Eye hazard characterization of an optical klystron free electron laser beam

A free electron laser (FEL) uses an accelerated electron beam to generate laser light. By adjusting the electron beam energy and other parameters, FELs can generate tunable, coherent light over a range from ultraviolet to millimeter wavelengths. Many FELs are building-sized systems that remain at the site of construction, and are not produced for sale or commercial distribution. Federal laser regulatory requirements for hazard characterization and laser classification do not apply to such noncommercial FELs, so much of the information normally provided to end users by laser manufacturers is not available. Nevertheless, some basic characterization of the FEL beam hazard is warranted to allow development of adequate and appropriate control measures. The FEL’s wide spectral range and variable pulse repetition frequency makes hazard characterization challenging. This article describes an approach for characterizing the eye hazard associated with the coherent beam of the Optical Klystron 4 (OK4/Duke) storage ring FEL located in the Free Electron Laser Laboratory on the campus of Duke University in Durham, North Carolina.