SASE FEL at the TESLA Facility, Phase2

The last description of the TESLA Test Facility FEL has been written in 1995 (TESLA-FEL report 95-03). Since then, many changes have developed compared to the design,partially because the design was incomplete, partly because of gained knowledge over thepast few years. In addition, what used to be known as phase II of the project has beensubdivided into a finer time scale, starting with the first beam through the machine until thecomplete user facility with its different possible extensions.This report is therefore an upgrade of the above mentioned Conceptual Design Report. Itis by no means complete or final, but gives a more complete overview of the present statusof knowledge on present and future developments towards the TTF-FEL user facility