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Nuclear Science User Facilities 114 Figure 2. The crystallographic orientation of the area in the TEM image on the left is mapped on the right. Accomplishments The work was initiated in February 2014 resulting in the successful completion of all experimental work for the two phases both on unir- radiated and irradiated samples as indicated inTable 1.The integration of all project results and papers is still to be performed although some results have already been prepared for confer- ence or workshop presentations. 2-4 Summary of Phase 1 results Research on unirriadiated SiC and sample optimization for ASTAR 2.3 Sample fabrication techniques as well as sample characteristics can criti- cally influence the quality of the data collected. Researchers initially evalu- ated the influence of sample thickness on the quality of the orientation data generated byASTAR. It is extremely difficult to prepare samples thinner than 80 nm from these materials due to the brittle nature of neutron-irradiated SiC.Although the original study plan included three FIB-prepared samples only two samples of varying thickness Figure 1 were analyzed.The thick- nesses of five areas on these two samples were determined by electron energy loss spectroscopy EELS e.g. location and height of the plasmon peak.Three areas were found to be approximately 80 nm thick while two others were found to be approximately 120 nm thick. It is extremely difficult to prepare FIB lamellae thinner than the measured 80 nm due to the brittle nature of neutron-irradiated SiC as demonstrated by the fractured regions shown in Figure 1 center.The crystallographic information in the latter two areas was collected using theASTAR system on the TecnaiTF30-FEG STwin at CAES. The Index parameter calculated by ASTAR was taken to be the primary indicator of data quality with higher values of the Index parameter indi- cating a higher confidence in the crystallographic orientation assigned by the software.An example of an area analyzed along with the orientation map is shown in Figure 2. Some boundaries between grains are slightly diffused due to the small grain size and grain overlap but in general the individual grains are clearly visible.The distribution of the Index parameter for each pixel in the five areas analyzed is shown in Figure 3. The frequency distributions of the thicker areas lie at higher values of the Index parameter compared to the thinner regions which makes it appear that thicker samples generally produce higher quality orientation data than thinner samples. However at some point grains overlap significantly resulting in the degradation of the orientation data and more diffused zones between grains.The critical thickness of the overlap is likely grain size dependent with that thickness decreasing with decreasing grain size. However the samples appear to be of sufficient overall thicknesses to produce