Table of Content

15 March 2013, Volume 33 Issue 1

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Plasma Physics

The “tadpole” localization in radial structure of geodesic acoustic mode

ZHANG Yang-zhong1, XIE Tao2

2013, 33(1):  1-6. 

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Based on the Braginskii’s cold ion fluid model，using the quasi-toroidal coordinate system, the two partial differential equations of perturbed density and electrostatic potential describing axial-symmetric (zero toroidal mode number) sound waves have been derived. The coupled equations are then solved for the geodesic acoustic mode (GAM) by making use of the WKB method and Langer transform to obtain the uniformly valid radial mode structure over WKB turning point, and the eigen-frequencies are determined. It is found that no continuum solution for GAM is possible. The near-zero mode frequencies are identified to be associated with the “high energy” excited states in a sense of Schrödinger equation. It is also argued that the radial structure consistency with GAM ordering demands the “tadpole” localization. The implication of the “tadpole” localization to “multi-GAM co-existence” observed is experimentally discussed.

Numerical simulation of MHD duct flow about laminar and turbulence model

HOU Jun, MAO Jie, PAN Hua-chen

2013, 33(1):  7-12. 

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The numerical analysis of full-developed flow of a liquid metal in a rectangular duct of constant cross-section with a uniform transverse magnetic field was proceeded in laminar and low-Reynolds number Lam/Bremhost turbulence model (for short LB model) using FLUENT software. The paper analyzed the influence of external magnetic field for velocity distribution and MHD pressure drop in turbulence model. Under the same Hartmann number conductions, the paper compared the velocity distribution and MHD pressure drop of laminar model and turbulent model. The solution of current density was obtained by means of induced magnetic field formulation. The result of numerical simulation proved that this was a feasible scheme to use the low-Reynolds LB turbulence model to calculate MHD duct flow. Comparison between laminar model and turbulent model show that laminar model made shorter entrance length, but the pressure drop in the duct increased. Turbulent model had more average speed and smaller pressure drop, but entrance length was longer.

Innovative researches on some important problems in fusion reactor tritium system design (Ⅰ)

DENG Bai-quan

2013, 33(1):  13-18. 

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How high are the tritium retention on the first wall surface and the total tritium inventory in PFC materials of a fusion reactor？How much are the tritium well depth and tritium well time during a fusion reactor start-up and initial operation phase？How high tritium recovery efficiency can be obtained in the ITER TBM solid breeder blanket with using purge gas? Can we find some effective mechanisms to solve the above mentioned problems? All of these problems are decisive key issues on the way to achieve the ITER final anticipant goals and to attain realistic fusion energy application ultimately. In the first part of this article, the first two questions have been answered. Some innovative researches on above mentioned rest problems are performed and some new schemes for reducing tritium retention and improving tritium recovery efficiency are proposed in the second part of this article to be published next issue, such as, sponge mechanism based on deuterium saturated PFC materials; deuterium and beryllium co-deposition layer created on first wall surface; SPB scheme for enhancing isotope exchange rate and tritium recovery efficiency of purge gas in ceramic breeder blanket based on the catalyzed electrical polarization rotations, resulted from applied low frequency electric-field, of Li4SiO4 grain and purge gas molecular particles and so on，will be explored.

Influence of modulation instability induced by Langmuir turbulence in plasma

HAO Dong-shan

2013, 33(1):  19-24. 

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According to the model of multi-photon nonlinear Compton scattering, the influence of the modulation instability in the plasma induced by Langmuir turbulence under the multi-photon nonlinear Compton scattering has been studied. The revised equations for the strong Langmuir turbulence, dispersion and the time increasing rate of the modulation instability have been given out using a new mechanism of the strong Langmuir turbulence and modulation instability formed by the incident light and Compton scattered optical, and the equations are simulated. The results show that the even acute collapsing is induced by Compton scattering in the plasma, and the time increasing rate of the modulation instability near the plasma surface is markedly increased because of the strong Langmuir turbulence induced by the final collapsing, the modulation instability is even quickly developed, the even strong optical field peak is increased, and the clear thin wires of all the laser field is formed.

Influence of launcher-phase difference on power deposition and current profile of lower hybrid current drive in EAST

YANG Jie, LI Ai-xia, MA Yang-Cheng, YANG Qun, SHI Xing-jian

2013, 33(1):  25-29. 

