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In recent years, technological innovation has acquired a fundamental role in the agri-food sector and in particular in food quality control. The development of technology allowed to improve the quality of the food before it is placed on the market. Recently, non-invasive techniques such as those operating in the THz spectral band were applied to the field of food quality control. In the laboratories of the ENEA centre in Frascati, close to Rome-Italy, has been developed a THz imaging system operating in reflection mode and an experimental setup able to measure both reflection and transmission of the samples in the frequency range between 18-40 GHz. With these two setups will distinguish rotten and healthy hazelnuts acquiring in real time both images of the fruit inside the shell by using the imaging system and the transmission data exploiting the 18-40 GHz system.

THz radiation is non-ionizing and non-invasive. Exploiting these features, THz technologies could be used to perform inspections on food quality control. The objective of this study is to discriminate healthy and rotten hazelnuts by using a 97 GHz imaging system.

In recent years, the concept of smart agriculture has entered our collective daily routine by radically modifying the methods by which crop monitoring was previously carried out. More precisely, the term smart farming focuses its attention on the use technologies already present on the market like, sensors (multispectral, hyperspectral, thermal and terahertz sensors), WNS (wireless sensor network) and drones capable to reduce the human work in the fields, optimizing at the same time the quantity and quality of the products limiting the use of resources, as water, fertilizers, pesticides and herbicides. Recently, one of the most important problem in the field of precision farming is the availability of water; unfortunately, this factor becomes more critical from year to year. To resolve this problem, the first step is to reduce consumption and rationalize the use of water by adjusting the water supply to the needs of the systems in order to increase its yield while saving money. In this respect, the development of non-destructive techniques operating in the THz spectral region has allowed to monitor in real time the water content present in leaves and plants. In fact, due to the strong water absorption and reflection in this spectral region, this feature can be exploited to detect the water content of leaves and plants helping us to intervene promptly in cases where the plant needs water, avoiding so does water stress, but above all trying to use our primary resource adequately by reducing waste. About this, Imaging and Time-Domain Spectroscopy (THz-TDS) techniques have been applied to monitor soil conditions, drought stress and presence of pathogens on the plants. In this review, we focus our attention on the latest research carried out on monitoring the water content present in leaves through THz technologies. Moreover, we pose particular attention in the description of our system set composed by a 97 GHz transmitter-receiver able to analyze the spatial distribution of the water inside a leaf.

The rapid advance of terahertz technologies in terms of radiation generators, systems, and scientific or industrial applications has put a particular focus on compact sources with challenging performances in terms of generated power (peak and/or average), radiation time structure, and frequency band tunability. Free electron laser (FEL)-based sources are probably the best candidates to express such a versatility, there are a number of schemes that have been investigated over the years to generate coherent radiation from free electrons in the mm-wave and terahertz regions of the spectrum, covering a wide frequency range from approximately 100 GHz to 10 THz. This paper proposes novel schemes for exploring the limits in the performance of radio frequency-driven free-electron devices in terms of ultrashort pulse duration, wide bandwidth operation, and energy recovery for near continuous wave (CW) operation. The aim of the present work is to demonstrate the feasibility of an FEL achieving performance comparable to a conventional photoconductive THz source, which is commonly used for time-domain spectroscopy (TDS), in terms of bandwidth and pulse duration. We will also demonstrate that a THz FEL could be very powerful and flexible in terms of tailoring its spectral features.

