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The first phase of the SPARX project, now funded by MIUR (Research Department of Italian Government), is an R&D activity focused on developing techniques and critical components for future X-ray FEL facilities. This project is the natural extension of the activities under development within the ongoing SPARC collaboration. The aim is the generation of electron beams characterized by an ultra-high peak brightness with a linear accelerator based on the upgrade of the existing Frascati 800 MeV LINAC and to drive a single pass FEL experiment in the range of 3-5 nm, both in SASE and SEEDED FEL configurations, exploiting the use of superconducting and exotic undulator sections. In this paper we discuss the present status of the collaboration.

The current trends and recent developments of Free Electron Lasers in the two spectral regions laying at the boundaries of the electromagnetic spectrum are reviewed in this paper.

SPARC and SPARX are two different initiatives toward an X-ray FEL SASE source at LNF. SPARC is a high gain FEL project devoted to provide a source of visible and VUV radiation while exploiting SASE mechanism. An advanced Photo-Injector system, emittance self-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, (530 nm). The production of flat top drive laser beams, high peak current bunches, and an 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 towards the 13.5 and 1.5 nm operating wavelengths, at 2.5 GeV. The first phase of the SPARX project, fiinded by Government Agencies, will be focused on R&D activity on critical components and techniques for future X-ray facilities as described in this paper.

The mechanism of nonlinear harmonic generation in the exponential gain regime, which is driven by bunching at the fundamental wavelength, may provide a path toward both enhancing and extending the usefulness of an x-ray free- electron laser (FEL) facility. Related exotic generation schemes, which exploit properties of harmonic production in various undulator topologies, have been discussed both in the past and more recently. Using three different numerical simulation codes, we explore the possible utility of such schemes (e.g., harmonic afterburners and biharmonic undulators) at future light source facilities.

A 5 MeV FEL facility has been realized at the ENEA Research Center in Frascati, Italy. This facility is devoted to the testing of Cerenkov FEL devices and other compact FEL configurations. Power up to 50 W in 4 microsecond(s) pulse has been generated in a Cerenkov FEL at wavelengths ranging from 0.8 to 1.6 mm using different dielectric guides. Other planned activities include the testing of short-period undulators in a small size waveguide FEL designed to operate in the sub-millimeter region. Operating characteristics and predicted performance are presented.

A program to construct a test superconducting electron linear accelerator (LISA) is in progress at Frascati INFN National Laboratories. The electron beam will be used to realize a FEL in the infrared region 11 - 18 μm in collaboration with a group of ENEA-CRE Frascati. The characteristics of the electron beam, the undulator and the expected performances of the FEL are described. Some future developments - energy doubling, energy recovery, third harmonic operation - are briefly presented. Such improvements aim to realize a high power, high efficiency FEL exploiting the features of a SC linac.© (1989) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

We discuss the main limitations of a single pass FEL device within the framework of the Lawson-Penner law. We show that very good performances can be obtained, in principle. Finally we point out that under suitable conditions the short wavelenght region (namely, visible and UV) may be covered by an FEL operating with a low energy electron beam machine.© (1984) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.