TIME EVOLUTION OF CHARGE STATES IN AN ELECTRON-CYCLOTRON-RESONANCE ION-SOURCE

The production of high charge-state ions in an electron cyclotron reso nance ion source has been studied as a function of time using a pulsed Nd:YAG laser to ablate heavy metal (bismuth) ions into the plasma. Th e time required to produce a charge state has been measured by observi ng the arrival time of the ions at a Faraday cup after the source anal yzing magnet. The results of these measurements have been compared to a simple sequential ionization model and are found to be in good agree ment with the data. The data can be used to characterize the plasma el ectron density, electron temperature, and neutral atom density, since these are the only three adjustable parameters in the model and are su fficient to achieve good agreement for the time evolution of all obser ved charge states. (C) 1996 American Institute of Physics.