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SPARC (acronym of ‘‘Sorgente Pulsata ed Amplificata di Radiazione Coerente’’, i.e. Pulsed and Amplified Source of Coherent Radiation) is a single pass free-electron laser designed to obtain high gain amplification at a radiation wavelength of 500 nm. Self-amplified spontaneous emission has been observed driving the amplifier with the high-brightness beam of the SPARC linac. We report measurements of energy, spectra, and exponential gain. Experimental results are compared with simulations from several numerical codes.

We present the first results of a novel collaboration activity between ENEA Frascati Particle Accelerator Laboratory and University La Sapienza Guidance and Navigation Laboratory in the field of Radiation Hardness Assurance (RHA) for space applications. The aim of this research is twofold: (a) demonstrating the possibility to use the TOP-IMPLART proton accelerator for radiation hardness assurance testing, developing ad hoc dosimetric and operational procedures for RHA irradiations; (b) investigating system level radiation testing strategies for Commercial Off The Shelf (COTS) components of interest for SmallSats space missions, with focus on devices and sensors of interest for guidance, navigation and control, through simultaneous exploration of Total Ionizing Dose (TID), Displacement Damage (DD) dose and Single-Event Effects (SEE) with proton beams. A commercial 6-axis integrated Micro Electro-Mechanical Systems (MEMS) inertial navigation system (accelerometer, gyroscope) was selected as first Device Under Test (DUT). The results of experimental tests aimed to define an operational procedure and the characterization of radiation effects on the component are reported, highlighting the consequence of the device performance degradation in terms of the overall navigation system accuracy. Doses up to 50 krad(Si) were probed and cross sections for Single-Event Functional Interrupt (SEFI) evaluated at a proton energy of 30 MeV.

The Intensity Modulated Proton Linear Accelerator for Cancer Therapy (TOP-IMPLART) is under development and construction by ENEA in collaboration with the Italian Institute of Health (ISS) and the Oncological Hospital Regina Elena-IFO with financial support of Regione Lazio. Its peculiar time structure (few microseconds pulse width) and very high peak intensity (≍ 109 proton/pulse) demand for ad hoc dose delivery monitors (DDM). The TOP-IMPLART DDM is based on ionization gas chambers. One segmented chamber prototype uses Micro Pattern Gaseous Detector technology for the 2-dimensional simultaneous x/y readout; the charge collected from each active segment (strips with pad-like shape) is readout by a dedicated gain-adaptable electronics. Two small, highly sensitive, integral ionization chambers, using the same electronics, complement the 2D chamber for the monitor of the single pulse beam charge, down to 1 pC/pulse. While under development and deployment of its accelerating modular cavities, the linear TOP-IMPLART beam is improved thanks also to the continuous monitoring and characterization by these devices, whose responses are periodically compared to calibrated dosimetric detectors such as real-time active microDiamond sensor, passive Alanine pellets, intrinsically stable integral Faraday Cup. Different calibration campaigns have been recently conducted to measure the recombination and dose-rate effects on the above ionization chambers. The outcome of these measurements shows clear electron-ion recombination in the chamber active volume, largely related to the high beam intensity and its small transverse cross section. Those effects can be taken into account and used to correct the actual measurement of the DDM. In this paper, the TOP-IMPLART project and the DDM devices are shortly presented and details of the above experimental studies are discussed.

A short period undulator (1.4 cm) has been designed for the SPARC-FEL test facility and has been realized in collaboration with KYMA Srl. It has been installed on the undulator line at SPARC. The undulator, operating in a delta like mode, has been used as radiator in a segmented configuration. The first stage being provided by the five undulators of the SPARC FEL source "old" chain, with period 2.8 cm. The KYMA undulator has a quatrefoil structure, a high magnetic field homogeneity and focuses both in vertical and radial directions. The two sections, namely the bunching and radiating parts, are arranged in such a way that the second is adjusted on a harmonic of the first. Laser action occurring in the second part, is due to the bunching acquired in the first. Simulations of the temporal and spectral profiles in different electron beam operating conditions are reported, as well as the evolution of the longitudinal phase space. The agreement with the experimental results is discussed The importance of this experiment is at least threefold: 1) It proves that the segmented undulator can successfully be operated 2) It proves that the laser emission in the last undulator is entirely due to the bunching mechanism, being no second harmonic signal present in the first segment 3) Encourages various improvements of the configuration itself, as e.g. the use of a further undulator with variable magnetic field configuration in order to obtain a laser field with adjustable polarization. © 2015 SPIE.

The two-dimensional single shot transverse coherence of the Self-Amplified Spontaneous Emission of the SPARC-LAB Free-Electron Laser was measured through the statistical analysis of a speckle field produced by heterodyning the radiation beam with a huge number of reference waves, scattered by a suspension of particles. In this paper we report the measurements and the evaluation of the transverse coherence along the SPARC-LAB undulator modules. The measure method was demonstrated to be precise and robust, it does not require any a priori assumptions and can be implemented over a wide range of wavelengths, from the optical radiation to the x-rays.

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.

We report measurements demonstrating the concept of the free-electron laser (FEL) superradiant cascade. Radiation (λrad=200 nm) at the second harmonic of a short, intense seed laser pulse (λseed= 400 nm) was generated by the cascaded FEL scheme at the transition between the modulator and radiator undulator sections. The superradiance of the ultrashort pulse is confirmed by detailed measurements of the resulting spectral structure, the intensity level of the produced harmonics, and the trend of the energy growth along the undulator. These results are compared to numerical particle simulations using the FEL code GENESIS 1.3 and show a satisfactory agreement. © 2013 American Physical Society.

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 view of a quantum electrodynamics test, a "double" free-electron laser (FEL) oscillator is proposed as a possible device for head-on photon-photon collisions in vacuum. The oscillator is conceived in order to produce two laser beams in the same cavity by two counterpropagating electron beams. The latter are in turn exploited to produce gamma photons by backward Compton scattering of the intracavity FEL radiation itself. In view of an effective device design, specific ranges of values for the various parameters, that characterize the system, are individualized for operation at the maximum of the γ-γ scattering cross section. An estimate of the collision rate in definite device configurations is provided. © 2013 Optical Society of America.