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abstract:
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The Inverse Free Electron Laser (IFEL) is capable, in
principle, of reaching accelerating gradients of up to
1 GV/m making it a prospective accelerator scheme for
linear colliders. The Neptune IFEL at UCLA utilizes a 15
MeV Photoinjector-generated electron beam of 0.5 nC
and a CO2 laser with peak energy of up to 100 J, and will
be able to accelerate electrons to 100 MeV over an 80 cm
long, novel helical permanent-magnet undulator. Past
IFELs have been limited in their average accelerating
gradient due to the Gouy phase shift caused by tight
focusing of the drive laser. Here, laser guiding is
implemented via an innovative Open Iris-Loaded
Waveguide Structure (OILS) scheme which ensures that
the laser mode size and wave front are conserved through
the undulator. The results of the first phase of the
experiment are discussed in this paper, including the
design and construction of a short micro-bunching
undulator, testing of the OILS waveresults of corresponding simulations.waveguide to test the coupling by observing a micro-
bunching. Then, as a second step, we will build a long
waveguide and a tapered undulator (80 cm).
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