An enhancement in J, of YBa&Cu307 single crystals in a magnetic field is observed after irradiation with 1-MeV electrons. Typically, a factor-of-2 increase in J, is deduced from magnetic hysteresis loops at 10 K and 1 T with H~~c. This enhancement is about 2 of that produced by proton and neutron irradiations under similar measurement conditions. In situ transmission-electron-microscopy studies found no visible defects induced by electron irradiation, which means that point defects or small clusters (of size &2 nm) are responsible for the extra pinning. Annealing studies suggest that effective pinning centers for H~~c do not include oxygen vacancies in the Cu-0 chains. Based on calculations of cross sections for displacements on the different sublattices, and in conjunction with the results of a J, calculation by Kes, we suggest that the most likely pinning defect is the displacement of a Cu atom from the CuO~-plane sites.
In situ observation is of great value in the study of radiation damage utilizing electron or ion irradiation. We summarize the facilities and give examples of work found around the world. In situ observations of irradiation behavior have fallen into two broad classes. One class consists of long-term irradiation, with observations of microstructural evolution as a function of the radiation dose in which the advantage of in situ observation has been the maintenance of specimen position, orientation, and temperature. A second class has involved the recording of individual damage events in situations in which subsequent evolution would render the correct interpretation of ex situ observations impossible. In this review, examples of the first class of observation include ion-beam amorphization, damage accumulation, plastic flow, implant precipitation, precipitate evolution under irradiation, and damage recovery by thermal annealing. Examples of the second class of observation include single isolated ion impacts that produce defects in the form of dislocation loops, amorphous zones, or surface craters, and single ion impact-sputtering events. Experiments in both classes of observations attempt to reveal the kinetics underlying damage production, accumulation, and evolution.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.