Table of Content

15 June 2008, Volume 28 Issue 2

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Plasma Physics

Observations of SMBI penetration depth in the HL-2A tokamak with divertor configuration

FENG Bei-bin, YAO Liang-hua, LI Wei, CHEN Cheng-yuan, FENG Zhen

2008, 28(2):  97-100. 

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The penetration depth of supersonic molecule beam injection (SMBI) is observed by using a set of detector array, which is composed of 22-channel H_α detectors, in the HL-2A tokamak with divertor configuration. The results show that there are two H_α emission peaks in the radial direction when the gas backing pressure is more than 1MPa, the second peak is localized at r/a~0.8, which indicates that there are still some hydrogen particles penetrating into the separatrix over 5cm even though more particles are dissociated or ionized at the edge plasma (SOL) region.

Simplified analysis of the MHD instability in Z-pinch plasmas

DING Ning, ZHANG Yang, LIU Quan

2008, 28(2):  101-104. 

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Based on the theoretical model of Haines, the whole development procedure of MRT instability in the metal wire array Z-pinch implosion is divided into four phases. Using ZP-0D program, the effects of load parameters and the driving conditions on the MRT instability are researched. Calculation results suggest that the wire number increase could significantly improve the Z-pinch plasma stability, which benefits the increase of plasma temperature and mass density when it comes to the stagnation, and benefits the X-ray yield as well.

Study on sawtooth activities of HT-7 tokamak using soft X-ray diagnostic

DUAN Yan-min, CHEN Kai-yun, HU Li-qun

2008, 28(2):  105-110. 

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Several arrays of soft X-ray diagnostic are developed on the HT-7 tokamak and used to study the sawtooth oscillations. The occurrence and characteristics of the sawtooth are related closely with the discharge conditions such as electron density N_e, electron temperature T_e, safety factor qα on the plasma edge, as well as the wall condition, etc. In lower hybrid current drive (LHCD) plasmas, an m/n=1/1 mid-mode oscillation can be observed, which appears during sawtooth ramps, rapidly-develops, saturates, damps and disappears before the sawtooth collapse. The sawtooth behaviors in ohmically heated plasma and LHCD plasma are discussed and summarized.

Ablation effect to solid irradiated by high power laser-plasma punched wave under Compton scattering

HAO Xiao-fei, HAO Dong-shan

2008, 28(2):  111-114. 

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Using the multi-photon nonlinear Compton theory, the ablation effects to the solid irradiated by the high power laser-plasma punched wave under Compton scattering was studied, the formulas for the power density of the high power laser-plasma punched wave and the melted temperature of the ablation target material, boiling temperature and heating time were derived, and the optimum experimentation conditions for the target material ablation hole irradiated by the high power laser-plasma punched wave were obtained. The results show that the heat generation index of the solid has improved, temperature distribution is changed, and the needing time and power for the effort point reaching the temperatures of the melting and boiling decrease than that before the scattering. When the energy of the laser-plasma punched wave is 250J and the distance between the punched wave and target material surface is 70~80mm, the effect of the ablation hole of the punched wave to the target material surface is better. When the time is in 1.2~3.6ms and the distance between the punched wave and target material surface is 28~80mm, the ablation effect is better. When the energy density is in 400~2800J•cm^-2, the ablation depth almost increase bad linearly, and the dimension of the ablation speck is inversed ratio along with the power density.

Role of ions (N₂⁺, N⁺) in the optical emission in nitrogen glow discharge plasma

ZHANG Lian-zhu, MENG Xiu-lan

2008, 28(2):  115-120. 

