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- Scheffel, Jan, 1954-, et al.
(author)
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Extrap Mode Confinement in Extrap T1-U
- 1997
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In: Plasma Physics and Controlled Fusion. - 0741-3335 .- 1361-6587. ; 39, s. 973-992
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Journal article (peer-reviewed)abstract
- An extensive series of experiments in the Extrap mode has been carried out on Extrap T1-U in an attempt to obtain hot, collisionless discharges. Using no external axial magnetic field, performance has been limited to low temperatures (≤ 15 eV) and low currents (≤ 20 kA) at high loop voltages 1.4 kV, leading to energy confinement times of only a few μs or Alfvén times. The discharge length is typically of the order of greater than 100 Alfve ́n times.Imposing a weak axial field (q(a) ≤ 0.15 at peak current) the temperature could be increased to 40 eV at toroidal currents ≤ 60 kA. Energy confinement times up to 15 Alfvén times (≈10 μs) were then obtained.The poor confinement is attributed to the weak axial magnetic field, generating strong instability-induced fluctuations and related radial transport in the core plasma. A turbulence core plasma transport model is suggested, based on theoretical evidence of linear instability in the kinetic regime.Self-generation of axial magnetic field is observed when the magnetic X-points, generated by the plasma current and an external octupole field, approach or pass beyond the wall.Edge transport appears to be dominated by line radiation and heat conduction to the wall along open field lines.
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| 2. |
- Scheffel, Jan, 1954-, et al.
(author)
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Kinetic Stability of the Finite Electron Temperature Z-pinch
- 1997
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In: Plasma Physics and Controlled Fusion. - 0741-3335 .- 1361-6587. ; 39:4, s. 559-568
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Journal article (peer-reviewed)abstract
- Large Larmor radius (LLR) stability of linear m = 0 and m = 1 modes in a Z-pinch has been studied using the Vlasov-fluid model (Arber et al1994 Phys. Rev. Lett. 72 2399; 1995 Phys. Rev. Lett. 74 2698). Ions have been modelled fully kinetically through the Vlasov equation, and electrons are treated as a zero temperature, massless fluid. In the present work an improved Vlasov-fluid model is used to investigate the effect of finite electron temperature on m = 0 modes. An electron energy equation is introduced, and results for both adiabatic and isothermal dynamics are presented. It is found that finite electron temperature has a destabilizing effect in general. As a result, the Z-pinch is only weakly stabilized by LLR effects.
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| 5. |
- Gorini, G, et al.
(author)
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Neutron spectrometry diagnostic of triton burn-up in deuterium fusion plasmas
- 1997
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In: PLASMA PHYSICS AND CONTROLLED FUSION. - : IOP PUBLISHING LTD. - 0741-3335. ; 39:1, s. 61-71
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Journal article (other academic/artistic)abstract
- Spectrometry measurements of neutrons from triton bum-up can provide information on fast ion confinement in deuterium plasmas. This study concerns the relationship between the burn-up neutron spectrum and the triton slowing-down distribution under classic
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| 6. |
- Pecseli, HL, et al.
(author)
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Lower-hybrid wave cavities detected by instrumented spacecrafts
- 1997
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In: PLASMA PHYSICS AND CONTROLLED FUSION. - : IOP PUBLISHING LTD. - 0741-3335. ; 39:5A, s. 227-236
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Journal article (other academic/artistic)abstract
- Localized electrostatic wave packets in the frequency region of lower-hybrid waves have been detected by instrumented rocket payloads and recently also by the instruments on the FREJA satellite. These waves are often associated with local density depletio
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