Author: Penco, G.
Paper Title Page
WEXC02
 Enhanced Seeded Free Electron Laser Performance with a "Cold" Electron Beam  
 
  • G. Penco
    Elettra-Sincrotrone Trieste S.C.p.A., Basovizza, Italy
  
  In a seeded free-elec­tron laser op­er­at­ing in high gain har­monic gen­er­a­tion (HGHG) as FERMI, the har­monic con­ver­sion ef­fi­ciency de­creases at high har­mon­ics and the qual­ity of the pulses is in­creas­ingly af­fected by the elec­tron beam phase space dis­tor­tions. The lower the elec­tron time-slice en­ergy spread the higher har­monic of the seed is ef­fi­ciently ob­tained. The op­ti­miza­tion of the FERMI pho­toin­jec­tor and of some linac pa­ra­me­ters has al­lowed a re­duc­tion of the rel­a­tive slice en­ergy spread to the level of few times of 105. With these new con­di­tions, the FEL can be op­er­ated with­out the need for a laser heater to sup­press mi­cro-bunch­ing in­sta­bil­i­ties and this "cold" beam has al­lowed the gen­er­a­tion of ex­treme UV pulses with pulse en­ergy ex­ceed­ing 1 mJ, and with peak power of about 10 GW. We de­scribe the elec­tron beam char­ac­ter­i­za­tion and the FEL per­for­mance im­prove­ment, in­clud­ing the ex­ten­sion of the range of har­mon­ics of the seed which can be am­pli­fied, up to the twenty-fifth har­monic, i.e., 10 nm.  
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