開催報告：日米高エネルギー密度セミナー（Speaker: Dr. Akifumi Yogo, Osaka University）

日米高エネルギー密度セミナーを４月１２日に開催しました。

大阪大学レーザーエネルギー学研究所とLLNL高エネルギー密度科学センターと共同で、HEDSの様々な計算・実験的側面を取り上げ今後も毎月開催予定です。

第１回は大阪大学レーザー科学研究所の余語 覚文先生に「レーザー駆動中性子によるシングルショット共鳴分光の実現」 のタイトルで、PRXに発表された最新の研究成果に関し講演いただきました。

–Speaker—
Professor Akifumi Yogo
Institute of Laser Engineering, Osaka University

–Title–
Laser-Driven Neutron Generation Realizing Single-Shot Resonance Spectroscopy

–Abstract–
Neutrons are a powerful tool for investigating the structure and properties of materials. Ultracompact laser-driven neutron sources (LDNS) are attracting interest as the next-generation neutron source after nuclear reactors and accelerator-based facilities. However, understanding the laser-driven ion acceleration mechanism for neutron generation and establishing the scaling law on the neutron yield are essential to improve the feasibility of LDNS. Here, we report on the mechanism that accelerates ions with spectra suitable for the neutron generation and identify how neutron yield changes with laser power.
We focus a laser on a foil of deuterated polystyrene. This generates a plasma that sources and accelerates ions, which in turn bombard a block of beryllium that acts as the neutron source. By measuring the ion spectra, we identify distinct rates of expansion of different ion species, which play a key role in the formation of the ion field. We also find that the neutron yield increases with the fourth power of the laser intensity on the target, which offers a guideline for eventually increasing the neutron flux.
Finally, we demonstrate single-shot analysis of composite materials by neutron resonance transmission analysis. With an energy resolution of 2.3% nearly 2 m from the LDNS, this leads to the analysis of elements and isotopes in less than a microsecond, allowing for high-speed nondestructive inspection.