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Final results of the first phase of the PROTO-SPHERA experiment: obtainment of the full current stable screw pinch and first evidences of the jet + torus combined plasma configuration

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Plasma Science and Technology 2024年第2期26卷 31-43页

作者： Paolo MICOZZI Franco ALLADIO Alessandro MANCUSO Vincenzo ZANZA Gerarda APRUZZESE Francesca BOMBARDA Luca BONCAGNI Paolo BURATTI Francesco FILIPPI Giuseppe GALATOLA TEKA Francesco GIAMMANCO Edmondo GIOVANNOZZI Andrea GROSSO Matteo IAFRATI Alessandro LAMPASI Violeta LAZIC Simone MAGAGNINO Simone MANNORI Paolo MARSILI Valerio PIERGOTTI Giuliano ROCCHI Alessandro SIBIO Benedetto TILIA Onofrio TUDISCO FSN Dipartimento Fusione e tecnologie per la Sicurezza Nucleare ENEA Agenzia Nazionale per Le Nuove Tecnologie Energia e lo Sviluppo Economico SostenibileFrascati(Rome)00044Italy IAPS Istituto di Astrofisica e Planetologia Spaziali INAF Istituto Nazionale di AstrofisicaRome O133Italy Physics Department University of Pisa Faculty of Natural Sciences Mathematics and PhysicsPisa 56127 Italy

In astrophysics, the boundary conditions for plasma phenomena are provided by nature and the astronomer faces the problem of understanding them from a variety of observations [Hester J J et al 1996 Astrophys. J. 456 225], on the other hand, in laboratory plasma experiments the electromagnetic boundary conditions become a major problem in the set-up of the machine that produces the plasma, an issue that has to be investigated step by step and to be modified and adapted with great patience, in particular in the case of an innovative plasma confinement experiment. The PROTO-SPHERA machine [Alladio F et al 2006 Nucl. Fusion 46 S613] is a magnetic confinement experiment, that emulates in the laboratory the jet + torus plasma configurations often observed in astrophysics: an inner magnetized jet of plasma centered on the(approximate) axis of symmetry and surrounded by a magnetized plasma torus orthogonal to this jet. The PROTO-SPHERA plasma is simply connected, i.e., no metal current conducting rod is linked to the plasma torus, while instead it is the inner magnetized plasma jet(in the following always called the plasma centerpost) that is linked to the torus. It is mandatory that no spurious plasma current path modifies the optimal shape of the plasma centerpost. Moreover, as the plasma torus is produced and sustained, in absence of any applied inductive electric field, by the inner plasma centerpost through magnetic reconnections [Taylor J B and Turner M F 1989 Nucl.Fusion 29 219], it is required as well that spurious current paths do not surround the torus on its outboard, in order not to lower the efficiency of the magnetic reconnections that maintain the plasma torus at the expense of the plasma centerpost. Boundary conditions have been corrected,up to the point that the first sustainment in steady state has been achieved for the combined plasma.

关键词： laboratory plasmas magnetic confinement astrophysical plasmas

Analysis of the Plasma Properties Affected by magnetic confinement with Special Emphasis on Helicon Discharges

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Plasma Science and Technology 2014年第12期16卷 1111-1118页

作者：成玉国程谋森王墨戈杨雄李小康 College of Aerospace Science and Engineering National University of Defense and Technology

A one-dimensional radial non-uniform fluid model is employed to study plasma behaviors with special emphasis laid on helicon discharges. The plasma density ne, electron temperature Te, electron azimuthal and radial drift velocities are investigated in terms of the plasma radius rp, magnetic field intensity B0 and gas pressure p0, by assuming radial ambipolar diffusion and negligible ion cyclotron movement. The results show that the magnetic confinement plays an important role in the discharge equilibrium, especially at low pressure, which significantly reduces Te compared with the case of a negligible magnetic field effect, and higher B0 leads to a greater average plasma density. Te shows little variations in the plasma density range of 1011 cm-3- 1013 cm-3 for p0 〈 3.0 mTorr. Comparison of the simulation results with experiments suggests that the model can make reasonable predictions of Te in low pressure helicon discharges.

