D. Alesini

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.

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

The Project SPARC (Sorgente Pulsata e Amplificata di Radiazione Coerente), proposed by a collaboration among ENEA-INFN-CNR-Universitadi Roma Tor Vergata- INFM-ST, was recently funded by the Italian Government. 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 (SPARX proposal (1)). The SPARC collaboration identified a program based on two main issues: the generation of ultra-high peak brightness electron beams and experimental study of SASE-FEL process with generation of resonant higher harmonics. The SPARC project is being designed in order to encompass the construction of an advanced photo- injector producing a 150-200 MeV beam to drive a SASE-FEL in the optical range. The machine will be built at LNF, inside an underground bunker: it is comprised of an rf gun driven by a Ti:Sa laser, injecting into three SLAC accelerating sections. We foresee conducting investigations on the emittance correction(2) and on the rf compression techniques(3), which are expected to increase the peak current achievable at the injector exit up to kA level, with proper preservation of the transverse emittance. Although the system is expected to drive a FEL experiment, it can be used also to investigate beam physics issues like surface-roughness-induced wake fields, bunch-length measurements in the sub-ps range, emittance degradation in magnetic compressors due to CSR, and Compton backscattering production of sub-ps X-ray pulses.

Future seeding experiments at SPARC

This communication describes the research work plan that is under implementation at the SPARC FEL facility in the framework of the DS4 EUROFEL programme. The main goal of the collaboration is to study and test the amplification and the FEL harmonic generation process of an input seed signal obtained as higher order harmonics generated both in crystals (400 nm and 266 nm) and in gases (266 nm, 160 nm, 114 nm). The SPARC FEL can be con-figured to test several cascaded FEL layouts that will be briefly analysed.

DAΦNE upgrade: a new magnetic and mechanical layout

The DAΦNE Phi-factory upgrade, foreseen for the SIDDHARTA detector run in 2007, requires a new magnetic and mechanical layout to exploit the large Piwinski angle and crab waist concepts [1]. New permanent quadrupole magnets and aluminium vacuum chamber with thin window have been designed for the new interaction region, with the aim to reuse as far as possible the present magnetic and vacuum chamber components. A vacuum chamber of novel design will allow separating the beams at the second interaction region. The new layout together the new hardware components are presented.

Status of the SPARX FEL project

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 compression techniques.

UCLA Neptune Ramped Electron Bunch Experiment

A ramped electron bunch (i.e. one having a current density which rises linearly from the head to the tail and then drops sharply to zero) has been predicted to be an ideal drive beam for the plasma wake field accelerator due to the large transformer ratio it is capable of generating. A scheme was recently proposed for the creation of a relativistic electron bunch that approximates a ramped current profile [England, et al., AIP Conf. Proc. 647, p.884 (2002)], using a dogleg or dispersionless translating section as a bunch compressor. An experiment is underway at the Neptune laboratory using this scheme to create such a beam. The diagnostic being developed for measuring the temporal profile of the beam is an X‐Band transverse deflecting mode cavity.

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.