G. Messina

The SPARC project: a high-brightness electron beam source at LNF to drive a SASE-FEL experiment

Abstract The Project Sorgente Pulsata e Amplificata di Radiazione Coerente (SPARC), proposed by a collaboration among ENEA–INFN–CNR–Universita’ di Tor Vergata–INFM–ST, was recently approved by the Italian Government and will be built at LNF. The aim of the project is to promote an R&D activity oriented to the development of a coherent ultra-brilliant X-ray source in Italy. This collaboration has identified a program founded on two main issues: the generation of ultra-high peak brightness electron beams and of resonant higher harmonics in the SASE-FEL process, as presented in this paper.

Coherence effects in FEL radiation generated by short electron bunches

Abstract 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.

Above threshold operation of the ENEA free electron laser

Abstract Recent experimental results of the ENEA FEL experiment performed with a 20 MeV, 120 mA microtron and a linearly polarized pulsed electromagnetic undulator are reported.

Conceptual design of a high-brightness linac for soft X-ray SASE-FEL source

Abstract 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.

Long wavelength compact-FEL with controlled energy–phase correlation

Abstract 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.

THz-ARTE: non-invasive terahertz diagnostics for art conservation

The project THz-ARTE ldquoTerahertz Advanced Research TEchniques for non-invasive analysis in art conservationrdquo has recently been selected in the area of Technologies applied to Cultural Heritage in the framework of the Agreement between the Government of Italy and the Government of Japan on cooperation in Science and Technology.

Absorption and Diffusion Measurements of Biological Samples using a THz Free Electron Laser

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.

The SPARC/X SASE-FEL Projects

SPARC and SPARX are two different initiatives toward an Italian Free Electron Laser ~FEL! source operating in the Self Amplified Spontaneous Emission ~SASE! mode, in which several national research institutions are involved. SPARC is a high gain FEL project devoted to provide a source of visible and VUV radiation while exploiting the SASE mechanism. An advanced Photo-Injector system, emittance compensating RF-gun plus a 150 MeV Linac, will inject a high quality e-beam into the undulator to generate high brilliance FEL radiation in the visible region at the fundamental wavelength, ~;500 nm!. The production of flat top drive laser beams, high peak current bunches, and emittance compensation scheme will be investigated together with the generation of higher harmonic radiation in the VUV region. SPARX is the direct evolution of such a high gain SASE FEL toward the 13.5 and 1.5 nm operating wavelengths, at 2.5 GeV. To get the required value for the bunch peak current, Ipeak ’ 2.5 kA, the “hybrid” scheme, RF-compression stage plus magnetic chicane, is analyzed and compared with the more standard double stage of magnetic compression. The two options are reviewed considering the tolerance to the drive laser pulse phase jitter.

The ENEA F-CUBE facility: trends in RF driven compact FELs and related diagnostics

The Frascati FEL Facility F-CUBE (FEL-Compact for User Basic Experiment) currently operates in the mm-wave region providing about 600 hrs of beam time per year to users. This FEL is a low cost compact device intended to be the first step in making the FEL a laboratory tool. It exploits some unique features like short pulses with coherent emission seeding and the dispersion properties of a waveguide resonator at {open_quotes}zero slippage{close_quotes} to provide wide band tunability. The system is presently being upgraded to extend these characteristics into the far infrared. A new NdFeB permanent magnet undulator has been built and magnetic measurements have been performed. FEL tunability in the interval from 400 to 900 pm will be provided by the variation of the undulator gap and of the gap of the planar waveguide in the resonator. Due to the short electron bunch duration coherent spontaneous emission is expected also in this wavelength range. Its effect on the FEL performance will be discussed together with a comparison of different coherent emission mechanisms, like coherent transition radiation (CTR), which can be used as a diagnostic tool.

Status of the free electron laser experiment at the ENEA Frascati center

Abstract The status of the free electron laser experiment under realization at the ENEA Frascati center is described. The experimental results relevant to electron beam and spontaneous radiation are reported.