No abstract

Isotopic ratios of "'Kr/Kr in the ränge of 10~" were measured with accelerator mass spectrometry in pre-nuclear atmospheric krypton and in modern krypton. Within the experimental uncertainty (±30%) the "'Kr/Kr ratios were found to be the same. This establishes ^'Kr (t," = 230000 years) as a long-lived cosmogenic radionuclide essentially unaffected by anthropogenic contributions, and therefore well suited for dating applications. The anthropogenic "cleanliness" of "'Kr is in accord with estimates for contributions from various human activities.

In this paper we describe the first systematic measurement of beam neutralization (space charge compensation) in the ECR low energy transport line with a retarding field analyzer, which can be used to measure the potential of the beam. Expected trends for the space charge compensation levels such as increase with residual gas pressure, beam current, and beam density could be observed. However, the overall levels of neutralization are consistently low (<60%). The results and the processes involved for neutralizing ion beams are discussed for conditions typical for ECR injector beam lines. The results are compared to a simple theoretical beam plasma model as well as simulations.