An electron-transfer gas ion source with isobar separation for Cl−

The operation of a prototype AMS gas ion source that exploits resonant-electron transfer is described. A primary keV-energy negative atomic ion beam and an ICl gas target were used. ICl is potentially useful in 36Cl studies because of the instability of its sulphur analogue (S2I2) at room temperature. The 20 keV primary atomic negative ion beam from a sputter ion source was magnetically analysed before being sent into the electron-transfer gas ion source. This ion source had a gas cell at its entrance and a series of electrodes along its length to extract the secondary ions. The source produced a secondary beam of 8 or 10 keV Cl− ions. This beam was about 20% as intense as the Cu− beam that emerged from the secondary ion source with no ICl present. The results of this study validate the basic concept of an electron-transfer gas ion source based on resonant transfer from a primary beam to a gas.