Two massive asteroids hit Earth around 35.65 million years ago, but did not lead to any lasting changes in the Earth’s climate, according to a new study by UCL (University College London) researchers.

Seoul National University College of Engineering announced that Professor Yong-su Na’s research team from the Department of Nuclear Engineering (with Ph. D. student Yeong-sun Lee as the 1st author) has clarified the mechanism behind the generation of runaway electrons during the startup phase of a tokamak fusion reactor.

A research group led by Associate Professor Tatsuya Kobayashi, Assistant Professor Mikiro Yoshinuma, and Professor Katsumi Ida of the National Institute for Fusion Science (Toki City, Gifu Prefecture) has achieved a high-speed measurement of plasma distribution in phase-space using a data analysis method called phase-space tomography*1. Phase-space is expressed in terms of the coordinates of the position and velocity of plasma particles. Distortion of the plasma phase-space distribution can occur in high-temperature plasmas and is believed to have a significant impact on plasma performance. The research group conducted spectroscopic measurements to analyze the light emitted from plasma using three different types of devices, and measured the distortion of the plasma phase-space distribution with high precision, using phase-space tomography. They also found that the distortion is the result of efficient plasma heating mediated by waves. Observation of plasma phase-space distribution is an important theme not only in fusion plasmas but also in plasma research on celestial bodies, the sun, and auroras, and is expected to have a ripple effect.