关键词： helicon discharges magnetic confinement plasma property numerical simu-lation

The Enhanced Effect of Optical Emission from Laser Induced Breakdown Spectroscopy of an Al-Li Alloy in the Presence of magnetic Field confinement

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Plasma Science and Technology 2015年第8期17卷 687-692页

作者：刘平海然吴鼎肖青梅孙丽影丁洪斌 Key Laboratory of Materials Modification by Laser Ion and Electron BeamsChinese Ministry of EducationSchool of Physics and Optical Electronic TechnologyDalian University of Technology

In this paper, the influence of magnetic field strength on laser-induced breakdown spectroscopy （LIBS） has been investigated for various pressures. The plasma plume was produced by employing Q-switch Nd：YAG laser ablation of an A1-Li alloy operating at a 1064 nm wavelength. The results indicated that the LIBS intensity of the A1 and Li emission lines is boosted with an increase of magnetic strength. Typically, the intensity of the A11 and Li I spectral emissions can be magnified by 1.5-3 times in a steady magnetic field of 1.1 T compared with the field-free case. Also, in this investigation we recorded time-resolved images of the laser-produced plume by employing a fast ICCD camera. The results show that the luminance of the plasma is enhanced and the time of persistence is increased significantly, and the plasma plume splits into two lobes in the presence of a magnetic field. The probable reason for the enhancement is the magnetic confinement effect which increases the number density of excited atoms and the population of species in a high energy state. In addition, the electron temperature and density are also augmented by the magnetic field compared to the field-free case.

关键词： LIBS A1-Li alloy magnetic confinement EAST device

Spectral Enhancement of Laser-Induced Breakdown Spectroscopy in External magnetic Field

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Plasma Science and Technology 2015年第11期17卷 919-922页

作者：李丞高勋李奇宋超林景全 School of Science Changchun University of Science and Technology School of Chemistry & Environmental Engineering Changchun University of Science and Technology

In this paper the spectral enhancement of laser-induced breakdown spectroscopy （LIBS） for copper plasma in the presence of a magnetic field is investigated and the temporal- and spatial-resolved plasma emission spectra are analyzed. Experimental results show that the copper plasma atomic and ion spectra have been enhanced in the presence of the external magnetic field. In addition, the Cu I 521.82 nm spectral intensity evolution with delay time appears to have a double peak around the delay time of 2 μs, but that of Cu II 507.57 nm has a sharp decrease because of the electron-atom three body recombination process. The plasma temperature with magnetic confinement is lower than that of the case in the absence of magnetic fields. Finally, the spectral enhancement mechanisms of laser induced breakdown spectroscopy with magnetic confinement are analyzed.

关键词： laser induced breakdown spectroscopy spectral enhancement magnetic confinement

The Effect of an External magnetic Field on the Plume Expansion Dynamics of Laser-Induced Aluminum Plasma

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Plasma Science and Technology 2015年第8期17卷 693-698页

作者： Atif HUSSAIN 李奇郝作强高勋林景全 School of Science Changchun University of Science and Technology

In this work, we investigated the plasma morphology induced by a Nd：YAG laser with the aim of improving the understanding of the formation and dynamics of the plasma in two cases, with and without a magnetic field. Single laser pulse production of a plasma in the absence and presence of a magnetic field was performed with an aluminum target in air. A fast photography technique was employed to obtain information about the expansion dynamics and confinement of the aluminum plasma in each case. The generation of the laser plasma was allowed to expand at two locations with different magnetic field strengths, which correspond to the strength 0.58 T in the center of two magnetic poles and 0.83 T at a distance of 4 mm from the upper pole （N）. The plume showed lateral confinement at longer delays when the target was placed at the center of the two poles. When the target was placed at a distance of 4 mm from the upper pole it was observed that the plume was divided into two lobes at the initial stage and traveled towards the center of the magnetic field with further elapse of time.

关键词： plasma plume fast imaging magnetic confinement