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The effect of launcher-phase difference on power spectrum in EAST is studied by using the coupling code of MEC and LSC, and its consequent influence on power deposition and current profile of lower hybrid current drive is studied as well. It shows that with the increasing of , power deposition and current profile shift to inner layer rather than its originally shift to outer layer because the structure of power spectrum is changed. The most off-axis, the largest and the smallest driven current are respectively formed when =200°, =120°, =260°. Hence the power deposition and current profile of lower hybrid current drive can be controlled by selecting a proper launcher-phase difference.

Theoretical analysis of the induced current for vacuum vessel of EAST tokamak during a disruption

XU Wei-wei, LIU Xu-feng, SONG Yun-tao, LI Jun, ZHENG Jin-xing

2013, 33(1):  30-36. 

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The sudden disappearance of plasma current during a disruption will produce large induced current and resulting in electromagnetic forces on the vacuum vessel of tokamak. In this paper, development of the induced current on EAST after a disruption vacuum vessel is studied. Using the mutual matrix method, by simplifying the double-shell structure to several dozens of circular coils, distribution of induced current and resulting in electromagnetic force is simulated, and the variations of the induced current, magnetic field and electromagnetic forces are analysed with Fortran software codes. Results obtained can provide a theoretical basis for the future engineering design for tokamak device.

Nuclear Fusion Engineering and Technology

Analysis for the support structure of the poloidal field coils of HL-2M tokamak

CAO Cheng-zhi, LIU De-quan, LIN Tao, QIAO Tao

2013, 33(1):  37-42. 

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The static and dynamic structure analysis for the support structure of the poloidal field coils (PFCs) of HL-2M tokamak was carried out by ANSYS. The stress distribution, displacement and deformation in the typical loading cases were obtained. The results show that the support structure can meet the design requirements of the device. The results provide reference data for further optimization of the support structure.

Mechanical layout of transmission line for HL-2A ECRH system

CHEN Gang-yu, ZHOU Jun, HUANG Mei, XIA Dong-hui, RAO Jun

2013, 33(1):  43-47. 

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The 68GHz ECRH system consists of the 6 sets of 0.5MW/1s (1.5s) sub system, and the 140GHz ECRH system consists of the 2 sets of 1MW/3s sub system. Each sub system is connected with the transmission line by the antenna independently. The 68GHz ECRH system has non-vacuum transmission line that the main component is the over mode corrugated circular waveguide with the inner diameter of 80mm. The 140GHz ECRH system has vacuum transmission line that the main component is the over mode corrugated circular waveguide with the inner diameter of 63.5mm. The 68GHz ECRH system has been used for ECRH discharges successfully and the transmission efficiency can reach 90%. For the 140GHz ECRH system, the transmission line has been designed completely.

Preliminary simulation analysis on channel deformation during uniaxial diffusion welding

ZHONG Yuan, LUO Tian-yong

2013, 33(1):  48-53. 

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A simulation method based on ANSYS was proposed to evaluate channel deformation of cooling plate during uniaxial diffusion welding process for TBM. In order to verify the reliability of this method, results of simulation were compared with those of experiment conducted by using the low activated martensite steel. It is showed that large deformation occurred on the channels of cooling plate during uniaxial diffusion welding. The theoretical simulation results agree well with experiment results. It is indicated that this method will be helpful for the technology improvement of manufacturing cooling plate by uniaxial diffusion welding.

Test platform design of three-dimensional loading test for the prototype of ITER TF magnet supports

HOU Bing-lin, LI Peng-yuan, YANG Shu-juan, PAN Chuan-jie, LIAO Min, CHEN Hui, WANG Yue, ZHANG Bo

2013, 33(1):  54-59. 

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In order to gain the high reliability of the gravity support (GS), the three-dimensional mechanical loading test of GS，used for stimulating ITER operation load cases, should be performed using GS prototype. To carry out this test, a special test platform for GS prototype is designed based on the dangerous ITER operation load cases, and finite element analysis (FEM) of this platform is conducted. FEM analysis shows that the intensity and stiffness of the test platform are sufficed, and that it can meet the accuracy requirements of the three-dimensional loading test for GS prototype. An acceptable criterion for this platform is designed，and the reliability of the platform is testified by this criterion.

Numerical simulation for seismic response of ITER toroidal field coil and gravity support system

CHEN Ling-li, PENG Hai-qiang, CHEN Zhen-mao, ZHANG Yang

2013, 33(1):  60-65. 

