TY - JOUR
T1 - Comparison and Combination of Imaging Techniques for Three Dimensional Analysis of Electrical Trees
AU - Schurch, R
AU - Rowland, S M
AU - Bradley, R S
AU - Withers, Philip
N1 - This work was partially funded by the RCUK's Energy Programme through the Top & Tail Transformation programme grant, EP/I031707/1 (http://www.topandtail.org.uk/). Roger Schurch would like to acknowledge the scholarship support of CONICYT (Chilean Research Council). Philip Withers would like to acknowledge funding from EPSRC for the Manchester X-ray Imaging Facility under EP/F007906/1 and EP/F028431/1. Robert Bradley would like to acknowledge funding from Carl Zeiss XRM. The authors thank Dr. Tobias Starborg in the EM facility at the Faculty of Life Sciences in the University of Manchester for his assistance, and the Wellcome Trust for equipment grant support to the EM facility.
PY - 2015/4/9
Y1 - 2015/4/9
N2 - Imaging of electrical trees has been an important tool for studying the phenomenon. The authors have previously shown that electrical trees can be three-dimensionally (3D) imaged and virtual replicas generated using X-ray Computed Tomography (XCT) or Serial Block-Face Scanning Electron Microscopy (SBFSEM). Here these techniques are evaluated and compared for 3D analysis of electrical trees along with conventional optical methods. A number of types of laboratory created trees showing range of morphologies were grown and examined to delineate the capabilities of each technique. Cross-sectional images and virtual replicas of the electrical trees from XCT and SBFSEM techniques were compared both qualitatively and quantitatively. SBFSEM provides greater detail than XCT, evidenced by imaging smaller sub-branches and when comparing parameters such as the number of tree channels, tree length or tree volume captured. On average, SBFSEM captures almost double the number of tree channels per slice than XCT, and virtual replicas in most of the cases have larger volumes. However, SBFSEM is a destructive technique, which makes the imaging process less reliable than XCT and not suitable for multi-stage of tree growth experiments. For full analysis, a combination of imaging techniques is proposed. Optical methods are used first to monitor tree growth. Then, micro-XCT which provides pixel size down to ~0.4 µm with a field of view of around 1 mm × 1 mm, can be used to reveal the overall 3D structure of a normal/mature electrical tree. Nano-XCT can be used to explore in more detail regions of interest, with a pixel size of ~65 nm, but a limited field of view of 65 µm. Finally, sections of the tree can be analyzed in even greater detail using SBFSEM, which can provide resolutions below 50 nm. Using this approach, a deeper and more complete analysis of the structure of electrical trees can be achieved.
AB - Imaging of electrical trees has been an important tool for studying the phenomenon. The authors have previously shown that electrical trees can be three-dimensionally (3D) imaged and virtual replicas generated using X-ray Computed Tomography (XCT) or Serial Block-Face Scanning Electron Microscopy (SBFSEM). Here these techniques are evaluated and compared for 3D analysis of electrical trees along with conventional optical methods. A number of types of laboratory created trees showing range of morphologies were grown and examined to delineate the capabilities of each technique. Cross-sectional images and virtual replicas of the electrical trees from XCT and SBFSEM techniques were compared both qualitatively and quantitatively. SBFSEM provides greater detail than XCT, evidenced by imaging smaller sub-branches and when comparing parameters such as the number of tree channels, tree length or tree volume captured. On average, SBFSEM captures almost double the number of tree channels per slice than XCT, and virtual replicas in most of the cases have larger volumes. However, SBFSEM is a destructive technique, which makes the imaging process less reliable than XCT and not suitable for multi-stage of tree growth experiments. For full analysis, a combination of imaging techniques is proposed. Optical methods are used first to monitor tree growth. Then, micro-XCT which provides pixel size down to ~0.4 µm with a field of view of around 1 mm × 1 mm, can be used to reveal the overall 3D structure of a normal/mature electrical tree. Nano-XCT can be used to explore in more detail regions of interest, with a pixel size of ~65 nm, but a limited field of view of 65 µm. Finally, sections of the tree can be analyzed in even greater detail using SBFSEM, which can provide resolutions below 50 nm. Using this approach, a deeper and more complete analysis of the structure of electrical trees can be achieved.
KW - Electrical trees, Three-dimensional, 3D, Imaging, Optical, X-ray, XCT, SEM, SBFSEM
U2 - 10.1109/TDEI.2014.004730
DO - 10.1109/TDEI.2014.004730
M3 - Article
VL - 22
SP - 709
EP - 719
JO - I E E E Transactions on Dielectrics and Electrical Insulation
JF - I E E E Transactions on Dielectrics and Electrical Insulation
IS - 2
ER -