Abstract: Methods and systems for controlling a filament of an electron emitter associated with an ion reaction cell in accordance with various aspects of the present teachings may account for inter-filament and inter-instrument variability and can provide improved reproducibility in EAD experiments and ease of use. In some aspects, a method of operating an ion reaction device of a mass spectrometer system is provided. The method comprises applying a calibration drive voltage to a filament of an electron emitter associated with an ion reaction cell and determining a value representative of the calibration electron emission current generated by the filament while having the calibration drive voltage applied thereto. A calibration saturation voltage can be determined by iteratively increasing the calibration drive voltage applied to the filament and determining the value of the calibration electron emission current at each corresponding calibration drive voltage until the filament reaches a saturation condition.