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Micro-focus X-ray Radiography and Tomography (MIXRAD)

Instrumentation Description

Computed tomography:

Micro-focus X-ray Computed Tomography (micro-CT) is an attractive radiation-based research technique that provides high quality micron-level information of the interior of samples non-destructively. The principle of the technique is based  on the attenuation of X-rays through absorption and scattering, where the transmitted intensity is recorded in micro-CT as digital projections. X-rays are strongly attenuated by materials that contain heavy atoms, and weakly by light ones. A familiar example is the radiographs/projections taken of the human body where X-rays pass easily through the flesh that primarily comprises  and is attenuated stronger by the more dense bones. This preferential attenuation shows up as contrast in the observed transmission images. There is therefore a correlation between density and X-ray attenuation with contrast becoming less evident in substances with similar densities. The inherent non-destructive nature and the high-quality data  are very useful for applications in a wide range of scientific fields that include geology, anatomy, palaeoanthropology, agricultural sciences, chemistry, engineering, etc. Micro-CT investigations also form the basis to more advanced tomographic synchrotron-based investigations. Consequently, feasibility results from the MIXRAD facility equips South African researchers and students to formulate high quality proposals to motivate access to synchrotron light source facilities where beam time is highly competitive.

Technical

A series of projection images are measured at sequential rotational steps up to a full rotation of the sample. From these step measurements a reconstruction process  technically converts the 2D projection data into 3D virtual volume data. The MIXRAD laboratory is equipped with the required resources for rapid reconstruction – reconstruction parameters are optimised automatically independently of the intuitive opinion of the operator. The final reconstruction is a 3D volume file which can be directly imported into visualisation software that allows and enables extraction of  different observations by digital segmentation of the reconstructed image.

Benchmarking

The micro-CT system is a commercial laboratory-based system which is well maintained and calibrated annually to ensure the highest data quality. The instruments scientists that run the micro-CT system are certified to provide the highest quality data possible.

Estimate of data acquisition times

Typical sample scanning times range from 30 minutes to  hours. Time per sample acquisition depends on factors that include the sample complexity/composition, size and the sensitivity contrast desired.

Data reconstruction and analysis

Data reconstruction and analysis depends on information required and number of samples. This can range from hours to months. The instrument scientists offer comprehensive training on data analysis for users. A service can be provided for commercial clients that involves all aspects of scanning, reconstruction and data analysis.

Referencing the instrument in publications

Jakobus W. Hoffman and Frikkie C. De Beer.  Characteristics of the Micro-Focus X-ray Tomography System at the MIXRAD Facility at NECSA in South Africa. 18th World Conference on Nondestructive Testing, April 2012, Durban, South Africa (WCNDT 2012)

https://www.ndt.net/article/wcndt2012/papers/37_wcndtfinal00037.pdf

Instrument scientists

Mr. Robert Nshimirimana – robert.nshimirimana@necsa.co.za

Dr. Lunga Bam – lunga.bam@necsa.co.za

Mr. Jakobus Hoffman – jakobus.hoffman@necsa.co.za

Apply for beam time

Download the beam time request form, and submit to the instrument scientists as well as the User Office at UserOffice@necsa.co.za.

 

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