UCLA, Los Angeles, California
ENEA C.R. Frascati, Frascati (Roma)
PSI, Villigen
Narrow bandwidth FEL operation is one of the main challenges for future FEL facilities. Several schemes have been proposed to obtain a narrower bandwidth than that achievable with self amplified spontaneous emission starting from shot-noise. In this work the properties of two such schemese (high gain harmonic generation and self-seeding) are investigated and compared taking into account several non-ideal beam effects, with particular attention paid to the effect of bandwidth broadening associated to non-linear longitudinal phase-space. The comparison between the two schemes has been carried out with numerical simulations performed with GENESIS 1.3 and PERSEO FEL codes using both an idealized beam and realistic beams obtained with start to end simulations.
ENEA C.R. Frascati, Frascati (Roma)
Istituto Nazionale di Fisica Nucleare, Milano
INFN/LNF, Frascati (Roma)
We propose an experiment of self seeding at SPARC. The experiment would be done at visible/UV wavelengths where high reflectivity mirrors at normal incidence are available and its implementation would require only minor modifications of the existing SPARC layout. The new FEL configuration might significantly extend the SPARC FEL wavelength range of operation and would present several advantages as a higher brightness in wavelength tunable conditions together with a reduction of the demands in terms electron beam peak current and beam quality.
Universita' degli Studi di Milano, Milano
Istituto Nazionale di Fisica Nucleare, Milano
INFN/LNF, Frascati (Roma)
ENEA C.R. Frascati, Frascati (Roma)
ENEA-Bologna, Bologna
Rome University La Sapienza, Roma
INFN-Roma, Roma
We describe a possible experiment aimed at generating sub-picosecond high brightness electron bunches with the SPARC photoinjector, which produce optical single spike radiation pulses in the regime of self-amplified spontaneous emission. The main purpose of the experiment is the production of short electron bunches as long as few SASE cooperation lengths by means of the Velocity Bunching technique. The measure of the properties of the electron beam, the determination of shape and spectrum of the radiation pulse and the validation of the single spike scaling laws will be analysed in order to foresee future operations at shorter wavelength with SPARX. We present in this paper start-to-end simulations of the beam production and FEL performance, statistical analysis and behaviour on the harmonics. The experience gained from this experiment will help in the configuration of the VUV and X-ray FEL SPARX to obtain FEL pulses below 10 fs.
INFN/LNF, Frascati (Roma)
Istituto Nazionale di Fisica Nucleare, Milano
Università di Roma II Tor Vergata, Roma
ENEA C.R. Frascati, Frascati (Roma)
INFN-Roma II, Roma
UCLA, Los Angeles, California
INFN-Roma, Roma
The optimization of the beam brightness is one of the main objectives of the research and development efforts in rf-photoinjectors devoted to short wavelength FELs. The velocity bunching experiment at SPARC has recently demonstrated the possibility of increasing the beam current via RF compression at low energies, while compensating the self-fields induced emittance degradation by means of continuous magnetic focusing. The result is an increase of the beam brightness by about one order of magnitude. Stable compression ratio up to a factor 12 has been observed. Characterization of longitudinal phase spaces an measure of projected and slice emittances, as a function of the injection phase in the first accelerating structure and for different solenoids field values are presented. Comparisons with simulations are also reported.
ENEA C.R. Frascati, Frascati (Roma)
INFN/LNF, Frascati (Roma)
Istituto Nazionale di Fisica Nucleare, Milano
SOLEIL, Gif-sur-Yvette
CEA, Gif-sur-Yvette
INFN-Roma II, Roma
UCLA, Los Angeles, California
INFN-Roma, Roma
The SPARC FEL can be operated in both SASE and seeded modes. A major part of the second stage of the commissioning, currently in progress, is dedicated to the characterization of the SASE radiation. Simultaneously, we are finalizing the experimental setup for seeding. We present an in-situ characterization of the two input seeds that are foreseen: both are obtained via harmonic generation, the first one in crystal (400 and 266 nm) and the second in rare gas (Argon). We also describe the specific diagnostics implemented for the electron-seed overlap in the undulator, together with the diagnostics for radiation analysis (2D spectrometer and FROG). The seeding will enable the operation of the SPARC FEL in original cascaded configurations.