5,579 research outputs found
Overview of ASDEX Upgrade results
The ASDEX Upgrade (AUG) programme is directed towards physics input to critical
elements of the ITER design and the preparation of ITER operation, as well as addressing
physics issues for a future DEMO design. Since 2015, AUG is equipped with a new pair of
3-strap ICRF antennas, which were designed for a reduction of tungsten release during ICRF
operation. As predicted, a factor two reduction on the ICRF-induced W plasma content could
be achieved by the reduction of the sheath voltage at the antenna limiters via the compensation
of the image currents of the central and side straps in the antenna frame. There are two main
operational scenario lines in AUG. Experiments with low collisionality, which comprise
current drive, ELM mitigation/suppression and fast ion physics, are mainly done with freshly
boronized walls to reduce the tungsten influx at these high edge temperature conditions. Full
ELM suppression and non-inductive operation up to a plasma current of Ip = 0.8 MA could
be obtained at low plasma density. Plasma exhaust is studied under conditions of high neutral
divertor pressure and separatrix electron density, where a fresh boronization is not required.
Substantial progress could be achieved for the understanding of the confinement degradation
by strong D puffing and the improvement with nitrogen or carbon seeding. Inward/outward
shifts of the electron density profile relative to the temperature profile effect the edge stability
via the pressure profile changes and lead to improved/decreased pedestal performance.
Seeding and D gas puffing are found to effect the core fueling via changes in a region of high
density on the high field side (HFSHD).
The integration of all above mentioned operational scenarios will be feasible and
naturally obtained in a large device where the edge is more opaque for neutrals and higher
plasma temperatures provide a lower collisionality. The combination of exhaust control
with pellet fueling has been successfully demonstrated. High divertor enrichment values of
nitrogen EN 10 have been obtained during pellet injection, which is a prerequisite for the
simultaneous achievement of good core plasma purity and high divertor radiation levels.
Impurity accumulation observed in the all-metal AUG device caused by the strong neoclassical
inward transport of tungsten in the pedestal is expected to be relieved by the higher
neoclassical temperature screening in larger devices.European Commission (EUROfusion 633053
Real time phase-slopes calculations by correlations using FPGAs
J. Trujillo Sevilla ; M. R. Valido ; L. F. Rodríguez Ramos ; E. Boemo ; F. Rosa ; J. M. Rodríguez Ramos, “Real time phase-slopes calculations by correlations using FPGAs,” Proc. SPIE 7015, Adaptive Optics Systems, 70153B (July 11, 2008), Norbert Hubin; Claire E. Max; Peter L. Wizinowich
, 7015 (Issue) 70153B, (2008). Copyright © 2008 SPIE Society of Photo‑Optical Instrumentation Engineers. One print or electronic copy may be made for personal use only. Systematic reproduction and distribution, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited.ELT laser guide star wavefront sensors are planned to handle an expected amount of data to be overwhelmingly large
(1600x1600 pixels at 700 fps). According to the calculations involved, the solutions must consider to run on specialized
hardware as Graphical Processing Units (GPUs) or Field Programmable Gate Arrays (FPGAs), among others.
In the case of a Shack-Hartmann wavefront sensor is finally selected, the wavefront slopes can be computed using
centroid or correlation algorithms. Most of the developments are designed using centroid algorithms, but precision ought
to be taken in account too, and then correlation algorithms are really competitive.
This paper presents an FPGA-based wavefront slope implementation, capable of handling the sensor output stream in a
massively parallel approach, using a correlation algorithm previously tested and compared to the centroid algorithm.
Time processing results are shown, and they demonstrate the ability of the FPGA integer arithmetic in the resolution of
AO problems.
The selected architecture is based in today’s commercially available FPGAs which have a very limited amount of
internal memory. This limits the dimensions used in our implementation, but this also means that there is a lot of margin
to move real-time algorithms from the conventionalThis work has been partially supported by “Programa Nacional de Diseño y Producción Industrial" (Project DPI 2006-
07906) of the “Ministerio de Educación y Ciencia" of the Spanish Government, and by “European Regional
Development Fund" (ERDF)
Mean field study of structural changes in Pt isotopes with the Gogny interaction
The evolution of the nuclear shapes along the triaxial landscape is studied
in the Pt isotopic chain using the selfconsistent Hartree-Fock-Bogoliubov
approximation based on the Gogny interaction. In addition to the
parametrization D1S, the new incarnations D1N and D1M of this force are also
included in our analysis to asses to which extent the predictions are
independent of details of the effective interaction. The considered range of
neutron numbers 88<N<26 includes prolate, triaxial, oblate and spherical ground
state shapes and serves for a detailed comparison of the predictions obtained
with the new sets D1N and D1M against the ones provided by the standard
parametrization Gogny-D1S in a region of the nuclear landscape for which
experimental and theoretical fingerprints of shape transitions have been found.
