Collisionality and safety factor scalings of H-mode energy transport in the MAST spherical tokamak

A factor of 4 dimensionless collisionality scan of H-mode plasmas in MAST shows that the thermal energy confinement time scales as [formula]. Local heat transport is dominated by electrons and is consistent with the global scaling. The neutron rate is in good agreement with the ¿* dependence of tE,th. The gyrokinetic code GYRO indicates that micro-tearing turbulence might explain such a trend. A factor of 1.4 dimensionless safety factor scan shows that the energy confinement time scales as [formula] . These two scalings are consistent with the dependence of energy confinement time on plasma current and magnetic field. Weaker qeng and stronger ¿* dependences compared with the IPB98y2 scaling could be favourable for an ST-CTF device, in that it would allow operation at lower plasma current

Collisionality and safety factor scalings of H-mode energy transport in the MAST spherical tokamak

A factor of 4 dimensionless collisionality scan of H-mode plasmas in MAST shows that the thermal energy confinement time scales as [formula]. Local heat transport is dominated by electrons and is consistent with the global scaling. The neutron rate is in good agreement with the ¿* dependence of tE,th. The gyrokinetic code GYRO indicates that micro-tearing turbulence might explain such a trend. A factor of 1.4 dimensionless safety factor scan shows that the energy confinement time scales as [formula] . These two scalings are consistent with the dependence of energy confinement time on plasma current and magnetic field. Weaker qeng and stronger ¿* dependences compared with the IPB98y2 scaling could be favourable for an ST-CTF device, in that it would allow operation at lower plasma current

The evolution of Palaeolake Flixton and the environmental context of Star Carr, NE. Yorkshire: stratigraphy and sedimentology of the Last Glacial-Interglacial Transition (LGIT) lacustrine sequences

The basal topography and sediments recording the Last Glacial-Interglacial Transition (LGIT) from Palaeolake Flixton, North Yorkshire have been reinvestigated by a detailed auger and borehole survey. The data presented here, from the area to the north of Flixton Island and the River Hertford, suggests the basal topography of Palaeolake Flixton is irregular with deep and areally small basins interspersed within a gravel surface ca. 21 m OD. At its shallowest the gravel surface is ca. 2 m below current land surface and the deeper, steep-sided basins are up to 9 m in depth. Examination of the sediment sequences indicates the deeper basins accumulate sediments from the Dimlington Stadial (DS), Windermere Interstadial (WI), Loch Lomond Stadial (LLS) and the Holocene, whilst the shallower sequences only record the Holocene. The configuration of the deposits in the basins suggest that lake levels declined during the WI from 24 to 23 m OD and then fell further during the LLS to ca. 20.90 m OD. The lake water levels then rose slowly during the Holocene to a height of between 23 and 24 m OD. These fluctuations in lake water level at the transition from the LLS to Holocene perhaps indicate that the configuration of the water body during the resettlement of the area in the Mesolithic was different to previous reconstructions, with lower water levels and a greater area of land exposed for habitation. This highlights the potential for additional preservation of archaeological assemblages in the area of the former lake. Moreover the complex basal stratigraphy suggests that a systematic analyses of the Palaeolake Flixton sedimentary archive is required to resolve high-resolution palaeoclimate data from this lake sequence

Progress in simulating turbulent electron thermal transport in NSTX

Nonlinear simulations based on multiple NSTX discharge scenarios have progressed to help differentiate unique instability mechanisms and to validate with experimental turbulence and transport data. First nonlinear gyrokinetic simulations of microtearing (MT) turbulence in a high-beta NSTX H-mode discharge predict experimental levels of electron thermal transport that are dominated by magnetic flutter and increase with collisionality, roughly consistent with energy confinement times in dimensionless collisionality scaling experiments. Electron temperature gradient (ETG) simulations predict significant electron thermal transport in some low and high beta discharges when ion scales are suppressed by E x B shear. Although the predicted transport in H-modes is insensitive to variation in collisionality (inconsistent with confinement scaling), it is sensitive to variations in other parameters, particularly density gradient stabilization. In reversed shear (RS) Lmode discharges that exhibit electron internal transport barriers, ETG transport has also been shown to be suppressed nonlinearly by strong negative magnetic shear, s<<0. In many high beta plasmas, instabilities which exhibit a stiff beta dependence characteristic of kinetic ballooning modes (KBM) are sometimes found in the core region. However, they do not have a distinct finite beta threshold, instead transitioning gradually to a trapped electron mode (TEM) as beta is reduced to zero. Nonlinear simulations of this "hybrid" TEM/KBM predict significant transport in all channels, with substantial contributions from compressional magnetic perturbations. As multiple instabilities are often unstable simultaneously in the same plasma discharge, even on the same flux surface, unique parametric dependencies are discussed which may be useful for distinguishing the different mechanisms experimentally

Perturbative momentum transport in MAST L-mode plasmas

Non-axisymmetric magnetic fields are used to perturbatively probe momentum transport physics in MAST L-mode plasmas. The low beta L-mode target was chosen to complement previous experiments conducted in high beta NSTX H-mode plasmas (β N = 3.5-4.6) where an inward momentum pinch was measured. In those cases quasi-linear gyrokinetic simulations of unstable ballooning micro-instabilities predict weak or outward momentum convection, in contrast to the measurements. The weak pinch was predicted to be due to both electromagnetic effects at high beta and low aspect ratio minimizing the symmetry-breaking of the instabilities responsible for momentum transport. In an attempt to lessen these electromagnetic effects at low aspect ratio, perturbative experiments were run in MAST L-mode discharges at lower beta (β N = 2). The perturbative transport analysis used the time-dependent response following the termination of applied 3D fields that briefly brake the plasma rotation (similar to the NSTX H-mode experiments). Assuming time-invariant diffusive (χ ℓ) and convective (V ℓ) transport coefficients, an inward pinch is inferred with magnitudes, (RV ℓ/χ ℓ) = (-1)-(-9), similar to those found in NSTX H-modes and in conventional tokamaks. However, if experimental uncertainties due to non-stationary conditions during and after the applied 3D field are considered, a weak pinch or even outward convection is inferred, (RV ℓ/χ ℓ) = (-1)-(+5). Linear gyrokinetic simulations indicate that for these lower beta L-modes, the predicted momentum pinch is predicted to be relatively small, (RV ℓ/χ ℓ) sim ≈ -1. While this falls within the experimentally inferred range, the uncertainties are practically too large to quantitatively validate the predictions. Challenges and implications for this particular experimental technique are discussed, as well as additional possible physical mechanisms that may be important in understanding momentum transport in these low aspect ratio plasmas. </p

Maturidade emocional, locus de controle e ansiedade em pré- adolescentes obesos

Investigou-se aspectos do funcionamento psicológico como a maturidade emocional, locus de controle e ansiedade em pré-adolescentes obesos, através dos instrumentos: Teste do Desenho da Figura Humana (DFH), Escala de Locus de Controle para crianças e Escala de Ansiedade "RCMS". Os resultados não apontaram uma tendência específica quanto ao locus de controle ser mais interno ou externo. Em relação à ansiedade, enquanto traço de personalidade, a maioria dos sujeitos situou-se dentro do esperado para seu grupo etário. No DFH os índices relativos à Escala Evolutiva e à Escala Emocional encontraram-se também dentro do esperado, em sua maior parte. Tais resultados sugerem que não existe diferença entre pré-adolescentes obesos e pré-adolescentes em geral, quanto às variáveis estudadas. Entretanto, ser obeso pode estar associado a dificuldades de elaboração de aspectos evolutivos e emocionais para alguns indivíduos