Pupeza, I.I.PupezaEidam, T.T.EidamKaster, J.J.KasterBernhardt, B.B.BernhardtRauschenberger, J.J.RauschenbergerOzawa, A.A.OzawaFill, E.F.E.F.FillUdem, T.T.UdemKling, M.F.M.F.KlingLimpert, J.J.LimpertAlahmed, Z.A.Z.A.AlahmedAzzeer, A.M.A.M.AzzeerTünnermann, A.A.TünnermannHänsch, T.W.T.W.HänschKrausz, F.F.Krausz2022-03-112022-03-112011https://publica.fraunhofer.de/handle/publica/37101510.1117/12.877532An Yb-based 78-MHz repetition rate fiber-amplified frequency comb is used to investigate the power scaling limitations of a standard-design bow tie high-finesse enhancement cavity for XUV generation. With a Xenon gas jet in the 22-?m-radius focus, the 200-fs intra-cavity circulating pulse reaches a maximum of 20 kW of time-averaged power. A novel cavity design is presented, conceived to overcome the observed enhancement limitations and offering the prospect of few-nm high-power high-harmonic generation. Several applications which come into reach for the first time are discussed.enenhancement cavityXUVMHz high-harmonic generation620conference paper