ENEA Research Centre Research Articles

LIBS experiments for quantitative detection of retained fuel

Laser Induced Breakdown Spectroscopy (LIBS) provides chemical information from atomic and ionic plasma emissions generated by laser vaporization of a sample. At the ENEA research center, in collaboration with IPPLM, an equipment has been set up to qualitatively and quantitatively determine the chemical composition of impurities deposited on Plasma Facing Components (PFC). The strength of the LIBS, for its capability of light elements detection, is fully exploited to determine the deuterium content since this element can be considered as the best choice proxy for tritium; the latter being is of great importance in assessing safe conditions to assure the continuous operation in nuclear fusion tokamak.Here we present the results of the Double Pulse LIBS (DP-LIBS) probing of deuterated samples with the simultaneous optical detection by medium-resolution and high-resolution spectrometer. Deuterium emission at 656.1nm has been detected then the elemental composition has been quantified by applying the Calibration Free (CF) approach. The obtained results demonstrate that the DP-LIBS technique combined with CF analysis is suitable for the quantitative determination of tritium content inside the PFCs of next fusion devices like ITER.

Fusion related research with laser-induced-breakdown-spectroscopy on metallic samples at the ENEA-Frascati laboratory.

The study of plasma-wall interactions is of paramount importance for continuous and fault free operations in thermonuclear fusion research to monitor the damages of plasma facing components (PFCs), plasma pollution from impurities and wall retention of hydrogen isotopes, like tritium. These needs make laser-induced-breakdown-spectroscopy (LIBS) a suitable candidate for a real time monitoring of PFCs in the current and next generation fusion devices, like ITER. It is also worthwhile for the quantitative analysis of surfaces, with micro-destructivity of the sample and depth profiling capabilities with sub-micrometric sensitivity. In this paper LIBS spectroscopy is exploited as a valid diagnostic tool for PFCs at the ENEA Research Center in Frascati (Italy) and at the Institute of Plasma Physics and Laser Microfusion (IPPLM) of Warsaw (Poland). The activities have been focused on LIBS characterization of samples simulating PFCs surfaces eroded/redeposited or contaminated from nuclear fuel after or during the normal operation of the reactor.

Theoretical and experimental procedure for scaling-up RDF gasifiers: The Gibbs Gradient Method

The thermodynamic Model “Gibbs Free Energy Gradient Method” (GMM), published on the Vol. 90 (2011) of this Journal and validated with literature data, is now applied to the simulation of an experimental campaign realized at the ENEA Research Centre of Trisaia (Italy). The GMM well reproduces the experimental results of steam gasification of refuse-derived fuel (RDF) obtained on two laboratory and pilot scale rotary kilns.Consequently, the experimental syngas composition is put in relation to the main process parameters through a new approach incorporating the GMM for identifying a reliable correlation between the extent of reactions and the gasifier temperature. This correlation appears independent from the scale of the rotary kiln and the residence time in the investigated range of variables. On this basis, the GMM is adapted to become a tool for designing industrial gasifiers starting from experimental data since the required final composition of the syngas and the required performances may be obtained by designing a gasification zone operating at the temperature calculated by the proposed method. It is believed that this procedure is extendable to other geometries and different type of apparatus by studying and including the effect of other parameters.

Comparison of Photovoltaic plant power production prediction methods using a large measured dataset

