This paper presents the latest results on confinement studies in the TJ-II stellarator. The inherently strong plasma–wall interaction of TJ-II has been successfully reduced after lithium coating by vacuum evaporation. Besides H retention and low Z, Li was chosen because there exists a reactor-oriented interest in this element, thus giving special relevance to the investigation of its properties. The Li-coating has led to important changes in plasma performance. Particularly, the effective density limit in NBI plasmas has been extended reaching central values of 8 × 10¹⁹ m⁻³ and T _e ≈ 250–300 eV, with peaked density, rather flat T _e profiles and higher ion temperatures. Due to the achieved density control, a second type of transition has been added to the low density ones previously observed in ECRH plasmas: higher density transitions characterized by the fall in Hα emission, the onset of steep density gradient and the reduction in the turbulence; which are characteristics of transition to the H mode. Confinement studies in ECH plasmas indicate that lowest order magnetic resonances, even in a low shear environment, locally reduce the effective electron heat diffusivities, while Alfven eigenmodes destabilized in NBI plasmas can influence fast ion confinement.

This review analyses the different gesture recognition systems through a timeline, showing the different types of technology, and specifying which are the most important features and their achieved recognition rates. At the end of the review, Leap Motion sensor possibilities are described in detail, in order to consider its application on the field of sign language. This device has many positive characteristics that make it a good option for sign language. One of the most important conclusions is the ability of the Leap Motion sensor to provide 3D information from the hands for due identification.

This paper presents an overview of experimental results and progress made in investigating density control using Li-coating, transport and L–H transitions in TJ-II. The Li-coating changes drastically the plasma–wall interaction, decreasing the recycling, and enlarges substantially the operational range of the device delaying the appearance of radiative collapse that happens for higher densities, which permits confinement properties of much denser plasmas to be studied. Moreover, L–H mode transition has only been achieved after Li-coating in TJ-II. The effect of rational surfaces on heat transport is studied showing a decrease in heat diffusivity close to their position, and it is also seen that rational surfaces located in the edge make L–H transition easier. TJ-II findings provide a new guideline for understanding the trigger mechanism of the L–H transition pointing out the importance of low frequency fluctuating sheared E × B flows. The properties of fast-ion confinement are described as well as the effects of impurities on radiation profiles, showing two types of profiles the bell and the dome shape, the latter being more prone to radiative collapse.

Interferometry is used for measuring line average electronic densities in fusion plasmas. The W7-X stellarator will employ a two-color CO₂ (10.591 μm) and CO (5.295 μm) heterodyne-infrared interferometer as an electronic density measurement diagnostic. The frequency displacement is 40 MHz for the CO₂ wavelength and 25 MHz for the CO, so these values will fix the heterodyne frequencies. Because the frequency gap between the two carriers is wide enough and the detector sensitivity is similar for both wavelengths, it is possible to use a single detector for the two signals; nevertheless, they should be split with filters. Traditionally, the intermediate-frequency signals should be filtered, downconverted to a lower frequency by the use of analog circuitry, and then processed. A new approach is proposed. The intermediate-frequency signals are directly sampled by means of high-speed analog-to-digital converters followed by a digital diplexer and a specific phase-meter processor implemented in a field-programmable gate array. Preliminary results from the W7-X infrared interferometer prototype, without plasma, are presented.

This work presents the behavioral simulation in an FPGA of a novel processing system for measuring line average electronic density in the TJ-II stellarator diagnostic, Infra-Red Two-Color Interferometer. Line average electronic density is proportional to phase difference between probing and reference signals of the interferometer, as the Appleton–Hartree cold plasma model states. The novelty of the approach is the development of a real time measuring system where research work has been carried out in two ways: a new interpolation algorithm and the implementation of a new specific processor on an FPGA.\ud \ud The main goal of this new system is to measure line plasma electronic density for several channels in real time, also it will be useful to eliminate intermediate mixing frequency stages (the output signals coming from the interferometer are going to be directly sampled) and finally to generate real time density signals for control purposes in TJ-II and in other diagnostics. This device is intended to be the new data acquisition-processing system for the future six channel infrared interferometer that requires at least 14 input signals. The knowledge acquired could be useful in the design of W7-X and ITER IR-interferometer data acquisition and processing systems

Infrared (IR) interferometry is a method for measuring the line-electron density of fusion plasmas. The significant performance achieved by FPGAs in solving digital signal processing tasks advocates the use of this type of technology in two-color IR interferometers of modern stellarators, such as the TJ-II (Madrid, Spain) and the future W7-X (Greifswald, Germany). In this work the implementation of a line-average electron density measuring system in an FPGA device is described. Several optimizations for multichannel systems are detailed and test results from the TJ-II as well as from a W7-X prototype are presented.