A method of operating a focused ion beam device for emitting during operation a focused ion beam including ions of a gas generated at a first partial pressure, comprising cleaning an emitter tip positioned in an emitter tip region of the focused ion beam device, the cleaning comprises introducing the gas into the emitter tip region such that the gas has a second partial pressure of at least two times the first pressure. Further, a focused ion beam device is provided, comprising a gas field emitter tip (13) in an emitter tip region emitting an ion beam including ions of a gas, a gas inlet for supplying a gas with different pressures (110), a gas outlet (120), a pressure measurement device for measuring the pressure in the emitter tip region and a control unit (130) for controlling switching between an operation mode and a cleaning mode, further controlling the pressures in the emitter tip region and being connected to the pressure measurement device.