Progress in thermonuclear fusion energy research based on deuterium plasmas magnetically confined in toroidal tokamak devices requires the development of efficient current drive methods. Previous ...experiments have shown that plasma current can be driven effectively by externally launched radio frequency power coupled to lower hybrid plasma waves. However, at the high plasma densities required for fusion power plants, the coupled radio frequency power does not penetrate into the plasma core, possibly because of strong wave interactions with the plasma edge. Here we show experiments performed on FTU (Frascati Tokamak Upgrade) based on theoretical predictions that nonlinear interactions diminish when the peripheral plasma electron temperature is high, allowing significant wave penetration at high density. The results show that the coupled radio frequency power can penetrate into high-density plasmas due to weaker plasma edge effects, thus extending the effective range of lower hybrid current drive towards the domain relevant for fusion reactors.
•PROTO-SPHERA is a new concept of spherical torus with closed flux surfaces and a force-free Screw Pinch with open flux surfaces.•A two colour interferometer is the diagnostic system to measure the ...line density and to characterize this uncommon plasma.•For the high densities and its rate variation which can provoke a beam refraction a CO2 laser is the wavelength choice.•A two-colour vibration compensation system is foreseen by using a He-Ne laser.•The interferometer was assembled in a laboratory, a test interferometric signal has been observed.
PROTO-SPHERA (Spherical Plasma for Helicity Relaxation Assessment) is a new concept of torus that aims to produce a spherical torus with closed flux surfaces and a force-free Screw Pinch with open flux surfaces, fed by electrodes. In order to verify the stability of the configuration and the technical components of the PROTO-SPHERA initial arc, the initial Phase-1 experiment was built, and its plasma, in the year 2108, has reached both the total current (10 kA) and total duration (1 s) targets.
A two colour interferometer is one of the diagnostic system proposed to provide PROTO-SPHERA with the measurement of its electron density, which is currently of the order of ∼1020 m−3. It will allow to obtain line density, necessary to characterize this uncommon plasma, as integrate measurement along the equatorial plane. The design and the interferometer characteristics are described in this paper.
The PROTO-SPHERA load assembly Papastergiou, S.; Alladio, F.; Mancuso, A. ...
Fusion engineering and design,
11/2005, Letnik:
74, Številka:
1
Journal Article, Conference Proceeding
Recenzirano
PROTO-SPHERA is a proposed spherical torus where a hydrogen plasma arc, in a form of a screw pinch field fed by electrodes, replaces the central conductor. This simply connected magnetic ...configuration, if fusion relevant, might strongly simplify the design of a fusion reactor. The machine design philosophy, basic geometry and operating conditions together with the major components like the vacuum vessel, coils, electrodes, protection components, divertor, etc. are analyzed. The thermal and electromagnetic behavior as well as the predicted and permitted key stresses will be discussed in order to demonstrate that the design, construction and reliable operation of the machine are feasible. Reference is also made to the proposed Multi-Pinch experiment using the START vacuum vessel to demonstrate the feasibility and stability of the PROTO-SPHERA configuration.
Evaluating the fairness of electoral reforms is a critical requirement for electoral accountability in any democracy. There is, however, no research measuring the expected seat benefit for incumbent ...reformers in newly democratized countries. Much of this delay is due to the technical difficulties of generalizing previous seat‐vote models to multiparty races, a problem that has limited both subnational and cross‐national comparisons of electoral regime change. Using a multilevel Bayesian model we solve this analytical problem and produce comparable estimates of partisan bias and majoritarian bias across the Argentine provinces. Our model estimates the effect of reforms across many electoral regimes and can be applied to comparative analyses of electoral reforms within and across countries. In the particular case of Argentina, we show large seat premiums for incumbent parties initiating electoral reforms.
Pellet injection on START and MAST Ribeiro, C; Akers, R; Alladio, F ...
Fusion engineering and design,
11/2001, Letnik:
58
Journal Article, Conference Proceeding
Recenzirano
Cryogenic pellet injection has been used in START and it is under commissioning for MAST for fuelling and diagnostics. In START NBI, heated plasmas fuelled with deuterium pellets, high normalized ...density (Greenwald number
N
G≤1.1) with good energy confinement time (
τ
E/
τ
E
elmf
ITER97≤1.3) both at high beta (
β
T≤25%,
β
N≤4.9) have been obtained for time scales close to the energy confinement time (∼
τ
E). In addition, high fuelling efficiency (∼100%) have also been simultaneously observed. A complete pellet injection programme is currently under development in MAST, including the commissioning of a eight pellet injector, technical aspects of launching pellets through guide tubes, dedicated diagnostics, and modelling.
This article presents a new method for estimating the electron temperature of the Protosphera's screw pinch. The temperature radial profile is obtained by a self-consistent modeling of a 1D MHD ...equilibrium along with a 0D power balance of the plasma column, given measurements and estimates of the axial pinch plasma current, of the plasma rotational frequency and, at the equatorial plane, of the electron density radial profile, of the edge poloidal magnetic field, of the edge electron temperature and of the neutrals pressure in the vacuum vessel. The plasma is considered in equilibrium with its neutral phase and in constant rotation. A MATLAB code has been developed with the aim of estimating the MHD radial equilibrium profiles, the thermodynamic plasma state and the neutrals profile. The numerical estimates are compared with available experimental data showing a good agreement.
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