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2003
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2003
The nature of intermittency, long observed in magnetic fusion devices, was revisited lately [G. Antar et al. , Phys. Rev. Lett. 87 , 065001 (2001)]. It was shown that intermittency is caused by large-scale events with high radial velocity reaching about 1/10th of the sound speed. These type of structures were named ‘‘avaloids.’’ In the pres…
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2003
The high-ß magnetically confined plasmas in spherical tori (ST), like NSTX and MAST, provide a unique opportunity for a wide variety of applications of electron Bernstein waves (EBW). These applications range from heating of the ST plasma to modifying and controlling its current profile. Using the fully relativistic dielectric tensor for a Maxwell…
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2003
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2002
Spontaneous acceleration of ions to suprathermal energies is observed during magnetic reconnection in the Mega-Ampere Spherical Tokamak (MAST). A high-energy tail is observed in the iondistribution function following each internal reconnection event in Ohmic discharges. This phenomenon is explained in terms of runaway ion acceleration in the electr…
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2002
Neutral atoms in the tokamak edge affect the electric field and plasma flow through charge exchange. Here, it is shown that these effects depend sensitively on the poloidal location of the atoms. It is found that the radial electric field and toroidal flow velocity in a collisional edge plasma are largest if the atoms are concentrated on the inboar…
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2002
Results from MAST provide a first test of neoclassical tearing mode physics in the spherical tokamak (ST). The mode accounts for the main performance limit in conventional tokamaks. Its behavior in the ST is remarkably well described by existing theoretical models, although it is more readily seeded by sawtooth events in these scenarios. Modeling c…
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2002
H -mode plasmas have been achieved on the MAST spherical tokamak at input power considerably higher than predicted by conventional threshold scalings. Following L - H transition, a clear improvement in energy confinement is obtained, exceeding recent international scalings even at densities approaching the Greenwald density limit. Transition is acc…
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2002
Integrated predictive modeling simulations are carried out using the BALDUR transport code [Singer et al. , Comput. Phys. Commun. 49 , 275 (1982)] for high confinement mode (H-mode) and low confinement mode (L-mode) discharges in the Mega-Amp Spherical Tokamak (MAST) [Sykes et al. , Phys. Plasmas 8 , 2101 (2001)]. Simulation results, obtained using…
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2002
Spontaneous transitions from the low ‘‘L-mode’’ to high ‘‘H-mode’’ of tokamak plasma confinement, first observed during neutral beam heating experiments on ASDEX, are now routinely achieved in many tokamak experiments. The H-mode regime is attractive as it offers the possibility of enhanced confinement, and thus a route towards a mo…
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