郭硕鸿讲座（第七十五期）（2025年4月17日10:30）：Pulsed Neutron Diffraction

主持人：王猛 教授

报告摘要：It has been over 60 years since pulsed neutrons were first proposed as a tool for material structure characterization. With the advent of the worldwide construction of high intensity proton accelerators, significant progress has been made in recent years. Today, scientific results from these facilities are frequently published in major peer-reviewed journals. In China, opportunities are expanding with the emergence of the CSNS, a proton accelerator-based pulsed neutron facility.

In this lecture, I will begin by explaining time-of-flight (TOF) diffraction, which is a technological core, and I will then introduce its standard applications and offer some suggestions for you to develop new ones. Finally, I will present a recent study conducted with my last graduate student in Japan, who was from Korea. As the topic was outside my main area of expertise, we submitted the work to a highly competitive journal—and it was recently accepted and published.

The advantage of the TOF diffraction method is to utilize the wide range of energy spectra simultaneously. In contrast, angle-dispersive diffraction methods only utilize a part of neutron spectra by cutting out by a monochromator. This allows for more efficient use of the generated neutrons and enables applications that take full advantage of the pulsed time structure. Compared to the first-generation TOF diffractometers, the intensity gain now reaches up to 10⁵, which greatly enhances the characterization of advanced materials.

The neutron probe is particularly effective due to its high sensitivity to light elements and magnetic moments. Its excellent penetration capability also makes it valuable for in situ characterization of materials within operating devices.

Lastly, I will briefly introduce two key directions in neutron powder diffraction: high-precision measurements and high-speed (rapid) measurements. The former enables detection of subtle distortions (on symmetry-breaking phenomena) that were previously unobservable. The latter includes operando diffraction techniques.

报告人简介：Takashi Kamiyama received Ph.D. degree in 1987 at Department of Physics, Tohoku University. In 2005, he became the professor for High Energy Accelerator Organization and Graduate University for Advanced Studies. In 2006, he received a concurrent position as a professor at Hokkaido University. He was Dean of Sokendai, School of High Energy Accelerator Science from 2014 to 2016 and from 2018 to 2020. In 2021,he   became the Emeritus  Professor of High Energy Accelerator Research Organization and Senior Adviser of China Spallation Neutron Source (CSNS), Institute of High Energy Physics.

Takashi Kamiyama led the Structure Science Group of J-PARC and the Institute of Materials Science of KEK. He have been studying materials science of many quantum electronic materials and energy materials. He have led the construction of four neutron powder diffractometers, SuperHRPD and SPICA of J-PARC, and Vega and Sirius of KEK.  He is a leader in the development of powder diffraction data analyses software suite, Z-Code. He was an advisor of iMATERIA of J-PARC for industrial neutron use.

Award:

2007 Academic Award of The Crystallographic Society of Japan

2008 Best Paper Award of The Iron and Steel Institute of Japan

2020 Technology Award, Japanese Society of Neutron Science