The applications of Terahertz (THz) technologies have significantly developed in recent years, and the complete understanding of the biological effects of exposure to THz radiation is becoming increasingly important. In a previous study, we found that THz radiation induced genomic damage in fetal fibroblasts. Although these cells demonstrated to be a useful model, exposure of human foetuses to THz radiation is highly improbable. Conversely, THz irradiation of adult dermal tissues is cause of possible concern for some professional and nonprofessional categories. Therefore, we extended our study to the investigation of the effects of THz radiation on adult fibroblasts (HDF). In this work, the effects of THz exposure on HDF cells genome integrity, cell cycle, cytological ultrastructure and proteins expression were assessed. Results of centromere-negative micronuclei frequencies, phosphorylation of H2AX histone, and telomere length modulation indicated no induction of DNA damage. Concordantly, no changes in the expression of proteins associated with DNA damage sensing and repair were detected. Conversely, our results showed an increase of centromere-positive micronuclei frequencies and chromosomal nondisjunction events, indicating induction of aneuploidy. Therefore, our results indicate that THz radiation exposure may affect genome integrity through aneugenic effects, and not by DNA breakage. Our findings are compared to published studies, and possible biophysical mechanisms are discussed. Environ. Mol. Mutagen. 59:476-487, 2018. © 2018 Wiley Periodicals, Inc.

In this paper, we report on Vis-IR hyperspectral and terahertz imaging investigations carried out on a fresco painting on tavella depicting St. John Baptist, by Alessandro Gherardini (1655-1726). Measurements took place at the Restoration Laboratories of the former "Polo Museale della Toscana," in Florence, in the framework of the Italy-Japan collaborative project THz-ARTE. We show how the hyperspectral data made it possible to determine the state-of-conservation of Gherardini's painting, while reflection imaging measurements performed at 97 GHz provided a qualitative evaluation of the position of defects inside the tavella.

Electron Cyclotron Resonance Heating (ECRH) systems in future fusion devices, like the DEMO-nstration reactor, foresee an operational frequency in the range 230–280 GHz to match the plasma characteristics. Cyclotron Auto Resonance Masers (CARMs) could represent an alternative to gyrotrons as effective source of mm and sub-mm waves and the project of a 250 GHz, 0.5 MW CARM has been undertaken at ENEA. Mode converters from the TE10 in WR3 rectangular waveguide to the operational mode (TE53) are required to perform the RF cold test of Bragg reflectors and cavities. In this paper an improved and feasible structure for the TE11 to TE04 conversion, in oversized circular waveguides, using only two transitions with profile and radius optimized in order to obtain high efficiencies and sufficient bandwidth, has been designed and the simulation results are presented. The first transition is a TE11/TE01 serpentine mode converter in circular waveguide (efficiency of 95%) with average radius of 1.48 mm and an appropriate number of geometrical periods. The second one, a TE01/TE04 rippled wall mode converter with efficiency of 97%, consists of a single conversion section with an average radius of 3 mm and sixteen sinusoidal periods instead of three conversion sections (TE01/TE02, TE02/TE03, TE03/TE04) in cascade, thus reducing the complexity and the length of the full transition chain.

In recent years, THz imaging techniques have been used in several fields of application. At the beginning of the century, the low availability of powerful THz sources was one of the limiting factors to the advancement of THz technology. At the ENEA center in Frascati, two Free Electron Lasers (FELs) operating in the THz spectral region were available at that time, making it possible to exploit all the features of THz imaging. In this paper, we will describe an alternative THz imaging technique, developed over 15 years of studies at the ENEA center of Frascati, and its application in the art conservation field, reporting the latest results of such studies on the optical properties of pigments in the GHz-THz region of the spectrum, on the possibility of detecting biological weeds under mosaic tiles and on the THz analysis of ancient leather wallpapers. This alternative technique was first developed in the framework of a bilateral collaboration between Japan and Italy, the THz-ARTE Project, which involved NICT (Tokyo), NNRICP (Nara), ENEA (Frascati) and IFAC-CNR (Florence). Most of the THz imaging techniques at that time were based on THz-Time Domain (THz-TD) devices. In the paper will be described how this alternative technique is able to measure the phase of the reflected radiation, thus providing information on the optical properties of the materials under study, such as mural paintings and mosaics. This makes it possible to detect the presence of hidden artworks, additional elements under paint layers, and dielectric materials. To describe the potential and the limits of this alternative imaging technique we will start from a description, in chapter 2, of the first THz imaging setup at the ENEA center of Frascati, based upon a THz Free Electron Laser. A description of the theoretical principle underlying this technique will be given in chapter 3. The first results in the field of art conservation are summarized in chapter 4, while the new results of a systematic study on the optical properties of pigments are reported in chapter 5. In chapter 6 the realization of a portable THz imaging device, and its application &ldquo, on site&rdquo, for the analysis of frescoes are shown. The success of this prototype lead to the identification of different types of artworks as possible targets to be studied. New results about the ability of detecting water, and possibly the water content of biological weeds, under mosaic tiles are described in chapter 7, while new experimental measurements on Leather Wallpapers, both &ldquo, in situ&rdquo, and in a laboratory environment, are discussed in chapter 8. A final analysis on the pro and the cons of this alternative imaging technique and on its possible utilization with the developed prototype is carried out in chapter 9, together with the considerations on possible future developments and its potential use as an extension of other imaging techniques.

