Results from helical axis stellarators

Helical axis stellarators produce magnetic surfaces of high rotational transform and moderate shear solely by means of external currents, with the promise of high b. Several machines with quite different toroidal, helical, and ‘‘bumpy’’ Fourier components of magnetic field are now producing results, including high quality magnetic surfaces, confinement mode transitions, configuration studies, and confinement consistent with International Stellarator Scaling ~ISS95! scaling up to Te;2 keV. These devices permit concept evaluation over an unprecedented configuration space, and allow basic comparisons with those designed by established and alternative optimization strategies

The MOSS camera on H-1NF

We have configured the modulated optical solid-state spectrometer, a recently developed high-resolution instrument for plasma Dopplerspectroscopy, as an imaging spectroscopiccamera. The camera features a wide field of view (∼10°), large aperture (40 mm), and high spectral resolution ν/Δν greater than 10 000. The camera installation on the H-1NF Heliac is described, together with the steps in the design process, including field widening. Calibration and characterization of the instrument function is discussed and the instrument performance is illustrated with some sample results of spatially resolved ion temperature measurements in H-1NF

The aerodynamic design of an advanced rotor airfoil

An advanced rotor airfoil, designed utilizing supercritical airfoil technology and advanced design and analysis methodology is described. The airfoil was designed subject to stringent aerodynamic design criteria for improving the performance over the entire rotor operating regime. The design criteria are discussed. The design was accomplished using a physical plane, viscous, transonic inverse design procedure, and a constrained function minimization technique for optimizing the airfoil leading edge shape. The aerodynamic performance objectives of the airfoil are discussed

Electron Spin Resonance (ESR) Dating in Karst Environments

Electron spin resonance (ESR) dating has been developed for many materials, including hydroxyapatite in enamel, bone, and some fish scales, aragonite and calcite in travertine, molluscs, and calcrete, and quartz from ash, which have many potential applications in karst settings. Although the complexity of the signals in some materials has hampered routine application, research is solving these problems to make the method even more widely applicable. When tested against other dating tech­niques, age agreement has usually been excellent. Generally, the most reliable applications seem to be tooth enamel, some mol­lusc species, calcite deposits, and quartz minerals. ESR dating uses signals resulting from trapped charges created by radia­tion in crystalline solids. Ages are calculated by comparing the accumulated dose in the dating sample with the internal and external radiation dose rates produced by natural radiation in and around the sample. For fossils and authigenic minerals, no zeroing is necessary to obtain accurate ages. In sediment which contains reworked mineral clasts, ESR can be used to date the age of the mineral grain itself if it was not zeroed during ero­sion. For dating the sedimentation age, however, ESR signals must have been zeroed in order to give the correct age. High pressure, heating, and in some minerals, light exposure and grinding can zero an ESR signal, but some like hydroxyapatite have very high stability at surface temperatures. For materi­als that absorb uranium (U) during their burial history, such as teeth, bones, or mollusc shells, the age calculation considers their U uptake by cross calibrating with U series or U/Pb dat­ing or by assuming different uptake models. Some difficulties in calculating the external dose rate can be overcome by ap­plying the ESR isochron method, in which the sample acts as its own dosimeter. In open-air karst environments, changes in the external dose rate due to altered sediment cover, and hence, changing cosmic dose rates, need to be modelled. For all karst environments, sedimentary water concentration and mineralogical variations with time also need to be considered. Many ESR applications are currently used in karst settings, but several more are also possible