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 Intensity distribution of optical emission caused by collisions between ions (N₂⁺, N⁺) and nitrogen neutral ground-state molecular and the role of ions (N₂⁺, N⁺)in the optical emission of nitrogen glow discharge plasma are

investigated by a combined Monte Carlo model with electrons and the heavy particles. The various impact excitations

and optical emissions produced by ions (N₂⁺, N⁺) distribute in the cathode dark space and the light intensities

gradually increase towards the cathode, and total intensities increase with the discharge voltage. Relative to impact

excitations and emissions caused by electron, a secondary intensity maximum near the cathode is produced by the

collisions between ions (N₂⁺, N⁺) and molecule N₂, and the effect of atomic ions N⁺ on the impact emission can be

stronger than the molecular ions. When the voltage is rather low, the emission caused by the ions collisions can be

disregarded. The simulating results offer a good explanation for the experimental data of optical emission

spectroscopy under two typical kinds of N₂ glow discharge and provide reference evidences for spectroscope data

analysis in plasma diagnosis.

Molecular dynamic simulation of the interaction between C₆₀ clusters and plasmas

WANG Gui-qiu

2008, 28(2):  121-124. 

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The interaction between C₆₀ clusters and dense plasmas has been studied using the molecular dynamic simulation (MDS). In the framework of linearized Vlasov-Poisson theory, the analytical expression of stopping power of the cluster is obtained with the classic plasma dielectric function. The Coulomb explosions of the cluster are studied by solving the motion equations. The effect of projectile velocity, plasma density and electron temperature on stopping power and Coulomb explosion of the cluster are discussed, respectively. The results show that the wake effects can reduce the speed of Coulomb explosions, and even stabilize the cluster structure, the Coulomb explosion will proceed faster in the situations of high velocity, low plasma density or high plasma temperature.

The spectra of strong Langmuir turbulence in a laser-plasma

LIU Xiao-lan, LIU San-qiu, YANG Xiao-song

2008, 28(2):  125-128. 

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The spectra of strong Langmuir turbulence (SLT) are numerically obtained by calculating the complete Zakharov equations near the critical surface in a laser-plasma. The obtained figures show that Langmuir wave collapse is the main mechanism of energy transfer along the SLT spectra from the small-k region to the large-k region, and the Langmuir wave appears to be filament during the SLT collapse. Fitting the average energy density of Langmuir wave, the energy density function of Langmuir spectrum is obtained.

Theoretical calculation of average ionization stage of Sn plasma by SHML model

YAN An-ying1, JIANG Ming1, QI Zuo-tao2, BAO Xing-ming3

2008, 28(2):  129-131. 

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The screened hydrogen-ion model with l splitting is proposed to calculate the average ionization stage (AIS) of Sn plasma in the temperature of 100～2000eV and density of 0.001～10g•cm^-3. The relationships of AIS with density and temperature are given, and the “flat-roof” phenomenon is discussed.

On consistency of the ensemble averages of plasma turbulent fluctuation diagnostic data with the turbulent concepts

QIN Yun-wen

2008, 28(2):  132-135. 

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The basic questions in the ensemble averages of plasma micro-turbulence data are discussed. It is proposed that the ratio of the fluctuation average to its rms value be implemented to inspect its random degree if the time-average is adopted as the ensemble average. The precision of the approximation, characterizing the ensemble-average with samples-average, is determined by the relative magnitude of the total data-time length and the fluctuation correlation time. It appears that the data analysis is not always consistent with fundamental plasma turbulence concepts in some cases, and therefore the related discussion and comments are made.

Nuclear Fusion Engineering and Technology

Development of the high-voltage power supply of ECRH system on HL-2A tokamak

XUAN Wei-min, YAO Lie-ying, LI Qing, MAO Xiao-hui, SHAO Kui,CHEN Yu-hong, WANG Y

2008, 28(2):  136-141. 

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The main high voltage power supply of the ECRH system on HL-2A tokamak is described. The output voltage is managed by adopting the star-point control technique, and the fast rising and falling of the output voltage can be realized by implementing the high-voltage modulation technology based on TM-703FB modulator, by which the fast protection of this system can be performed. The output-voltage ripple in this system is less than 1% due to the feed-forward compensation and feedback control technologies, the output parameters, -60kV/(25A×4)/1s, can meet the requirements of the ECRH system on HL-2A tokamak experiments.

