Evidence of a thermo-diffusion pinch on particle transport in FTU discharges close to density limit

Abstract In FTU, the density profile in the presence of large MARFE becomes more and more peaked with increasing density, forming strong density gradients close to the radial region affected by the MARFE. The temperature at the edge drops to few eV, driving a drop of the whole profile. The estimated particle source cannot justify the change of the density gradient, which instead is well-explained by a change of the pinch. A thermo-diffusion term well-describes the pinch evolution and the experimental behavior of the density at those radii where temperature measurements are reliable

A multichannel reflectometer for edge density profile measurements at the ICRF antenna in ASDEX upgrade

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 10 mu s, which corresponds to a cut-off density ranging from 10(18) divided by 10(19)m(-3) in the Right cut-off of the X-mode propagation, for standard toroidal magnetic field values of AUG

dynamic and frequency behaviour of the marfe instability on ftu

The Frascati Tokamak Upgrade (FTU) device can operate at high electron density regimes of the order of 1020m−3, where the MARFE instability is present at various plasma current and magnetic field values. When the MARFE is well developed and oscillating, its movement causes continuous density fluctuation, contaminating the integral density measurements. The amplitude and frequency of these density fluctuations are well revealed by the high resolution interferometer available on FTU, the dependence of the frequency versus basic plasma parameters is investigated in this paper.A specific experimental session on FTU, including some discharges with reversed toroidal magnetic field, and pushing the plasma column towards the internal or external side of the vacuum chamber, respectively, has shown that, when the plasma column is distant from the toroidal limiter, the MARFE is stable and does not oscillate around the mid plane. For these last cases the MARFE localization with respect to the ion drift direction, which can influence the stable and unstable positions, is also discussed. Keywords: Tokamak, MARFE, Greenwald limit, Single particle motion, Ion drift, Plasma radiatio

Implementation of the new multichannel X-mode edge density profile reflectometer for the ICRF antenna on ASDEX Upgrade

A new multichannel frequency modulated continuous-wave reflectometry diagnostic has been successfully installed and commissioned on ASDEX Upgrade to measure the plasma edge electron density profile evolution in front of the Ion Cyclotron Range of Frequencies (ICRF) antenna. The design of the new three-strap ICRF antenna integrates ten pairs (sending and receiving) of microwave reflectometry antennas. The multichannel reflectometer can use three of these to measure the edge electron density profiles up to 2 x 10(19) m(-3), at different poloidal locations, allowing the direct study of the local plasma layers in front of the ICRF antenna. ICRF power coupling, operational effects, and poloidal variations of the plasma density profile can be consistently studied for the first time. In this work the diagnostic hardware architecture is described and the obtained density profile measurements were used to track outer radial plasma position and plasma shape

Citokininek, a növényi in vitro fejlődés kulcsregulátorai

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The NUMEN heavy ion multidetector for a complementary approach to the neutrinoless double beta decay

Neutrinos are so far the most elusive known particles, and in the last decades many sophisticated experiments have been set up in order to clarify several questions about their intrinsic nature, in particular their masses, mass hierarchy, intrinsic nature of Majorana or Dirac particles. Evidence of the Neutrinoless Double-Beta Decay (NDBD) would prove that neutrinos are Majorana particles, thus improving the understanding of the universe itself. Besides the search for several large underground experiments for the direct experimental detection of NDBD, the NUMEN experiment proposes the investigation of a nuclear mechanism strongly linked to this decay: the Double Charge Exchange reactions (DCE). As such reactions share with the NDBD the same initial and final nuclear states, they could shed light on the determination of the Nuclear Matrix Elements (NMEs), which play a relevant role in the decay. The physics of DCE is described elsewhere in this issue, while the focus of this paper will be on the challenging experimental apparatus currently under construction in order to fulfil the requirements of the NUMEN experiment. The overall structure of the technological improvement to the cyclotron, along with the newly developed detection systems required for tracking and identifying the reaction products and their final excitation level are described