The electromagnetic radiation, in the range from IR to X-rays, is widely used in the field of art conservation and diagnostics. In the last few years a new interest was devoted to the longer wavelengths, in the so called "THz region" of the spectrum, due to the peculiar characteristics of the radiation in this spectral range, that make it ideal for applications in this field [1]: it's low photon energy and its ability to penetrate dielectric materials. This high penetration capabilities were used to demonstrate the possibility to detect artwork hidden under layers of other dielectric materials [2]-[4]. Making use of phase-sensitive techniques it is also possible to get information on the optical properties of the materials under study and to obtain images that include spectroscopic information about the sample [5]. Moreover, radiation in the THz range is strongly reflected and absorbed by water, and this feature can be used to study degradation in mural paintings and mosaics. © 2018 IEEE.

The applications of Terahertz (THz) technologies have significantly developed in recent years, and the complete understanding of the biological effects of exposure to THz radiation is becoming increasingly important. In a previous study, we found that THz radiation induced genomic damage in fetal fibroblasts. Although these cells demonstrated to be a useful model, exposure of human foetuses to THz radiation is highly improbable. Conversely, THz irradiation of adult dermal tissues is cause of possible concern for some professional and nonprofessional categories. Therefore, we extended our study to the investigation of the effects of THz radiation on adult fibroblasts (HDF). In this work, the effects of THz exposure on HDF cells genome integrity, cell cycle, cytological ultrastructure and proteins expression were assessed. Results of centromere-negative micronuclei frequencies, phosphorylation of H2AX histone, and telomere length modulation indicated no induction of DNA damage. Concordantly, no changes in the expression of proteins associated with DNA damage sensing and repair were detected. Conversely, our results showed an increase of centromere-positive micronuclei frequencies and chromosomal nondisjunction events, indicating induction of aneuploidy. Therefore, our results indicate that THz radiation exposure may affect genome integrity through aneugenic effects, and not by DNA breakage. Our findings are compared to published studies, and possible biophysical mechanisms are discussed. Environ. Mol. Mutagen. 59:476-487, 2018. © 2018 Wiley Periodicals, Inc.

In the last decades, technological development has led to an increasing use of devices and systems based on microwave radiation. The increased employment of these devices has elicited questions about the potential long-term health consequences associated with microwave radiation exposure. From this perspective, biological effects of microwave radiation have been the focus of many studies, but the reported scientific data are unclear and contradictory. The aim of this study is to evaluate the potential genotoxic and cellular effects associated with in vitro exposure of human fetal and adult fibroblasts to microwave radiation at the frequency of 25 GHz. For this purpose, several genetic and biological end points were evaluated. Results obtained from comet assay, phosphorylation of H2AX histone, and antikinetochore antibody (CREST)-negative micronuclei frequency excluded direct DNA damage to human fetal and adult fibroblasts exposed to microwaves. No induction of apoptosis or changes in prosurvival signalling proteins were detected. Moreover, CREST analysis showed for both the cell lines an increase in the total number of micronuclei and centromere positive micronuclei in exposed samples, indicating aneuploidy induction due to chromosome loss.

