G. Russo

Upward continuation of scattered potential field data

Numerous methods have been used for upward continuation, but most of them require data on a regular grid. Gridding can introduce errors that affect the continued data in an unpredictable way. To avoid this problem, we design a continuation operator used for the direct continuation of scattered data on a 3-D basis. In this approach a harmonic function, satisfying the constraints imposed by the measured data, is developed. The continuation is written in the form of a linear combination of the measured data, but it depends on the arbitrary choice of the topographic zero level. However, the coefficients of the linear combination depend only on the position of the data points. This allows the zero level to be estimated on the basis of the continuation of synthetic anomalies calculated between the starting and ending surface. An important feature of the method is its local character, which allows the reduction of computation time. Also, the stability of the method for noisy data is reasonably good. The method is applied to both synthetic and real cases. Synthetic examples show how gridding-related errors may affect the continuation when an irregular distribution of data points and a variable topography are considered.

3D ultra-high resolution seismic imaging of shallow Solfatara crater in Campi Flegrei (Italy): New insights on deep hydrothermal fluid circulation processes

Seismic tomography can be used to image the spatial variation of rock properties within complex geological media such as volcanoes. Solfatara is a volcano located within the Campi Flegrei, a still active caldera, so it is of major importance to characterize its level of activity and potential danger. In this light, a 3D tomographic high-resolution P-wave velocity image of the shallow central part of Solfatara crater is obtained using first arrival times and a multiscale approach. The retrieved images, integrated with the resistivity section and temperature and the CO2 flux measurements, define the following characteristics: 1. A depth-dependent P-wave velocity layer down to 14 m, with Vp < 700 m/s typical of poorly-consolidated tephra and affected by CO2 degassing; 2. An intermediate layer, deepening towards the mineralized liquid-saturated area (Fangaia), interpreted as permeable deposits saturated with condensed water; 3. A deep, confined high velocity anomaly associated with a CO2 reservoir. These features are expression of an area located between the Fangaia, water saturated and replenished from deep aquifers, and the main fumaroles, superficial relief of the deep rising CO2 flux. Therefore, the changes in the outgassing rate greatly affect the shallow hydrothermal system, which can be used as a “mirror” of fluid migration processes occurring at depth.

A grid monitoring model over network-aware IaaS cloud infrastructure

Grid systems can take advantage from monitoring services to improve the reliability from the user point of view and to accelerate diagnostic and troubleshooting. However, the distributed nature of the computing infrastructure introduces several problems regarding the implementation, deployment, updating and management of the monitoring subsystem and these problems can affect the effectiveness of the monitoring activity itself. In this paper, we illustrate a new distributed monitoring model for multiregional grid infrastructure. Stressing the IaaS paradigm and the storage auto-replica, we propose a very flexible architecture over a cloud domain extended on a geographical scale that allows to manage, reconfigure and modify each monitoring component for each site on the grid. The proposed architecture is based on a complete network management system relying on the introduction of network services that are able to create on-demand layer-2 interconnection among sites. As a case study, we present the computing infrastructure deployed in the south of Italy for scientific applications, which is based on the gLite/EMI middleware and we propose a possible scenario for supporting the grid infrastructure in Southern Italy.

A digital approach to automatic control of a long-baseline interferometric antenna for gravitational wave detection

A digital control system is probably the best technical solution to the problem of automatic control of the Virgo interferometric antenna for gravitational wave detection, provided that very critical specifications concerning residual noise introduced by the digital system in the measurement band are met. For this purpose, a model of the digital system has been developed and tested to quantify the main sources and levels of noise. Experimental measurements, obtained using a prototype of the automatic control system, and theoretical analysis of the performances of the digital control loops have demonstrated the feasibility of a digital control system.

A three‐dimensional Qp imaging of the shallowest subsurface of Campi Flegrei offshore caldera, southern Italy

To improve the knowledge of the shallowest subsurface of Campi Flegrei caldera, a 3-D P wave attenuation tomography of the area was performed. We analyzed about 18,000 active seismic traces, which provided a dataset of 11,873 Δt* measurements, e.g. the differential traveltimes to quality factor ratios. These were inverted through an adapted tomographic inversion procedure. The 3-D tomographic images reveal an average QP about 70, interpreted as water-saturated volcanic and marine sediments. An arc-like, low-QP structure at 0.5-1 km depths was interpreted as a densely fractured, fluid saturated rock volume, well matching the buried rim of Campi Flegrei caldera. The spatial distribution of high and low-QP bodies in the inner caldera is correlated with low-VP values and may reflect either the differences in the percentage of fluid saturation of sediments or the presence of vapor state fluids beneath fumaroles manifestations.

