RFQD - a Decelerating Radio Frequency Quadrupole for the CERN Antiproton Facility

The RFQD is designed to decelerate antiprotons of momentum 100 MeV/c (kinetic energy 5.33MeV)down to a kinetic energy variable between ~10 keV and 120 keV. Inside the RFQ body, at ground potential, the rf structure of the four-rod type is mounted on insulating supports. It can be biased between plus/minus 60 kV dc to achieve the continuous adjustment of output energy required by the ASACUSA experiment at the CERN Antiproton Decelerator AD. The different parts of the system are described and the present status reported

Soliton core filling in superfluid Fermi gases with spin-imbalance

In this paper the properties of dark solitons in superfluid Fermi gases with spin-imbalance are studied by means of a recently developed effective field theory [S. N. Klimin, J. Tempere, G. Lombardi, J. T. Devreese, Eur. Phys. J. B 88, 122 (2015)] suitable to describe the BEC-BCS crossover in ultracold gases in an extended range of temperatures as compared to the usual Ginzburg-Landau treatments. The spatial profiles for the total density and for the density of the excess-spin component, and the changes of their properties across the BEC-BCS crossover are examined in different conditions of temperature and imbalance. The presence of population imbalance is shown to strongly affect the structure of the soliton excitation by filling its core with unpaired atoms. This in turn influences the dynamical properties of the soliton since the additional particles in the core have to be dragged along thus altering the effective mass.Comment: 9 pages, 9 figure

Scattering induced dynamical entanglement and the quantum-classical correspondence

The generation of entanglement produced by a local potential interaction in a bipartite system is investigated. The degree of entanglement is contrasted with the underlying classical dynamics for a Rydberg molecule (a charged particle colliding on a kicked top). Entanglement is seen to depend on the structure of classical phase-space rather than on the global dynamical regime. As a consequence regular classical dynamics can in certain circumstances be associated with higher entanglement generation than chaotic dynamics. In addition quantum effects also come into play: for example partial revivals, which are expected to persist in the semiclassical limit, affect the long time behaviour of the reduced linear entropy. These results suggest that entanglement may not be a pertinent universal signature of chaos.Comment: Published versio

Clear sky fraction above Indonesia: an analysis for astronomical site selection

We report a study of cloud cover over Indonesia based on meteorological satellite data, spanning over the past 15 years (from 1996 to 2010) in order to be able to select a new astronomical site capable to host a multi-wavelength astronomical observatory. High spatial resolution of meteorological satellite data acquired from {\it Geostationary Meteorological Satellite 5} ({\it GMS 5}), {\it Geostationary Operational Environmental Satellite 9} ({\it GOES 9}), and {\it Multi-functional Transport Satellite-1R} ({\it MTSAT-1R}) are used to derive yearly average clear fractions over the regions of Indonesia. This parameter is determined from temperature measurement of the IR3 channel (water vapor, 6.7 $\mu$m) for high altitude clouds (cirrus) and from the IR1 channel (10.7 $\mu$m) for lower altitude clouds. Accordingly, an algorithm is developed to detect the corresponding clouds. The results of this study are then adopted to select the best possible sites in Indonesia to be analysed further by performing in situ measurements planned for the coming years. The results suggest that regions of East Nusa Tenggara, located in south-eastern part of Indonesia, are the most promising candidates for such an astronomical site. Yearly clear sky fraction of this regions may reach better than 70 per cent with an uncertainty of 10 per cent.Comment: 15 pages, 13 figures, and 4 table

The Assumption of Poisson Seismic-Rate Variability in CSEP/RELM Experiments

Evaluating the performances of earthquake forecasting/prediction models is the main rationale behind some recent international efforts like the Regional Earthquake Likelihood Model (RELM) and the Collaboratory for the Study of Earthquake Predictability (CSEP). Basically, the evaluation process consists of two steps: 1) to run simultaneously all codes to forecast future seismicity in well-defined testing regions; 2) to compare the forecasts through a suite of statistical tests. The tests are based on the likelihood score and they check both the time and space performances. All these tests rely on some basic assumptions that have never been deeply discussed and analyzed. In particular, models are required to specify a rate in space-time-magnitude bins, and it is assumed that these rates are independent and characterized by Poisson uncertainty. In this work we have explored in detail these assumptions and their impact on CSEP testing procedures when applied to a widely used class of models, i.e., the Epidemic-Type Aftershock Sequence (ETAS) models. Our results show that, if an ETAS model is an accurate representation of seismicity, the same "right" model is rejected by the current CSEP testing procedures a number of times significantly higher than expected. We show that this deficiency is due to the fact that the ETAS models produce forecasts with a variability significantly higher than that of a Poisson process, invalidating one of the main assumption that stands behind the CSEP/RELM evaluation process. Certainly, this shortcoming does not negate the paramount importance of the CSEP experiments as a whole, but it does call for a specific revision of the testing procedures to allow a better understanding of the results of such experiments

Control of Material Damping in High-Q Membrane Microresonators

We study the mechanical quality factors of bilayer aluminum/silicon-nitride membranes. By coating ultrahigh-Q Si3N4 membranes with a more lossy metal, we can precisely measure the effect of material loss on Q's of tensioned resonator modes over a large range of frequencies. We develop a theoretical model that interprets our results and predicts the damping can be reduced significantly by patterning the metal film. Using such patterning, we fabricate Al-Si3N4 membranes with ultrahigh Q at room temperature. Our work elucidates the role of material loss in the Q of membrane resonators and informs the design of hybrid mechanical oscillators for optical-electrical-mechanical quantum interfaces

The ETAS model for daily forecasting of Italian seismicity in the CSEP experiment

This paper investigates the basic properties of the recent shallow seismicity in Italy through stochastic modeling and statistical methods. Assuming that the earthquakes are the realization of a stochastic point process, we model the occurrence rate density in space, time and magnitude by means of an Epidemic Type Aftershock Sequence (ETAS) model. By applying the maximum likelihood procedure, we estimates the parameters of the model that best fit the Italian instrumental catalog, recorded by the Istituto Nazionale di Geofisica e Vulcanologia (INGV) from April 16th 2005 to June 1st 2009. Then we apply the estimated model on a second independent dataset (June 1st 2009- Sep 1st 2009). We find that the model performs well on this second database, by using proper statistical tests. The model proposed in the present study is suitable for computing earthquake occurrence probability in real time and to take part in international initiatives such as the Collaboratory Study for Earthquake Predictability (CSEP). Specifically we have submitted this model for the daily forecasting of Italian seismicity above Ml4.0