P. Musumeci

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.

Experimental Testing of Dynamically Optimized Photoelectron Beams

We discuss the design of and initial results from an experiment in space‐charge dominated beam dynamics which explores a new regime of high‐brightness electron beam generation at the SPARC photoinjector. The scheme under study employs the tendency of intense electron beams to rearrange to produce uniform density, giving a nearly ideal beam from the viewpoint of space charge‐induced emittance. The experiments are aimed at testing the marriage of this idea with a related concept, emittance compensation. We show that this new regime of operating photoinjector may be the preferred method of obtaining highest brightness beams with lower energy spread. We discuss the design of the experiment, including developing of a novel time‐dependent, aerogel‐based imaging system. This system has been installed at SPARC, and first evidence for nearly uniformly filled ellipsoidal charge distributions recorded.

The LLNL/UCLA high gradient inverse free electron laser

We describe the Inverse Free Electron Accelerator currently under construction at Lawrence Livermore National Lab. Upon completion of this accelerator, high brightness electrons generated in the photoinjector blowout regime and accelerated to 50 MeV by S-band accelerating sections will interact with > 4 TW peak power Ti:Sapphire laser in a highly tapered 50 cm undulator and experience an acceleration gradient of > 200 MeV/m. We present the final design of the accelerator as well as the results of start-to-end simulations investigating preservation of beam quality and tolerances involved with this accelerator.

High‐Gradient High‐Energy‐Gain Inverse Free Electron Laser Experiment Using a Helical Undulator

In this paper we present the design of the high‐gradient, high‐energy‐gain IFEL accelerator proposed for construction at the ATF beamline in BNL. We plan to accelerate the ATF electron beam from 50 MeV to 120 MeV using a 60 cm long tapered permanent magnet helical undulator designed at UCLA and the existing ATF 0.5 TW CO2 laser system. The experiment will obtain a record 120 MV/m gradient and >70 MeV energy gain and will be an important step in the development of compact IFEL accelerators for the mid‐high energy range (up to 1–2 GeV).

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.