Caichao Jiang

Preliminary Experimental Study of Ion Beam Extraction of EAST Neutral Beam Injector

Neutral beam injection is recognized as one of the most effective means for plasma heating. The preliminary data of ion beam extraction is obtained on the EAST neutral beam injector test-stand. Beam extraction from the ion source of EAST-NBI is verified by measuring the beam current with a Faraday cup and by analyzing the results obtained by means of water calorimetric measurement on the temperature rises of water cooling the accelerator electrodes.

First plasma of megawatt high current ion source for neutral beam injector of the experimental advanced superconducting tokamak on the test bed.

High current ion source is the key part of the neutral beam injector. In order to develop the project of 4 MW neutral beam injection for the experimental advanced superconducting tokamak (EAST) on schedule, the megawatt high current ion source is prestudied in the Institute of Plasma Physics in China. In this paper, the megawatt high current ion source test bed and the first plasma are presented. The high current discharge of 900 A at 2 s and long pulse discharge of 5 s at 680 A are achieved. The arc discharge characteristic of high current ion source is analyzed primarily.

Design of Neutral Beam-Line of EAST

Neutral beam injector for EAST is designed to deliver deuterium beams with a power of 2 MW to 4 MW at an energy of 50 keV to 80 keV into the plasma with a beam dimension of 12 cm × 48 cm. Considering the beam generation and transmission, a columniform beam-line of Φ 250 cm × 400 cm is designed with a neutralizer, ion dump, calorimeter, bending magnet and cryopanels. The arrangement of the internal elements for the beam-line is reported. A rectangular sleeve coupled to the ion source is employed as the neutralizer. At the downstream of the neutralizer, a dipole magnet separates the residual ions from the beam passage with a reflection radius of 42 cm for the full energy particles. The calorimeter and the ion dump serve as high heat flux components, which will work as thermal inertia targets in the first phase of operation.

The R&D progress of 4 MW EAST-NBI high current ion sourcea)

A high current ion source, which consists of the multi-cusp bucket plasma generator and tetrode accelerator with multi-slot apertures, is developed and tested for the Experimental Advanced Superconducting Tokamak neutral beam injector. Three ion sources are tested on the test bed with arc power of 80 kW, beam voltage of 80 keV, and beam power of 4 MW. The arc regulation technology with Langmuir probes is employed for the long pulse operation of ion source, and the long pulse beam of 50 keV @ 15.5 A @ 100 s and 80 keV @ 52A @ 1s are extracted, respectively.

Arc discharge regulation of a megawatt hot cathode bucket ion source for the experimental advanced superconducting tokamak neutral beam injector

Arc discharge of a hot cathode bucket ion source tends to be unstable what attributes to the filament self-heating and energetic electrons backstreaming from the accelerator. A regulation method, which based on the ion density measurement by a Langmuir probe, is employed for stable arc discharge operation and long pulse ion beam generation. Long pulse arc discharge of 100 s is obtained based on this regulation method of arc power. It establishes a foundation for the long pulse arc discharge of a megawatt ion source, which will be utilized a high power neutral beam injection device.

Overview of Development Status for EAST-NBI System ∗

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.

Development and preliminary results of radio frequency ion source.

A radio frequency (RF) ion source was designed and developed for neutral beam injector. A RF driver test bed was used with a RF generator with maximum power of 25 kW with 1 MHz frequency and a matching box. In order to study the characteristic of RF plasma generation, the capacitance in the matching box was adjusted with different cases. The results show that lower capacitance will better the stability of the plasma with higher RF power. In the future, new RF coils and matching box will be developed for plasma generators with higher RF power of 50 kW.

Performance of positive ion based high power ion source of EAST neutral beam injector

The positive ion based source with a hot cathode based arc chamber and a tetrode accelerator was employed for a neutral beam injector on the experimental advanced superconducting tokamak (EAST). Four ion sources were developed and each ion source has produced 4 MW @ 80 keV hydrogen beam on the test bed. 100 s long pulse operation with modulated beam has also been tested on the test bed. The accelerator was upgraded from circular shaped to diamond shaped in the latest two ion sources. In the latest campaign of EAST experiment, four ion sources injected more than 4 MW deuterium beam with beam energy of 60 keV into EAST.

Note: A new regulation method of stable operation of high power cathode ion source

The hot cathode ion source will tend to be unstable when operated with high power and long pulse. In order to achieve stable operation, a new regulation method based on the arc power (discharge power) feedback control was designed and tested on the hot cathode ion source test bed with arc discharge and beam extraction. The results show that the new regulation method can achieve stable arc discharge and beam extraction. It verifies the success of feedback control of arc source with arc power.

Feasibility Analysis of 1-D Carbon Material in Application of Negative Particle Beam Diagnostics

Abstract An important feature of the China Fusion Engineering Test Reactor (CFETR) project is the additional heating obtained from the injection of neutral beams based on accelerated negative ions. For the neutral beams based on negative ions, the most important measurements are beam uniformity, beamlet divergence, and stripping losses. According to the CFETR requirement, the maximum allowed beam divergence angle and beam nonuniformity are 6 mrads and ±10%, respectively. As one-dimensional (1-D) carbon tiles have large ratio between perpendicular conductivity and parallel conductivity and high stability, they can be used for beam uniformity and beamlet divergence measurement. This paper investigates the influence on the response of 1-D carbon tile having the thermal characteristics and features of some dedicated diagnostics. Simulations show that it will be possible to verify experimentally whether the beam meets the requirement about the maximum allowed value. This work lays a foundation for design and application of high-precision beam diagnostic targets.