Nowadays the estimation of power production yield by stand-alone and grid-connected Photovoltaic (PV) plants is crucial for technical and economic feasibility design analyses. The main goal is to overcome renewables unpredictability by properly estimating the power production and by suitably balancing generation and consumption. In this context, many methods can be applied to forecast renewables energy production. The scope of this paper is a comparative analysis of three different methods to estimate the power production of a preexisting PV plant. It is installed at ENEA Research Centre located in Portici (South Italy) and it is integrated in a Micro Grid (MG) configuration. In detail a phenomenological model proposed by Sandia National Laboratories and two statistical learning models, a Multi-Layer Perceptron (MLP) Neural Network and a Regression approach, are compared. These models are deeply different also in terms of required input data and parameters. In detail, phenomenological model application requires the availability of design parameters and technical devices specifications. Statistical machine learning models need, however, input variable previously acquired datasets. The a-Si/μc-Si PV plant, installed at Portici, represents an adequate case study for the three models comparison, as both design and acquired data are available. In fact, the plant was designed at the ENEA Research Centre so this makes possible the knowledge of the design parameters and, being a part of the MG, its data are continuously acquired and transmitted to other network devices. Obtained results demonstrate more accurate power predictions can be reached by statistical machine learning approaches. The main novelty of the paper consists in the optimization of the considered models by the appropriate identification of the minimum and more representative training dataset. Authors underline the unnecessary use of thousands samples by suitably selecting the dataset size and samples by means of a Genetic Algorithm. The optimization strategy effectiveness is verified comparing the prediction performances obtained employing the optimal dataset with those obtained with a randomly chosen dataset. In this scenario, Genetic Algorithm strategy represents a successful approach to the suitable identification of statistical models datasets.

Thin-film deposition and characterization for neutron detection applications

Solid state physics experimental techniques and characterization tools can provide a valuable contribution to the research and development activity on He-free neutron detection systems, for both detector assessment and performance improvement. Presently, a He replacement strategy relies on the use of 6Li - and/or 10B -based neutron-to-charged particle converters coupled to radiation detectors (solid state, gaseous and scintillators). These topics have been discussed during a devoted session within the HeRe (He- Replacement) in Italy Workshop held in Frascati at the ENEA Research Centre, and this paper aims at presenting a brief overview on possible deposition and characterization techniques of thin films that have been subject of discussion.

Development of an Advanced Simulation Model for Solar Cooling Plants

Abstract Solar Cooling systems represent an effective solution to increase the use of solar energy in buildings, satisfying cooling demand in a sustainable and efficient way. Although the reference technologies are mature (solar collectors, absorption chillers, adsorption chillers, etc.), these systems often require detailed studies to define control techniques, management integration systems and energy optimization [1,2]. This work has been focused on the development and calibration of a dynamic simulation model of a solar cooling system in order to create an efficient and robust tool to support the phases of planning and management. The model was developed in Matlab-Simulink ambient taking as a reference the system installed at the building F-51 of ENEA Research Center “Casaccia” in Rome. The calibration carried out made the model representative of reality with an average error of 10% and it has allowed us to quantify the benefits obtained by some optimization measures in order to make the maximum primary energy savings in the overall operation of the system. The simulation model can help to increase the commercial deployment of solar cooling systems when used to identify the layout of plant and the associated control strategies that maximize the system's efficiency and profitability of the investment.

Shroud like coloration of linen, conservation measures and perception of patterns onto the Shroud of Turin

We present new experimental results on ultraviolet laser processing of linen fabrics that complete and update the previous studies at the ENEA Research Centre of Frascati seeking a coloration mechanism able to reproduce the microscopic complexity of the body images embedded onto the Shroud of Turin. The achievement of a Shroud-like coloration of linens by using vacuum ultraviolet light pulses allowed to recognize the main photochemical reactions possibly involved in the coloration process. The identification of these reactions offered hints for long-term conservation measures of the body images on the Shroud of Turin. Finally, we discuss how image processing of photographs of the Shroud may cause misleading effects, which led some researchers to perceive, e.g., inscriptions and a second face on the backside of the cloth, which are unlikely to be on the Shroud, confirming that there is a narrow boundary between image enhancement and manipulation.

Chemical Composition of Fine and Coarse Aerosol Particles in the Central Mediterranean Area during Dust and Non-Dust Conditions

