Silvio Migliori

The role of medium size facilities in the HPC ecosystem: the case of the new CRESCO4 cluster integrated in the ENEAGRID infrastructure

Medium size HPC clusters play an important role in the HPC landscape in that they provide both the training environment for system scalability and a flexible production field for a large class of numerical problems. In this poster we present CRESCO4, the latest medium size HPC cluster purchased by ENEA, in operation since few months. CRESCO4 is part of a family of HPC systems, all integrated within ENEAGRID, a large infrastructure for cloud computing, which includes all the computational facilities installed at several ENEA sites in Italy.

3D modeling and remote rendering technique of a high definition cultural heritage artefact

Abstract Recent improvements in 3D laser scanning technology allow to reliably and accurately digitize the external shape of many physical objects with high definition and accuracy. Moreover the resulting 3D models can be used for digital documentation as well as to perform different analysis such as measurements, conservation monitoring, feature extractions and possibly virtual restoration. In recent years, the number of range scanners has been growing rapidly and surface reconstruction algorithms have been developing by the open-source community. This diffusion among cultural heritage institutions gives the scientific society a wide range of 3D hardware capturing devices and software solutions. Many researchers, however, do not have access to scanning facilities or dense polygonal models. In this paper is presented the whole pipeline from the creation of a high resolution 3D model of an ‘Acquasantiera’ to its Remote Rendering on the world wide web without any loss of details or accuracy.

Development of a Two-Stage Pneumatic Repeating Pellet Injector for the Refueling of Long-Pulse Magnetic Confinement Fusion Devices

Next-step fusion devices, like the International Thermonuclear Experimental Reactor (ITER), and future fusion power plants will require a flexible plasma fueling system, including both gas puffing and high- and low-speed pellet injection. To sustain core plasma density, relatively large pellets penetrating beyond the separatrix will have to be provided at a repetition rate of ∼1 Hz for very long pulse operation. In the context of a cooperative agreement between the U.S. Department of Energy and the Euratom-ENEA Association, Oak Ridge National Laboratory (ORNL) has collaborated with ENEA Frascati to demonstrate the feasibility of a high-speed (2 to 3 km/s) repeating (≃1-Hz) pneumatic pellet injector for long-pulse operation. A test facility was assembled at ORNL that combined a Frascati repeating two-stage light-gas gun and an existing ORNL deuterium extruder, equipped with a pellet chambering mechanism/gun barrel assembly. It was operated in the course of three joint experimental campaigns between September 1993 and May 1995. The results of the first two campaigns appear in an earlier paper. Here, the results are reported of the third campaign, during which the original objectives ofthe collaboration were met. Both performance and reliability of the system were improved, with the facilitys being capable of delivering sequences of 2.7-mm deuterium pellets at a repetition rate of 1 Hz and velocities up to 2.5 km/s. The test facility was also briefly operated with neon pellets to explore the potential to produce fast killer pellets. Speeds of 1.7 km/s were easily achieved using a piston mass of43 g. Higher speeds should be achievable with a system specifically designed for neon or other high-Z gases.

High‐speed repeating hydrogen pellet injector for long‐pulse magnetic confinement fusion experiments

The projected fueling requirements of future magnetic confinement fusion devices [e.g., the International Thermonuclear Experimental Reactor (ITER)] indicate the need for a flexible plasma fueling capability, including both gas puffing and low‐ and high‐speed pellet injection. Conventional injectors, based on single‐stage pneumatic guns or centrifuges, can reliably provide frozen pellets (1‐ to 6‐mm‐diam sizes) at speeds up to 1.3 km/s and at suitable repetition rates (1 to 10 Hz or greater). Injectors based on two‐stage pneumatic guns and ‘‘in situ’’ condensation of hydrogen pellets can reliably achieve velocities over 3 km/s; however, they are not suitable for long‐pulse repetitive operations. An experiment in collaboration between Oak Ridge National Laboratory (ORNL) and ENEA Frascati is under way to demonstrate the feasibility of a high‐speed (≳2 km/s) repeating (∼1 Hz) pneumatic pellet injector for long‐pulse operation. A test facility has been assembled at ORNL, combining a Frascati repeating two‐st...

High-speed repetitive pellet injector for plasma fueling of magnetic confinement fusion devices

The projected fueling requirements of future magnetic confinement devices for controlled thermonuclear research [e.g., the International Thermonuclear Experimental Reactor (ITER)] indicate that a flexible plasma fueling capability is required. This includes a mix of traditional gas puffing and low- and high-velocity deuterium-tritium pellets. Conventional pellet injectors (based on light gas guns or centrifugal accelerators) can reliably provide frozen hydrogen pellets (1- to 6-mm-diam sizes tested) up to /spl sim/1.3-km/s velocity at the appropriate pellet fueling rates (1 to 10 Hz or greater). For long-pulse operation in a higher velocity regime (>2 km/s), an experiment in collaboration between Oak Ridge National Laboratory (ORNL) and ENEA Frascati is under way. This activity will be carried out in the framework of a collaborative agreement between the U.S. Department of Energy and European Atomic Energy Community-ENEA Association. In this experiment, an existing ORNL hydrogen extruder (equipped with a pellet chambering mechanism/gun barrel assembly) and a Frascati two-stage light gas gun driver have been combined on a test facility at ORNL. Initial testing has been carried out with single deuterium pellets accelerated up to 2.1 km/s with the two-stage driver; in addition, some preliminary repetitive testing (to commission the diagnostics) was performed at reduced speeds, including sequences at 0.5 to 1 Hz and 10 to 30 pellets. The primary objective of this study is to demonstrate repetitive operation (up to /spl sim/1 Hz) with speeds in the 2- to 3-km/s range. In addition, the strength of extruded hydrogen ice as opposed to that produced in situ by direct condensation in pipe guns can be investigated. The equipment and initial experimental results are described.

