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Plasma Sci. Technol.  
  Plasma Sci. Technol.--2015, 17 (3)   Published: 14 February 2015
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Basic Plasma Phenomena

Nonplanar Shock Excitations in a Four Component Degenerate Quantum Plasma: the Effects of Various Charge States of Heavy Ions

Plasma Sci. Technol. 2015, 17 (3): 177-182 ;  doi: 10.1088/1009-0630/17/3/01
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A theoretical study on the nonlinear propagation of nonplanar (cylindrical and spherical) electrostatic modified ion-acoustic (mIA) shock structures has been carried out in an unmagnetized, collisionless four component degenerate plasma system (containing degenerate elec- tron fluids, inertial positively as well as negatively charged light ions, and positively charged static heavy ions). This investigation is valid for both non-relativistic and ultra-relativistic limits. The modified Burgers (mB) equation has been derived by employing the reductive perturbation method, and used to numerically analyze the basic features of shock structures. It has been found that the effects of degenerate pressure and number density of electron and inertial positively as well as negatively charged light ion fluids, and various charging state of positively charged static heavy ions significantly modify the basic features of mIA shock structures. The implications of our results to dense plasmas in astrophysical compact objects (e.g., non-rotating white dwarfs, neutron stars, etc.) are briefly discussed.

Magnetically Confined Plasma

Impurity Emission Behavior in the Soft X-Ray and Extreme Ultraviolet Range on EAST

SHEN Yongcai (沈永才) 1,2,LYU Bo (吕波) 1,DU Xuewei (杜学维) 3,et al.
Plasma Sci. Technol. 2015, 17 (3): 183-187 ;  doi: 10.1088/1009-0630/17/3/02
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Spectroscopy in the soft X-ray and extreme ultraviolet (XEUV) region is very im- portant in magnetic fusion research. Recently, two flat-field spectrometers that utilize a varied line spacing grating to image the spectra of 1-13 nm and 5-50 nm were installed on EAST for core impurity emission monitoring and impurity transport study. The instruments were proven to be capable of observing spectral lines from low-Z impurities (Li, C, O, N, Ar, etc.) and highly ionized medium- and high-Z impurities (Fe, Cr, Ni, Cu, Mo, etc.). For example, spectra in the wavelength intervals of 1-2 nm and 5-13 nm contained strong metal lines, especially molybdenum lines during H-mode phases. Argon and nitrogen lines were also observed, which were injected for diagnostic purposes. Impurity lines were identified and compared to measurements on other magnetic fusion research devices. Detailed measurements of radial emission profiles from various impurity line emissions were also presented.

Results of ICRF Heating Experiments from the EAST 2010 Campaign

HE Zhongxin (何钟鑫), ZHANG Xinjun (张新军), ZHAO Yanping (赵燕平), et al.
Plasma Sci. Technol. 2015, 17 (3): 188-190 ;  doi: 10.1088/1009-0630/17/3/03
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Radio frequency (RF) plasma heating in ion cyclotron range of frequencies (ICRF) was successfully performed on the Experimental Advanced Superconducting Tokamak (EAST). This is mainly because lithium wall conditioning was routinely used to reduce both impurity and hydrogen (H) recycling and to improve the ICRF power absorption. Mainly ICRF heating of the H minority regime at 27 MHz has been applied in deuterium plasmas. The ion cyclotron resonance heating (ICRH) is found to depend strongly on plasma preheating. The ICRH efficiency can be much improved in conjunction with the lower hybrid wave (LHW). Effective ion and electron heating was observed with the H minority heating mode. The increase of the stored energy reached 30 kJ in L-mode plasma by using the ICRF power of 1.0 MW alone when the H cyclotron resonance layer was at plasma center.

Low Temperature Plasma

Study of the Characteristics of DC and ICP Hybrid Discharge Plasmas

WANG Zhan (王战) 1,GAO Wei (高巍) 1,ZHANG Peng (张彭) 1,et al.
Plasma Sci. Technol. 2015, 17 (3): 191-195 ;  doi: 10.1088/1009-0630/17/3/04
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In this paper, the double-discharge plasma generated by radio frequency (RF) and direct current (DC) has been investigated. In comparison with their single-frequency counterpart, the interaction between the two excitations is significant and beneficial. The results show that the RF discharge can effectively increase the DC discharge current and decrease the DC voltage; meanwhile the DC discharge is favorable to feed abundant high energy seed electrons to the ICP discharge sustaining at 13.56 MHz for the latter to acquire higher plasma density and lower plasma potential by increasing the ionization rate. The innovative design has been demonstrated to facilitate more homogeneous performance with higher plasma density.

