S. Bertolucci

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.

Effects of nonlinear terms in the wiggler magnets at DA/spl Phi/NE

Analysis of the experimental observations and comparison with magnetic measurements have pointed out relevant nonlinear terms in the DA/spl Phi/NE wigglers and in the C corrector magnets. Different optics configurations aimed at reducing the impact of nonlinear terms have been studied and their effects on the collider performances are presented.

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.

The Project Plasmonx for Plasma Acceleration Experiments and A Thomson X-Ray Source at SPARC

We present the status of the project PLASMONX, recently approved by INFN. This project, based on a collaboration between INFN and CNR-IPCF, aims at a long term upgrade of the SPARC system with the goal to develop at LNF an integrated facility for advanced beam-laser-plasma research in the field of advanced acceleration techniques and ultra-bright X-ray radiation sources and related applications. The project, in its first phase, foresees the development at LNF of a High Intensity Laser Laboratory (HILL) whose main component is a 100 TW-class Ti: Sa laser system synchronized to the SPARC photo-injector. Experiments of self-injection and acceleration of electrons into laser driven plasma waves will be conducted at HILL-LNF, early in this first project phase. Eventually an additional beam line will be built in the SPARC bunker in order to transport the SPARC electron beam at an interaction point, where a final focus system will allow to conduct experiments either of laser-beam co-propagation in plasma waves for high gradient acceleration, or experiments of laser-beam head-on collisions to develop a Thomson source of bright ultra-short X-ray radiation pulses, with X-ray energies tunable in the range 20 to 1000 keV and pulse duration from 30 fs to 20 ps. Preliminary simulations of plasma acceleration with self-injection are illustrated, as well as external injection of the SPARC electron beam.

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.

Status report on DA/spl Phi/NE

DA/spl Phi/NE, the Frascati LNF /spl Phi/-factory, is providing luminosity for the KLOE experiment since July 2000. A steady increase of daily integrated luminosity in KLOE has been obtained, due to interspersed machine physics studies. The main results are: increase of single bunch luminosity by reduction of the effects of nonlinear terms in the machine, background reduction, refill of the colliding beams while keeping the KLOE detector taking data and increase of stable stored current. A fraction of machine time has been used to tune luminosity and reduce background in the DEAR configuration. The luminosity delivered to DEAR was sufficient to conclude the first phase of the experiment.

Experimental results with the SPARC emittance-meter

The SPARC project foresees the realization of a high brightness photo-injector to produce a 150-200 MeV electron beam to drive a SASE-FEL in the visible light. As a first stage of the commissioning a complete characterization of the photoinjector has been accomplished with a detailed study of the emittance compensation process downstream the gun-solenoid system with a novel beam diagnostic device, called emittance meter. In this paper we report the results obtained so far including the first experimental observation of the double emittance minimum effect on which is based the optimised matching with the SPARC linac.

Non Linear Beam Dynamics at DAPHINE

Studies and measurements have been performed at DAΦ NE to improve dynamic aperture, beam lifetime and beam-beam performance. Measured tune scans for different working points are presented. After the measurement of an octupole-like term in the wiggler field, decoherence meas- urements with wigglers on and off have been performed. The effect of this cubic term on the chromaticity and dy- namic aperture is presented. . The Kloe experiment is routinely collecting data. The non-linearities present in the machine play a major role affecting the dynamic aperture, the beam lifetime, (with relation to the background and the integrated luminosity), and the beam-beam behaviour (single bunch luminosity). The study moved from extensive beam lifetime measurements vs. betatron tunes in both rings resulting in a high sensitivity of the machine to high order resonances (section 2). The deco- herence measurements, (dynamic tracking), with the wig- glers powered on and off show the effect of a strong dependence of the tune on the betatron amplitude oscillation, (section 3). The presence of a cubic term in the wiggler is accounted for the residual non-linear chromaticity of the machine even with sextupoles off. The strength of the octupole thin lens to be taken into account in each pole, found from the chromaticity measurements, agrees with the value obtained from the measurements of the betatron tunes vs. the localised orbit bumps inside the wiggler (6). The effect on the dynamic aperture is described in section 5.

SPARC/X projects

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.

Conceptual Design of a Soft X-ray SASE-FEL Source

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, bringing 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 a RF compressor.