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报告内容摘要：
    Damage by fast neutrons takes the form of “local explosions” reaching very high temperatures. As the damaged region cools down, lattice defects are “quenched in”, resulting in near-simultaneous creation of a large number of atomic displacements in a small cascade volume. This mode of creation of displacement damage has two characteristics. Firstly, extensive annealing occurs, which only allows a small fraction of the initial displacements to survive as vacancies and interstitials and their clusters, which constitute the primary damage. Through the introduction of production bias, it was already shown in Silkeborg (1989) that the macroscopic manifestation of the damage effects depends almost completely on 3 parameters characterizing the primary damage. To obtain a quantitative description of these parameters naturally becomes the objective of investigation of many recent studies on cascade initiation. Indeed, to relate the primary irradiation damage to the neutron energy spectra is obviously a crucial first step in correlating irradiation damage among different irradiation facilities for design and regulatory functions.
    A second characteristic of cascade damage is the strongly correlated point-defect production in discrete packages. As a result of the random nature of cascade initiation, strong stochasticity is introduced into the arrival and annihilation of point defects at sinks. It is intuitively clear that fluctuations are of primary importance in processes such as the evolution of in-cascade clusters, the nucleation of voids and interstitial loops. For example, an interstitial cluster that has been annihilated due to a surge of vacancies cannot be revived by interstitials that arrive afterwards, even though the average interstitial flux may be larger. The identification of relevant parameters to characterize cascades in this regard is also needed to complete the research on Primary Radiation Damage from nuclear reaction to point-defects.
    This talk is about the characterization of irradiation damage to allow correlation of irradiation effects measured in different irradiation facilities, or in reactors of the same type but between different locations.

报告人简介：
Professor Woo graduated from The University of Hong Kong in Physics and Mathematics, got his PhD in Theoretical Solid-State Physics from University of Waterloo (Canada), and was awarded the D.Sc. degree from HKU in recognition of his contribution in materials science and engineering. Professor Woo was one of the highest ranking scientists of Atomic Energy of Canada where he has served for 22 years, before returning to join The Hong Kong Polytechnic University in 1996, where he was Chair Professor for 16 years, first in the field of mechanical engineering, and then in the field of solid-state electronics. He is currently Chair Professor of Nuclear Engineering of City University of Hong Kong. He was one of the pioneers of multiscale multiphysics materials modeling. His 200+ journal publications cover areas including computational materials science, irradiation damage theory and ferroelectric thin film structures. He is a member of the Hong Kong Academy of Engineering Sciences.