Single-charge pumps are the main candidates for quantum-based standards of the unit ampere because they can generate accurate and quantized electric currents. In order to approach the metrological requirements in terms of both accuracy and speed of operation, in the past decade there has been a focus on semiconductor-based devices. The use of a variety of semiconductor materials enables the universality of charge pump devices to be tested, a highly desirable demonstration for metrology, with GaAs and Si pumps at the forefront of these tests. Here, we show that pumping can be achieved in a yet unexplored semiconductor, i.e. germanium. We realise a single-hole pump with a tunable-barrier quantum dot electrostatically defined at a Ge/SiGe heterostructure interface. We observe quantized current plateaux by driving the system with a single sinusoidal drive up to a frequency of 100 MHz. The operation of the prototype was affected by accidental formation of multiple dots, probably due to disorder potential, and random charge fluctuations. We suggest straightforward refinements of the fabrication process to improve pump characteristics in future experiments 2021 The Author(s). Published by IOP Publishing Ltd.

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Among its results, the ReDSHIFT project has developed a software tool for spacecraft operators, space agencies and research institutions to design the end-of-life of Earth-based missions and to study the interaction with the space debris environment. As part of this, the “Disposal Mapping” module, presented in this paper in its structure and algorithm, computes the end-of-life disposal strategy for missions whose operational orbit is in the orbital region from Low-Earth orbit to Geostationary Earth orbit. Given the initial orbit, the available ?v on board and the spacecraft characteristics in terms of cross area and mass, the options for end-of-life disposal are given and compared; namely, end-of-life disposal via one or a sequence of impulsive manoeuvres, end-of-life disposal through the use of a solar/drag sail or end-of-life through a hybrid sail plus an impulsive manoeuvre.@en