Maximum Charge State Research Articles

Collision experiment on highly ionized ions using a vacuum spark source

Cross sections for one-electron capture by Fe 6+ in H 2 have been measured at collision energies below 10 keV by using a vacuum spark ion source. It is found that the cross sections are little dependent on the collision energy and their values are around 6×10 −15 cm 2. This ion source, which has no electrode for ion extraction, can produce multicharged ions from several hundreds of eV to several tens of keV and the maximum charge state of 16 in Fe at the discharge energy of 125 J (capacitor: 10.4 μF, operation voltage: 5 kV). With an ion selection system of 2.7 m time-of-flight and a 127° electrostatic analyzer of 1% resolving power, 10 2−10 3 ions/pulse are obtained. Because of the poor reproducibility of the discharge, ions which have captured an electron from the target molecule and ions which have not reacted, are measured simultaneously during one discharge with a microchannel plate which has two collectors at the back.