In situ current measurement in a compact broad ion source for helium and other ions

Compact broad beam ion sources with a small area footprint enable widespread applications of irradiation experiments. However, the lack of beam deflection and neutral particle traps for short beamlines poses a challenge to accurate fluence measurements. Here, a solution by measuring the current in a mobile Faraday cup placed close to the edge of a broad ion beam is presented. In combination with sputter experiments this accounts for the beam profile and divergence. To account for the neutralization due to charge transfer empirical factors are measured and compared with literature data. A comparison to a known ion source yielded a deviation within the limits of uncertainty between the implanted fluence and the fluence measured with the presented method. This proves the reliability of our in situ measurement of ion fluence.