In some embodiments, a time of flight mass spectrometer can comprise an input orifice for receiving ions, a first ion accelerator stage for accelerating the ions along a first path, at least one ion reflector for receiving said accelerated ions and redirecting said ions along a second path different than the first path, a detector for detecting at least a portion of the ions redirected by said at least one ion reflector, and at least first and second field free drift regions disposed between said first acceleration stage and said detector, wherein said second field free region is disposed in proximity of the detector. In some embodiments, the lengths of the field free drift regions can be selected so as to provide 1st and 2nd order corrections of the time of flight of the ions with respect to variation in their initial positions.