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The technology is now becoming mature for diagnostics using large portions of the electromagnetic spectrum simultaneously, in the form of THz pulses. THz radiation-based techniques have become feasible for a variety of applications, e.g., spectroscopy, imaging for security, medicine and pharmaceutical industry. In particular, time-domain spectroscopy (TDS) is now being used also for plasma diagnostics in various fields of application. This technique is promising also for plasmas for fusion applications, where plasma characteristics are non-uniform and/or evolve during the discharge This is because THz pulses produced with femtosecond mode-locked lasers conveniently span the spectrum above and below the plasma frequency and, thus, can be used as very sensitive and versatile probes of widely varying plasma parameters. The short pulse duration permits time resolving plasma characteristics while the large frequency span permits a large dynamic range. The focus of this work is to present preliminary experimental and simulation results demonstrating that THz TDS can be realistically adapted as a versatile tokamak plasma diagnostic technique. [ABSTRACT FROM AUTHOR]

A multichannel reflectometer will be built for the new three-straps ICRF antenna of ASDEX Upgrade (AUG), to study the density behavior in front of it. Ten different accesses to the plasma are available for the three reflectometer channels that can be interchanged without breaking the machine vacuum. Frequency is scanned from 40 GHz to 68 GHz, in 10ms, which corresponds to a cut-off density ranging from 1018 1019m??3 in the Right cut-off of the X-mode propagation, for standard toroidal magnetic field values of AUG. [ABSTRACT FROM AUTHOR]

The breakdown and plasma start-up in ITER are well known issues studied in the last few years in many tokamaks with the aid of calculation based on simplified modeling. The thickness of ITER metallic wall and the voltage limits of the Central Solenoid Power Supply strongly limit the maximum toroidal electric field achievable (0.3 V/m), well below the level used in the present generation of tokamaks. In order to have a safe and robust breakdown, the use of Electron Cyclotron Power to assist plasma formation and current rump up has been foreseen. This has raised attention on plasma formation phase in presence of EC wave, especially in order to predict the required power for a robust breakdown in ITER. Few detailed theory studies have been performed up to nowadays, due to the complexity of the problems. A simplified approach, extended from that proposed in ref[1] has been developed including a impurity multispecies distribution and an EC wave propagation and absorption based on GRAY code. This integrated model (BK0D) has been benchmarked on ohmic and EC assisted experiments on FTU and AUG, finding the key aspects for a good reproduction of data. On the basis of this, the simulation has been devoted to understand the best configuration for ITER case. The dependency of impurity distribution content and neutral gas pressure limits has been considered. As results of the analysis a reasonable amount of power (1 - 2 MW) seems to be enough to extend in a significant way the breakdown and current start up capability of ITER. The work reports the FTU data reproduction and the ITER case simulations. [ABSTRACT FROM AUTHOR]

A study of light neutron-rich nuclei has been performed at the INFN-LNS laboratory in Catania (Italy) by the (18O, 16O) reaction at 84 MeV incident energy on 9Be, 11B and 13C targets. The 16O ejectiles have been momentum analyzed and detected at forward angles by the MAGNEX magnetic spectrometer. The energy spectra of 15C show several known low lying states up to about 7 MeV excitation energy and unknown resonant structures at higher excitation energy. The strong excitation of these latter together with the measured width of about 2 MeV FWHM could indicate the presence of collective modes of excitation connected to the transfer of a correlated neutron pair. Also considerations regarding the reaction mechanism and the nuclei involved in the transfer seem to confirm such a conclusion. Similar features characterize the energy spectra of the 11Be and 13B nuclei. The achieved mass resolution (about 1/160) guarantying the identification of the reaction products corresponding to different reaction channels has allowed to study the relative yields for the different reaction channels. The measured yields show an enhancement of the two-neutron transfer channel compared to the one-neutron transfer. This result seems to indicate that the (18O, 16O) reaction proceeds mainly by the direct transfer of the neutron pair and that the second order processes are negligible. [ABSTRACT FROM AUTHOR]

Recent experiments indicated that a further non-inductive current, besides bootstrap, should be necessary for developing advanced scenario for ITER. The lower hybrid current drive (LHCD) should provide such tool, but its effectiveness was still not proved in operations with ITER-relevant density of the plasma column periphery. Progress of the LH deposition modelling is presented, performed considering the wave physics of the edge, and different ITER-relevant edge parameters. Operations with relatively high edge electron temperatures are expected to reduce the LH// spectral broadening and, consequently, enabling the LH power to propagate also in high density plasmas (// is the wavenumber componenent aligned to the confinement magnetic field). New results of FTU experiments are presented, performed by following the aforementioned modeling: they indicate that, for the first time, the LHCD conditions are established by operating at ITER-relevant high edge densities. [ABSTRACT FROM AUTHOR]

