Lewandowski, J.R. Field, R.C. Fisher, A.S. Nuhn, H.-D. Welch, J.J. WEP001 undulator radiation FEL cavity gun 2015 2015-12 A significant source of radiation signals in the LCLS Undulator have been identified as being generated by dark current emitted from the LCLS RF Photocathode Gun. Radiation damage to magnets over time can lead to degraded performance and significant cost for replacement. A method of using an existing transverse deflector cavity with a modified RF pulse has been tested and shows promise for eliminating the radiation dose from RF gun dark current that is generated in time before and after the production beam pulse.