In this paper we discuss characteristics of detectors and their experimental applications in the Far Infared (FIR) and lower THz spectral range: 50-3000 GHz (6mm-100 μm), with special attention to Plasma Diagnostics, THz-TDS and Free Electron Lasers (FEL). The International System of Units (SI) will be used throughout [1]. © 2018 IEEE.

In this paper, we present a comprehensive discussion of the results obtained after in vitro exposure of human fetal fibroblasts and human adult fibroblasts to pulsed radiation in a wide band between 100 and 150 GHz and to continuous wave radiation at 25 GHz. In order to assess potential effects of exposure, the genome integrity, cell cycle, cytological ultrastructure, and proteins expression were evaluated.

THz radiation is strongly absorbed, as well as reflected, by water. This spectral feature can be exploited to detect the presence of water under the surface of mural paintings and mosaics. In this study we report on the capability of our 3D reflective THz imaging system to detect water under samples simulating a fresco or a mosaic. © 2017 IEEE.

A mode conversion from the TE10 in WR3 rectangular waveguide to the TE53 in an oversized circular waveguide is required to perform the cold test of a Bragg resonator for a high power 250 GHz Cyclotron Auto-Resonance Maser (CARM) under development at the Frascati ENEA research centre. High operating frequency and oversized cylindrical cavity (exceeding any previous CARM experiment) make the design particularly challenging. An initial transition, aimed at transforming the TE10 in WR3 rectangular waveguide into the TE11, in a circular waveguide, is performed using a linear taper, a well-assessed device. Then a serpentine mode converter in circular waveguide with average radius of 1.48 mm and appropriate length has been adopted for the conversion into the TE01 mode. The subsequent transducers, for not-rotating (TE0m) and rotating (TE53) modes, are provided by means of rippled wall mode converters with small periodic perturbations of waveguide radius. The ripple period corresponds approximately to the beat wavelength (?b = 2p/(ßm-ßn)) with ßm and ßn the wavenumbers of the two interacting modes. For not-rotating modes an efficient conversion has been obtained by cascading single step TE01 to TE02, TE02 to TE03 and TE03 to TE04 mode converters. For each of them, profiles, radius and number of periods have been optimized in order to obtain low levels of unwanted spurious modes, low reflection and sufficient bandwidth. As the modes to convert (TE04 to TE53) present similar wavenumbers, the most appropriate method for the conversion consists in a three-periods rippled-wall mode converter made by a helically corrugated waveguide with an average radius of 4 mm and five azimuthal variations. The longitudinal profile of the ripples has been properly smoothed to avoid steps between the circular waveguide and the corrugated converter.In this paper the conversion chain will be described and the simulation results (S-parameters, efficiency and electric field) of each single converter will be reported. Finally some considerations about the high precision micromachining technique to be used, such as copper electroforming and Computer Numerically Controlled (CNC) milling, for the construction of these high frequency components, will be presented. © 2018 Electromagnetics Academy. All rights reserved.

The 0.1-30 THz frequency range routinely studied with time-domain spectroscopy (TDS), has an unquestionable diagnostic potential for tokamak plasmas, thus THz-TDS applications appear to be the natural evolution of FIR and submillimeter wave diagnostics. By illuminating the plasma with a THz beam, phase, intensity and polarization of reflected and transmitted wave can be simultaneously detected, potentially measuring several plasma parameters with a single diagnostic. © 2016 IEEE.

