A radiation source has been developed and implemented from Cˇerenkov emission that is intended to provide an intense continuum from the infrared to 600 A˚. Parasitic use of the primary electron beam at the Stanford Linear Accelerator Center (SLAC) together with a novel optical geometry for light collection can give a focused and tunable ultraviolet beam with 104kW/m2⋅sr brightness, 10−2spectral purity, and with the pulsed, 5 ps time structure of the SLAC electron beam. Measurements of emission characteristics in the visible part of the spectrum correlate closely with the predicted performance.