Top: the background subtracted pulse-height spectrum obtained for CD₃CDOD⁺ using the IID system without the grid in front of the detector. The large peak at high energy is due to particles impacting at full beam energy. If losses of heavy fragments that miss the detector due to their high transverse energy would occur, one or two smaller peaks at lower energies would indicate that. It is clear that no losses of heavy fragments are observed. The sharp feature at very low mass/energy is due to noise in the detector system. Bottom: the background subtracted pulse-height spectrum obtained for CD₃CDOD⁺ using the IID system with the grid inserted in front of the detector. The three major peaks are due to signals from passing fragments containing one, two or three heavy atoms, respectively.