ULTRAVIOLET LASER AT DESY. A free electron laser (FEL) built at the DESY lab in Hamburg by the international TESLA collaboration has achieved a beam of radiation with a wavelength of only 93 nm. FELs normally operate in the following way: a beam of energetic electrons passes through a series of S curves (an undulator) where they are made to radiate light which is stored inside a mirrored cavity. The photons, reflecting back and forth in the cavity, help to stimulate the electrons to radiate even more, thus amplifying the higher-energy light beam. The resultant light is tunable and coherent. At wavelengths below about 150 nm, however, mirrors are not effective and light accumulation cannot occur. Scientists of the TESLA collaboration have now succeeded at DESY in carrying out a scheme suggested 20 years ago: give up the accumulation of light in an optical cavity and let the radiation amplify itself in a single pass as the electrons travel through a very long undulator section, thereby increasingly interacting with the radiation. The product is essentially coherent synchrotron radiation. The TESLA collaboration consists of 38 institutes from 9 countries. Major hardware contributions came from DESY, Italy, France and the USA (US institutes: ANL, Cornell, Fermilab, UCLA). The work with the UV laser is part of an effort to produce an x-ray laser with 6-nm light (by the year 2003). And beam-optics lessons learned might in turn contribute to a more ambitious plan to develop a next-generation linear 500-GeV electron linear collider with integrated x ray lasers called TESLA. (Joerg Rossbach, rossbach@desy.de; www.desy.de/pr-info/News; figure at Physics News Graphics)