structure of the cryocondensation pump. The lowest pressure of 7.2 ? 10?6 Pa was achieved in the vacuum chamber, which indicated that this type of liquid helium cryocondensation pump could meet the requirement of the NBI system quite well.

Numerical Simulation of Subcooled Boiling Inside High-Heat-Flux Component with Swirl Tube in Neutral Beam Injection System ⁄

In order to realize steady-state operation of the neutral beam injection (NBI) system with high beam energy, an accurate thermal analysis and a prediction about working conditions of heat-removal structures inside high-heat-flux (HHF) components in the system are key issues. In this paper, taking the HHF ion dump with swirl tubes in NBI system as an example, an accurate thermal dynamic simulation method based on computational fluid dynamics (CFD) and the finite volume method is presented to predict performance of the HHF component. In this simulation method, the Eulerian multiphase method together with some empirical corrections about the inter-phase transfer model and the wall heat flux partitioning model are considered to describe the subcooled boiling. The reliability of the proposed method is validated by an experimental example with subcooled boiling inside swirl tube. The proposed method provides an important tool for the refined thermal and flow dynamic analysis of HHF components, and can be extended to study the thermal design of other complex HHF engineering structures in a straightforward way. The simulation results also verify that the swirl tube is a promising heat removing structure for the HHF components of the NBI system.

Performance of Diagnostic Neutral Beam for the HT-7 Tokamak

Diagnostic neutral beam (DNB), combined with spectral diagnostics, is employed to measure the ion temperature in HT-7. The factors affecting the extracted beam are studied in the experiment for the high performance diagnostic neutral beam. A 6.5 A extracted hydrogen current at 43 keV of 100 ms was obtained after optimization. The extracted beam has a proton ratio as high as 40%, and can penetrate into the core plasma after neutralization to measure the ion temperature effectively.