Characterization and calibration measurements of two Cherenkov probes have been performed in ENEA Frascati's laboratories. Different kinds of radiation have been used, from visible light to x-rays, in order to evaluate possible spurious responses of the probes. Moreover, a preliminary calibration is presented, as well as a first evaluation of the minimum single probe's detectable flux performed through an electron beam of 2.3 MeV. Additional results have been obtained thanks to spectrometry analysis, which gave deeper insights of the phenomena occurring inside the probes. In particular, a continuous emission spectrum, associated to cathodoluminescence, has been observed to dominate in the Cherenkov range, showing that scintillating phenomena are not negligible in this kind of probes. Results on non-thermal electron losses from recent FTU experimental campaigns are also presented. The signals acquired are compared to those from other diagnostics like x-rays, neutron and gamma detectors or plasma magnetic activity, showing good correlation between them. The analysis focuses on the capability and sensitivity of the probes to measure runaway electrons losses with energy discrimination in presence of perturbations due to kinetic and magnetic reconnection phenomena. © 2018 IOP Publishing Ltd.

Although terahertz (THz) radiation was first observed about 100 years ago, this portion of the electromagnetic spectrum at the boundary between the microwaves and the infrared has been, for a long time, rather poorly explored. This situation changed with the rapid development of coherent THz sources such as solid-state oscillators, quantum cascade lasers, optically pumped solid-state devices, and novel coherent radiator devices. These in turn have stimulated a wide variety of applications from material science to telecommunications, from biology to biomedicine. Recently, there have been two related compact coherent radiation devices invented able to produce up to megawatts of peak THz power by inducing a ballistic bunching effect on the electron beam, forcing the beam to radiate coherently. An introduction to the two systems and the corresponding output photon beam characteristics will be provided.

A comprehensive study of the in-vitro exposure of human fibroblasts to millimeter waves in a wide spectral region is under way. The evaluation of different biological endpoints as result of exposure to pulsed radiation in the frequency range 100-150 GHz with the ENEA Compact FEL is reported. A new exposure set-up for irradiation to CW radiation in the range 18-40 GHz will also be presented. © 2015 IEEE.

We present the state of development of a THz-based Time-Domain Spectroscopy (TDS) system for FTU Tokamak. TDS is ideal to measure plasma characteristics that are non-uniform and/or evolve during the discharge: THz pulses (0.1-2 THz) produced with femtosecond mode-locked lasers (790 nm) conveniently span the spectrum above and below the plasma frequency and, thus, can be used as very sensitive and versatile probes of widely varying plasma parameters. This work is based on an existing collaboration between ENEA Frascati and the Photonics Group at Clarendon Laboratory, Oxford University, where a THz-TDS experimental apparatus has been assembled and characterised. The spectral response of diagnostic-relevant components and materials has been tested. The instrument is now being equipped with fiber-optics to guide the laser beam to the THz Emitter and Receiver to ease access through the Tokamak ports. Broadband THz pulse propagation in plasma has been simulated using a simple, yet effective Fourier Transform-based model. In the Tokamak environment, THz TDS can be used in conjunction with other diagnostic techniques, such as, interferometry and ECE, for the simultaneous measurement of dispersion and absorption to launch a bridge between major areas of research in the science landscape. (C) 2015 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license.

In recent years, terahertz (THz) radiation has been widely used in a variety of applications: medical, security, telecommunications and military areas. However, few data are available on the biological effects of this type of electromagnetic radiation and the reported results, using different genetic or cellular assays, are quite discordant. This multidisciplinary study focuses on potential genotoxic and cytotoxic effects, evaluated by several end-points, associated with THz radiation. For this purpose, in vitro exposure of human foetal fibroblasts to low frequency THz radiation (0.1-0.15. THz) was performed using a Compact Free Electron Laser. We did not observe an induction of DNA damage evaluated by Comet assay, phosphorylation of H2AX histone or telomere length modulation. In addiction, no induction of apoptosis or changes in pro-survival signalling proteins were detected. Moreover, our results indicated an increase in the total number of micronuclei and centromere positive micronuclei induction evaluated by CREST analysis, indicating that THz radiation could induce aneugenic rather than clastogenic effects, probably leading to chromosome loss. Furthermore, an increase of actin polymerization observed by ultrastructural analysis after THz irradiation, supports the hypothesis that an abnormal assembly of spindle proteins could lead to the observed chromosomal malsegregation. © 2015 Elsevier B.V.

