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Coherent Scattering of Light by Bose-Einstein Condensation in a Tight confinement

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Chinese Physics Letters 2007年第12期24卷 3396-3399页

作者：屈求智周蜀渝龙全徐震刘亮王育竹 Key Laboratory of Quantum optics Shanghai Institute of Optics and Fine Mechanics Chinese Academy of Sciences Shanghai 201800

We have observed strong scattering of a probe light by dilute Bose-Einstein condensate （BEC） ^87Rb gas in a tight magnetic trap. The scattering light forms fringes at the image plane. It is found that we can infer the real size of the condensation and the number of the atoms by modelling the imaging system. We present a quantitative calculation of light scattering by the condensed atoms. The calculation shows that the experimental results agree well with the prediction of the generalized diffraction theory, and thus we can directly observe the phase transition of BEC in a tight trap.

关键词： LIGHT -- Scattering BOSE-Einstein condensation MAGNETIC traps plasma confinement

Hydrogenic Donor in a Spherical Quantum Dot with Different confinements

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Chinese Physics Letters 2009年第8期26卷 309-312页

作者： A. John Peter K. Navaneethakrishnan Govt. Arts College Melur-625 106 Madurad India Madurai Kamaraj-University Madurai-625 021 India

Binding energies of a hydrogenic donor in a spherical GaAs quantum dot surrounded by Ga1-xA4xAs matrix are calculated. The results are presented for realistie barrier heights corresponding to different values of x （x 〈 0.4）. The calculations are performed under two different conditions：（i） a spherical dot with square well confinement and （ii） a dot with parabolic potential well confinement. The results show that （i） the donor ionization energies are always higher under parabolic confinement as compared to a dot of the same radius under square well confinement and （ii） the oscillator strengths coupling ground state with excited states are two orders larger under parabolic confinement. Our results are in agreement with the results of other researchers.

关键词： ELECTRON donor-acceptor complexes QUANTUM dots BINDING energy OSCILLATOR strengths plasma confinement QUANTUM wells GALLIUM arsenide semiconductors

Observation of chaotic ELMs in HL-2A tokamak

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Chinese Physics B 2011年第5期20卷 310-314页

作者：黄渊聂林余德良刘春华冯震段旭如 Southwestern Institute of Physics

The high confinement mode （H-mode） operation is recently obtained in HL-2A divertor configuration, the corresponding edge localized mode （ELM） is recognized as being of type III. Time intervals in ELM time series are analysed to obtain the information about the ELM process. Signatures of unstable periodic orbits （UPOs） are detected, which are indicators of chaos and may be used to control the big ELM events.

关键词： tokamak plasma plasma confinement edge localized modes chaotic systems

Review of the experiments for energetic particle physics on HL-2A

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plasma Science and Technology 2018年第9期20卷 93-105页

作者： X T DING W CHEN Southwestern Institute of Physics Chengdu 610041People＇s Republic of China

This paper reviews the energetic particle（EP） experiments during electron cyclotron resonance heating（ECRH） and neutral beam injection in the HL-2 A tokamak.A number of important results are summarized,which relate to ITER physics,including the behavior of the multi-mode instability,the nonlinear interaction between wave-wave and wave-particles,the losses of EP induced by the instabilities,the effect of the EP instabilities on the thermal plasma confinement and the control of the EP instabilities by means of *** experiments indicate that when the drive is great enough,the nonlinear effects and the multi-mode coexistence may play an important role,which affect the transport both of the EPs and the background plasma confinement,and these instabilities could be *** new phenomena about the EP induced instabilities discovered recently on the device,such as high frequency reversed shear Alfvén eigenmodes,Alfvénic ion temperature gradient modes,the geodesic acoustic mode induced by energetic electrons excited by interaction between tearing mode and beta induced Alfvén eigenmode and double e-fishbone in negative magnetic shear discharges etc,have also been presented in the paper.

关键词： HL-2A tokamak energetic particle Alfven eigenmode plasma confinement

Modelling effect of magnetic field on material removal in dry electrical discharge machining

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plasma Science and Technology 2017年第2期19卷 79-88页

作者： Abhishek GUPTA Suhas S JOSHI Department of Mechanical Engineering Indian Institute of Technology BombayPowaiMumbai 400 076India

One of the reasons for increased material removal rate in magnetic field assisted dry electrical discharge machining （EDM） is confinement of plasma due to Lorentz forces. This paper presents a mathematical model to evaluate the effect of external magnetic field on crater depth and diameter in single- and multiple-discharge EDM process. The model incorporates three main effects of the magnetic field, which include plasma confinement, mean free path reduction and pulsating magnetic field effects. Upon the application of an external magnetic field, Lorentz forces that are developed across the plasma column confine the plasma column. Also, the magnetic field reduces the mean free path of electrons due to an increase in the plasma pressure and cycloidal path taken by the electrons between the electrodes. As the mean free path of electrons reduces, more ionization occurs in plasma column and eventually an increase in the current density at the inter-electrode gap occurs. The model results for crater depth and its diameter in single discharge dry EDM process show an error of 9%-10% over the respective experimental values.