A two-month field campaign was carried out from May to June 2010 at a remote site (Trisaia ENEA Research Centre) in the Southern Italy aiming to identify and quantify the changes of aerosol chemical composition in the presence of Saharan dust. The 24-hr PM_(10) and PM_(2.5) filter samples were analyzed by mass, carbonaceous species, inorganic ions and elemental composition. Saharan dust transport events were identified with two approaches: one recommended by EC (2011) and one based on indicators derived from measurements. Three indicators were used: PM_(2.5)/PM_(10) mass concentrations ratio, Ca/Al ratio and Al concentration. Based on these criteria, four Saharan dust transport events were identified, but only one had elevated dust concentration and leaded to an exceedance of the European short-term (24 hour) limit value of 50 μg/m^3 for PM_(10) (June 16^(th)). The comparison of chemical composition of fine and coarse aerosol fractions during dust and non-dust conditions shows that the presence of dust increases NH_4 and nssSO_4 concentrations in the fine fraction and NO_3 and nssSO_4 concentrations in the coarse fraction. OC and EC concentrations also increase in the fine fraction during dust transport. The uptake of primary and secondary species, inorganic and organic, by dust particles changes their composition and, thus, their properties and this may have implications for human health and climate change.

The radiation fields around a proton therapy facility: A comparison of Monte Carlo simulations

A proton therapy test facility with a beam current lower than 10nA in average, and an energy up to 150MeV, is planned to be sited at the Frascati ENEA Research Center, in Italy. The accelerator is composed of a sequence of linear sections. The first one is a commercial 7MeV proton linac, from which the beam is injected in a SCDTL (Side Coupled Drift Tube Linac) structure reaching the energy of 52MeV. Then a conventional CCL (coupled Cavity Linac) with side coupling cavities completes the accelerator. The linear structure has the important advantage that the main radiation losses during the acceleration process occur to protons with energy below 20MeV, with a consequent low production of neutrons and secondary radiation. From the radiation protection point of view the source of radiation for this facility is then almost completely located at the final target. Physical and geometrical models of the device have been developed and implemented into radiation transport computer codes based on the Monte Carlo method. The scope is the assessment of the radiation field around the main source for supporting the safety analysis. For the assessment independent researchers used two different Monte Carlo computer codes named FLUKA (FLUktuierende KAskade) and MCNPX (Monte Carlo N-Particle eXtended) respectively. Both are general purpose tools for calculations of particle transport and interactions with matter, covering an extended range of applications including proton beam analysis. Nevertheless each one utilizes its own nuclear cross section libraries and uses specific physics models for particle types and energies. The models implemented into the codes are described and the results are presented. The differences between the two calculations are reported and discussed pointing out disadvantages and advantages of each code in the specific application.

Electricity production by biomass steam gasification using a high efficiency technology and low environmental impact

The integration of biomass gasification and fuel cell represents in theory an energy effective solution for decentralised CHP production. At the ENEA Research Centre of Trisaia the direct coupling of an existing biomass gasification pilot plant to a molten carbonate fuel cell (MCFC) with a capacity of 125kWe is in progress.Being pressurised at 3.5bar, MCFC shall be combined to a gas turbine in order to establish an efficient process scheme for its industrial scale application. Assuming an optimised gas composition, free of methane and other light hydrocarbons, an overall conversion efficiency minor to 40% is estimated via an appositely developed model based on thermodynamic models. Even this value is one-third higher with respect to conventional gasification for decentralised CHP production, the commercial perspective of the proposed technology still proves to be modest, unless remarkable improvements in stack conversion efficiency, durability and cost are achieved, as well as an impressive plant simplification.The main goal of the paper is the integration of a biomass steam gasification plant with a molten carbonate fuel cell with the advantage of a power production plant with a low CO2 emission compared with the traditional power generator fuelled by fossil.

Fine carbonaceous aerosol characteristics at a coastal rural site in the Central Mediterranean as given by OCEC online measurements

In order to know the variability and to understand the sources of carbonaceous aerosol in the Central Mediterranean area, a two month (May and June 2010) field campaign was carried out at Trisaia ENEA Research Centre (Italy). The semi-continuous measurements of organic carbon (OC) and elemental carbon (EC) showed one order of magnitude variation during the campaign, with very low EC concentrations. The diurnal variation of EC was similar to the diurnal variation of NO2 concentration, of number concentration of aerosol particles with diameters between 0.25 and 2.5μm and of traffic flow while the diurnal variation of OC was more related to the meteorological conditions. The increase of OC observed early in the morning may be due to an increase of the secondary organic aerosol (SOA) fraction, in low wind conditions, increasing solar radiation and in the presence of air masses rich in volatile organic compounds (VOC) transported from the NW, and due to the presence of primary biological aerosol particles such as bacteria, spores and pollen.

