Start of SPIDER operation towards ITER neutral beams

Heating Neutral Beam (HNB) Injectors will constitute the main plasma heating and current drive tool both in ITER and JT60-SA, which are the next major experimental steps for demonstrating nuclear fusion as viable energy source. In ITER, in order to achieve the required thermonuclear fusion power gain Q=10 for short pulse operation and Q=5 for long pulse operation (up to 3600s), two HNB injectors will be needed [1], each delivering a total power of about 16.5 MW into the magnetically-confined plasma, by means of neutral hydrogen or deuterium particles having a specific energy of about 1 MeV. Since only negatively charged particles can be efficiently neutralized at such energy, the ITER HNB injectors [2] will be based on negative ions, generated by caesium-catalysed surface conversion of atoms in a radio-frequency driven plasma source. A negative deuterium ion current of more than 40 A will be extracted, accelerated and focused in a multi-aperture, multi-stage electrostatic accelerator, having 1280 apertures (~ 14 mm diam.) and 5 acceleration stages (~200 kV each) [3]. After passing through a narrow gas-cell neutralizer, the residual ions will be deflected and discarded, whereas the neutralized particles will continue their trajectory through a duct into the tokamak vessels to deliver the required heating power to the ITER plasma for a pulse duration of about 3600 s. Although the operating principles and the implementation of the most critical parts of the injector have been tested in different experiments, the ITER NBI requirements have never been simultaneously attained. In order to reduce the risks and to optimize the design and operating procedures of the HNB for ITER, a dedicated Neutral Beam Test Facility (NBTF) [4] has been promoted by the ITER Organization with the contribution of the European Union\u2019s Joint Undertaking for ITER and of the Italian Government, with the participation of the Japanese and Indian Domestic Agencies (JADA and INDA) and of several European laboratories, such as IPP-Garching, KIT-Karlsruhe, CCFE-Culham, CEA-Cadarache. The NBTF, nicknamed PRIMA, has been set up at Consorzio RFX in Padova, Italy [5]. The planned experiments will verify continuous HNB operation for one hour, under stringent requirements for beam divergence (< 7 mrad) and aiming (within 2 mrad). To study and optimise HNB performances, the NBTF includes two experiments: MITICA, full-scale NBI prototype with 1 MeV particle energy and SPIDER, with 100 keV particle energy and 40 A current, aiming at testing and optimizing the full-scale ion source. SPIDER will focus on source uniformity, negative ion current density and beam optics. In June 2018 the experimental operation of SPIDER has started

Evidences of accumulation points in cascade regenerative phenomena observed in high voltage dc devices insulated by long vacuum gaps

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Nasal polyposis : more than a chronic inflammatory disorder : a disease of mechanical dysfunction : the São Paulo position

Introduction The importance of our study lies in the fact that we have demonstrated the occurrence of mechanical dysfunction within polypoid tissues, which promotes the development of polyps in the nasal cavity. Objective To change the paradigm of nasal polyposis (NP). In this new conception, the chronic nasal inflammatory process that occurs in response to allergies, to pollution, to changes in the epithelial barrier, or to other factors is merely the trigger of the development of the disease in individuals with a genetic predisposition to an abnormal tissue remodeling process, which leads to a derangement of the mechanical properties of the nasal mucosa and, consequently, allows it to grow unchecked. Data Synthesis We propose a fundamentally new approach to intervening in the pathological process of NP, addressing biomechanical properties, fluid dynamics, and the concept of surface tension. Conclusion The incorporation of biomechanical knowledge into our understanding of NP provides a new perspective to help elucidate the physiology and the pathology of nasal polyps, and new avenues for the treatment and cure of NP

The Use of Hexaamineruthenium(III) Redox Marker for the characterization of SAM-Au Amperometric Sensors

Chemically modified electrodes (CME's) by self-assembled monolayers (SAM's) of alkanethiols are extensively studied because of their potential applications in many fields from surface chemistry, to biochemistry, to electroanalytical chemistry. The layer defectivity is one of the most critical feature that affects the reproducibility of the final sensors, hence a careful electrode design and preparation is required. In the present work the preparation and characterization of long chain thiol Au-SAM's of controlled defectivity is described. In particular, the apparent standard rate constants of the Ru(NH3)63+/2+ redox couple are determined as a function of the degree of coverage for three different linear chain alkylthiols (n-decane-, n-dodecane- and n-octadecane-thiol). The results are discussed in term of the electron transfer model at partially blocked surfaces

Seasonal variations of heat flux at the water-sediment interface in very shallow lagoons

Temperature measurements were taken at five levels in a homogeneous zone of silty sediments and very shallow water (1m) in the Lagoon of Venice. Temperature decreased with depth. A penetration depth of 230 cm and a phase lag between temperature maxima at various levels are observed and confirmed by typical values of thermal diffusivity for silty muds. The energy stored in the water from late winter to late summer is about 2 X 10 super(3) cal cm super(-1) while in the same period, the energy stored in the sediment down to the penetration depth is about 1.7 X cal cm super(-1). The theoretical value of energy stored in the whole sediment is 2.1 X 10 super(-1) cal cm super(-1). Simple calculations based on the assumed conductivity of silty mud indicate that the heat flux through the water-sediment interface is on the order of 10 super(-4) cal cm super(-2) sec. super(-1), that is, 1/10 of the annual excursion of the incident solar flux at Venice's latitude

Soluzioni dell'equazione di diffusione applicate all'essiccamento di un terreno

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SOLUTION OF THE DIFFUSION EQUATION APPLIED TO DATA COLLECTED IN A NATURAL DRYING SOIL

Data collected during some successive field experiments, carried out in the natural sandy soil of the Hydrological Station of the Lido Beach of Venice during summer periods, suggest the following considerations on experimental and theoretical aspects.1)Evaporation may be evaluated using soil volumetric water content (q) profiles obtained by TDR technique.2)The two major stages of evaporation (atmosphere-limited and soil-limited stages) can be recognised only with the best possible vertical resolution of the TDR measurement (5 cm). Indeed, a superficial soil layer (about 20 cm) poorly equipped doesn't allow to measure properly the fast changes in soil volumetric water content (precipitation, strong solar heating and so on) and, of course, evaporation.3)Experimental soil moisture profiles trend shows a concavity change as the drying process goes on. This inflection may not be theoretically obtained by the solution of the diffusion equation with a constant diffusivity or with diffusivity being a monotonic increasing function of q. The solution presents the quoted inflection considering a non-monotonic diffusivity (presence of a minimum) or adding a source term to the diffusion equation. The problem has been studied considering different initial and boundary conditions, different diffusivity functions and possible source terms

PLANNING AND PRELIMINARY ACTIVITY FOR SOIL MOISTURE MEASUREMENTS DURING NEXT MAP SOP/IOP

Ground measurements and remotely sensed measurements of soil moisture are foreseen at selected sites in the Lago Maggiore (Val d'Ossola) target area during special and intensive observing periods of MAP, planned for next September-November 1999. The Osservatorio Geofisico (University of Modena) working group will collect soil volumetric water content measurements by means of Time Domain Reflectometry (TDR) technique. The TDR system is equipped with a multiplexer so that many probes can be automatically scanned at fixed time intervals. The probes were installed at the end of March 1999 in the middle of a uniform meadow suitable to be seen by an airborne microwaves radiometer. Fourteen TDR wave-guides were buried at different depths in the first 70 cm soil layer. The readings are collected each four hours to compute, from the soil water content profile trend, the cumulative evaporation during the MAP SOP campaign and to be used as ground truth data for the remotely sensed measurements