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Here, we present the design and test-operation performance of a low-temperature field emission (FE) system which can be employed to image and characterize the FE beam from low-temperature tips. Three radiation shields cooled by liquid helium and liquid nitrogen cryostats surround the FE tips and anodes completely. Once the FE system is cooled down to 5 K, experiments can run for more than 15 h without interruption. The design allows not only for the exchange of tips and anodes by load-lock equipment but also for the adjustment of tip–anode distance using a piezo-tube. Test runs in projection microscopy mode have presented clear diffraction-fringe patterns near the shadows of nano objects at temperatures from room temperature to 5.5 K, indicating that the system is well suited for the investigation of the coherence of electron beam from FE tip.

Real-time microscopic observation of emission fluctuation on Mo-tip field emitter array caused by introduced gasElectron induced nanodeposition of tungsten using field emission scanning and transmission electron microscopes J.Emission stability of a field emitter array observed by an emission microscope An extreme high vacuum field emission microscope ͑XHV FEM͒ was constructed for the study of inherent fluctuations of field emission ͑FE͒ current. The damping and fluctuation behaviors of FE current from clean W͑111͒ tips at 90 K were observed using the XHV FEM. Exposure to XHV of 7.5ϫ 10 −10 Pa continued to damp FE current for more than 2000 min. The fluctuation ͑ϳ0.01% ͒ of FE current ͑1 nA͒ for the clean W͑111͒ tips was comparable to the corresponding shot noise fluctuation ͑0.005%͒, demonstrating the suitability of the XHV FEM for the inherent fluctuation study of the FE process. After saturating the tip surface with hydrogen, the FE current showed fluctuations of Ͻ0.1%

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