The development of a micro-NRA setup for boron analsis

Abstract

Microanalysis of very low quantities of boron is required for various studies in geology and material science. This (analysis) was done at the nuclear microprobe chamber of Material Research Group in iThemba LABS. Since the solid angle of the annular Surface Barrier Detector is smaller and its position relative to the sample relatively far, the boron statistics are not optimal as will be seen in the study. Therefore an analytical set-up consisting of four large area PIN detector photodiodes was developed. Experimentally, the nuclear reaction 11B(p, a.1/Be showed to be free of interterences and gives good detection limits. The nuclear reaction gives a broad spectrum at Ep of 675 keV. The problem of back scattered protons was overcome by selecting a cut-off area where it is expected that the resultant alpha particles showing the presence of boron will be emanating. The standards were Boron Nitride, NIST, tourmaline and glasses. The glasses were prepared by first making a matrix base material thereafter infuse boron as Boron Oxide. The samples were then analyzed using SEM/EDS techniques to acquire elemental abundances using EMP which proved to be not conclusive as a lot of problems were observed. That's due to the fact that final obtained values didn't correspond to the initial calculated values. The acquired SEM images were used though positively as they help in positioning of the glasses during experiments during both EMP and NMP. The lowest obtained minimum detection limit was of a NIST 614 standard at l .3μg/g for 0.303μC accumulated charge. The linear trend formed in the absence of the glasses gave a perfect agreement which meant that there were some discrepancies with them.