Development of New Experimental Facilities at the Lund Nuclear Microprobe Laboratory

University dissertation from Department of Physics, P.O. Box 118, SE-221 00 Lund, Sweden

Abstract: Ion beam analysis techniques are now well established as research tools for a broad range of multidisciplinary scientific fields. The ability to focus an ion beam down to micrometer size has expanded and strengthened the capability of IBA techniques to a higher level. A new field “Nuclear microprobe (NMP) analysis” has been developed over the past decades, in which most IBA techniques are used and, in addition, a new group of imaging techniques has been developed. A high-resolution scanning nuclear microprobe can provide maps of distributions of elements with high sensitivity and can analyse very small structures. The power of NMP lies mainly in its lateral resolution (beam spot size) and the amount of current it can deliver on the target. So the quest for the smallest possible beam spot size with sufficient beam current is an active field of research. Even if the NMP has much more to offer, conventional IBA techniques are still suitable in some scientific fields of research, due to their simplicity and the shorter run times required. In this work two new beamlines have been designed and constructed at the Lund NMP laboratory. The first part of the thesis is based on the design and construction of a broad beam facility called “macro beamline” including the quantitative calibration of the PIXE set-up in this beamline. For a better performance and quantification with PIXE the peak tailing of the X-ray detector has been characterized. This beamline has subsequently been successfully used to analyse a large number of PIXE samples with a beam of millimetre size. The second part of the thesis describes the design and construction of a new sub-micron beamline, where a focused beam with sub-micron resolution is expected. In designing this beamline all the necessary parameters were carefully considered and a detailed theoretical investigation was done using computer code PRAM. A two-stage doublet configuration has been chosen as the focusing system based on these calculations. Our two-stage system is unique in that the first stage act as an independent microprobe. Experimentally, two of the key functions for a successful set-up, the four high quality magnetic quadrupole lenses and a special 8-element annular X-ray detector have been investigated and characterized. This large area X-ray detector will facilitate work with a much lower beam current. A large and flexible chamber, with sample stage movable with high precision and a optical viewing system of high magnification, has also been constructed. Special care has been taken to insulate the beamline and the chamber from vibration.

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