关键词： electrical discharge machining dry EDM plasma confinement magnetic field

Measurements of total absolute collision cross section of ultracold Rb atom using magneto-optic and pure magnetic traps

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Chinese Optics Letters 2011年第6期9卷 9-12页

作者：王继成王月媛王跃科方光宇刘树田 Department of Physics Harbin Institute of Technology

The implementation of a technique to measure total collision cross sections using laser-cooled rubidium atoms along with the introduction of room-temperature background gases, confined in both magnetooptic and magnetic traps, is proposed. Atom loss from the trap and total collision cross section can be inferred from the knowledge of the density of background gases. The measured cross sections from the magneto-optic and magnetic traps are represented, compared, and found to be significantly different. The measurements using this technique have a very small error in the range of approximately 2%-7%.

关键词： Atoms Magnetos plasma confinement Rubidium

Study on Ceramic Cutting by plasma Arc

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厦门大学学报（自然科学版） 2002年第S1期41卷 55-56页

作者： XU Wen-ji 1, FANG Jian-cheng 2, LU Yi-shen 1 (1. School of Mechanical Engineering, Dalian University of Technology, Dalian 116023, China 2. College of Mechanical Engineering and Automation, Huaqiao University, Quanzhou 362011, China)

Engineering ceramics are typical difficult-to-machine materials because of high hardness and brittleness. PAC (plasma Arc Cutting) is a very important thermal cutting process and has been successfully used in cutting stainless steel and other difficult-to-machine alloys. PAC’s application in cutting ceramics, however, is still limited because the most ceramics are not good electronic conducts, and transferred plasma arc cannot be produced between cathode and work-piece. So we presented a method of plasma arc cutting engineering ceramics with additional anode. To reduce the kerf width and to improve the kerf quality, the hydro-magnetically confined plasma arc is used to cut engineering ceramic plates. By experiments and analyses the mechanism and characteristics of hydro-magnetic confined plasma are discussed and the effects of secondary confinement on cutting quality, arc properties, and optimal process parameters are presented. When the nozzle diameter is 3 mm, the kerf width of the Al 2O 3 ceramic plate with 6 mm thickness is less than 4.6 mm, and the cutting speed reaches to 0.9～1.2 m/min. Both theoretical analysis and experimental results have proved the feasibility and validity of the newly advanced hydro-magnetic plasma arc cutting, and the following conclusion can be drawn: (1)Synthesizing the advantages of both the water-constriction and magnetic constriction, the hydro-magnetic constriction of plasma arc forms a three-dimensional constriction with improved shape and uniformity of arc column, narrower kerfs, minimal beveling of cuts and higher dross-free cutting speeds than those under either water-constriction or magnetic constriction alone.(2)Hydro-magnetic constriction is capable of improving arc stability, which is reflected in the higher arc voltage at which arc-extinction occurs, than that under any single constriction. (3)For a given diameter of nozzle, quality cut can be produced by using a lower arc current than usually required in conventional plas

关键词： plasma cutting engineering ceramic plasma confinement

Experimental characteristics of a lower hybrid wave multi-junction coupler in the HT-7 tokamak

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Chinese Physics B 2006年第12期15卷 2989-2999页

作者：丁伯江单家方刘甫坤方瑜德韦维吴振伟陈忠勇徐汉东王茂蒋敏张公让黄峰赵燕平匡光力无 Institute of plasma Physics Chinese Academy of Sciences Hefei 230031 China HT-7 team

A phase-controlled lower hybrid wave （LHW） multi-junction （M J） coupler （3（rows）×4（columns）×4 （subwaveguides）） has been developed in the HT-7 tokamak. Simulations show that it is more effective for driving plasma current than an ordinary phase-controlled LHW antenna （3（rows）× 12（columns））（traditional coupler）. The plasm-wave coupling experiments show that the reflection coefficient （RC） is below 10%, implying that the MJ grill can launch the wave into the plasma effectively. The effect of power spectrum launched by the MJ coupler on RC indicates that an optimal condition is requisite for a better coupling in the lower hybrid current drive （LHCD） experiments, Studies indicate that the drive efficiency of the MJ antenna is higher than that of the traditional one, which is mainly ascribed to the discrepancy in impurity concentration, plasma temperature, and spectrum directivity. An improved confinement with an electron internal transport barrier is obtained by LHCD. The analysis shows that the modified negative （low） magnetic shear and the change of radial electric field profile due to LHCD are possible factors responsible for the eITB formation.

关键词： antenna plasma heating plasma confinement

Estimating optical lattice alignment by RF spectroscopy

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Chinese Optics Letters 2012年第9期10卷 1-5页

作者：炜熊张胤马兆远陈徐宗 School of Electronics Engineering and Computer Science Peking University Shanghai Institute of Optics and Fine Mechanics Chinese Academy of Science State Key Laboratory of Precision Spectroscopy East China Normal University

A method that uses radio frequency （RF） spectroscopy to evaluate the alignment of an optical lattice is proposed and demonstrated. A one-dimensional （1D） optical lattice is applied along the long axis of a cigar-shaped Bose-Einstein condensate （BEC） in a magnetic trap. The RF spectra of condensates with and without the optical lattice are analyzed, measured, and compared with the condition in which the lattice is misaligned with the BEC. The proposed method greatly optimizes the optical alignments of the lattices.

关键词： Alignment Optical materials plasma confinement Radiofrequency spectroscopy Statistical mechanics