Finite element modal analysis of the gravity support for ITER

HOU Bing-lin, PAN Chuan-hong, LI Peng-yuan

2008, 28(2):  142-145. 

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The 3-D finite element model with 20° sector of the gravity support system is created using ANSYS, and then the modal analysis is carried out with Subspace method. The preceding 10 intrinsic frequencies and vibration patterns of the gravity support system are solved and the trait of vibration patterns is analyzed.

Optimization design and buckling analysis of the straight-line duct for ITER feeder

WANG Kai-song1, ZHAO Han1, SONG Yun-tao2, YANG Qin-xi2

2008, 28(2):  146-149. 

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Based on the stress intensity principle, the structure dimensions of the straight-line duct for the ITER feed-through have been optimized by FEM static analysis. The analyses of eigen buckling and non-linearity buckling have been done depending on the FEM stability criterion, and the critical pressure load is 1.21MPa. The structure safety under the normal operation condition (safety coefficient 12.1) or fault operation condition (safety coefficient 6.05) has been tested by our results, which are the foundation of the further engineering development.

Development of the ECRH water-cooling system in HL-2A tokamak

YANG Jia-xin, ZHANG Jin-song, YANG Ji-fang, LIU Guang-yu, TANG Fang-qun, TIAN Pei-hong

2008, 28(2):  150-153. 

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The ECRH water cooling system of HL-2A tokamak has been successfully developed，the maximum flux and

pressure of this system reach 94m³.h^-1 and 0.6MPa, respectively. The system design, the pressure control, and the

parameter measurement are briefly introduced; the water-resistance calculation under high voltage condition has been

done, and the leak electric current in the cooling water loop of the gyrotron-anode has been measured to be less than 1mA.

Magnetic field measurement for the superconducting magnet of ECRH on HL-2A tokamak

BAI Xing-yu1, HUANG Mei2, RAO Jun2

2008, 28(2):  154-157. 

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Magnetic field distribution of the ECRH superconducting magnet on HL-2A tokamak has been measured, and the results show that the normalized axial magnetic induction is not less than 0.992 in the area of 20mm around the center, the fluctuation of magnetic field is not more than 1.48% on the whole center plane, the stray field near the magnet surface is not more than 50mT; and these satisfy the experiments.

New method for measuring the high-voltage isolation parameters of HL-2A tokamak ECRH system

SI Li-peng, RAO Jun, WANG Ming-wei

2008, 28(2):  158-162. 

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A new method for measuring the high-voltage isolating parameters by using the LiNbO3 optical-intensity modulator on the HL-2A tokamak ECRH system is introduced. The measurement results indicate the isolation voltage more than 100kV, the responding time less than 0.1μs and the linearity error less than 1%. Some problems and the feasibility of the method are also discussed.

Design of CR superconducting dipole magnet in German FAIR project

ZHU Yin-feng, WU Wei-yue, WU Song-tao, XU Hou-chang, LIU Chang-le

2008, 28(2):  163-166. 

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The engineering design of CR (collector ring) superconducting magnet of German FAIR (facility for antiproton and ion research) project is introduced. 3-D model is formed by CATIA, and the magnetic filed of 1/4 magnet is analyzed with ANSYS. Then the displacement and stress of the coil case, liquid helium (LHe) case, especially, the maximal displacement and stress when quenching happens are calculated based on the analysis of magnetic field. These results are necessary for manufacturing the formal magnet.

Non-Fusion Plasma Applications

In situ measurements of OH radicals in dielectric barrier discharge plasmas with cw-cavity ring-down spectroscopy

LIU Zhong-wei, ZHAO Guo-li, WANG Jian, ZHU Ai-min, YANG Xue-feng, XU Yong

2008, 28(2):  167-171. 