Prediction of Equivalent Electrical Parameters of Dielectric Barrier Discharge Load Using a Neural Network

GUO Tangtang (郭瑭瑭) 1,LIU Xingliang (刘星亮) 1,HAO Shiqiang (郝世强) 1,et al.
Plasma Sci. Technol. 2015, 17 (3): 196-201 ;  doi: 52.80.?s
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A reliable, efficient and economical power supply for dielectric barrier discharge (DBD) is essential for its industrial applications. However, the equivalent load parameters compli- cate the design of power supply as they are variable and varied nonlinearly in response to varied voltage and power. In this paper the equivalent electrical parameters of DBD are predicted using a neural network, which is beneficial for the design of power supply and helps to investigate how the electrical parameters influence the equivalent load parameters. The electrical parameters includ- ing voltage and power are determined to be the inputs of the neural network model, as these two parameters greatly influence the discharge type and the equivalent DBD load parameters which are the outputs of the model. The voltage and power are decoupled with pulse density modula- tion (PDM) and hence the impact of the two electrical parameters is discussed individually. The neural network model is trained with the back-propagation (BP) algorithm. The obtained neural network model is evaluated by the relative error, and the prediction has a good agreement with the practical values obtained in experiments.

Characteristics of Low Power CH 4 /Air Atmospheric Pressure Plasma Jet

ZHANG Jun (张军), XIAO Dezhi (肖德志), FANG Shidong (方世东), et al.
Plasma Sci. Technol. 2015, 17 (3): 202-208 ;  doi: 10.1088/1009-0630/17/3/06
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A low power atmospheric pressure plasma jet driven by a 24 kHz AC power source and operated with a CH 4 /air gas mixture has been investigated by optical emission spectrometer. The plasma parameters including the electron excitation temperature, vibrational temperature and rotational temperature of the plasma jet at different discharge powers are diagnosed based on the assumption that the kinetic energy of the species obeys the Boltzmann distribution. The electron density at different power is also investigated by H β Stark broadening. The results show that the plasma source works under non-equilibrium conditions. It is also found that the vibrational temperature and rotational temperature increase with discharge power, whereas the electron excitation temperature seems to have a downward trend. The electron density increases from 0.8×10 21 m −3 to 1.1×10 21 m −3 when the discharge power increases from 53 W to 94 W.

Plasma Technology

Degradation of Acid Orange 7 in an Atmospheric-Pressure Plasma–Solution System (Gliding Discharge)

NI Mingjiang (倪明江), YANG Huan (杨欢), CHEN Tong (陈彤), et al.
Plasma Sci. Technol. 2015, 17 (3): 209-215 ;  doi: 10.1088/1009-0630/17/3/07
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In this work, a plasma-solution system was applied to the degradation of Acid Orange 7 (AO7). The effects of initial concentration and type of feed gases (air, oxygen, nitrogen or argon) were studied. As the initial concentration increased from 100 mg/L to 160 mg/L, the discolouration rate of AO7 decreased from 99.3% to 95.9%, whereas the COD removal rate decreased from 37.9% to 22.6%. Air provided the best discolouration and COD removal rates (99.3% and 37.9%, respectively). In the presence of a zero-valent iron (ZVI) catalyst, the AO7 COD removal rate increased to 76.4%. The degradation products were analysed by a GC-MS, revealing that the degradation of the dye molecule was initiated through the cleavage of the −N=N− bond before finally being converted to organic acids.

Effect of Argon Addition on Morphology and Structure of Diamond Films (from Microcrystalline to Nanocrystalline)

LV Lin (吕琳) 1,WANG Jianhua (汪建华) 1,2,WENG Jun (翁俊) 1,2,et al.
Plasma Sci. Technol. 2015, 17 (3): 216-220 ;  doi: 10.1088/1009-0630/17/3/08
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Micro-/nanocrystalline diamond films deposited in Ar/H 2 /CH 4 microwave plasmas have been studied, with argon flow rates in the range of 70-100 sccm. The effects of argon addition on morphology, surface roughness, quality and structure were investigated by scanning electron microscopy, surface profiler, Raman spectrometer and X-ray diffraction (XRD). It is demonstrated that when the argon flow rate is 70 sccm or 75 sccm, well-faceted polycrystalline diamond films can be grown at a low substrate temperature less than 610 o C. With the increase in the argon flow rate, the smooth crystallographic planes disappear gradually. Instead, rough crystallographic planes made up of small aggregates begin to take shape, resulting from the increase in the secondary nucleation rate. Nanocrystalline diamond films were obtained at a flow rate of 100 sccm, and all of the prepared diamond films were smooth, with a surface roughness (Ra) less than 20 nm. Raman analyses reveal that the amount of amorphous carbon increases significantly with the increase in argon flow. The results of XRD show that crystalline size and preferential orientation of diamond films depend on the argon content in the plasmas.

