A pre-sample charge measurement system for quantitative NMP-analysis

In many IBA applications the main aim is to obtain quantitative figures characterizing the sample. Normally charge, i.e. number of probe particles, is used for normalization and is measured either by collecting the charge deposited in the sample or by collecting the particle in a post-sample Faraday cup or in combination. Both these techniques have drawbacks and results can be difficult to compare for samples with different matrix composition.In this work, we present an upgraded design and test results from the Lund NMP pre-sample charge measurement system. The system presented is based on a pre-sample beam deflection controlled by the beam scanning system for the nuclear microprobe. It can be operated in different modes, but during normal operation the beam is blanked once per pixel and the corresponding charge is collected during the beam-off period. The system does not only measure an average of the beam current during data collection, but actually a pixel-by-pixel normalization is possible. Data of the system performance are presented and in addition illustrations of how quantitative measurements both for PIXE and elastic scattering can be made more reliable.