The MAST motional Stark effect diagnostic

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 π or σ polarized emission. Avalanche photodiode detectors with digital phase-sensitive detection measure the harmonics of a pair of photoelastic modulators operating at 20 and 23 kHz, and thus the polarization state. The π component is observed to be significantly stronger than σ, in reasonably good agreement with atomic physics calculations, and as a result, almost all channels are now operated on π. Trials with a wide filter that admits the entire Stark pattern (relying on the net polarization of the emission) have demonstrated performance almost as good as the conventional channels. MSE-constrained equilibrium reconstructions can readily be produced between pulses.This work was funded partly by the United Kingdom Engineering and Physical Sciences Research Council under Grant No. P/G003955 and by the European Communities under the contract of association between Euratom and CCFE

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 BτE,th ∝ ν-0.82±0.1*e. Local heat transport is dominated by electrons and is consistent with the global scaling. The n

Aerodynamic investigations of ventilated brake discs.

The heat dissipation and performance of a ventilated brake disc strongly depends on the aerodynamic characteristics of the flow through the rotor passages. The aim of this investigation was to provide an improved understanding of ventilated brake rotor flow phenomena, with a view to improving heat dissipation, as well as providing a measurement data set for validation of computational fluid dynamics methods. The flow fields at the exit of four different brake rotor geometries, rotated in free air, were measured using a five-hole pressure probe and a hot-wire anemometry system. The principal measurements were taken using two-component hot-wire techniques and were used to determine mean and unsteady flow characteristics at the exit of the brake rotors. Using phase-locked data processing, it was possible to reveal the spatial and temporal flow variation within individual rotor passages. The effects of disc geometry and rotational speed on the mean flow, passage turbulence intensity, and mass flow were determined. The rotor exit jet and wake flow were clearly observed as characterized by the passage geometry as well as definite regions of high and low turbulence. The aerodynamic flow characteristics were found to be reasonably independent of rotational speed but highly dependent upon rotor geometry

Lateinisch scīre und Verwandtes

Angesichts der formalen und semantischen Schwierigkeiten, die sich bei der gängigen Herleitung von lat. scīre ‘wissen’ aus der Wurzel *sekH- ‘schneiden’ von lat. secāre etc. ergeben, wird hier vorgeschlagen, scīre vielmehr mithilfe von Thurneysens ‘pius-Gesetz’ als y-Präsens zur Wurzel *(s)keuh1- ‘schauen, wahrnehmen’ von lat. cavēre, ahd. scouwōn usw. zu stellen. Dafür sprechen zum einen die innerhalb der 4. Konjugation ausnahmehafte Futur- und Imperfektbildung von scīre, zum andern die in der sprachvergleichenden Metapherforschung oft beobachtete Entstehung von Verben des Wissens aus Verben der visuellen Wahrnehmung. Dieselbe Wurzel *(s)keuh1- dürfte ferner dem Adjektiv ob-scūrus ‘düster, undurchsichtig’ sowie dem Nomen scurra ‘Gaffer, Witzbold’ zugrundeliegen