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Powder Instrument For Transition In Structure Investigations (PITSI)

Instrumentation Description The PITSI (Sesotho name for Zebra) instrument is located at the SAFARI-1 research reactor of the South African Nuclear Energy Corporation (Necsa) SOC Limited. It enables medium resolution neutron powder diffraction capability for the study of crystallographic structures, chemical composition and magnetic phenomena in solid and powdered polycrystalline materials. Neutron powder diffraction complements and extends the capabilities of conventional X-ray diffraction with regard to the following: Scattering off nuclei: 
  • Interaction strength atomic number independent: Sensitivity to light elements and their presence in heavy elements, distinguishing between neighbouring elements in 3d, 4f and 5f  bands, etc.
  • Unlike X-ray diffraction, Neutron diffraction do not suffer form-factor fall off
  • Magnetic interaction with unpaired electrons enables studies of magnetic phenomena
  • Superior penetrating capabilities enables non-destructive in-situ parametric studies as function of temperature, pressure, magnetic field, chemical exchange of energy-storage materials such as Li batteries, etc.
Technical Project Examples In-situ phase transformation studies of pure Fe rod to identify the chemical phases, determine transition temperature of alpha ferrite to the austenite phase,  and the change in structural parameters such as the lattice.  
In-situ magnetic studies of Cr84.7Re15.3 alloy to characterise magnetic order, determine magnetic phase transition temperatures and the Neel temperature. The (1 1 0) magnetic reflection of Cr in the alloy decreases in intensity upon heating in accordance with the suppression of the antiferromagnetic behaviour (Neutron diffraction study of the Cr84.7Re15.3 allo;BS Jacobs, ARE Prinsloo, AM Venter, ZN Sentsho, AJ Studer and CJ Sheppard)  
Chemical phase quantification (Rietveld technique) in multiphase oxides (6 phases in this case). The inset shows the equivalent XRD pattern. Specifically note the presence of high intensities in the small d region (large diffraction angles, up to 120°).  
Quantification of retained austenite in heat-treated ferritic steel. The inset shows the equivalent XRD pattern where predominantly only the ferrite peaks are detected.   Data reduction and analysis Data reduction is primarily performed in-house using custom-developed software called ScanManipulator and is available online here: https://github.com/Deon-Marais/ScanManipulator [D Marais, A.M. Venter and J Markgraaff, Data processing at The South African Nuclear Energy Corporation SOC Ltd (Necsa) neutron diffraction facility. Proceedings of SAIP2015. (2016) 198-203. (ISBN: 978-0-620-70714-5)] Data can then be analysed using various products such as Topas (https://www.bruker.com/products/x-ray-diffraction-and-elemental-analysis/x-ray-diffraction/xrd-software/topas.html) , GSAS-2 (https://subversion.xray.aps.anl.gov/trac/pyGSAS) or Fullprof (https://www.ill.eu/sites/fullprof/php/programs.html) Referencing the instrument in publications A.M. Venter, P.R. van Heerden, D. Marais, J.C. Raaths, Z.N. Sentsho, PITSI: The neutron powder diffractometer for transition in structure investigations at the SAFARI-1 research reactor, Physica B: Physics of Condensed Matter 551 (2018) 422-425.  (http://dx.doi.org/10.1016/j.physb.2017.12.017) Instrument scientists(s) Ms. Zeldah Sentsho, MSc.Physical Science Zeldah.Sentsho@necsa.co.za +27 (0) 12-305-5918 Prof. Andrew Michael Venter, PhD. Physics Andrew.Venter@necsa.co.za +27 (0) 12 305 5038 Apply for beam time Download the beam time request form, and submit it to the instrument scientists as well as the User Office at UserOffice@necsa.co.za.  

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