Nuclear Fusion and Plasma Physics

Simulation and analysis of lower hybrid current drive on EAST tokamak

LI Miao-hui, DING Bo-jiang, KONG Er-hua, ZHANG Lei, SHAN Jia-fang, LIU Fu-kun, WANG Mao, XU Chan-dong

2011, 31(4): 289-296.

Asbtract ( )

PDF (3748KB) ( )

References | Related Articles | Metrics

The calculation processes and consideration on the physical regime of C3PO, a ray-tracing code, and LUKE, a fast numerical solver for the 3-D Fokker-Planck equation, are presented. Bounce average is used and the relativistic and particle-trapped effects are taken into account in the codes. The simulation and analysis of plasma current influence on rays propagation and current drive (CD) efficiency in EAST divertor configuration have been carried out using these codes. The numerical results indicate that, with the increase of plasma current, the rotation of the poloidal rays trajectory becomes faster, the power deposition profile shifts on axis, and the CD efficiency becomes higher. In addition, it is discovered that the trajectory provided high N||-upshift when the ray propagated towards the edge density cut-off at the top of the chamber and then bounced back towards the plasma centre. When the effect of radial diffusion of fast electrons is considered, the shape of driven current becomes broad, but CD efficiency decreases due to the radial loss and collisional loss of electrons moving to the region where collision is serious. While the diffusion coefficient is assumed to be 1.5m²•s^-1, the modeling result of driven current approaches to the experimental value.

Studies on calibration method and FFT analysis in power measurement of pulse-modulated RF signal

HUO Wei-gang, SU Cheng, SUN Bin, DING Zhen-feng

2011, 31(4): 297-304.

Asbtract ( )

PDF (1877KB) ( )

References | Related Articles | Metrics

The capability of a commercial-available voltage/current probe, intended to monitor steady or slowly-varying RF signals, is improved to measure pulse-modulated RF signals. The improvement is realized by means of combination of voltage/current probe sensor and a digital oscilloscope. The outputs of voltage/current probes are acquired with the digital oscilloscope, and their amplitudes and phase difference are obtained with FFT. Under different frequencies, current/voltage amplitude and phase difference are calibrated in order to calculate RF power. The phase difference between voltage and current is the key factor influencing calibration coefficients. Results show the calibrated current/voltage probe can provide reliable and repetitive measurements. FFT method is problematic in analyzing nonstationary amplitude-modulated voltage and current signals, and the pulsed RF power can be only reliably calculated at time when reactive power is zero.

Application of break-in-slope method in calculating HL-2A ECRH power deposition

LI En-ping, FENG Zhen, LIU Chun-hua, YAO Ke, NIE Lin, HUANG Yuan

2011, 31(4): 305-309.

Asbtract ( )

PDF (1471KB) ( )

References | Related Articles | Metrics

The basic theory of break-in-slope method in calculating the profile of auxiliary heating power deposition is presented. Using this method, the profile of ECRH power deposition is carried out by analyzing electron temperature and density at the time of ECRH injection on HL-2A for the first time. The applicability of this method is proved.

Numerical simulation of subcooled flow boiling and application to the EAST plasma facing components

KANG Qing-lan1, SONG Yun-tao1, HUANG Sheng-hong2, WANG Zhong-wei1, JI Xiang1

2011, 31(4): 310-314.

Asbtract ( )

PDF (1304KB) ( )

References | Related Articles | Metrics

Numerical simulation approaches to subcooled boiling and their application to EAST plasma facing components (PFC) was described. A two-fluid model implemented with a wall boiling model based on a wall heat flux partition algorithm was used to solve control equations for mass, momentum and energy, which coupled with additional closure relations describing the exchange of two phases at the interface. A user-defined function (UDF) was written to define the source terms of phase exchange and specify the customized parameters of the multiphase. And the physical model was verified by experimental data of Lee et al. Also the simulation of the EAST plasma facing components was done with subcooled flow boiling method for EAST PFCs cooling structure optimization.

Influence on electron movement in laser-plasma produced by multi-photon nonlinear Compton scattering

HAO Xiao-fei, SUN Fu-zhao, HAO Dong-shan

2011, 31(4): 315-319.

