Quasi-continuous wave operation of multi-megawatts electron beam in the JAERI superconducting RF linac FEL driver

Recently, the JAERI superconducting rf linac based FEL has successfully been lased to produce a 0.1 kW FEL light and about 70 kW electron beam output in quasi continuous wave operation. The 1 kW class output as our present program goal will be achieved to modify the optical outcoupling method in the FEL optical resonator and to improve the electron beam optics and basic performances in the JAERI FEL driver. As our next program goal is a 100 kW class FEL light and multi-MW class electron beam output in average, quasi continuous wave operation of a multi-MW electron beam will be planned in the JAERI superconducting rf linac FEL driver facility within a few years. Conceptual and engineering design options needed for such a very high power operation will be discussed to modify and to upgrade the existing facility in the conference.