Centro Nacional De Aceleradores Research Articles

Determination of nitrogen in metallic phases using the [formula omitted](d, pγ) 15N nuclear reaction

Analysis of nitrogen in metallic materials using X-ray spectrometry (EDS, PIXE) is subjected to large errors due to two factors: the low nitrogen contents in the steels (usually below 0.3 wt.%) and the presence of interfering L-lines of the main metallic components (Fe, Cr, Ni, … ). These factors prevent the use of SEM, TEM, micro-PIXE and other microanalytical techniques for the quantitative determination of nitrogen in metallic phases, non-metallic inclusions, precipitates, etc. In this case the deuteron induced gamma-ray emission (DIGE or d-PIGE) is known to be a very suitable method. In this work we describe the methodology for the use of the 14 N (d, pγ) 15N nuclear reaction at a deuteron energy of 1.4 MeV to measure low nitrogen levels in steel, using both macro and microbeam analysis. DIGE experiments were performed in the universal chamber and in the scanning nuclear microprobe at the Centro Nacional de Aceleradores in Seville, using steel standards with nitrogen contents ranging between 0.008 and 0.35 wt.%. These results give a value for the detection limits for nitrogen in the steels of 0.001 wt.% for the macrobeam and 0.04 wt.%. for the microbeam. Results are applied, in combination with d-PIXE (or DIXE), RBS and electron imaging to the determination of the nitrogen partitioning ratio between α-Fe and γ-Fe in an austenitic–ferritic duplex stainless steel.

External microbeam set-up at the CNA (Sevilla) and its application to the study of Tartesic jewellery

A new external microbeam system has been installed recently at the +45° beam line of the 3 MV Pelletron accelerator at the Centro Nacional de Aceleradores (Sevilla, Spain). The facility, based on the system from Oxford Microbeams (OM), includes two sets of slits, a doublet of magnetic quadrupole focusing lenses, a Faraday cup and an accurate positioning device. In addition, a beam profile monitor (BPM) and a quartz viewer have been installed in the line to facilitate the microbeam production. The first PIXE application of the new facility was made in the field of Archaeometry, on the study of Tartesic gold artefacts (700–500 BC, SW of Spain) from Ébora and other archaeological sites. The aim of the analysis was to perform an exhaustive and systematic study about the soldering procedures that were employed by the goldsmiths along the Valley of Guadalquivir River after the Phoenician colonisation.

CNA: The first accelerator-based IBA facility in Spain

The recently created Centro Nacional de Aceleradores (National Center for Accelerators, CNA) in Seville emerges as the first ion beam analysis facility in Spain. The laboratory is based on a 3 MV tandem accelerator model 9SDH-2 of NEC and it is primarily focused on material research and modification by means of IBA techniques: PIXE, RBS, NRA, PIGME and ERDA. The ions are delivered by two ion sources: Alphatross radio-frequency source and SNICS-II sputtering source. The ion beam handling system includes equipment for beam focusing, steering and diagnosis, a 90° analyzing magnet and a seven-port switcher magnet. A system based on magnetic steerers has been installed for high-precision beam energy scanning. In this paper the main elements of the laboratory will be described, focusing on the electronic equipment, detectors and the four beamlines planned for the moment: channeling line, microbeam line, multipurpose vacuum chamber and external microbeam. Moreover, the characteristics of the system as observed until now by means of performance tests, beam energy spread measurements and energy calibration experiments will be summarized.