Abstract: A time-of-flight spectrometer includes a gridless ion source for generating ions. The ions are reflected by a reflector and detected in a detector. Different types of ions, indicative of the chemical make-up of a sample, have different times of flight. The ion source includes apertured gridless electrodes to establish a specific potential distribution. The potential distribution can be established utilizing electrodes having apertures of varying diameters. The spectrometer also includes mechanical structure for varying the angle of the detector.