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2011
Among dust particles of various origins collected in the MAST vessel, large quantities of carbon nanoparticles are observed. They are produced in the coldest plasma regions from the nucleation of carbonaceous species originating from physical and chemical erosion of the graphitic plasma facing components. On the other hand, laboratory plasmas studi…
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2011
Access into H-mode is studied in the MAST tokamak when plasma is fuelled by cryogenic pellets. It is shown that pellet fuelling from the high field side allows access to Hmode in plasmas heated by neutral beams. Simple and two-stage L-H transitions are identified. The results of comparison of the L-H transitions with pellet injection with transitio…
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2011
The sawtooth instability in tokamak plasmas results in a periodic reorganization of the core plasma. A typical sawtooth cycle consists of a quiescent period, during which the plasma density and temperature increase, followed by the growth of a helical magnetic perturbation, which in turn is followed by a rapid collapse of the central pressure. The …
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2011
The edge of a Tokamak plasma is interesting due to its geometrical structure that is difficult to model either analytically or computationally, its tendency to form "transport barriers" with increased confinement of energy and momentum, and the edge-localised instabilities associated with transport barriers that threaten the lifetime of components …
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2010
Instabilities of Alfvén Eigenmodes (AEs) are often excited by a super-Alfvénic population of fast ions accelerated with ion cyclotron resonance heating (ICRH) or produced by neutral beam injection (NBI) in present-day tokamaks. In view of the next-step burning plasma experiments with super-Alfvénic alpha-particles, the experimental data on AE in…
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2010
A major upgrade to the ruby Thomson scattering (TS) system has been designed and implemented on the Mega-ampere spherical tokamak (MAST). MAST is equipped with two TS systems, a Nd:YAG laser system and a ruby laser system. Apart from common collection optics each system provides independent measurements of the electron temperature and density profi…
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2010
A new diagnostic is developed to reconstruct the plasma boundary using visible wavelength images. Exploiting the plasma’s edge localized and toroidally symmetric emission profile, a new coordinate transform is presented to reconstruct the plasma boundary from a poloidal view image. The plasma boundary reconstruction is implemented in MATLAB and a…
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2010
Recently, Bayesian probability theory has been used at a number of experiments to fold uncertainties and interdependencies in the diagnostic data and forward models, together with prior knowledge of the state of the plasma, to increase accuracy of inferred physics variables. A new probabilistic framework, MINERVA, based on Bayesian graphical models…
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2010
A motional Stark effect MSE diagnostic is now installed and operating routinely on the MAST spherical tokamak, with 35 radial channels, spatial resolution of 2.5 cm, and time resolution of 1 ms at angular noise levels of 0.5°. Conventional albeit very narrow interference filters isolate or polarized emission. Avalanche photodiode detectors with di…
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2010
A new Thomson scattering diagnostic system has been designed and is being built now on the COMPASS tokamak at the Institute of Plasma Physics ASCR in Prague IPP Prague in the Czech Republic. This contribution focuses on design, development, and installation of the light collection and detection system. High spatial resolution of 3 mm will be achiev…
Showing 321 - 330 of 530 UKAEA Paper Results