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Jia Fu,Yuejiang Shi,Yingying Li,Fudi Wang,Sheng Liu,Jian Zhang,Jun Li,Yiyyun Huang,Yuanlai Xie,Zhimin Liu,Chundong Hu,Chundong Hu,DNB Team,William Rowan,He Huang 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.58 No.5
A diagnostic neutral beam (DNB) has been installed on the HT-7 tokamak for the measurement of charge exchange recombination spectroscopy (CXRS). The H_α-light Doppler shift spectroscopy from the drifted duct is measured to determine the components of the neutral beam. The fractions of neutral beam species are investigated under a wide range of arc voltages and extraction high voltages of the beam aimed to the optimized species fractions for the CXRS applications. A magnet ring is used to improve the magnetic property of the ion source. The result shows that the full-energy component fractions increase from 19 to 25 percent with optimization of the beam operation, but with a dramatic increase of the water component. There are nine optical fiber channels observing one section of the beam simultaneously for this spectroscopy, which provides information of the power profiles of the beam. The full width at half maximum (FWHM) of the beam profile is 8 cm, as measured by using the spectroscopy.
Suppression of stray electrons in the negative ion accelerator of CRAFT NNBI test facility
Yang Yuwen,Wei Jianglong,Xie Junwei,Gu Yuming,Xie Yahong,Hu Chundong 한국원자력학회 2023 Nuclear Engineering and Technology Vol.55 No.3
Comprehensive Research Facility for Fusion Technology (CRAFT) is an integration of different demonstrating or testing facilities, which aim to develop the critical technology or composition system towards the fusion reactor. Due to the importance and challenge of the negative ion based neutral beam injection (NNBI), a NNBI test facility is included in the framework of CRAFT. The initial object of CRAFT NNBI test facility is to obtain a H0 beam power of 2 MW at the energy of 200e400 keV for the pulse duration of 100 s. Inside the negative ion accelerator of NNBI system, the interactions of the negative ions with the background gas and electrodes can generate abundant stray electrons. The stray electrons can be further accelerated and dumped on the electrodes or eject from the accelerator. The stray electrons, including the ejecting electrons, cause the unwanted particle and heat flux onto the electrodes and the inner components of beamline (especially the temperature sensitive cryopump). The suppression of the stray electrons from the CRAFT accelerator is carried out via a series of design and simulation works. The paper focuses the influence of different magnetic field configurations on the stray electrons and the character of the ejecting electrons.
Simulations for the cesium dynamics of the RF-driven prototype ion source for CRAFT N-NBI
Yalong Yang,Yong Wu,Lizhen Liang,Jianglong Wei,Rui Zhang,Yahong Xie,Wei Liu,Chundong Hu Korean Nuclear Society 2024 Nuclear Engineering and Technology Vol.56 No.4
To realize an initial objective of the negative ion-based neutral beam injection (N-NBI) at the Comprehensive Research Facility for Fusion Technology (CRAFT) test facility, which targets an H<sup>0</sup> beam power of 2 MW at an energy of 200-400 keV and a pulse duration of 100 s, it is crucial to study the cesium dynamics of the negative ion source. Here a numerical simulation program CSFC3D is developed and applied to simulate the distribution and time dynamics of cesium during short pulses. The calculations show that most of the cesium on the plasma grid (PG) area originates from the release of cesium that is accumulated within the ion source in the plasma phase. Increasing the wall temperature reduces the loss of cesium on the wall of the ion source. Furthermore, the thickness of the cesium monolayer is directly influenced by the PG temperature. Both simulated and experimental results demonstrate that maintaining the PG temperature between 180 ℃ and 200 ℃ is essential for enhancing the performance of the ion source and optimizing the cesium behavior.
Yongjian Xu,Yuwen Yang,Jianglong Wei,Ling Yu,Wen Deng,Rixin Wang,Yuming Gu,Chundong Hu,Yahong Xie Korean Nuclear Society 2024 Nuclear Engineering and Technology Vol.56 No.2
As an effective methods of plasma heating, neutral beam injection (NBI) systems based on negative hydrogen ion sources will be utilized in future magnetic-confinement nuclear fusion experiments. Because of the collisions between the fast negative ions and the neutral background gas, the positive ions are inevitable created in the acceleration region in the negative NBI system. These positive ions are accelerated back into the ion source and become high energy backstreaming ions. In order to explore the characters of backstreaming ions, the track and power deposition of backstreaming H<sup>+</sup> beam is estimated using the experimental and simulation methods at NNBI test facility. Results show that the flux of backstreaming positive ions is 1.93 % of that of negative ion extraction from ion source, and the magnet filed in the beam source has an effect on the backstreaming positive ions propagation.