A new two-stage pellet injector for FTU

The most recent steps for developing injectors that meet the requirements of the Frascati Tokamak Upgrade are described. Details of a cryostat capable of building 1.6-mm-diameter deuterium pellets are given. Such pellets have been successfully accelerated up to 2.8 km/s with good repeatability, using a relatively large two-stage gun (0.5-m long, 3.5-cm diameter) as a propeller. A miniature version of the propeller was developed and tested using plastic pellets. Velocities of up to 3.2 km/s were obtained. The final goal is to build a complete miniature system capable of very high pellet velocities using reduced volumes of propelling gas.<<ETX>>

Experimental study of the propellant gas load required for pellet injection with ITER-relevant operating parameters

An existing pipe gun test facility at ORNL was used for an experimental study of propellant gas loads required for ITER-relevant pellet injection, with the key objective of determining the minimal amount of gas required for optimal pellet speeds. Two pellet sizes were tested, with nominal 4.4 and 3.2 mm diameters comparable to pellets planned for fueling and ELM pacing in ITER, respectively. A novel scheme was used to freeze solid pellets from room temperature gas; this facilitated operations at higher temperatures (14.5 to 16.5 K, similar to those planned for extruder operations for ITER pellet injectors) and thus lower pellet breakaway pressures and gas loads. Most of the single-shot D2 pellet tests were carried out with a relatively low H2 propellant gas load of ~0.0133 bar-L. Some limited testing was also carried out with a mixed propellant gas that consisted mostly of D2, which is more representative of the gas that will be used for ITER pellet injection. In testing it was found that this reference gas load resulted in pellet speeds in close proximity to a speed limit (~300 m/s) previously determined in a series of tests with D2 pellets shot through a mock-up of the curved guide tubes planned for the ITER installation (for pellet fueling from the magnetic high-field side). The equipment, operations, and test results are presented and discussed, with emphasis on the relevance for ITER operations.

Remote rendering and visualization of large textured 3D models

There is an increasingly urgent need, expressed by the scientific community and by the end users, to exploit web resources in order to analyse, process, visualize and interact remotely and in real time with 3D high definition models of Cultural Heritage artefacts and monuments. Many sharing platforms are currently developing thanks to user contributions. However this goal has not been yet reached successfully. Complex mesh models cannot be displayed interactively online on consumer computers, without downloading locally the entire model or accepting the compromise solution that the model is blurred and fuzzy during the interaction. Thus a key aspect is the quality with which the content is “distributed”, and, at the same time, the certainty of copyright protection. The platform implemented and here presented allows an efficient and effective multi-user online sharing of high quality 3D textured models without the need for the users to download it locally but exploiting the performances of a remote HPC infrastructure.

Acceleration of neon pellets to high speeds for fusion applications

The injection of impurity pellets into the plasmas of tokamak fusion reactors has been proposed as a technique to lessen the deleterious effects of plasma disruptions. Equipment and techniques that were previously developed for pneumatic hydrogen pellet injection systems and used for plasma fueling applications were employed for a limited experimental study with neon pellets. Isotopic hydrogen pellets doped with neon have previously been used for injection into fusion plasmas to study impurity particle transport, and pure neon pellets are applicable for disruption studies. Using a repeating pneumatic injector in the laboratory, it was found that the formation and acceleration of 2.7‐mm‐diam neon pellets were relatively straightforward; reliable operation was demonstrated with both a single‐ and a two‐stage light gas gun, including velocities of ∼700 m/s with a single‐stage injector and up to 1740 m/s with a two‐stage injector. Based on the operating sequences and successful tests demonstrated in the labor...

A Parallel Code for Time-Dependent acoustic Scattering Involving Passive or Smart Obstacles

A highly parallelizable numerical method to solve three-dimensional time-dependent acoustic obstacle scattering problems involving passive or smart, furtive, realistic obstacles is presented. ‘‘Realistic’’ obstacles have complex geometries, ‘‘passive’’ obstacles do not react by taking an action to pursue a goal when hit by an incoming wave, and ‘‘smart furtive’’ obstacles, when hit by an incoming wave, pursue the goal of being undetectable by circulating a suitable pressure current on their boundaries. Incoming wave packets containing time-harmonic waves of small wavelengths when compared with the characteristic dimension of the obstacles are considered. The features of the computational method proposed to solve these scattering problems that can be exploited in a parallel and/or distributed computing environment are presented. Numerical experiments involving a simplified version of the NASA space shuttle are discussed. The websites: http://www.econ.univpm.it/ recchioni/scattering/w12, http://www.econ.univpm.it/recchioni/scattering/w14 contain animations and virtual reality applications showing some numerical experiments relative to the problems studied. A more general reference to the work of some of the authors and of their coworkers in acoustic and electromagnetic scattering is the website: http://www.econ. univpm.it/recchioni/scattering.