We discuss an extensive set of experimental results about the spectroscopic properties of different materials in THz spectral range, as part of the development of a THz-based Plasma Diagnostic for Nuclear Fusion Applications. The Terahertz (THz) band of the electromagnetic spectrum is defined as the frequency range between microwaves and midinfrared light [1,2]. Since 2010 a successful collaboration between ENEA Frascati and the Photonics Group at Clarendon Laboratory, Oxford University, has been in place to extend the use of THz Time Domain Spectroscopy (TDS) techniques to harsh environment applications, namely Tokamak Plasma diagnostics for Fusion research [3]. The simultaneous use of large portions of the electromagnetic spectrum in the form of THz pulses produced with femtosecond mode-locked lasers provides an appealing tool to diagnose plasma phenomena spanning above and below the plasma frequency [4]. THz pulses can be used as very sensitive and versatile probes of widely varying plasma parameters especially for diagnostic applications in Tokamaks where plasma characteristics are non-uniform and evolve during the discharge. We designed and assembled a table-top free-air THz-TDS setup based on a femtosecond infrared laser pulse (790 nm) and photoconductive GaAs plates [2]. The system has been designed with a great deal of flexibility, to experiment different solutions for coupling optical systems, path difference scan and Group Velocity Delay (GVD) compensation. Recently we used a commercial Advantest TAS7500TS Terahertz Analysis System for a preliminary test of the long range optics and to measure the spectroscopic properties of materials and components relevant for Plasma Physics diagnostics, over an unprecedentedly large spectral range.

SPARC-X is a two branch project consisting in the SPARC test facility dedicated to the development and test of critical subsystems such as high brightness photoinjector and a modular expandable undulator for SASE-FEL experiments at 500 nm with seeding, and the SPARK facility aiming at generation of high brilliance coherent radiation in the 1.5-13 nm range, based on the achieved expertise. The projects are supported by MIUR (Research Department of Italian Government) and Regione Lazio. SPARC has completed the commissioning phase of the photoinjector in November 2006. The achieved experimental results are here summarized together with the status of the second phase commissioning plans. The SPARK project is based on the generation of ultra high peak brightness electron beams at the energy of 1 and 2 GeV generating radiation in the 1.5-13 nm range. The construction is at the moment planned in two steps starting with a 1 GeV Linac. The project layout including both RF-compression and magnetic chicane techniques has been studied.

FELs based on SASE are believed to be powerful tools to explore the frontiers of basic sciences, from physics to chemistry to biology. Intense R&D programs have started in the USA and Europe in order to understand the SASE physics and to prove the feasibility of these sources. The allocation of considerable resources in the Italian National Research Plan (PNR) brought about the formation of a CNR–ENEA–INFN–University of Roma “Tor Vergata” study group. A conceptual design study has been developed and possible schemes for linac sources have been investigated, leading to the SPARX proposal. We report in this paper the results of a preliminary start to end simulation concerning one option we are considering based on an S-band normal conducting linac with high-brightness photoinjector integrated in an RF compressor.

The aim of the present study is toinvestigate the genotoxic effect of THzradiation in human peripheral bloodlymphocytes following 20 minutes exposureto 1 mW average power Free Electron Laserradiation in the frequency range 120–140GHz. For this purpose 9 healthy donors wereemployed and cytokinesis block techniquewas applied to study micronucleusfrequency and cell proliferation. Theresults obtained indicate that all theelectromagnetic conditions adopted so far do not alter the investigated parameters,suggesting absence of direct chromosomaldamage and alteration of cell cyclekinetics (two tailed paired Student's test:p> 0.05 in all cases).