Asbtract ( )

PDF (614KB) ( )

References | Related Articles | Metrics

Using the model of multi-photon nonlinear Compton scattering，the influences on the electron movement in the plasma produced by the multi-photon nonlinear Compton scattering are studied，a new mechanism of the acceleration electrons in a mixed field produced by the coupling optical formed by the incident laser and scattered optical and the self-magnetic field formed by the action of the coupling optical and the plasma has been given out，and the momentum and energy equations of electrons are revised and simulated. The results show that when the amplitude of the electric field of the mixed field and its magnetic field amplitude is equal，the circle round resonance electron can be accelerated to very high energy in the action times of the circle round resonance electron and the mixed field. The electron accelerated energy is increased along with the increasing of the coupling optical peak value，the cycles of the energy change are decreased along with the increase of the coupling initial angle of the electron，and the accelerated energy is faster increased at the initial stage，then slowly increased，finally hastened stability state along with the increase of the coupling initial transverse speed of the electron.

Comparison between capacitively coupled VHF and high frequency discharge in H₂

YAO Fu-bao, HAO Ying-ying, ZHANG Lian-zhu, ZHAO Hai-tao

2011, 31(4): 320-326.

Asbtract ( )

PDF (1578KB) ( )

References | Related Articles | Metrics

This paper presents PIC/MC model of capacitively coupled very-high-frequency discharge in hydrogen. We take into account 21 kinds of collisions of charged particles (e, H⁺,H₂⁺, H₃⁺) with H₂, have simulated the electric field distribution, potential distribution, density and mean energy distribution of electrons and hydrogen ions ( H⁺, H₂⁺, H₃⁺), and have compared with those of the frequency of 13.56MHz. The simulation results show that the plasma space potential is enhanced with the increase of driving frequency, which results in the increase of electric field near the two electrodes. Besides, rf sheath thickness becomes thin and the mean energy of electron and H₃⁺ is decreased, while their total density is increased with the increase of frequency. H₃⁺ is the dominant ion in the H₂ very-high-frequency discharge, its density being two or three orders of magnitude higher than that of H₂⁺.

Study on mean ionization state for tungsten plasma

HUANG Hua, JIANG Ming, MA Bo, WU Shuang, YANG Zhi-jian, GOU Fu-jun

2011, 31(4): 327-332.

Asbtract ( )

PDF (659KB) ( )

References | Related Articles | Metrics

Under the local thermodynamics equilibrium condition, the mean ionization state about tungsten plasma is calculated by SHML model with temperatures in the range of 0.3keV to 10keV and density in the range of 0.001g•cm^-3 to 0.1g•cm^-3. It is studied that the mean ionization state for tungsten plasma is related to temperature and density. The results show that Wu ionization is reducing as the increase of density, but increasing as the rise of temperature. And the mean ionization state for tungsten plasmas appears three steps in graph as the rise of temperature. This article researches the relationship between ionization state and ionization potential, and explains why steps appear.

Design of feedback control system for HL-2M tokamak

ZHANG Guo-hui, XIA Fan, SONG Xian-ming, LUO Cui-wen, SONG Xiao, ZHAO Li, LIAO Min

2011, 31(4): 332-338.

Asbtract ( )

PDF (4620KB) ( )

References | Related Articles | Metrics

The conceptual design of HL-2M control system is simply presented, and the feedback control system which is the most important part of the whole control system is mainly introduced，feedback control program is rewrited. In order to satisfy the further requirements from control system in HL-2M, the feedback control system program has been redesigned. Some improvement of methods on how to achieve partial functions has been done. The real-time communication network will be builded based on reflection memory cards, and the structure of feedback control system is constructed through the real-time network. In the Linux operating system, simulation tests have been made on new feedback control system with old experiment data, the result of tests shows well and meets the expected requirements.

R&D for discharge management platform of HL-2M tokamak

SONG Xiao, XIA Fan, SONG Xian-ming, ZHANG Guo-hui, PAN Yu-dong, PAN Li

2011, 31(4): 339-343.

Asbtract ( )

PDF (1294KB) ( )

References | Related Articles | Metrics

Main function of discharge management platform for HL-2M tokamak is to provide a platform for operator to run timing system, PLC logic protect system and plasma feedback control system. During discharge interval, the operator uses it to preset the control parameters and waveforms for the next shot, to configure the operation parameters for all subsystems, The communication way based on reflective memory (RFM) is responsible for transmitting the control parameters and waveforms to all subsystems effectively and reliably. The results of commissioning between our platform and other subsystem shows that its design is reasonable, and its operation is reliable.

Activation calculation analysis for the China 2×6 solid breeder test blanket module

HAN Jing-ru, CHEN Yi-xue, ZHANG Guo-shu, CAO Qi-xiang

2011, 31(4): 344-349.

