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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
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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2004
A bremsstrahlung diagnostic has been deployed on the Mega Ampere Spherical Tokamak ( MAST ) , with matrix viewing of the full plasma cross section in a narrow region of the continuum free of spectral lines. An uncooled CCD detector is used to provide 100 Hz 128 3 128 matrix viewing of the plasma emissivity which is spectrally selected using an inte…
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2004
Spectral imaging diagnostics that view the full plasma cross section are used on MAST with sensor resolutions and frame rates of up to 256 x 512 chords and 130 Hz, respectively. The incident and solid angles of filter illumination are fully controllable. Image splitting and spectral selection with separate filters are performed in the telecentric r…
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2004
The generalized Charney-Hasegawa-Mima equation is unstable to a four wave modulational instability whereby a coherent, monochromatic drift wave can drive a band of modes and associated zonal flows unstable. Although initially the fastest growing modes dominate, a secondary nonlinear instability later drives the longest wavelength zonal flow and its…
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2003
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2003
A dual laser Thomson scattering system is implemented in the Mega Amp Spherical Tokamak (MAST). The complementary features of each approach are exploited. One system is ideally suited to measuring detailed profile behavior across the plasma while the other is ideally suited though not exclusively to studying fast changing events and general charact…
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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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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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2001
Showing 111 - 120 of 139 UKAEA Paper Results