Low Friction-Coefficient TiBCN Nanocomposite Coatings Prepared by Cathode Arc Plasma Deposition

LIN Baozhu (林宝珠) 1,WANG Lingling (王玲玲) 1,WAN Qiang (万强) 2,et al.
Plasma Sci. Technol. 2015, 17 (3): 221-227 ;  doi: 10.1088/1009-0630/17/3/09
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TiBCN nanocomposite coatings were deposited on cemented carbide and Si (100) by a cathode arc plasma system, in which TiB 2 cathodes were used in mixture gases of N 2 and C 2 H 2 . X-ray diffraction shows that TiB 2 and Ti 2 B 5 peaks enhance at low flow rates of C 2 H 2 , but they shrink when the flow rate is over 200 sccm. An increase of deposition rate was obtained from different TiBCN thicknesses for the same deposition time measured by scanning electron mi- croscopy. Atomic force microscopy shows that the surface roughnesses are ∼10 nm and ∼20 nm at C 2 H 2 flow rates of 0-100 sccm and of 150-300 sccm, respectively. High resolution transmis- sion electron microscopy and X-ray photoelectron spectroscopy show that the coatings consist of nanocrystal phases Ti 2 B 5 , TiB 2 and TiN, and amorphous phase carbon and BN. The average crystal sizes embedded in the amorphous matrices are 200 nm and 10 nm at C 2 H 2 flow rates of 200 sccm and 300 sccm, respectively. In Raman spectra, the D- and G-bands increase with C 2 H 2 flows at low flow rates, but weaken at high flow rates. The microhardness of the coatings decreases from 28.6 GPa to 20 GPa as the C 2 H 2 increases from 0 sccm to 300 sccm, and the ball-on-disk measurement shows a dramatic decrease of the friction coefficient from 0.84 to 0.13. The reason for the reduced hardness and friction coefficient with the change of C 2 H 2 flow rates is discussed.

Degradation of Aniline Wastewater Using Dielectric Barrier Discharges at Atmospheric Pressure

WU Haixia (武海霞) 1,FANG Zhi (方志) 2,XU Yanhua (徐炎华) 1
Plasma Sci. Technol. 2015, 17 (3): 228-234 ;  doi: 10.1088/1009-0630/17/3/10
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Aniline is a toxic water pollutant detected in drinking water and surface water, and this chemical is harmful to both human and aquatic life. A dielectric barrier discharge (DBD) reactor was designed in this study to investigate the treatment of aniline in aqueous solution. Discharge characteristics were assessed by measuring voltage and current waveforms, capturing light emission images, and obtaining optical emission spectra. The effects of several parameters were analyzed, including treatment distance, discharge power, DBD treatment time, initial pH of aniline solutions, and addition of sodium carbonate and hydrogen peroxide to the treatment. Aniline degradation increased with increasing discharge power. Under the same conditions, higher degradation was obtained at a treatment distance of 0 mm than at other treatment distances. At a discharge power of 21.5 W, 84.32% of aniline was removed after 10 min of DBD treatment. Initial pH significantly influenced aniline degradation. Adding a certain dosage of sodium carbonate and hydrogen peroxide to the wastewater can accelerate the degradation rate of aniline. Possible degradation pathways of aniline by DBD plasmas were proposed based on the analytical data of GC/MS and TOC.

Fusion Engineering

Numerical Simulation of Azimuthal Uniformity of Injection Currents in Single-Point-Feed Induction Voltage Adders

WEI Hao (魏浩) 1,2,SUN Fengju (孙凤举) 2,YIN Jiahui (尹佳辉) 1,2,et al.
Plasma Sci. Technol. 2015, 17 (3): 235-240 ;  doi: 10.1088/1009-0630/17/3/11
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In order to investigate the injection current uniformity around the induction cell bores, two fully electromagnetic (EM) models are respectively established for a single-stage induc- tion cell and an induction voltage adder (IVA) with three cells stacked in series, without considering electron emission. By means of these two models, some factors affecting the injection current uni- formity are simulated and analyzed, such as the impedances of adders and loads, cell locations, and feed timing of parallel driving pulses. Simulation results indicate that higher impedances of adder and loads are slightly beneficial to improve injection current uniformity. As the impedances of adder and loads increase from 5 ? to 30 ?, the asymmetric coefficient of feed currents decreases from 10.3% to 6.6%. The current non-uniformity within the first cell is a little worse than that in other downstream cells. Simulation results also show that the feed timing would greatly affect current waveforms, and consequently cause some distortion in pulse fronts of cell output voltages. For a given driving pulse with duration time of 70-80 ns, the feed timing with a time deviation of less than 20 ns is acceptable for the three-cell IVAs, just causing the rise time of output voltages to increase about 5 ns at most and making the peak voltage decrease by 3.5%.

