Nuclear Instruments and Methods in Physics Research A 483 (2002) 157–161 Operation of the European storage ring FEL at ELETTRA down to 190 nm M. Trov " o a, *, J.A. Clarke b , M.E. Couprie c , G. Dattoli d , D. Garzella c , A. Gatto e , L. Giannessi d , S. G . unster f , N. Kaiser e , M. Marsi a , M.W. Poole b , D. Ristau f , R.P. Walker a a Sincrotrone Trieste, 34012 Trieste, Italy b CLRC Daresbury Laboratory, Warrington, UK c CEA/SPAM and LURE, Orsay, France d ENEA, Frascati, Italy e Fraunhofer Institut f . ur Angewandte Optik und Feinmechanik, Jena, Germany f Laser Zentrum Hannover, Germany Abstract Recent improvements in the performance of the European storage ring FEL at ELETTRA including shorter wavelength operation (190 nm), wider tunability and increased power are described. We report briefly also on initial use for experimental studies. r 2002 Elsevier Science B.V. All rights reserved. PACS: 29.20.Dh; 41.60.Cr Keywords: Storage ring; Free-electron laser 1. Introduction The European storage ring Free-Electron Laser (FEL) project at ELETTRA [1] began officially in May 1998 with partial funding from the European Commission over a 3-year period. 1 The final goal is the development of a combined UV/VUV FEL + synchrotron radiation user facility. First lasing at 350nm (February 2000), and subsequent operation at 220 nm (May 2000) were reported at last year’s FEL Conference [2]. In this article we report on further progress in improving FEL performance and understanding its characteristics, as well as initial tests of using the FEL radiation for user experiments. In particular, following successes at the NIJI-IV (212 nm) [3] and Duke (193.7 nm) [4] storage ring FELs in the important objective of reaching shorter wavelengths, we have so far reached 190nm. Attention has also been given to increasing tunability and output power. A significant factor in obtaining these improvements has been the particular effort devoted to mirror development, described in more detail in Ref. [5]. *Corresponding author. Tel.: +39-040-375-8218; fax: +39- 040-375-8653. E-mail address: mauro.trovo@elettra.trieste.it (M. Trov " o). 1 RTD Contract No. ERBFMGECT980102. 0168-9002/02/$-see front matter r 2002 Elsevier Science B.V. All rights reserved. PII:S0168-9002(02)00303-0