ECRH is suited for MHD control in tokamaks and this is well known since the several pioneering experiments investigating MHD stabilization either for confinement increase or for avoidance of disruptions originated by such instabilities. The first of these objectives has been strongly pursued up to the design of a system for neoclassical tearing mode stabilization in ITER based on the use of ECRH/ECCD, whereas the second one has been mostly neglected, despite the initial good results obtained on small tokamaks (RTP, T-10 and JFT-2M) in which ECRH was used to avoid disruptions originated by MHD limits or strong gas puffing. In the last years ECRH has been used again for disruption control on the Frascati Tokamak Upgrade (FTU) and on ASDEX Upgrade (AUG). Disruptions have been obtained by density limit and by impurity injection and an accurate power deposition scan has been performed. Full avoidance has been demonstrated on both tokamaks, confirming the need of a precise power localization and of the existence of a power threshold. The results of past experiments will be reviewed on the basis of the results recently obtained in FTU and AUG, together with a preliminary analysis of the applicability of this disruption control technique to ITER, by extrapolation of the power thresholds found in AUG and FTU. [ABSTRACT FROM AUTHOR]

Light elements lithium, beryllium and boron (LiBeB) were used in the last years as 'possible probe' for a deeper understanding of some extra-mixing phenomena occurring in young Main-Sequence stars. They are mainly destroyed by (p,α) reactions and cross section measurements for such channels are then needed. The Trojan Horse Method (THM) allows one to extract the astrophysical S(E)-factor without the experience of tunneling through the Coulomb barrier. In this work a résumé of the recent results about the 11B(p,α0)8Be and 10B(p,α)7Be reactions is shown. [ABSTRACT FROM AUTHOR]

A complete comparison between the theory and the measurements in polarimetry was done by using the Far Infrared Polarimeter at JET. More than 300 shots were analyzed, including a wide spectrum of JET scenarios in all critical conditions for polarimetry: high density, high and very low fields, high temperatures. This work is aimed at the demonstration of the robustness of the theoretical models for the JET polarimeter measurements in the perspective of using these models for ITER like plasma scenarios . In this context, an assessment was performed on how the line-integrated plasma density along the central vertical chord of FIR polarimeter could be evaluated using the Cotton-Mouton effect and its possible concrete use to correct fringe jumps of the interferometer. The models considered are: i) the rigorous numerical solution of the Stokes propagation equations, using dielectric tensor evaluated from JET equilibrium and Thomson scattering [1,2]; ii) two types of approximated solutions [2,3] and iii) the Guenther empirical model [4] that considers the mutual effect between Cotton-Mouton and Faraday rotation angle. The model calculations have been compared with polarimeter measurements for the Cotton-Mouton phase shift. The agreement with theory is satisfactory within the limits of experimental errors [3]. [ABSTRACT FROM AUTHOR]

The Trojan Horse Method allows for the measurements of cross sections in nuclear reactions between charged particles at astrophysical energies. The basic features of the method are discussed and recent applications are presented. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

The astrophysically relevant 7Li+p→α+α reaction was investigated via the THM by selecting the quasi-free contribution to the measured 3He+7Li→α+α+d three-body process. This investigation is mainly aimed at testing the validity of the pole approximation in the THM against the bound structure of the Trojan-horse nucleus. The three-body experiment was performed at 33 MeV, corresponding to a 7Li-p relative energy ranging from 0.2 to 7 MeV. The quasi-free 7Li+p cross-section was compared with the free reaction cross-section as well as with indirect data from a previous THM experiment. The good agreement between data sets throughout the energy range investigated provided a very important validity test of the pole approximation for the THM. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

The cross section of 8Li(α,n)11B is very important for the study of primordial nucleosinthesys models. In this paper we report on the production of a 8Li beam via the 7Li(d,p)8Li reaction at the Laboratori Nazionali del Sud. Also, a novel experimental technique for measuring the reaction 8Li(α,n)11B at energies of astrophysical interest has been implemented and tested. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

The characteristics of a new multidetector based on the use of Monolithic Silicon Telescopes are presented. Using suitable ion implantation techniques, the ΔE and residual energy stages of the telescopes have been integrated on a single Si chip, obtaining a typical thickness for the ΔE stage of the order of 2μm. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

