Lessons from FLASH
The free-electron laser facility FLASH at DESY, Germany finished its second user period scheduled from November 2007 to August 2009. Together with the first user period, up to now 600 days have been devoted to user operation. In addition, a large part of beamtime has been allocated for machine studies for further developments, including beamtime for XFEL and ILC R&D. FLASH provides trains of fully coherent 10 to 50 femtosecond long laser pulses in the wavelength range from 40 nm to 6.8 nm. The SASE radiation contains also higher harmonics; several experiments have successfully used the third and fifth harmonics. The smallest wavelength used was 1.59 nm. The talk will give a summary of the user operation at FLASH and discuss lessons learned and future prospects and plans to upgrade of the facility.