There is a strong demand for small foot-print high-flux hard X-rays machines in order to enable a large variety of science activities and serve a multidisciplinary user community. For this purpose, two compact Inverse Compton Sources (ICSs) are currently being developed in Italy. The most recent one is the Bright and Compact X-ray Source (BriXS) which has recently been proposed to produce very energetic X-rays (up to 180 keV) and high photon flux (up to 10<sup>13</sup> photons/s with expected bandwidth of 1-10%). BriXS will be installed in Milan and it will enable advanced large area radiological imaging applications to be conducted with mono-chromatic X-rays, as well as allowing basic fundamental science of matter and health sciences at both pre- and clinical levels. Based on an energy-recovery linac (ERL) scheme and superconducting technology, BriXS will operate in CW regime with an unprecedented electron beam repetition rate of 100 MHz. The second Italian ICS light source is the Southern Europe Thomson back-scattering source for Applied Research (STAR) which is currently installed at the University of Calabria (UniCal). STAR is a compact machine that has been designed to produce monochromatic and tunable, ps-long, polarized X-ray beams in the range 40-140 keV with a photon flux up to 10<sup>10</sup> photons/s and energy bandwidth below 10%. The electron beam injector is based on normal-conducting technology in S-Band with a repetition rate up to 100 Hz.
Our team has been examining several architectures for short-wavelength, coherent light
sources. We are presently exploring the use and role of advanced, high-peak power lasers for both
accelerating the electrons and generating a compact light source with the same laser. Our overall
goal is to devise light sources that are more accessible by industry and in smaller laboratory
settings. Although we cannot and do not want to compete directly with sources such as third-generation
light sources or that of national-laboratory-based free-electron lasers, we have several
interesting schemes that could bring useful and more coherent, short-wavelength light source to
more researchers. Here, we present and discuss several results of recent simulations and our future
steps for such dissemination.
We analyze the possibility of producing two color X or γ radiation by Thomson/Compton back-scattering between a high intensity laser pulse and a two-energy level electron beam, constituted by a couple of beamlets separated in time and/or energy obtained by a photoinjector with comb laser techniques and linac velocity bunching. The parameters of the Thomson source at SPARC_LAB have been simulated, proposing a set of values for a realistic experiments.
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.
We present the experimental evidence of the generation of coherent and statistically stable Free-Electron Laser (FEL) two color radiation obtained by seeding an electron double peaked beam in time and energy with a single peaked laser pulse. The FEL radiation presents two neat spectral lines, with time delay, frequency separation and relative intensity that can be accurately controlled. The analysis of the emission shows a temporal coherence and regularity in frequency significantly enhanced with respect to the Self Amplified Spontaneous Emission (SASE).
The INFN Strategic Project PLASMONX (PLASma acceleration and MONochromatic X-ray production) deals with
the creation of a High Intensity Laser Laboratory at LNF (HILL@LNF) beside the SPARC bunker, with which it will
communicate via a channel for the propagation of laser beams. In this laboratory FLAME ( Frascati Laser for
Acceleration and Multidisciplinary Experiments), a 200TW, 30fs, 10Hz Ti:Sapphire Laser, will be set up.
The main goals of this project are:
1) demonstration of high-gradient acceleration of relativistic electrons injected into electron plasma waves excited
by ultra-short, super-intense laser pulses;
2) development of a monochromatic and tuneable X-ray source in the 20-1000 keV range, based on Thomson
Scattering of laser pulses by the 20-200 MeV electrons of the LINAC of the SPARC project.
One of the aims of the project consists in the realization of a pulsed source of ionizing radiation for R&D activity in
We present a study based on a parametric optimization of a Thomson Source operated in FEL mode. This deals with
the proposed scheme to use a high intensity laser pulse colliding with a high brightness electron beam of low to medium
energy (around 10 MeV). Electrons undulating in the incoming laser field may emit radiation in a FEL coherent mode as
far as some conditions are satisfied. A set of simple analytical formulas taking into account 3D effects is derived, in order
to express these conditions in terms of three free parameters, namely the wavelength of the colliding laser pulse, the FEL
ρ parameter, and the peak current carried by the electron beam. A few examples of possible operating points are
compared with results of 3D numerical simulations, showing the FEL coherent emission of X-rays by high brightness
electron beams colliding with high intensity laser beams carrying pulse energies of about 10 J.
The SPARX project consists in an X-ray-FEL facility jointly supported by MIUR (Research Department of Italian
Government), Regione Lazio, CNR, ENEA, INFN and Rome University Tor Vergata. It is the natural extension of the
ongoing activities of the SPARC collaboration. The aim is the generation of electron beams characterized by ultra-high
peak brightness at the energy of 1 and 2 GeV, for the first and the second phase respectively. The beam is expected to
drive a single pass FEL experiment in the range of 13.5-6 nm and 6-1.5 nm, at 1 GeV and 2 GeV respectively, both in
SASE and SEEDED FEL configurations. A hybrid scheme of RF and magnetic compression will be adopted, based on
the expertise achieved at the SPARC high brightness photoinjector presently under commissioning at Frascati INFNLNF
Laboratories. The use of superconducting and exotic undulator sections will be also exploited. In this paper we
report the progress of the collaboration together with start to end simulation results based on a combined scheme of RF
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.