Evaluating New Cluster Setup on 10Gbit/s Network to Support the SuperB Computing Model

The new era of particle physics poses strong constraints on computing and storage availability for data analysis and data distribution. The SuperB project plans to produce and analyzes bulk of dataset two times bigger than the actual HEP experiment. In this scenario one of the main issues is to create a new cluster setup, able to scale for the next ten years and to take advantage from the new fabric technologies, included multicore and graphic programming units (GPUs). In this paper we propose a new site-wide cluster setup for Tier1 computer facilities, aimed to integrate storage and computing resources through a mix of high density storage solutions, cluster file system and Nx10Gbit/s network interfaces. The main idea is overcome the bottleneck due to the storage-computing decoupling through a scalable model composed by nodes with many cores and several disks in JBOD configuration. Preliminary tests made on 10Gbit/s cluster with a real SuperB use case, show the validity of our approach.

Hybrid techniques for the digital control of mechanical and optical systems

One of the main requirements of a digital system for the control of interferometric detectors of gravitational waves is the computing power, that is a direct consequence of the increasing complexity of the digital algorithms necessary for the control signals generation. For this specific task many specialised non standard real-time architectures have been developed, often very expensive and difficult to upgrade. On the other hand, such computing power is generally fully available for off-line applications on standard Pc based systems. Therefore, a possible and obvious solution may be provided by the integration of both the the real-time and off-line architecture resulting in a hybrid control system architecture based on standards available components, trying to get both the advantages of the perfect data synchronization provided by the real-time systems and by the large computing power available on Pc based systems. Such integration may be provided by the implementation of the link between the two different architectures through the standard Ethernet network, whose data transfer speed is largely increasing in these years, using the TCP/IP and UDP protocols. In this paper we describe the architecture of an hybrid Ethernet based real-time control system protoype we implemented in Napoli, discussing its characteristics and performances. Finally we discuss a possible application to the real-time control of a suspended mass of the mode cleaner of the 3m prototype optical interferometer for gravitational wave detection (IDGW-3P) operational in Napoli.

A Centralized, Extensible, Multilayer Monitoring System for Distributed Infrastructures: The Atlas Tier2-Naples Experience

Services and Infrastructures monitoring is a crucial issue in a distributed computing environment that involves all the Grid architecture layers, from the network to the single application service. In this paper we propose a multi layer model that aims to integrate monitoring applications of different subsystems and to offer management and resource presentation services to the end-user and to system administrator, through a set of middleware components. After a discussion about the principal requirements, in the paper we identify a set of different access levels, then we design a general and extensible environment, which provides a single entry point, with different views depending on the user privileges. As a case of study, we describe the monitoring system implemented for the distributed Atlas Tier2 at Naples, the monitored subsystem, the functionality and the technologies used to map the requirements in a real use case.

Multiplicity studies and effective energy in ALICE at the LHC

In this work we explore the possibility to perform “effective energy” studies in very high energy collisions at the CERN large hadron collider (LHC). In particular, we focus on the possibility to measure in pp collisions the average charged multiplicity as a function of the effective energy with the ALICE experiment, using its capability to measure the energy of the leading baryons with the zero degree calorimeters. Analyses of this kind have been done at lower centre-of-mass energies and have shown that, once the appropriate kinematic variables are chosen, particle production is characterized by universal properties: no matter the nature of the interacting particles, the final states have identical features. Assuming that this universality picture can be extended to ion–ion collisions, as suggested by recent results from RHIC experiments, a novel approach based on the scaling hypothesis for limiting fragmentation has been used to derive the expected charged event multiplicity in AA interactions at LHC. This leads to scenarios where the multiplicity is significantly lower compared to most of the predictions from the models currently used to describe high energy AA collisions. A mean charged multiplicity of about 1000–2000 per rapidity unit (at η∼0) is expected for the most central Pb–Pb collisions at

Testing and evaluating storage technology to build a distributed Tier1 for SuperB in Italy

\sqrt{s_{{\text{NN}}}} = 5.5\,\text{TeV}