Plasma and Fusion Research

Volume 20, 2406004 (2025)

Regular Articles


Improvement of EUV Spectra by Optical Thickness Control
Tsukasa SUGIURA1), Masaki KUME1), Hiroki MORITA1), Shinichi NAMBA2) and Takeshi HIGASHIGUCHI1)
1)
Department of Electrical and Electronic Engineering, Utsunomiya University, Utsunomiya 321-8585, Japan
2)
Department of Advanced Science and Engineering, Hiroshima University, Higashihiroshima 739-8527, Japan
(Received 15 July 2024 / Accepted 16 September 2024 / Published 22 January 2025)

Abstract

In double pulse cross-laser irradiation configuration, we measured the extreme ultraviolet (EUV) spectral purity and emission energy around 6.x nm wavelength in laser produced Gd plasmas. It was found that the spectral purity of 4.1% within a 0.6% bandwidth (Δλ = 6.74 - 6.78 nm) at 6.76 nm to the total emission between wavelengths of 5 - 9 nm was improved by producing a low-density Gd plasma target, compared to the spectral purity of 1.6% for solid-Gd target plasma. A low-density plasma must be produced before the main heating laser pulse to enhance the spectral purity. We also reported the delay time dependence of the spectral purity irradiated by the 6-ns, 1-µm main laser pulse irradiation under the cross-laser-injection scheme.


Keywords

extreme ultraviolet (EUV), beyond EUV (B-EUV), gadolinium (Gd), highly charged ion (HCI)

DOI: 10.1585/pfr.20.2406004


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