Apparatuses (41, 91, 111, 115, 121, 151) and methods (31) for time-of-flight mass spectrometry providing effective pulsed conversion of continuous ion beams into pulsed ion packets is disclosed. Bunching of energetic continuous ion beams forms ion packets, which are filtered by a subsequent isochronous energy filter (49, 79, 81-84, 110). The bunching method is particularly suitable for ion sources with relatively large spatial emittance, otherwise unable to fir the acceptance of orthogonal accelerators. The method is particularly suitable for multi-reflecting TOF MS, which accommodates small size ion packets and where the duty cycle advantage of orthogonal accelerators is minor.