Asbtract ( )

PDF (1538KB) ( )

References | Related Articles | Metrics

Based on the new design of China 2×6 helium cooled solid breeder (CH-HCSB) test blanket module (TBM), three-dimensional activation calculation analysis was performed by using the Monte Carlo particle transport code MCNP and European activation code FISPACT. The results show that, at the beginning moment after shutdown, the total activity is 1.78×10¹⁶Bq, and the total afterheat is 3.01kW. They are both dominated by the structural material CLF-1. Meanwhile, the dominant radioactivity nuclides and reaction pathways have been identified. The results will provide useful indications for materials selection and further optimization design of the TBM. On basis of the calculated contact dose rate, the activated materials can be reused with the remote handling recycling options. That is effective for preventing from the radiation environmental hazard.

Structural design and analysis of in wall shielding for ITER

SHAO Zhu-zhen, WANG Chuan-li, SONG Yun-tao

2011, 31(4): 350-355.

Asbtract ( )

PDF (5067KB) ( )

References | Related Articles | Metrics

In order to shield the neutron current and reduce the ripple during the ITER fusion reaction process, the in-wall shielding structures have been inserted between the two shells of the ITER vacuum vessel, and the safety of the reaction could be ensured. The conceptual design, the design guideline, the detail design and the assembly scheme for the in-wall shielding have been introduced. Choosing one shielding block which formed the in-wall shielding structure as the research object, its heat-structure coupling analysis has been fulfilled, and component response stress is less than the allowable stress，and the rationality of its structural design has been validated.

Introduction of ITER TBM first wall fabrication methods and mockup fabrication

YE Xing-fu, FENG Kai-ming, LUO Tian-yong, ZHANG Guo-shu

2011, 31(4): 356-359.

Asbtract ( )

PDF (4808KB) ( )

References | Related Articles | Metrics

Four methods of TBM FW fabrication are introduced. A 304 stainless steel FW mockup was fabricated with Machining-EBW-Bending method. The fabricated FW mockup was cut along one of square channels and measured. The minimum area of the channel at the bending place was 85% of original. The thickness of the wall on the outside of the channel at the bending place was apparently reduced, but could be controlled by machining. To demonstrate the availability of this processing technique, the RAFM which actually used on FW should be used in future work.

Influence research on energy deposition in TFC of CN HCCB TBM for ITER

ZHAO Feng-chao, LI Zai-xin, ZHANG Guo-shu, FENG Kai-ming, CAO Qi-xiang

2011, 31(4): 360-364.

Asbtract ( )

PDF (4771KB) ( )

References | Related Articles | Metrics

Based on Alite model of ITER and CN HCCB TBM, research of influence on the energy deposition of TFC caused by CN HCCB TBM is carried out. The calculation is carried out by MCNP code, and a mesh-based weight window is used to reduce variance. The analysis indicates that installing CN HCCB TBM could reduce the energy deposition in TFC by 3%; most of the energy deposition is local in the 1-14 sectors of inner-side; the power density peak is located in the ninth sector and the required limits satisfied.

Langmuir probe and emission spectroscopy diagnosis of low pressure hydrogen plasma induced by helicon-wave

GAO Ying-xue, WU Wei-dong, DAI Yang, JIANG Fan

2011, 31(4): 365-371.

Asbtract ( )

PDF (2473KB) ( )

References | Related Articles | Metrics

The characteristics of helicon-wave hydrogen low pressure plasma were investigated by Langmuir probe and emission spectroscopy. The variation law of electron energy probability function (EEPF), effective electron temperature (T_eff), electron density (n_e) and hydrogen atom excited state density (n_H^*) were analyzed in relation of different experimental parameters by Druyvesteyn method and corona model. The results demonstrate that the peaks of higher energy of EEPF curves move toward lower energy with the increase of RF power, pressure and controlled magnetic field, T_effdecreases. The n_e increases and jumps with the increase of RF power from 25W to 35W, and the n_H^* increases linearly with the rise of RF power; the n_e and n_H^* increases firstly and then decrease with the rise of pressure; with the rise of controlled magnetic field, the n_e increase linearly and the n_H^* increases firstly and then decreases.

Preparation and researching progress of iron nanoparticle by plasma

YANG Li-mei, WANG Da-wang, ZHANG Yu-tao, MA Teng-cai

2011, 31(4): 372-378.

Asbtract ( )

PDF (4930KB) ( )

References | Related Articles | Metrics

Preparation of iron nanoparticle process with plasma technology is presented. Comparing with pyrolysis method and arc method to prepare iron nanoparticle, the new plasma method is efficient, clean, suitable for industrial production.

Nuclear Fusion and Plasma Physics Vol.31 (2011)

2011, 31(4): 379-384.

Asbtract ( )

PDF (216KB) ( )

Table of Content