Verification and Optimization of Vacuum Vessel Supports Design in KTX

LUO Zhiren (罗志仁) 1,YANG Qingxi (杨庆喜) 1,SONG Yuntao (宋云涛) 1,et al.
Plasma Sci. Technol. 2015, 17 (3): 241-246 ;  doi: 10.1088/1009-0630/17/3/12
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The Vacuum Vessel (VV) system is an essential component of Keda Torus for eX- periment (KTX), and various scenarios might take place on it. The VV’s supports should be adequately strong to stand against various loads on VV, which might happen in extreme scenarios. Therefore, the design of VV supports is verified in a single extreme scenario and is subsequently optimized in this report. The numerical simulation based on Finite Element theory is performed as the major method for analysis and optimization. The electromagnetic force in previous analyses serves as the load for the mechanical analyses of supports. During the optimization, the stresses of the VV supports decrease remarkably after introducing cotters. Finally, the optimum design has been worked out. It satisfies the requirements regarding the strength and convenience in assembly.

Synchronous Output Control System of Two Megawatt Hot Cathode Bucket Ion Sources for NBI

ZHAO Yuanzhe (赵远哲), WU Deyun (吴德云), HU Chundong (胡纯栋), et al.
Plasma Sci. Technol. 2015, 17 (3): 247-250 ;  doi: 10.1088/1009-0630/17/3/13
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Show Abstract ( 249 )

Synchronous output of one beam line’s two megawatt hot cathode bucket ion sources is required when Neutral Beam Injector (NBI) works on the Experimental Advanced Superconducting Tokamak (EAST). Neutral Beam Injector Control System (NBICS) realizes synchronous output and asynchronous output of two ion sources with network communication and hardware triggers. And the synchronous time can be set by operator. In synchronous mode, two megawatt hot cathode bucket ion sources can produce neutral beams at any relative time with higher energy than two sources’ asynchronous output. Two megawatt hot cathode bucket ion sources’ synchronous output makes an important contribution to NBI system of 4-8 MW with 10-100 s pulse length and provides more and better parameters for EAST physical experiments.

ITER Magnet Feeder: Design, Manufacturing and Integration

CHEN Yonghua (陈永华)1,2, Y. ILIN2, M. SU2, C. NICHOLAS2, P. BAUER2, et al.
Plasma Sci. Technol. 2015, 17 (3): 251-258 ;  doi: 10.1088/1009-0630/17/3/14
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Show Abstract ( 225 )

The International Thermonuclear Experimental Reactor (ITER) feeder procurement is now well underway. The feeder design has been improved by the feeder teams at the ITER Organization (IO) and the Institute of Plasma Physics, Chinese Academy of Sciences (ASIPP) in the last 2 years along with analyses and qualification activities. The feeder design is being progressively finalized. In addition, the preparation of qualification and manufacturing are well scheduled at ASIPP. This paper mainly presents the design, the overview of manufacturing and the status of integration on the ITER magnet feeders.

Preliminary Process Design of ITER ELM Coil Bracket Brazing

LI Xiangbin (李向宾) 1,2,SHI Yi (施毅) 1
Plasma Sci. Technol. 2015, 17 (3): 259-264 ;  doi: 10.1088/1009-0630/17/3/15
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With the technical requirement of the International Thermonuclear Experimental Reactor (ITER) project, the manufacture and assembly technology of the mid Edge Localized Modes (ELM) coil was developed by the Institute of Plasma Physics, Chinese Academy of Science (ASIPP). As the gap between the bracket and the Stainless Steel jacketed and Mineral Insulated Conductor (SSMIC) can be larger than 0.5 mm instead of 0.01 mm to 0.1 mm as in normal indus- trial cases, the process of mid ELM coil bracket brazing to the SSMICT becomes quiet challenging, from a technical viewpoint. This paper described the preliminary design of ELM coil bracket braz- ing to the SSMIC process, the optimal bracket brazing curve and the thermal simulation of the bracket furnace brazing method developed by ANSYS. BAg-6 foil (Bag50Cu34Zn16) plus BAg-1a paste (Bag45CuZnCd) solders were chosen as the brazing filler. By testing an SSMICT prototype, it is shown that the average gap between the bracket and the SSMIC could be controlled to 0.2- 0.3 mm, and that there were few voids in the brazing surface. The results also verified that the preliminary design had a favorable heat conducting performance in the bracket.

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