A compact THz Free Electron Laser (FEL) isbeing used to perform irradiation ofbiological samples to investigate possiblegenotoxic effects. In order to evaluate theexact radiation dose absorbed by the singlecomponents of the samples it is necessaryto study the optical properties of thesamples, separating the contributions tothe radiation attenuation coefficientcoming from absorption and from diffusion.Spectroscopic measurements have beenperformed on different biological samples, comparing the experimental results withtheoretical models.

Recent measurements at Frascati of the Smith–Purcell radiation emitted from the interaction of a 2.3 MeV (total) electron beam with a 2.5 mm grating show clear evidence of coherent enhancement of the radiation, with power levels exceeding 100 mW at emission angles around 90° relative to the beam direction. The experimental results are in reasonable agreement with theoretical predictions and suggest that Smith–Purcell radiation may offer a simple way of determining the shape and duration of short (picosecond) electron bunches.

In this paper, a comparison between the conventional Tera-Hertz (THz) sources and a THz radiator based on free electron devices is proposed. The basic idea of the exploitation of some of the features of the RF FELs will be presented together with some examples that could represent an appealing source to start with. A discussion about the link between the spectrum of the emitted radiation and the electron bunch length is presented. The necessity of generating very short bunch of electrons to be injected in the radiator is demonstrated.

The Terahertz imaging technique was applied to observe the preparation layer of wall paintings. The experimental results revealed the effect of the particle size of fillers and the possibility of internal interface observation by the THz pulse-echo imaging. © 2014 European Microwave Association.

The technology is now becoming mature for diagnostics using large portions of the electromagnetic spectrum simultaneously, in the form of THz pulses. THz radiation-based techniques have become feasible for a variety of applications, e.g., spectroscopy, imaging for security, medicine and pharmaceutical industry. In particular, time-domain spectroscopy (TDS) is now being used also for plasma diagnostics in various fields of application. This technique is promising also for plasmas for fusion applications, where plasma characteristics are non-uniform and/or evolve during the discharge This is because THz pulses produced with femtosecond mode-locked lasers conveniently span the spectrum above and below the plasma frequency and, thus, can be used as very sensitive and versatile probes of widely varying plasma parameters. The short pulse duration permits time resolving plasma characteristics while the large frequency span permits a large dynamic range. The focus of this work is to present preliminary experimental and simulation results demonstrating that THz TDS can be realistically adapted as a versatile tokamak plasma diagnostic technique. © 2014 American Institute of Physics.

This paper describes the scientific aims and potentials as well as the preliminary technical design of RUDE, an innovative tool for multi-disciplinary investigations in a wide field of scientific, technological and industrial applications. IRIDE will be a high intensity "particles factory", based on a combination of high duty cycle radio-frequency superconducting electron linacs and of high energy lasers. Conceived to provide unique research possibilities for particle physics, for condensed matter physics, chemistry and material science, for structural biology and industrial applications, IRIDE will open completely new research possibilities and advance our knowledge in many branches of science and technology. [RIDE is also supposed to be realized in subsequent stages of development depending on the assigned priorities. (C) 2013 Elsevier B.V. All rights reserved.

ENEA has a long term expertise in the development of powerful short-pulse mmwave and THz radiation sources driven by free electrons. Various electron-wave interaction schemes were successfully tested in the past, including Cerenkov and Smith-Purcell radiators as well as undulator devices. Two THz-FEL sources are currently available, covering altogether the spectral range from 90 GHz to 0.7 THz. Recently a novel Electro-Magnetic pulser, capable of providing both nanosecond THz electromagnetic (EM) radiation pulses and electrostatic (ES) pulses with identical time duration in one device has been designed and is currently under development. The pulser will allow, for the first time, direct comparison of EM and ES pulses on biological systems with peak electric fields that are significantly higher than any reported to date. ﾩ Springer Science+Business Media New York 2014.

A Cyclotron Auto-Resonance Maser (CARM) is under study at the ENEA Research Laboratories in Frascati as a electron cyclotron heating (ECH) source in plasma magnetic confinement devices like Tokamaks. The aim of the project is the realization of a test source at 250 GHz to verify heating mechanisms in high magnetic field Tokamaks and at the second harmonics ECH frequencies for which a higher energy exchange efficiency has been predicted.

