In this article I present our experience at the Magnet Technology Division of the MIT Francis Bitter Magnet Laboratory on liquid-helium (LHe)-free, persistent-mode MgB2 MRI magnets. Before reporting on our MgB2 magnets, I first summarize the basic work that we began in the late 1990s to develop LHe-free, high-temperature superconductor (HTS) magnets cooled in solid cryogen-I begin by discussing the enabling feature, particularly of solid nitrogen (SN2), for adiabatic HTS magnets. The next topic is our first LHe-free, SN2-HTS magnet, for which we chose Bi2223 because in the late 1990s Bi2223 was the only HTS available to build an HTS magnet. I then move on to two MgB2 magnets, I and II, developed after discovery of MgB2 in 2000. The SN2-MgB2 Magnet II-0.5-T/240-mm, SN2-cooled, and operated in persistent mode-was completed in January 2016. The final major topic in this article is a tabletop LHe-free, persistent-mode 1.5-T/70-mm SN2-MgB2 "finger" MRI magnet for osteoporosis screening-we expect to begin this project in 2017. Before concluding this article, I present my current view on challenges and prospects for MgB2 MRI magnets.

中文翻译：

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迈向无液氦、持久模式 MgB2MRI 磁体：FBML 经验

在本文中，我介绍了我们在麻省理工学院弗朗西斯苦味磁铁实验室的磁铁技术部门在无液氦 (LHe)、持久模式 MgB2 MRI 磁铁方面的经验。在报告我们的 MgB2 磁体之前，我首先总结了我们在 1990 年代后期开始开发在固体致冷剂中冷却的无 LHe、高温超导体 (HTS) 磁体的基本工作——我首先讨论了使能特性，特别是固体氮 (SN2)，用于绝热 HTS 磁体。下一个主题是我们的第一个不含 LHe 的 SN2-HTS 磁体，为此我们选择了 Bi2223，因为在 1990 年代后期 Bi2223 是唯一可用于构建 HTS 磁体的 HTS。然后，我继续介绍两个 MgB2 磁铁，I 和 II，它们是在 2000 年发现 MgB2 后开发的。 SN2-MgB2 磁铁 II-0.5-T/240-mm、SN2 冷却并以持久模式运行 - 于 1 月完成2016 年。