Zeiss GeminiSEM Series Instruction Manual

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ZEISS 3 Product and Functional Description | 3.2 Main ComponentsInfoA specimen can be stored in the airlock when the chamber is in any VP mode (Standard VP,NanoVP, or XVP).4 In store mode, however, the airlock needs to be re-pumped from time to time. This leadsto an unstable chamber pressure for a few seconds and influences the brightness of im-ages acquired with the VPSE or C2D detectors.3.2.2.3 Beam Gas Path Length (BGPL)When the beamsleeve aperture is inserted and you are working in Nano VP or XVP mode, a pa-rameter called Beam Gas Path Length (BGPL) is displayed in the Status Bar.The BGPL is the distance from the end of the beamsleeve aperture to the specimen. This meansthe BGPL is the distance that the primary beam has to travel through the low vacuum part of thesystem. Keeping the distance small means that scattering of the primary electrons on VP gas mol-ecules is kept small, resulting in good resolution and signal-to-noise ratio.The BGPL should be not lower than 1 mm, because charge compensation is incomplete in thiscase. You will have best results when the BGPL is between 1 and 2 mm.InfoWhen working in Nano VP or XVP mode the BGPL is the WD-like parameter which should beobserved carefully not to damage the beamsleeve. The BGPL is calculated by working distanceWD minus length of the beamsleeve, which is 6.17 mm.NOTICEShort Beam Gas Path Length (BGPL)Risk of damaging the beamsleeve and/or the specimen.4 Do not use a BGPL of less than 1 mm.Instruction Manual ZEISS GeminiSEM series | en-US | Rev. 2 | 349500-8138-000 33