Heating and Current Drive systems are of outstanding relevance in fusion plasmas, magnetically confined in tokamak devices, as they provide the tools to reach, sustain and control burning conditions. Heating systems based on the electron cyclotron resonance (ECRH) have been extensively exploited on past and present machines DEMO, and the future reactor will require high frequencies. Therefore, high power (≥1MW) RF sources with output frequency in the 200 - 300 GHz range would be necessary. A promising source is the so called Cyclotron Auto-Resonance Maser (CARM). Preliminary results of the conceptual design of a CARM device for plasma heating, carried out at ENEA-Frascati will be presented together with the planned R&D development. © 2014 AIP Publishing LLC.

A radio-frequency modulated electron beam passing through a magnetic undulator generates coherent spontaneous emission (CSE) when the electron bunch length is comparable to the FEL resonant wavelength. At long wavelengths, CSE can be significantly enhanced by a proper ramping of the electron energy within the bunch duration, since this allows the contributions of the individual electrons to be added in phase. In this paper, the physical principles of the coherent spontaneous emission are reviewed together with its main experimental features. An accelerating structure, constructed at ENEA-Frascati for the systematic investigation of energy–phase correlation effects, is described together with an analysis of the expected performance.

When a radio-frequency (RF) modulated electron beam passes through a magnetic undulator, coherent emission is produced if the electron bunch length is comparable to the emission wavelength. A method to enhance the coherent spontaneous emission by inducing a proper correlation between the energy and phase distribution of the electrons in the bunch will be presented in this work, together with the design of a device intended to systematically investigate the CSE as a function of the longitudinal phase-space distribution.

The basic principles of free electron generators of coherent radiation and the practical considerations related to the development of far infrared and sub-millimeter wave sources are discussed in this paper. The attention is focused on compact devices, which reduce the size and cost issue. A review of the main results obtained at the Frascati FEL Facility is presented together with the planned experiments.

An active two dimensional near field imaging of a High Electron Mobility Transistor (HEMT) used as THz detector has been performed. The reflective imaging system developed at the ENEA FEL Facility in Frascati has been used to this purpose. This imaging technique has shown to be particularly powerful in resolving various coupling mechanisms of the incident radiation with the device.

Novel resonator schemes to be tested on the ENEA compact far-infrared FEL are described in this paper. The design of a negative branch confocal unstable resonator is reported, which shows low sensitivity to angular misalignment and employs all-metal optics providing broad band output coupling.

Heating and Current Drive systems are of outstanding relevance in fusion plasmas, magnetically confined in tokamak devices, as they provide the tools to reach, sustain and control burning conditions. DEMO, and the future reactor will require higher frequency for ECH. Therefore, high power (≥1MW) RF sources with output frequency in the 200 - 300 GHz range would be necessary. © 2013 IEEE.

In the last few years there has been a growing interest in the study of coherent radiation from short electron bunches. The possibility of realizing compact FEL devices in the far-infrared and millimeter wave regions utilizing small to medium size radio-frequency (RF) accelerators has stimulated a number of theoretical and experimental investigations to clarify basic physics issues in this process. Coherent emission experiments will be reviewed in this paper. Measurements on the temporal and spectral characteristics of the coherent emission from a single bunch and on the coherence between consecutive bunches will be presented along with an analysis of the influence of coherence on the dynamics of the laser.

The Compact Advanced Terahertz Source (CATS) developed at ENEA during the past years has now been moved to a new bunker and upgraded for new application capabilities.

An accurate determination of the optical conductivity σ(ν) of high-Tc materials at low frequencies (ν

Reflection measurements of pigments used in artworks will be performed in the THz spectral range, utilizing the THz sources available at the ENEA research center of Frascati in collaboration with CISA3, University of California.