Status of UCLA Helical Permanent-Magnet Inverse Free Electron Laser

A helical undulator, utilizing permanent‐magnet of cylindrically symmetric (Halbach) geometry is being developed at UCLA’s Neptune Facility. The initial prototype is a short 10 cm, 7 periods long helical undulator, designed to test the electron‐photon coupling by observing the micro‐bunching is currently being constructed. The Neptune IFEL facility utilizes a 15 MeV Photoinjector‐generated electron beam of 0.5 nC interacting with CO2 of peak energy up to 100 J, estimated to have acceleration of 100 MeV/m. An Open Iris‐Loaded Waveguide Structure (OILS) scheme which conserves laser mode size and wave fronts throughout the undulator, is utilized to avoid Gouy phase shift caused by focusing of the drive laser. Undulator design was tested by computer simulations Radia and Genesis 1.3. Coherent Transition Radiation and Coherent Cherenkov Radiation will be used for micro‐bunching diagnostic. Currently permanent dipoles and their aluminum holders have been built, and the project is in its final state of assembly ...