CIRFEL

Compact, affordable free-electron lasers, such as the CIRFEL, which originally operated at Princeton University and is being reassembled at the University of Maryland, can provide high-peak-power, tunable radiation for research, medical, biomedical and material processing applications. The particular advantage of such photocathode-accelerator-driven FELs for these applications is their high brightness and picosecond pulse structure which yields very high peak dose with efficient energy deposition and minimal collateral damage. The broadband tunability of FELs permits the excitation of resonance phenomena and generates many different uses. AES is developing these devices for the surface treatment of materials, near-field IR microscopy, biomedical and other applications.

The CIRFEL S-band accelerator FEL delivers > 1/3 Watt of average IR power, tunable over the range of 7 to 20 microns when configured with an AES permanent magnet wiggler. Typical parameters for the basic system are shown in the table. The magnesium photocathode, installed in a removable backplate, is illuminated by the RF-mode locked 262 nanometer quadrupled output from a Nd:YLF laser. The measured data for the delivered 5 picosecond near Fourier-transform-limited ~ 13 micron IR spectrum can be seen in the upper right of the figure. Combined with alternate wigglers and booster cavities, the basic CIRFEL configuration can be adjusted to yield fundamental radiation from 3 to more than 200 microns. Delivered electron beam energies up to 25 MeV can be produced within the illustrated footprint and even higher energies can be provided for specialized applications and lower wavelength if desired. Alternate higher quantum efficiency cathodes utilizing preparation chambers can be ordered.

AES CIRFEL Lasing at Princeton University

The collage shows self-consistent lasing data: the control screen (upper left); the beamline (center); the output lasing signal (upper right); current, RF power and IR detector signals (lower left); beamline envelope simulation (lower right); and five to-scale OTR screen images of the electron beam, with their beamline and simulation locations identified.