5 Commissioning and First Operating Steps | 5.8 Working with Variable Pressure ZEISSParameter Ideal Ultimate LimitsPressure 60 Pa – 80 Pa 5 Pa – 500 Pa Trade off betweenskirt effect andcharge compensa-tionBeamsleeve bias 350 V 0 V – 400 V DischargesAcquisition condi-tionsDrift compensatedframe averageAll Specimen detailsmay move due tocharge buildupDetectors InLens (best image resolution) 150 Pa max, no to-pographyEsB (discrimination of charge buildup) Max. grid voltage1000 VVPSE/C2D 500 Pa, topographyaSTEM/VP-BSD Efficiency of diodedetectors decreasewith lower accelerat-ing voltage (70 % at1 kV)Field of view 350 μm or 800 μm for wide field lens700 μm or 1600 μm for Nano-twin lensDepending on beam-sleeve aperture usedand lens configura-tionEDX WD 10–12 mm; 350 μm beamsleeve aperture5.8.2.4 Changing to Nano VP or XVP ModeNOTICETouch alarm is not availableIn Nano VP mode touch alarm is only available when beamsleeve bias voltage reaches approxi-mately 200 V. In XVP mode touch alarm is not available.4 Avoid a Beam Gas Path Length (BGPL) of less than 1 mm.4 Watch the moving stage in TV mode.4 To stop the moving stage immediately, press F12 or press the Break push button of thedual joystick panel.InfoA higher pressure can be set within a few seconds. Achieving a lower pressure may requiresome more time, because the specimen chamber has to be evacuated by the pre-vacuumpump.Procedure 1. In the GeminiSEM Control panel, select the Control tab.2. In the Variable Pressure section, click Nano VP or XVP to start the pre-defined macro.The macro automatically performs the following actions:à If EHT is on, it is turned off.à The column chamber valve is closed.110 Instruction Manual ZEISS GeminiSEM series | en-US | Rev. 2 | 349500-8138-000