Synchrotron-Based X-ray Computed Tomography Discussion
Figure 8 : Stress exerted by the NiP microlattice as a function of time, acquired at the same time as the tomograms. Square symbols indicate times at which a tomogram was acquired. Black squares indicate the tomograms presented in Figure 7 .
falls toward the bottom of the loading stage at a calculated velocity of 2.3 km h -1 (1.4 mph). It should be noted that this particular ligament is absent in the reconstructed tomogram (not shown). This is due to the fact that the ligament is not imaged in a stationary position in each acquired radiograph that is used to reconstruct the tomogram, thus highlighting the fact that the total acquisition time for a tomogram must be significantly shorter than the desired dynamic process that is to be examined.
We have demonstrated that coupling a custom loading stage to a third-generation synchrotron-based micro-scale X-ray CT beam line can result in true in situ 3D imaging of advanced cellular structures during 10 -2 s -1 uniaxial compression. T e compression rate was chosen so that potential blurring of the acquired tomograms was eliminated. Adequate temporal resolution dictated the spatial resolution of the CT setup. No X-ray radiation-induced damage from the high fl ux synchrotron X-ray source was noted on either of these samples. However, other samples (such as silicone foams) did have a noticeable yellow discoloration, indicating radiation-induced damage. Also, the PMMA sleeve used to support the upper motor did yellow in the area where the beam passed through and was replaced. Over the following weeks, it shattered within the beam path area. T e largest problem with this type of data acquisition is in data handling and analysis. Large volumes of data were acquired for each sample imaged; reconstruction of a single tomogram resulted in a 4.8 GB fi le size, with a total of 96 GB per sample compression. T erefore, data reconstruction and data processing requires signifi cant amounts of PC processing time and signifi cantly depends on the hardware specifi cations of the processing PC. For example, the tomograms of the 3D printed foam required an edge-preserving smoothing step [ 31 ], which consumed approximately fi ve times the memory of the tomogram data set and took ~16 h to complete with our current processor.
Conclusions T e high photon fl ux of third-generation synchrotron sources, combined with the high-speed frame rate of commer- cially available camera systems, have allowed for true 4D micro-scale X-ray CT. Dynamic processes that occur on timescales within a second to tens of minutes can be adequately resolved, with an image resolution of tens of micrometers. T is all depends on the sample composition, scintillator performance, synchrotron source photon fl ux, and frame rate of the image acquisition camera. T ese data are then suitable for comparison to modeling eff orts, using the fi rst tomogram as an initial input and comparing the incremental tomograms to analogous modeled data sets.
Figure 9 : A series of radiographs of a NiP microlattice acquired during dynamic compression. The radiographs show the microlattice at different time intervals (and, consequently, at different rotation angles). The black arrow indicates a ligament that breaks off of the main body of the sample and falls to the bottom of the loading stage. The scale bar is in micrometers.
2015 May •
www.microscopy-today.com
Acknowledgements Los Alamos National Laboratory is operated by Los Alamos National Security LLC under contract number DE-AC52-06NA25396 for the US Department of Energy. Funding for this research was provided by the Enhanced Surveillance Campaign, Tom Zocco, Program Manager. T e authors wish to thank Doga Gursoy with his advice in using Tomopy. T is research used resources of the
17
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76