Identification of standard explosive traces by infrared laser spectroscopy: PCA on LPAS data

Infrared spectroscopy based methods are promising in the design of an integrated optical system for the real time detection and identification of explosive species to support homeland security. Infrared laser photoacoustic spectroscopy (LPAS) analysis of explosive compounds (DNT; TNT; RDX; HMX; TATP; PETN; TETRYL) and TOLUENE was reported. Standard commercial samples of the explosive species were analyzed in solid phase by a home made PAS apparatus equipped with a stabilized 10 W continuous wave CO2 laser source. A very small amount (less than 100 μg) of the sample was sufficient to produce a clear signal in a 3 cc volume PA cell. The spectral data were treated by a principal component analysis (PCA) based algorithm. In a three principal components representation of the results, every explosive species resulted to be very well distinguishable from each other, as well as from toluene and other solvents. The reported experimental activity was performed in the Molecular Spectroscopy Laboratory of ENEA Research Centre in Frascati in the frame of ISOTREX European Project.

Experimental validation of a probabilistic model for estimating the double axis PV tracking energy production

This work aims to study the impact of different models for the evaluation of the efficiency of a double axis PV tracking system on the monthly probability distribution function of the AC power. Two components of the global efficiency are analysed, that is: the effect of PV cells temperature on the module efficiency and the DC/AC converter efficiency. In particular, the temperature efficiency model combines basic parameters characterizing the array, with the local monthly average temperature and the monthly clearness index to yield a monthly average efficiency. The simulation results are compared with experimental data related to a 9.6kWp PV plant installed in ENEA research centre located in Portici, Naples (Italy). The tuning of the model is performed by both system measurements and environmental data.

The TOP-IMPLART project

A new proton therapy center is planned to be built in Rome, Italy. The project, named TOP-IMPLART, is developed by three institutions, ENEA (Agenzia Nazionale per le Nuove tecnologie, l’Energia e lo Sviluppo Economico Sostenibile - Italian national agency for new technologies, energy and sustainable economic development), ISS (Istituto Superiore di Sanita, Italian National Institute of Health) and IFO-IRE (Istituto Fisioterapico Ospedaliero - Istituto Regina Elena, Regina Elena, National Cancer Institute in Rome). The project is centered on a medium-energy proton accelerator designed as a sequence of linear accelerators. Two phases of construction are foreseen: the first (funded by the Italian Regione Lazio for 11 M€ spread over four years) with a maximum energy of 150 MeV and the second one up to 230 MeV. The segment up to 150 MeV is under construction and will be tested at the ENEA Research Center in Frascati before the transfer to IFO that is the clinical user. The basic concepts of the design are described here.

Simulation model of a molten carbonate fuel cell–microturbine hybrid system

Abstract A Hybrid System based on High Temperature Fuel Cells coupled to a Microturbine allows a high efficiency, low environmental pollution and it may be exploited as a CHP System producing heat and electricity both Grid Connected and Stand Alone; the overall electrical efficiency could reach a very high value (up to 60%) and total efficiency could be over 70% including the contribution due to heat recovery. In the context of wide research activities of ENEA on High Temperature Fuel Cells and Hybrid Systems – that involve materials, system BoP and fuels – a very great effort has been devoted to design and build, in the ENEA Research Centre of “Casaccia”, an experimental Test-Rig based on a Molten Carbonate Fuel Cells Emulator and a Microturbine, to evaluate components performance characteristics at different operating conditions. To obtain relevant and reliable data and to compare them to the future experimental test results, a careful numerical simulation analysis of an Hybrid System has been developed by the Authors and it is presented in this Article. The numerical models of the System components were implemented in IPSE Pro™; the performance characteristics have been derived by evaluating operational parameters at nominal and partial loads and, moreover, a sensitivity analysis – varying main working parameters – has been performed on steady state conditions. The simulations show in detail the behaviour of both the Hybrid System and the Subsystems varying the main parameters (output electrical power, inlet flow rates, working pressure, power density, etc.) including rotational speed configuration of Microturbine.

