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Balan, P.; Ionita, C.; Schrittwieser, R.; Silva, C.; Figueiredo, H.F.C.; Varandas, C.A.F.; Rasmussen, J.J.; Naulin, V. |
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Edge plasma measurements using emissive probes in ISTTOK |
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Year |
2006 |
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Plasma and Fusion Science |
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875 |
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105-110 |
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A probe array consisting of three emissive and one cylindrical probe was developed for edge plasma measurements in ISTTOK. The emissive probes measure the plasma potential, Phi(pl), independently of electron drifts or electron temperature fluctuations. The probe array has the advantage of to record the density, the poloidal and radial electric field, and their fluctuations simultaneously. Radial plasma profiles were recorded with and without negative edge biasing with an emissive electrode. The statistical properties of the poloidal electric field and of the turbulent particle flux, measured with cold and emissive probes, were compared. Both the root mean square of the poloidal electric field and the fluctuations-induced particle flux were found to be significantly larger when measured with the emissive probes, indicating that temperature fluctuations are important for the particle flux determination. The flux distribution was also found to be more peaked and asymmetric when measured with the emissive probes. A clear reduction of the turbulent particle flux and an improvement of the plasma confinement are observed during the negative emissive electrode biasing. |
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0094-243x |
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WOS:000244439700020 |
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IPFN @ jsousa @ |
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309 |
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Balan, P.; Schrittwieser, R.; Ionita, C.; Cabral, J.A.; Figueiredo, H.F.C.; Fernandes, H.; Varandas, C.; Adamek, J.; Hron, M.; Stockel, J.; Martines, E.; Tichy, M.; Van Oost, G. |
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Emissive probe measurements of plasma potential fluctuations in the edge plasma regions of tokamaks |
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Journal Article |
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2003 |
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Review Of Scientific Instruments |
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74 |
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3 |
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1583-1587 |
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The plasma potential Phi(pl) and its fluctuations (Phi) over tilde (pl) were measured by electron emissive probes in the edge plasma regions of two fusion experiments: the Instituto Superior Tecnico Tokamak (ISTTOK) (Lisbon, Portugal), and the Czech Academy of Sciences Tor-us (CASTOR) tokamak (Prague, Czech Republic). Into ISTTOK, three emissive probes were inserted outside the last closed flux surface (LCFS) on different minor radii. In CASTOR, two emissive probes, poloidally separated, and two cold cylindrical probes, mounted on the same shaft, were used, which could be radially shifted outside and inside the LCFS. The advantages of a sufficiently emissive probe are that in principle Phi(pl) and (Phi) over tilde (pl) can be measured directly, without being affected by electron temperature fluctuations or drifting electrons. (C) 2003 American Institute of Physics. |
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0034-6748 |
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WOS:000181530500042 |
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IPFN @ jsousa @ |
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777 |
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Bamford, R.; Gibson, K.J.; Thornton, A.J.; Bradford, J.; Bingham, R.; Gargate, L.; Silva, L.O.; Fonseca, R.A.; Hapgood, M.; Norberg, C.; Todd, T.; Stamper, R. |
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The interaction of a flowing plasma with a dipole magnetic field: measurements and modelling of a diamagnetic cavity relevant to spacecraft protection |
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2008 |
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Plasma Physics And Controlled Fusion |
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50 |
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12 |
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Here we describe a new experiment to test the shielding concept of a dipole-like magnetic field and plasma, surrounding a spacecraft forming a 'mini magnetosphere'. Initial laboratory experiments have been conducted to determine the effectiveness of a magnetized plasma barrier to be able to expel an impacting, low beta, supersonic flowing energetic plasma representing the solar wind. Optical and Langmuir probe data of the plasma density, the plasma flow velocity and the intensity of the dipole field clearly show the creation of a narrow transport barrier region and diamagnetic cavity virtually devoid of energetic plasma particles. This demonstrates the potential viability of being able to create a small 'hole' in a solar wind plasma, of the order of the ion Larmor orbit width, in which an inhabited spacecraft could reside in relative safety. The experimental results have been quantitatively compared with a 3D particle-in-cell 'hybrid' code simulation that uses kinetic ions and fluid electrons, showing good qualitative agreement and excellent quantitative agreement. Together the results demonstrate the pivotal role of particle kinetics in determining generic plasma transport barriers. |
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0741-3335 |
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WOS:000261046600035 |
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IPFN @ jsousa @ |
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532 |
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Bamford, R.A.; Kellett, B.; Bradford, W.J.; Norberg, C.; Thornton, A.; Gibson, K.J.; Crawford, I.A.; Silva, L.; Gargate, L.; Bingham, R. |
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Title |
Minimagnetospheres above the Lunar Surface and the Formation of Lunar Swirls |
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2012 |
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Physical Review Letters |
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109 |
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8 |
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081101 |
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0031-9007 |
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1290 |
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Bastos, C.; Bertolami, O.; Dias, N.C.; Prata, J.N. |
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Violation of the Robertson-Schrodinger uncertainty principle and noncommutative quantum mechanics |
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Journal Article |
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2012 |
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Physical Review D |
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86 |
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10 |
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105030 |
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We show that a possible violation of the Robertson-Schrodinger uncertainty principle may signal the existence of a deformation of the Heisenberg-Weyl algebra. More precisely, we prove that any Gaussian in phase space (even if it violates the Robertson-Schrodinger uncertainty principle) will always be a quantum state of an appropriate noncommutative extension of quantum mechanics. Conversely, all canonical noncommutative extensions of quantum mechanics display states that violate the Robertson-Schrodinger uncertainty principle. |
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1550-7998 |
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WOS:000311279300014 |
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1361 |
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