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We discuss the progress in the R&D program for a future upgrade of the European XFEL facility, namely for an operation in the continuous wave (cw) and long pulse (lp) modes, which will allow for significantly more flexibility in the electron and photon beam time structure. Results of cw/lp runs with preseries XFEL cryomodules and status of components needed for the new operation modes are presented here.

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A merged dual-gate power MOSFET is described which greatly improves the light-load energy efficiency of high-speed (PIMHz) low-voltage DC/DC conversion by dynamically reducing input capacitance and gate drive losses during lowcurrent load conditions. The W-switched MOSFET concept is experimentally verified using a TrenchFET employing a 30X reduction in input capacitance during light load. Efficiency improvements better than 25% and a decade increase in useable load current were confirmed for a 1-cell LiIon to 5-V boost converter, without adversely affecting the converter's transient response. Various figure-of-merits for W-switched MOSFETs are also proposed to analyze the limits of W-switching.

In the version of this Article originally published, the surname of the author N. Johansson was misspelled as 'Johannson'. In addition, in affiliation 17, "University of Łódź" was incorrect; it should have read "Łódź University of Technology". These errors have been corrected in the online versions of the Article and its Supplementary Information.