951 research outputs found
Applicazione della teoria dei valori estremi all’analisi statistica degli eventi di pioggia intensa nel varesotto (1991-2010)
No full textSupplemental_Material.Davy - Short-term changes in added sugar consumption by adolescents reflected in the carbon isotope ratio of fingerstick blood
No full textSupplemental_Material.Davy for Short-term changes in added sugar consumption by adolescents reflected in the carbon isotope ratio of fingerstick blood by Sarah V Liu, Lori B Moore, Tanya M Halliday, A Hope Jahren, Jyoti Savla, Valisa E Hedrick, Elaina L Marinik, and Brenda M Davy in Nutrition and Health</p
System for temperature and power flux measurements on the RFX first wall
No full textA thermal imaging system has been installed on the RFX at Consorzio RFX to investigate the phenomenology of the plasma wall interactions. The infrared camera, model Amber AE4128, is based on a 128×128 InSb focal plane array detector and operates in the range of 4.5–5 μm with an acquisition rate of 217 Hz and 12 bit of dynamic range. The system, absolutely calibrated, is sensitive from room temperature up to 3000 °C, with different setups. The experimental data are compared with the numerical results obtained by means of transient thermal analyses carried out on analytical and finite element models of a graphite tile
Status and Perspectives of a Reversed Field Pinch as a Pilot Neutron Source
No full textFusion-fission hybrid reactors are seen as a possible, mid-term, CO2-free energy source. Starting from the progress in understanding the reversed field pinch plasma confinement, a pilot neutron source with a configuration of R = 4 m and a = 0.8 m and a plasma current of up to 14 mega-ampére (MA) is proposed. A staged experimental approach, with increased complexity and investment, was identified to tackle the existing issues related to scientific and technological aspects and to test the D-T operation at reduced fusion power (P_fus ∼30 MW, Q ∼0.4 , continuous pulsed operation)
Particle control systems at the edge of RFP experiments
No full textPlasma performance in reversed field pinch (RFP) devices, as in the tokamak, is strongly affected by neutrals at the edge. So far only a few experiments have been dedicated to an active control of the neutral particle using conventional solutions of axisymmetric magnetic divertors or throat limiters. The alternative `vented pump limiter' concept is more attractive for an RFP experiment due to the edge plasma and confinement properties of this magnetic configuration. In this paper, the application of a vented pump limiter to an RFP is discussed and the prototype module of the vented pump limiter designed for the RFX experiment is presented. Finally, the optimization of this concept for a next step RFP device is presented
Particle diffusion coefficient at the edge of RFX
No full textThe radial particle diffusion coefficient D of the RFP experiment RFX has been derived from particle balance in the local scrape-off layer created by an instrumented limiter inserted into the edge region. The parallel particle flux incident on the limiter and its spatial decay are measured by Langmuir probes, whereas the connection lengths between the limiter and the wall are inferred from the images of a CCD camera with a Hα and N II filter, and ion sources are taken into account. The measured values of D are in the range 10-20 m2/s for plasma current in the range 300-400 kA. The radial profile of D exhibits a maximum close to the wall and it decreases to lower values at r/a around 0.90. The value of D and its profile at the edge appear to be consistent with those derived from the electrostatic turbulence driven particle flux and from the local density profile. The results are discussed in terms of the diffusion mechanism in the edge plasma and in the scrape-off layer, by assessing the perturbation produced by the limiter insertion
A continuously pulsed Reversed Field Pinch core for an ohmically heated hybrid reactor
No full textOutcomes from RFX-mod, the largest Reversed Field Pinch (RFP) experiment, have shown a substantial increase of the electron and ion temperatures versus the plasma current with a trend that allows hypothesizing significant D-T fusion processes in larger devices with higher plasma current. Such a device, in which the plasma is purely ohmically heated, could act as an efficient, robust and cheap fusion neutron source with a neutron rate to be used as the basis for a Fusion-Fission Hybrid Reactor (FFHR). The peculiar features of this neutron source can be summarized as: ohmically heated plasma, toroidal field winding rated for a low magnetic field (one-two orders of magnitude lower than in Tokamaks), very simple, robust and cheap construction, simple access for Remote Handling and easy maintenance. Almost continuous neutron production, as required in a hybrid reactor, is guaranteed by a continuously pulsed operation without the need of additional current drive systems. The aim of the paper is to investigate the relationship between the machine size (major and minor device radius), the attainable stored volt-seconds and, consequently, the maximum plasma current and pulse duration. The analysis uses the experimental RFX-mod data (electron temperatures, plasma currents, loop voltages during flat top) to extrapolate the performances of larger RFP devices with significant neutron production from D-T reactions. This study shows a realistic possibility, in an inductively operated RFP of larger size than RFX-mod, with plasma current 15–20 MA and temperature ≈ 10–15 keV, to reach the level of neutron generation of a fusion-fission hybrid reactor, leading to a neutron production rate in the range of 1019 n/s and a wall neutron load of 0.2 MW/m
Requirements and modelling of fast particle injection in RFX-mod tokamak plasmas
No full textThe planned upgrade of the RFX-mod device is a good opportunity to widen the operational space of the machine, in both RFP and tokamak configurations. Installation of a power neutral beam injector is also envisaged and a NB system compatible with RFX-mod, formerly installed in TPE-RX, is already available on site. In this work, the METIS simulator is used to study the feasibility of TPE-RX injector integration in RFX-mod circular tokamak plasmas. METIS code allows the simulation of a full tokamak discharge, with the addition of the neutral beam injection (NBI) which, in METIS, is described by a decay equation applied in a simplified geometry and an analytical solution of the Fokker–Planck equation. In this work, RFX-mod scenarios with NBI have been studied, with careful attention to the beam absorption and plasma response to the additional heating
Functional analysis for the diagnostic systems to support the exploitation of the Divertor Tokamak Test facility
No full textThe technical studies for the realization of the Divertor Tokamak Test (DTT) facility are ongoing and with the progress of the design an increasing level of integration between the various systems and subsystems is required. In particular, it is difficult to define the structure of the diagnostics collection, because they have to meet very different needs to contribute to the machine operations. Known methodologies of functional analysis can assist in this task. The diagnostics functions can be divided in three high-level categories, possibly overlapping: normal operations control, physics research and machine/personnel safety protection. These functions can be mapped to the measured quantities involved, which must be formalized in terms of performance specifications. Finally, these requirements must be associated, in the framework of DTT Requirements Management and traceability, to the diagnostic systems which actually perform these functions, with a primary, secondary or backup role. This latter categorization depends on the operating states foreseen for the machine, taking into account possible degraded (or advanced) states associated to the most significant accidental conditions and which diagnostics can be affected by them. The traceability of these requirements to primary project functional requirements (each having a required availability) and the assignment of a different role in the measurements for the diagnostics gives the possibility to compute a preliminary estimation of the availability of the individual systems with the help of logical diagrams like Fault Trees. The application of this methodology throughout the design of DTT helps to choose an optimal set of diagnostics that meet the functions and constraints of the machine
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