Time-resolved phase imaging based on the generation of pulsed coherent electron beams

2022 Fiscal Year Final Research Report

• Project/Area Number: 20K15174
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 29020:Thin film/surface and interfacial physical properties-related
• Research Institution: Osaka University
• Principal Investigator: Hatanaka Shuhei 大阪大学, 超高圧電子顕微鏡センター, 技術職員 (30838503)
• Project Period (FY): 2020-04-01 – 2023-03-31
• Keywords: コヒーレンス / 輝度 / 電子顕微鏡

Outline of Final Research Achievements

Thermionic emission guns, field emission guns, and photocathodes driven by laser irradiation are used as electron sources in electron microscopes. Most remarkable differences among them are coherence of electron beams and brightness. As the first step for the comparison between various electron guns, we quantitatively measured the spatial coherence of electron beams emitted from a lanthanum lanthanum hexaboride thermionic emission gun. In general, the spatial coherence at the specimen plane in transmission electron microscopes depends on not only electron sources but illumination lenses. To compare the intrinsic nature of electron sources, we reconstructed the phase space distribution of electron beams based on coherence measurements. From the phase space distribution, we precisely estimated the brightness. We developed an ultrafast electron microscope, and then applied the coherence measurement to electron beams emitted from photocathodes.

Free Research Field

電子ビーム、電子顕微鏡

Academic Significance and Societal Importance of the Research Achievements

電子ビームの空間コヒーレンスは、透過電子顕微鏡において高分解能電子顕微鏡法や位相イメージングといった測定で特に重要である。熱電銃について、これまで困難だった電子ビームのコヒーレンスの定量評価を実現し、電界放出電子銃との定量比較を実現した。本手法を、フォトカソードを備えた超高速電子顕微鏡に適用し、位相イメージングの一つである回折イメージングの実現が期待される。ピコ秒オーダーの時間分解能による位相イメージングは、時間変化する電磁場の直接イメージングなど、新しい応用が期待される。