What have we learned from the kilowatt IR-FEL at Jefferson lab?

Recent work at Jefferson Lab has demonstrated the concept of same cell energy recovery to attain high average power in a free-electron laser. Since this device was the first of its kind, we learned a great deal about how to design such systems as we learned to operate the prototype. We are in the process of building a laser with an average power in excess of 10 kW in the infrared and have point designs for even higher power. This work will summarize the problems which were thought to exist before the IR Demo based and what we have learned since the laser operated successfully. The upgrade has its own challenges and these will be described along with the proposed solutions. (C) 2002 Elsevier Science B.V. All rights reserved.