Paper 
Title 
Page 
MOPPH017 
1D Linear Intensity Spiking Evolution in a Single Shot of a SASE FEL

54 

 V. Petrillo
Universita' degli Studi di Milano, Milano
 L. Serafini, C. Maroli
INFNMilano, Milano



The analysis is based on the 1D MaxwellLorentz equations which are reduced to the usual averaged linear equation in the limit of vanishingly small radiation field A(z,t) and average length lm. It is shown that if this equation is solved with initial shot noise conditions in which the widths of the spikes and the average distance between successive spikes are both uniformly smaller than the cooperation length Lc, it may lead to large amplitude coherent signals. The intensity spiking RMS relative amplitude decreases from the 100% values it has at t=0, down to values of the order or less than 0.1% in time intervals from ten to twenty gain times.


TUPPH012 
Compact Xray FreeElectronLaser Based on an Optical Undulator

244 

 A. Bacci, C. Maroli, A. R. Rossi, L. Serafini
INFNMilano, Milano
 V. Petrillo
Universita' degli Studi di Milano, Milano
 P. Tomassini
INFNPisa, Pisa



The interaction between a very high brightness electron beam and a relativistically intense optical laser pulse produces X rays via coherent Thomson back scattering with FEL collective amplification. The phenomenon is, however, very selective, so that the characteristics of both electron and laser beam must satisfy tight requirements in terms of beam current, emittance, energy spread and laser amplitude stability within the pulse. The threedimensional equations governing the radiation phenomena have been studied in both linear and non linear regime and solved numerically for the particularly interesting values of wavelengths of 1 Ang, 1 nm and 12 nm. The performance of the collective Thomson source has been compared with that of an equivalent static undulator. A set of scaling laws ruling the phenomenon is also presented. The possibility of using an electron beam produced via LWFA in the bubble regime is investigated.


WEPPH018 
A High Brightness Xband Split Photoinjector Concept and Related Technological Challenges

370 

 D. Alesini, M. Migliorati, L. Palumbo, B. Spataro, M. Ferrario
INFN/LNF, Frascati (Roma)
 J. B. Rosenzweig
UCLA, Los Angeles, California
 L. Serafini
INFNMilano, Milano



Future light sources based on high gain free electron lasers, require the production, acceleration and transport up to the undulator entrance of high brightness (low emittance, high peak current) electron bunches. Wake fields effects in accelerating sections and in magnetic bunch compressors typically contribute to emittance degradation, hence the photoinjector design and its operation is the leading edge for high quality beam production. The state of the art photoinjector beam brightness can be in principle brought above the 10^{15} A/m^{2} threshold with an Xband gun and a proper emittance compensation scheme. We discuss in this paper an optimized design of a split Xband photoinjector, a convenient matching scheme with the downstream linac, based on the SPARC project experience, and the further technological developments required to reach such an appealing goal.


WEAAU02 
Direct Measurement of Phase Space Evolution in the SPARC High Brightness Photoinjector

284 

 D. Alesini, M. Bellaveglia, M. Boscolo, M. Castellano, A. Clozza, L. Cultrera, G. Di Pirro, A. Drago, A. Esposito, M. Ferrario, D. Filippetto, V. Fusco, A. Gallo, G. Gatti, A. Ghigo, M. Incurvati, C. Ligi, L. Pellegrino, R. Ricci, C. Sanelli, M. Serio, F. Sgamma, B. Spataro, F. Tazzioli, S. Tomassini, C. Vaccarezza, M. Vescovi, C. Vicario, E. Chiadroni
INFN/LNF, Frascati (Roma)
 A. Bacci
INFN/LASA, Segrate (MI)
 L. Catani, A. Cianchi
INFNRoma II, Roma
 S. Cialdi, A. R. Rossi, L. Serafini
INFNMilano, Milano
 L. Giannessi, M. Quattromini, C. Ronsivalle
ENEA C. R. Frascati, Frascati (Roma)
 M. Migliorati, A. Mostacci, L. Palumbo
Rome University La Sapienza, Roma
 P. Musumeci, J. B. Rosenzweig
UCLA, Los Angeles, California
 M. Petrarca
INFNRoma, Roma



The characterization of the transverse phase space for high charge density relativistic electron beams is a fundamental requirement in many particle accelerator facilities, in particular those devoted to fourthgeneration synchrotron radiation sources, such as SASE FEL. The main purpose of the SPARC initial phase was the commissioning of the RF photoinjector. At this regard, the evolution of the phase space has been fully characterized by means of the emittance meter diagnostics tool, placed in the drift after the gun exit. The large amount of collected data has shown not only that we can achieve the SPARC nominal parameters, but has also allowed for the first time a detailed reconstruction of the transverse phase space evolution along the drift, giving evidences of the emittance compensation process to occur as predicted by theory and simulations. In particular the peculiar behavior of a flat top longitudinal electron distribution compared to a gaussian distribution has been studied giving important insights for the correct matching with the following linac based on the double emittance minimum effect.



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