On-line measurement of proton beam current in pA range

A MeV proton beam with a current in the range of fA-nA is usually measured using a secondary beam signal that is dependent on a sample or requires noise-free accurate charge integration in a Faraday cup. We propose a simple on-line beam current measurement setup that can be used to directly measure beam current during ion beam analysis. A fast beam blanker is used to modulate the beam position after the last set of collimator slits in and out of a mini Faraday cup connected to fA-sensitive electrometer. Less than 100 fA current can be measured during an undisturbed irradiation with kHz sampling frequency. The fast, simple and easily controlled current measurement set-up is going to be routinely used for ion beam analysis and modification at the new Lund sub-micron beam line. (c) 2006 Elsevier B.V. All rights reserved.