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2005
Frequency sweeping (chirping) of high frequency magnetohydrodynamic modes is widely observed in tokamak plasmas. In this paper observations of chirping in neutral-beam-heated plasmas in the Mega-Amp Spherical Tokamak (MAST) [A. Sykes, R. J. Akers, L. C. Appel and et al. , Nucl. Fusion 41 , 1423 (2001)] are considered, and it is shown that these may…
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2005
In this Brief Report we study the measured and modeled Lyman- a intensity ratios for hydrogenlike Cl XVII in a deuterium base plasma in the Joint European Torus tokamak and examine the agreement between experiment and theory for a particular plasma shot. A collisional-radiative model is used to calculate the values of the intensity ratios using mea…
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2005
An analytic interatomic bond-order potential BOP is derived that depends explicitly on the group number of the sp -valent element. This is achieved by generalizing the previously published BOP for group-IV elements by extrapolating from half-full occupancy using a simple envelope function for the upper bound of the bond order. This interatomic pote…
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2005
The design of a power plant based on the spherical tokamak (ST) is being developed in order to explore its potential advantages. The plasma is operated in a double null configuration, forming both an upper and lower divertor. In order to accommodate the high erosion rates and heat fluxes developed in the divertors, a system based on a cascading flo…
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2004
The Mega Amp Spherical Torus ( MAST ) diagnostic needs are strongly influenced by physics goals that often require diagnostic integration and cross-mapping, especially in fine-scale investigations, such as transport barriers. Conversely, the unrivalled viewing access to the edge, scrape-off layer ( SOL ) and divertor regions, provided by the MAST o…
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2004
This paper presents a feasibility study for a motional Stark effect ( MSE ) [ F. M. Levinton et al. , Phys. Rev. Lett. 63 , 2060 ( 1989 )] diagnostic on the TCV tokamak. A numerical simulation code has been used to identify the optimal port arrangement and geometrical layout. It predicts the expected measurement accuracy for a range of typical plas…
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2004
A curved crystal spectrometer in Johann configuration has been implemented on MAST to obtain values for electron temperature, ion temperature and toroidal velocity. The spectrometer is used to examine medium Z impurities in the soft x-ray region by utilising a Silicon ( 111 ) crystal, bent using a 4 pin bending jig, and a CCD detector sD t =8 ms d …
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2004
Tearing modes often limit the performance of tokamak plasmas, because the magnetic islands which they generate lead to a loss of confinement, or even a disruption. A particularly dangerous instability is the neoclassical tearing mode, which can grow to a large amplitude because of the amplification effect that the bootstrap current has on an initia…
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2004
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2004
Operating a microchannel plate ( MCP ) in saturated mode provides a simple photon and particle counting detector. However, there is a finite recovery time after individual events during which individual microchannels no longer respond, reducing the overall sensitivity. At continuous high flux levels, the corrections from measured to true flux becom…
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