Gaussian beam steering (2 beams, ≈400 kW each) and toroidal field tuning are used to control ECRH localization for MHD stabilization and energy transport studies on FTU tokamak. It is shown that by locating the absorption of one beam inside the m = 2 island, and of a second one close to the s.t. inversion radius, both instabilities can be suppressed, with a significant impact on energy confinement. MHD suppression allows the analysis of the underlying energy transport. It is shown that the electron temperature and pressure profiles are stiff when ECRH is localized off-axis, and that a finite amount of heat pumping against the temperature gradient must be accounted for to explain steady-state profiles at high density (n[sub e0, line]≈10[sup 20]m[sup -3]). The resistance of the thermal response to change with the heating source term can be analyzed in terms of two models implying profile stiffness: the effect of a critical temperature gradient, possibly related to ETG modes, and the tendency of a tokamak plasma to stick to preferred profiles. In particular, it is shown that the assumption of constant magnetic entropy, implying relaxation of the toroidal current density, allows good reproduction of the experimental profiles and of the main observation of a step-wise radial profile of the effective electron thermal diffusivity. Profile stiffness is observed both at high density, with significant e-i coupling, and at low density when much less power is conducted through ions. [ABSTRACT FROM AUTHOR]

Steady state electron heat transport of FTU high density plasmas ([sub lin] ≈ 0.45-1 10[sup 20] m[sup -3]) during Electron Cyclotron Resonance Heating (ECRH) are compared to predictions of a model based on the assumption of a threshold gradient length, L[sub Tc], in the electron temperature T[sub e] beyond which electron thermal conductivity, χ[sub e], switches from low to high values. The model accounts for the stiffness of T[sub e] slope observed in FTU plasmas heated with quite different radial shapes of the ECRH power deposition profile. These profiles are achieved by toroidal field tuning and steering two gaussian beams delivering up to 850 kW to the plasma in a radial position, ρ, ranging from ρ ≈ 0.25 to ρ ≈ 0.5. Plasma response is modelled by assuming the electron conductivity as Χe = Χe0 + αT[sub e, sup 3/2] (1/L[sub T] 1/L[sub Tc])[sup ½]; here T[sub e, sup 3/2] reflects the gyro-Bohm assumption, Χe0 represents the heat transport for L[sub T] > L[sub Tc] while α, the so-called stiffness coefficient, is adjusted to cope with the observed experimental data. The term (1/L[sub T] - 1/L[sub Tc])[sup ½] which sets in for L[sub T] < L[sub Tc] mimics an extra transport possibly due to Electron Temperature Gradient (ETG) modes. All the analyzed discharges are well reproduced by the same critical gradient length, L[sub Tc], the same stiffness coefficient, α, and the same 'low' conductiviy Χe0. [ABSTRACT FROM AUTHOR]

In this work a neural network has been used to reconstruct the residual energy after the first stage and classify the atomic number of the particles detected in a Silicon-CsI ΔE-E telescope. The adopted net is described and the whole procedure has been compared with the standard calibration methods for the E stage. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Different aspects of the formation and decay of [sup 24]Mg in the collision [sup 13]N+[sup 11]B have been studied using a large solid angle and highly segmented Silicon strip detector. Results concerning the fusion cross section, the 6 α decay of [sup 24]Mg and the GDR gamma ray emission are discussed. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Laser-driven ion acceleration is a new approach for the particles acceleration, which allows obtaining ion beams with unique properties, such as short burst duration, large particle number, small size source size, low transverse emittance. Currently, two main acceleration mechanisms have been identified and investigated: target normal sheath acceleration (TNSA) and radiation pressure acceleration (RPA). Electrons dynamics and energies are strongly coupled to these acceleration mechanisms and they can be investigated with optical and X-ray techniques. The main aim of these studies are the identification of few physical observables that can be directly correlated to the proton emission obtained (in terms of reproducibility and intensity) in operations with different target material and structure and laser-target interaction parameters. [ABSTRACT FROM AUTHOR]

In this work the analysis of the 10B(23p, α)7Be and 11B(p, α)8Be reactions, studied via the indirect Trojan Horse Method (THM), is discussed. In the astrophysical context of light nuclei LiBeB depletion, the above mentioned reactions are the main responsible for the destruction of boron in the stellar interior. The THM application allows their investigation in the astrophysically relevant energy region, around the Gamow Peak (≈10 keV), overcoming the problems due to the presence of the Coulomb barrier and electron screening effect. The experimental procedure and the preliminary results are shown. [ABSTRACT FROM AUTHOR]

The 10B(p,α)7Be reaction is the main responsible for 10B destruction in stellar interior. In such environments the process takes places mainly through a resonant state of the compound 11C nucleus. The 10B(p,α)7Be reaction has been studied by means of the Trojan Horse Method using the 2H(10B,α7Be)n three-body reaction. The experiment was performed at the Laboratori Nazionali del Sud in Catania. The 10B(p,α)7Be reaction cross section has been extracted at low neutron momentum. [ABSTRACT FROM AUTHOR]

Because of the still present uncertainties on its rate, the 17O(p,α)14N is one of the most important reaction to be studied in order to get more information about the fate of 17O in different astrophysical scenarios. The preliminary study of the three-body reaction 2H(17O,α14N)n is presented here as a first stage of the indirect study of this important 17O(p,α)14N reaction through the Trojan Horse Method (THM) [ABSTRACT FROM AUTHOR]