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| 2. |
- Torounidis, Thomas, 1976, et al.
(författare)
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Gain and bandwidth characterization in fiber optical parametric amplifiers
- 2006
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Ingår i: IEEE Photonics Technology Letters. - 1041-1135 .- 1941-0174. ; 18:24, s. 2578-2580
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Tidskriftsartikel (refereegranskat)abstract
- The fiber optical parametric amplifier (FOPA) is characterized using a optical time-domain reflectometer-based technique. The measurement technique visualizes how the parametric gain and bandwidth evolves as a function of length. Both gain and bandwidth are measured and compared to theory and a good agreement is found between them, making this technique useful for characterization of FOPAs. The impact of zero dispersion wavelength variations in the fiber and polarization dependence of the measurement technique are also discussed.
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| 3. |
- Frassinetti, Lorenzo, et al.
(författare)
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Improved particle confinement in transition from multiple-helicity to quasi-single-helicity regimes of a reversed-field pinch
- 2006
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 97:17, s. 175001-
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Tidskriftsartikel (refereegranskat)abstract
- The quasi-single-helicity (QSH) state of a reversed-field pinch (RFP) plasma is a regime in which the RFP configuration can be sustained by a dynamo produced mainly by a single tearing mode and in which a helical structure with well-defined magnetic flux surfaces arises. In this Letter, we show that spontaneous transitions to the QSH regime enhance the particle confinement. This improvement is originated by the simultaneous and cooperative action of the increase of the magnetic island and the reduction of the magnetic stochasticity.
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| 4. |
- Frassinetti, Lorenzo, et al.
(författare)
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Role of locked mode in the effectiveness of pulsed poloidal current drive regime in the reversed-field pinch
- 2005
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Ingår i: Physics of Plasmas. - : AIP Publishing. - 1070-664X .- 1089-7674. ; 12:10, s. 100703-
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Tidskriftsartikel (refereegranskat)abstract
- The close relationship between the locked mode (LM) and pulsed poloidal current drive (PPCD) regime in a reversed-field pinch device is described. If the modes lock close to the shell gap then the LM is enhanced and there is a high probability that the PPCD will not improve plasma performance. The physical reason will be discussed. If the position of the locked mode is far from the shell gap then the PPCD is effective with a high probability. LM energy is reduced and the more the LM energy decreases, the better the plasma performance.
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| 5. |
- Frassinetti, Lorenzo, et al.
(författare)
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Toroidally localized soft x-ray expulsion at the termination of the improved confinement regime in the TPE-RX reversed-field pinch experiment
- 2006
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Ingår i: Physics of Plasmas. - : AIP Publishing. - 1070-664X .- 1089-7674. ; 13:4, s. 042502-
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Tidskriftsartikel (refereegranskat)abstract
- The pulsed poloidal current drive technique reduces the magnetic chaos that characterizes reversed-field pinch configurations and produces a regime with an improved confinement. In this paper, we describe that, in TPE-RX [Y. Yagi , Fusion Eng. Des. 45, 409 (1999)], the termination phase of this regime is due to the increase of the slinky structure that creates a stochastic region and produces the expulsion of energy in a localized toroidal position. Before the plasma reaches the improved confinement regime, the slinky distorts the chain of m=0 islands on the reversal surface. During this regime, the magnetic activity and the phase locking decrease, the distortion in the island chain disappears, and the confinement increases. At the termination of this regime the magnetic activity markedly increases, as well as the phase locking, recreating the distortion in the m=0 magnetic island chain. As a consequence, at the position of the distortion the plasma region inside the reversal surface is characterized by a rapid energy loss, and outside the reversal surface a toroidally localized energy expulsion is induced.
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