Ion trap mass spectrometer

摘要

By preventing the trapping efficiency of ions from largely depending on the mass-to-charge ratio, an ion trap mass spectrometer suitable for obtaining a high sensitive mass spectrum is provided. Ions of a specimen to be mass analyzed generated at an external ion source pass through an ion transportation portion and then injected into a space (ion trap volume) between the ring electrode and the end cap electrodes. An RF trap voltage power source applies an RF frequency Vxcos OMEGA t between the ring electrode and the end cap electrodes to form a radio frequency electric field in the ion trap volume. The RF trap voltage is changed so that the optimum trap frequency is in inverse proportion to 1/2 power of a mass-to-charge ratio while the ions are being trapped in the radio frequency electric field formed in the ion trap volume.