Structural evolution along the Pt chain is discussed in terms of the
deformation dependence of single particle energies.Comment: 18 pages, 10 figures. Accepted for publication in Phys. Rev.
An instrumental puzzle: the modular integration of AOLI
The Adaptive Optics Lucky Imager, AOLI, is an instrument developed to deliver
the highest spatial resolution ever obtained in the visible, 20 mas, from
ground-based telescopes. In AOLI a new philosophy of instrumental prototyping
has been applied, based on the modularization of the subsystems. This modular
concept offers maximum flexibility regarding the instrument, telescope or the
addition of future developments.Comment: 10 pages, 8 figures, Proc. SPIE 9908, Ground-based and Airborne
Instrumentation for Astronomy VI, 99082Z (August 9, 2016
Quadrupole-octupole coupling and the onset of octupole deformation in actinides
The evolution of quadrupole and octupole collectivity and their coupling is
investigated in a series of even-even isotopes of the actinide Ra, Th, U, Pu,
Cm, and Cf with neutron number in the interval .
The Hartree-Fock-Bogoliubov approximation, based on the parametrization D1M of
the Gogny energy density functional, is employed to generate potential energy
surfaces depending upon the axially-symmetric quadrupole and octupole shape
degrees of freedom. The mean-field energy surface is then mapped onto the
expectation value of the interacting-boson-model Hamiltonian in the boson
condensate state as to determine the strength parameters of the boson
Hamiltonian. Spectroscopic properties related to the octupole degree of freedom
are produced by diagonalizing the mapped Hamiltonian. Calculated low-energy
negative-parity spectra, reduced transition
rates, and effective octupole deformation suggest that the transition from
nearly spherical to stable octupole-deformed, and to octupole vibrational
states occurs systematically in the actinide region.Comment: 12 pages, 12 figure
Genomic analysis reveals the major driving forces of bacterial life in the rhizosphere
A global analysis of Pseudomonas putida gene expression performed during the interaction with maize roots revealed how a bacterial population adjusts its genetic program to the specific conditions of this lifestyle
High spatial resolution optical imaging of the multiple T Tauri system LkH{\alpha} 262/LkH{\alpha} 263
We report high spatial resolution i' band imaging of the multiple T Tauri
system LkH 262/LkH 263 obtained during the first commissioning
period of the Adaptive Optics Lucky Imager (AOLI) at the 4.2 m William Herschel
Telescope, using its Lucky Imaging mode. AOLI images have provided photometry
for each of the two components LkH 263 A and B (0.41 arcsec separation)
and marginal evidence for an unresolved binary or a disc in LkH 262.
The AOLI data combined with previously available and newly obtained optical and
infrared imaging show that the three components of LkH 263 are
co-moving, that there is orbital motion in the AB pair, and, remarkably, that
LkH 262-263 is a common proper motion system with less than 1 mas/yr
relative motion. We argue that this is a likely five-component gravitationally
bounded system. According to BT-settl models the mass of each of the five
components is close to 0.4 M and the age is in the range 1-2 Myr. The
presence of discs in some of the components offers an interesting opportunity
to investigate the formation and evolution of discs in the early stages of
multiple very low-mass systems. In particular, we provide tentative evidence
that the disc in 263C could be coplanar with the orbit of 263AB.Comment: 11 pages, 7 figures, Accepted 2016 May
Overview of progress in European medium sized tokamaks towards an integrated plasma-edge/wall solution
Integrating the plasma core performance with an edge and scrape-off layer (SOL) that leads
to tolerable heat and particle loads on the wall is a major challenge. The new European
medium size tokamak task force (EU-MST) coordinates research on ASDEX Upgrade
(AUG), MAST and TCV. This multi-machine approach within EU-MST, covering a wide
parameter range, is instrumental to progress in the field, as ITER and DEMO core/pedestal
and SOL parameters are not achievable simultaneously in present day devices. A two prong
approach is adopted. On the one hand, scenarios with tolerable transient heat and particle
loads, including active edge localised mode (ELM) control are developed. On the other hand,
divertor solutions including advanced magnetic configurations are studied. Considerable
progress has been made on both approaches, in particular in the fields of: ELM control with
resonant magnetic perturbations (RMP), small ELM regimes, detachment onset and control,
as well as filamentary scrape-off-layer transport. For example full ELM suppression has now
been achieved on AUG at low collisionality with n = 2 RMP maintaining good confinement
HH(98,y2) 0.95. Advances have been made with respect to detachment onset and control.
Studies in advanced divertor configurations (Snowflake, Super-X and X-point target divertor)
shed new light on SOL physics. Cross field filamentary transport has been characterised in a
wide parameter regime on AUG, MAST and TCV progressing the theoretical and experimental
understanding crucial for predicting first wall loads in ITER and DEMO. Conditions in the
SOL also play a crucial role for ELM stability and access to small ELM regimes.European Commission (EUROfusion 633053
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