Study of ion transmission for a linear mode Bradbury–Nielsen gate in ion mobility spectrometer

Abstract Fourier transform ion mobility spectrometer (FT-IMS) has the advantage of high ion utilization efficiency. Its two ion gates work in binary switch mode with square wave modulation function, which causes interference from high order scaled versions of the original spectrum. This problem can be avoided by using cosine modulation function, which requires the ion gates working in linear mode by quantitatively controlling its transmission in real time. In this paper, the influence of the structure parameters of Bradbury–Nielsen gate (BNG) and the electrical parameters on the ion transmission is investigated by SIMION simulation and experiment. The results show that the transmission in the open state is determined by the mechanical aperture ratio, and in the transition state is determined by the electric field ratio. In practical, the ion transmission can be quantitatively controlled by simply adjusting the voltage difference between adjacent wires when in the transition state. The nonlinearity between the transmission and the control voltage can be corrected by a simple calibration. This job proves the possibility of implementing a linear mode BNG, which can be used in further to improve the precision of the FT-IMS.