A method and apparatus for analyzing ions by determining times of flight include using a deflector to direct ions away from their otherwise intended or parallel course. Deflectors are used as gates, so that particular ions may be selected for deflection, while others are allowed to continue along their parallel or otherwise straight path, from the ion source, through a flight tube, and eventually, to a detector. According to the present invention, an extended Bradbury-Nielson gate, in the form of a series of plates, with equal but alternating opposite polarity potentials, is used as an ion deflector or gate.