First studies of pico- and nanoplankton populations by a laser scanning flow cytometer

The innovative laser scanning flow cytometer (LSFC) CLASS, developed at ENEA Research Center of Frascati, merges the ability to perform very fast analyses on a statistically significant number of particles to the capability of characterizing, from a morphological and optical point of view, cells even if they are not fluorescent. In this work two cultured populations of picoplankton and nanoplankton have been analyzed by means of CLASS to evaluate the future applicability of this system as a tool for the early detection of algal blooms. The analyses were performed on a red pigmented Synechococcus sp. and C hlamydomonas reinhardtii by measuring simultaneously the side scattering, scattering in the wide angular range 5–100°, fluorescence in two spectral bands and depolarization of the laser light by every single cell contained in the sample. The results highlighted the ability of CLASS to characterize cell populations in which standard flow cytometers encounter difficulties and in which the use of traditional time-consuming image analyses is often required, such as those characterized by different morphologies in a small size with little or no fluorescence. In particular the system presented was demonstrated to be suitable for the study of composition and changes in a phytoplankton population.

Photoacoustic spectroscopy of standard explosives in the MIR region

An emerging and important topic of interest in the field of homeland security is the identification and quantification of explosives. This paper brings new elements in the Laser Photoacoustic Spectroscopy (LPAS) based characterisation of some classical explosives (2,4-DNT; 2,6-DNT; HMX; TATP; PETN) in solid phase at CO 2 laser wavelengths, not yet reported in the literature to our knowledge. Moreover, we report our LPAS analysis of TNT and RDX, already previously studied with the same technique in the same spectral interval by different authors. The reported photoacoustic signals from standard commercial samples of the classical explosive substances were recorded in the 9–11 μm region, by a CO 2 laser based homemade optical apparatus. The underlying experimental activity was performed in the molecular spectroscopy laboratory of the ENEA Research Centre in Frascati.

Laser–plasma–source debris-related investigations: an aspect of the ENEA micro-exposure tool

Debris mitigation is still a critical issue for the development of extreme ultraviolet projection lithography (EUVL). Here, we describe the analysis of the efficiency of the debris-mitigation system (DMS) presently in use in the laser–plasma–source micro-exposure tool (MET) operating at the Frascati ENEA Research Center. Basic to such an analysis is a code specifically developed for processing the images of debris-flux-exposed glass slides. The code stands out as a tool for further plasma debris-related analyses.

Excimer-Laser-Driven EUV Plasma Source for Single-Shot Projection Lithography

We present a low-cost microexposure tool for projection lithography at 14.4 nm we have designed and operated at the ENEA Research Centre, Frascati. It is a laboratory-scale system based on a Schwarzschild-type projection optics which uses a laser-plasma soft X-ray source, equipped with a patented debris mitigation system in order to preserve the collector optics. As a preliminary result, we achieved a 90-nm optical resolution patterning on commercial resist. A sharp improvement in resolution size is expected when operating this tool by a large-output energy excimer laser in order to obtain a single-shot patterning.

Interaction of a smoothed laser beam with supercritical-density porous targets on the ABC facility

We present the results of experiments on the interaction of laser radiation with low-density porous targets performed on the ABC facility at the ENEA Research Centre (Frascati, Italy). Porous plastic targets with densities of 5 and 20 mg cm-3 were irradiated by a focused neodymium-laser beam at the fundamental frequency (λ = 1.054 μm) at a radiation intensity of 1013 W cm-2 at the target. The beam was preliminarily allowed to pass through an optical system intended to spatially smooth the radiation intensity over the beam cross section. The use a smoothed beam was important to discover in the plasma and in the accelerated dense material the features related to the porous structure of the target under conditions which rule out the effect of the inhomogeneities of the heating beam itself. The spatial plasma structure in the laser beam—target interaction region and at the rear side of the target were investigated by using optical schlieren plasma photography. The time dependent transmission of the laser radiation through the target was also investigated by imaging the target in transmitted radiation to a properly masked photodiode.