Tapping Thermodynamics of the One Dimensional Ising Model

We analyse the steady state regime of a one dimensional Ising model under a tapping dynamics recently introduced by analogy with the dynamics of mechanically perturbed granular media. The idea that the steady state regime may be described by a flat measure over metastable states of fixed energy is tested by comparing various steady state time averaged quantities in extensive numerical simulations with the corresponding ensemble averages computed analytically with this flat measure. The agreement between the two averages is excellent in all the cases examined, showing that a static approach is capable of predicting certain measurable properties of the steady state regime.Comment: 11 pages, 5 figure

First ozone reanalysis on Mars using SPICAM data

To further our understanding of important photochemical processes in the Martian atmosphere, a synthesis can be used to investigate the temporal and spatial agreement between model and observations and determine any possible causes of identified differences. In this study [1], we have assimilated, for the first time, total ozone into a Mars Global Circulation model (GCM) to study the ozone cycle

Phase transitions in the steady state behavior of mechanically perturbed spin glasses and ferromagnets

We analyze the steady state regime of systems interpolating between spin glasses and ferromagnets under a tapping dynamics recently introduced by analogy with the dynamics of mechanically perturbed granular media. A crossover from a second order to first order ferromagnetic transition as a function of the spin coupling distribution is found. The flat measure over blocked states introduced by Edwards for granular media is used to explain this scenario. Annealed calculations of the Edwards entropy are shown to qualitatively explain the nature of the phase transitions. A Monte-Carlo construction of the Edwards measure confirms that this explanation is also quantitatively accurate

A reanalysis of ozone on Mars from assimilation of SPICAM observations

We have assimilated for the first time SPICAM retrievals of total ozone into a Martian global circulation model to provide a global reanalysis of the ozone cycle. Disagreement in total ozone between model prediction and assimilation is observed between 45°S–10°S from LS=135–180° and at northern polar (60°N–90°N) latitudes during northern fall (LS=150–195°). Large percentage differences in total ozone at northern fall polar latitudes identified through the assimilation process are linked with excessive northward transport of water vapour west of Tharsis and over Arabia Terra. Modelling biases in water vapour can also explain the underestimation of total ozone between 45°S–10°S from LS=135–180°. Heterogeneous uptake of odd hydrogen radicals are unable to explain the outstanding underestimation of northern polar total ozone in late northern fall. Assimilation of total ozone retrievals results in alterations of the modelled spatial distribution of ozone in the southern polar winter high altitude ozone layer. This illustrates the potential use of assimilation methods in constraining total ozone where SPICAM cannot observe, in a region where total ozone is especially important for potential investigations of the polar dynamics

Survey and alignment concept for the SPIRAL2 accelerator (status report)

International audienceThe SPIRAL2 project located at the GANIL facility (Caen, France) has been studied since the beginning of 2003, and is now under construction. This project aims at delivering rare (radioactive) isotope beams with intensities not yet available with presently running machines. An important aspect of this project is that it is foreseen to deliver up to five different beams in parallel to the users. This paper is a status report on the survey and alignment techniques selected for installation of the SPIRAL2 accelerator device

The initial geodetic survey for the SPIRAL2 process installation

International audienceThe SPIRAL2 project located at the Grand Accélérateur National d'Ions Lourds (GANIL facility - Caen, France) has been studied since the beginning of 2003, and is now under construction. This project aims at delivering rare (radioactive) isotope beams with intensities not yet available with presently running machines. An important aspect of this project is that it is foreseen to deliver up to five different beams in parallel to the users. This paper is focused mainly on the initial geodetic survey for the SPIRAL2 process installation. The positioning of the process and by extension of the buildings is subject to an important constraint due to the future connection of the radioactive beam line to the existing accelerator (see Fig.3). In order to reach the performances, a geodetic reference network (surface network) linked to the local survey network of the existing accelerator is designed [1]. The surface network will be transferred to the floor of the SPIRAL2 accelerator tunnel (9m under the ground), in order to define the underground reference network for the process setup. Final goal of the initial geodetic survey is to align process components of accelerator according to design within required tolerances

Overview on the preliminary geodetic network for SPIRAL2 process installations at GANIL

The SPIRAL2 project located at the Grand Accélérateur National d'Ions Lourds (GANIL facility - Caen, France) is now under construction. This project aims at delivering rare (radioactive) isotope beams with intensities not yet available with presently running machines. An important aspect of this project is that it is foreseen to deliver up to five different beams in parallel to the users. This paper is focused mainly on the preliminary geodetic network for the SPIRAL2 process installation. The positioning of the process and by extension of the buildings is subject to an important constraint due to future connection of the radioactive beam line to the existing accelerator complex. To reach the required accelerator performances, a geodetic surface network made up of concrete monuments around the construction is linked to the local network of the existing accelerator [1]. The surface network has been transferred to the slab of the accelerator tunnel at -2 level (-9.50 m) in order to define the underground reference network for the process setup. Final goal of the geodetic network is to allow the alignment of the process accelerator components [2] [3] [4] [5] [6] according to design within required tolerance. Various tolerances objectives will be given

Tapping Spin Glasses

We consider a tapping dynamics, analogous to that in experiments on granular media, on spin glasses and ferromagnets on random thin graphs. Between taps, zero temperature single spin flip dynamics takes the system to a metastable state. Tapping, corresponds to flipping simultaneously any spin with probability $p$. This dynamics leads to a stationary regime with a steady state energy $E(p)$. We analytically solve this dynamics for the one dimensional ferromagnet and $\pm J$ spin glass. Numerical simulations for spin glasses and ferromagnets of higher connectivity are carried out, in particular we find a novel first order transition for the ferromagnetic systems.Comment: 5 pages, 3 figures, RevTe

Status report on survey and alignment activities @ GANIL-SPIRAL2 facilities (CEA/CNRS, Caen, France)

International audienceThe over 30 years old GANIL laboratory (heavy ionsnational accelerator) is still delivering beams that interestthe nuclear physicist community. That is why AGATA(Advanced GAmma Tracking Array, a Europeancollaboration of 12 countries) settled at GANIL for a 4years campaign. This π gamma-ray detector requested aquite strong effort in term of 3D positioning metrologyand in term of environment adaptation.Furthermore, since 2013, GANIL is constructing andinstalling the SPIRAL2 facility: a superconducting linearaccelerator and experimental areas that represent 150mlong beam lines. Two injectors (ions, protons anddeutons), a RFQ, a medium energy beam line, a 30m longLINAC (26 supraconducting accelerating cavities) andhigh energy beam lines supplying two experimental hone dedicated to neutron and the other containing S3(Super Separator Spectrometer).This project requested full time survey and alignmentwork from the underground network linked to historicalGANIL coordinates system to the process installation stiin progress