Fig. 1. (a) SRIM simulation results showing the irradiation damage and injected Kr & H concentrations as a function of irradiation depth in the CeO2 irradiated by 400 keV Kr+ & 30 keV H2+ dual beam under the fluence of 7.74 × 1013 Kr+/cm2 and 2.38 × 1013 H2+/cm2; (b) Irradiation damage and injected Kr & H concentrations as a function of irradiation time in the in-situ monitored region with the thickness of about 100 nm.

Fig. 2. In-situ BF TEM micrographs showing the evolution of dislocation loops at 1073 K, which were captured at the two-beam diffraction conditions of (a-f) g=$11\bar{1}$ near [011] zone axis during Kr+ & H2+ dual-beam synergetic irradiation and (g–i) g=200 near [011] zone axis during Kr+ single-beam irradiation. The irradiation damage and H concentration were written directly above each image. All images have the same magnification.

Fig. 3. BF TEM images of the CeO2 TEM foil after Kr+ & H2+ dual-beam synergetic irradiation to 0.8 dpa & 36 appm H, which were captured at two-beam diffraction condition near [011] zone axis with (a) g=$11\bar{1}$; (b) g=$02\bar{2}$; and (c) g=$\bar{1}1$$\bar{1}$.

Fig. 4. In-situ BF TEM images taken at g=$11\bar{1}$ near [011] zone axis display the rotation of habit plane of dislocation loops in the CeO2 foil during Kr+ & H2+ dual-beam synergetic irradiation. The irradiation damage and H concentration: (a) 0.2 dpa+9 appm H; (b) 0.4 dpa+18 appm H; and (c) 0.8 dpa+36 appm H.

Fig. 5. In-situ BF TEM images of the Kr+ single-beam irradiated CeO2 with the irradiation doses of (a1)–(c1) 1.0 dpa and (a2)–(c2) 2.1 dpa at 1073 K. Imaging was performed by using the [011] zone axis. The diffraction vectors adopted are (a1) and (a2) g=$11\bar{1}$; (b1) and (b2) g=200; (c1) and (c2) g=$\bar{1}$$1\bar{1}$.

Fig. 6. Comparative analysis of (a) Average diameter vs. irradiation damage and (b) Areal density of dislocations vs. irradiation damage in the CeO2 foils during 400 keV Kr+ & 30 keV H2+ dual-beam synergetic irradiation and 400 keV Kr+ single-beam irradiation.

Fig. 7. In-situ under-focused BF TEM images showing the evolution of gas bubbles in the CeO2 during 400 keV Kr+ & 30 keV H2+ dual-beam synergetic irradiation (a1-e1) and 400 keV Kr+ single-beam irradiation (a2-e2). The irradiation dose and hydrogen concentration were written directly above each image.

Fig. 8. The variation of (a) the average bubble diameter, (b) the bubble areal number density, and (c) the swelling with the increase of irradiation damage in the CeO2 during 400 keV Kr+ & 30 keV H2+ dual-beam synergetic irradiation and 400 keV Kr+ single-beam irradiation at 1073 K.