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An apparatus of continuous wave cavity ring-down spectroscopy (cw-CRDS) has been constructed with the noise (RMS) equivalent absorption 3×10^-9 cm^-1. In situ quantitative measurements of •OH radicals in dielectric barrier discharge (DBD) plasmas at low pressure using cw-CRDS are described. The influence of discharge voltage and pressure on number density of OH has been investigated. Results show that the OH production increases at low pressure with increasing discharge pressure; however, the number density of OH decreases due to electron attachment of H₂O at higher pressure. The number density of OH radical increases with increasing discharge voltage and discharge frequency because of the increase of electron density and electron energy.

Impact to discharge characteristic and acceleration effect of plasma aerodynamic actuators configurations

LI Yi-wen1, LI Ying-hong1, WU Yun1, LIANG Hua1, SU Chang-bing1, LIU Li-bin2

2008, 28(2):  172-176. 

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Under normal atmosphere environment, experimental investigation on discharge characteristics and acceleration effects of plasma aerodynamic actuators with normal, semicircle and sawtooth configurations were performed. Frequency-discharge, voltage-discharge current and the boundary induced velocity were measured under different motivation parameters. The experimental results indicate that when the basic design parameters of plasma aerodynamic actuators were given, discharge voltages and discharge currents vary with the configurations but resonance frequency keeps the same, however, the induced gas flow velocities also change. It is also found that the ion streams produced by semicircle and sawtooth plasma aerodynamic actuator have very damage effects to insulation materials.

Simulation on characteristics of cylinder reactor dielectric barrier discharge

HE Tao, DING Ke, ZHANG Jing, GUO Ying

2008, 28(2):  177-181. 

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Two-dimensional simulation research on coaxial cylinder reactor dielectric barrier discharge at atmospheric pressure have been carried out using XOOPIC software. The process of micro-discharge form and evolution reappeared and the life-span of micro-discharge was about 4ns in the atmospherical argon discharge with the 20kHz and 5kV power supply. The distribution of electronics density, ion density, barrier surface charge density and electric field with the space and time were obtained. Extreme values of electron density, ion density and barrier surface charge density exist around anode on the dielectric surface. Comparing with typical flat panel DBD, electronics density and field intensity in the filamentary characteristic increase 2~3 order of magnitude.

Metre-scale atmospheric plasma modification equipment and its application to textile materials

LI Chi1, TANG Xiao-liang1, 2, 3, YAN Zhi-ren1, QIU Gao1, 2, 3

2008, 28(2):  182-186. 

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An approach of one-meter-scale surface modification equipment using dielectric barrier discharge (DBD) plasma at atmospheric pressure is presented. The relationships among the electricity parameters such as discharge voltage, discharge power and discharge frequency are analyzed by using this improved DBD equipment. The modification results of PET, PBT and wool are given; the SEM images of three materials are shown and the related hydrophilic properties are analyzed.

Optimization design and performance evaluation of non-equilibrium plasma reactor for waste water treatment

ZHANG Yan-zong, ZHENG Jing-tang, WANG Guang-chang, SANG Yu-quan, CHEN Hong-gang

2008, 28(2):  187-192. 

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The monolithic construction of the non-equilibrium plasma reactor is optimized and the performance of the reactor was estimated on the basis of orthogonal and single factor experiments. The experimental results show that the primary and secondary factor influencing degradation efficiency is the height of air layer, the height of aqueous solution and the gas flow, respectively. The best result is obtained when the needles length in water is 5mm, the electrode gap is 17mm and the gas flow is 96L•h^-1. The degradation efficiency can be improved when positive pulse was applied to the high voltage electrode and the ground electrode was made of stainless steel mesh with mesh size of 0.42mm. The design, fixed the stainless steel mesh barriers in the solution for pretreatment, increases the utilization factor of ozone. Although the degradation efficiency and COD removal are decreased with the increase of initial solution concentration, the absolute conversion amount of organic contamination increases in the same time. The repeated tests indicate that the experiment error is less than 3.5%.