Plasma discharge experiments of a Faraday shieldless driver for high-power and long-pulse radio frequency ion source for NBI application.

Due to the high stability and less maintenance, the radio frequency (RF) driven ion source is preferred for the neutral beam injection (NBI) system. In a popular design of the RF ion source for NBI application, a Faraday shield (FS) is installed inside the RF plasma driver to protect the discharge tube. However, the FS also brings some drawbacks, such as lowering the RF power transfer and increasing the processing difficulty.

Design of infrared radiation diagnostic calorimeter for the prototype radio frequency driven negative ion source for neutral beam injection.

In order to study the generation and extraction of negative ions for neutral beam injection application, a prototype radio frequency driven negative ion source and the corresponding test bench are under construction at the Institute of Plasma Physics, Chinese Academy of Sciences. A new design of infrared radiation diagnostic calorimeter for testing beam characteristics is put forward. Compared with the conventional calorimeter, the calorimeter adopts the block structure (8 × 28 tungsten hexahedron blocks) and modularization design (4 modules), so it has higher precision and good scalability.

Preliminary design of diagnostic system for negative neutral beam injector at ASIPP.

According to the latest physics design of the China Fusion Engineering Test Reactor (CFETR), two neutral beam injectors (NBIs), which deliver a total of 40 MW in not less than 3600 s with 1 MeV D, are demanded to support current drive and plasma rotation. To minimize the risks and time to provide the CFETR with reliable NBIs, a negative NBI test facility will be developed at the Institute of Plasma Physics, Chinese Academy of Science. Its mission is to understand the characteristics of the RF driven ion source and negative ion generation and extraction and to improve RF efficiency and beam quality.

Research and development progress of radio frequency ion source for neutral beam injector at ASIPP.

Neutral beam injection (NBI) is one of the most effective tools of four auxiliary plasma heating methods for fusion plasma heating and current drive. Now, a next generation fusion device, China Fusion Engineering Test Reactor, is under design, and a large negative NBI is foreseen. In order to demonstrate the key technology and performance of a negative ion source, a negative radio frequency (RF) ion source test facility has been developed since 2017 in the Institute of Plasma Physics, Chinese Academy of Science.

Optimization design of magnetic filter for the prototype RF negative ion source at ASIPP.

For a prestudy of the key science and technology of the RF negative ion source for fusion application, a negative RF ion source test facility was developed at the Institute of Plasma Physics, Chinese Academy of Science (ASIPP). The magnetic filter field in front of the extraction system plays an important role in reducing the loss of negative hydrogen ions and inhibiting coextraction of electrons. The existing filter field of the prototype ion source is generated by permanent magnets arranged on both sides of the expansion chamber; the gradient and the uniformity of the field are poor, resulting in a large plasma distribution unevenness in the experiment.

Structure design and analysis of RF ion source for negative ion source test facility.

A negative ion source acts as a critical part in a neutral beam injector (NBI). A high current ion source is required for the high-power NBI. In this paper, a prototype radio frequency (RF) ion source and its test facility are developed in the Institute of Plasma Physics, Chinese Academy of Sciences, to demonstrate the key technology of the high power negative ion source.

Physics and engineering design of 400 keV H accelerator for negative ion based neutral beam injection system in China.

A research project of the China Fusion Engineering Test Reactor (CFETR) Negative ion-based Neutral Beam Injection (NNBI) prototype has been started in China. The objectives of the CFETR NNBI prototype are to produce a negative hydrogen ion beam of >20 A up to 400 keV for 3600 s and to attain a neutralization efficiency of >50%. In order to identify and optimize the design of the negative ion accelerator, a self-consistent model has been developed to consider all key physics and engineering issues (electric and magnetic fields, background gas flow, beam optics, beam-gas interaction, secondary particle trajectories, power deposition on grids, heat removal design, and mounting pattern).

Investigation of the adhesive bonding technology for the insulator structure of EAST neutral beam injector.

A key issue on the development of EAST ion source was the junction design of insulator structure, which consists of three insulators and four supporting flanges of electrode grid. Because the ion source is installed on the vertical plane, the insulator structure has to withstand large bending and shear stress due to the gravity of whole ion source. Through a mechanical analysis, it was calculated that the maximum bending normal stress was 0.