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A finite element model of the toroida field (TF) coil and gravity support system is established at first by taking its cyclic symmetry condition into account. The first ten order natural frequencies and their corresponding modal vectors of the system are calculated then by using the ANSYS software. Based on these modal information and the spectrum analysis method, the displacement response distribution of the TF system is obtained finally by using the standard seismic spectrum given in ITER EDA report. Furthermore, the feasibility of the numerical model is validated by comparing its results with those of a simplified model of single degree of freedom.

Characteristics of Halo current in EAST and estimate of divertor load

CHEN Da-long, SHEN Biao

2013, 33(1):  66-71. 

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In tokamak experiment, the plasmas with elongated cross-section is inherently unstable against vertical displacement, which easily results in disruption when the disruption induced Halo currents flow in the vaccum vessel, large Halo current will produce large damage to the divertor support. The Halo current features were researched in EAST by the Rogowski coils installed in the divertor. By analyzing Halo current at various places, it is found that the Halo currents are toroidal asymmetric, with peaking factor typically 2.5 and the maximum value of 0.65. These results are effective in analysis of EAST vacuum vessel electromagnetic loads.

Parameters optimization for EAST divertor W/Cu water-cooling monoblocks

WANG Jian, SONG Yun-tao, GUO Hou-yang, YAO Da-mao, LUO Guang-nan, XU Tie-jun

2013, 33(1):  72-77. 

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The structure of a new divertor cooling module is introduced for EAST superconducting tokamak. By using the FLUENT finite elemente software, the steady state thermal analysis was performed for the model with different parameters so as to quantifictional study the change rule the heat exchanged capacity with its parameters. Preliminary range of the optimized parameters is given for EAST to provide the reference for design and manufacture of water-cooling W/Cu divertor, which is very important to the research of divertor for tokamak and fusion reactor.

Numerical simulation of loss of vacuum accident in STARDUST

LIU Lei-lei, TONG Li-li, JIANG Jiao-feng, CAO Xue-wu

2013, 33(1):  78-82. 

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The numerical model for fusion dust experimental device STARDUST was established to calculate the velocity field in the experimental device under different conditions at the loss of vacuum accident(LOVA). And the numerical computation results had been compared with the experimental results. It shows that the numerical calculations carried out by the computational fluid dynamics method attained the purpose for reproducing the experimental physics process. In comparison with other turbulence models, the RNG k-ε turbulence model is more suitable for the numerical simulation of this computation. Numerical computation can predict the risk of LOVA.

Non-Fusion Plasma Applications

Hydrogen extraction from liquid lithium-lead alloy by gas-liquid contact method

XIE Bo, WENG Kui-ping, HOU Jian-ping, YANG Guang-ling, ZENG Jun

2013, 33(1):  83-87. 

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Hydrogen extraction experiment from liquid lithium-lead alloy by gas-liquid contact method has been carried out in own liquid lithium-lead bubbler (LLLB). Experimental results show that, He is more suitable than Ar as carrier gas in the filler tower. The higher temperature the tower is, the greater hydrogen content the tower exports. Influence of carrier gas flow rate on the hydrogen content in the export is jagged, no obvious rule. Although the difference between experimental results and literature data, but it is feasible that hydrogen isotopes extraction experiment from liquid lithium-lead by gas-liquid contact method, and the higher extraction efficiency increases with the growth of the residence time of the alloy in tower.

Study on the technique for precision measurement of density of SiO2 foam shells

MA Xiao-jun, GAO Dang-zhong, MENG Jie

2013, 33(1):  88-91. 

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The measuring method based on vertical scanning interference and combined with the relation between refraction index and density of SiO2 foam shells is introduced, and the relation is analyzed according to formulas of Lorentz-Lorenz and Gladstone-Dale. The experimental result and measuring uncertainty evaluation indicate that the precision measurement of density of low density SiO2 foam shells can be realized by using the vertical scanning interference technique and combining with Gladstone & Dale analysis method, and the measuring uncertainty is about 5%.

Measurement of heavy particle temperature in a gliding arc discharge driven by the transverse magnetic field at atmospheric pressure

LI Hui, TAO Xiao-ping

2013, 33(1):  92-96. 

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A generator of the gilding arc discharge, which is driven by the transverse magnetic field, is used to produce non-equilibrium plasma at atmospheric pressure. The spectra of N2 and OH radical are used to estimate the heavy particle temperature of the gliding arc plasma jet. Compared with the heavy particel temperature of the magnetically stabilized gliding arc discharge, the heavy particle temperature obtained from N2 spectrum is lower. Whereas, the heavy particle temperature obtained from OH radical spectrum is the same order as that of the magnetically stabilized gliding arc discharge, and is approximately in the range of 2400 K to 2700 K.