Design considerations for the JAERI industrial 1.3micron 40kW highly-efficient FEL driven by the superconducting rf linac

As the JAERI superconducting rf linac based free-electron laser (FEL) has successfully been lased to produce a 2.34kW FEL light and 100kW electron beam output in quasi continuous wave(qCW) operation recently, it exceeded twice of the 1kW program goal. As our next program goal, a 40 kW FEL light and 4 MW electron beam output in qCW operation is planned in the JAERI superconducting rf linac based FEL facility. Conceptual design considerations needed for such a very high power operation will be discussed to improve the existing facility.