Development of low-cost MgB2/solid N2 MRI magnets

描述（由申请人提供）： 该计划的具体目的是证明低成本的可行性和实用性，即，超导磁共振成像（MRI）磁体系统，专门用于小型医院、农村社区和欠发达国家。MRI系统采用二硼化镁（MgB 2）复合导体和创新的低温设计/操作概念。我们通过构建和运行0.5 T/80 cm孔径演示磁体来实现这一特定目标，该磁体除了缺乏MRI级空间均匀性外，还满足0.5 T/80 cm MRI磁体系统的关键操作要求。我们相信，商业MRI磁体制造商将基于本文提出的演示系统设计此类MRI磁体。该演示系统为MRI超导磁体技术引入了两个重要的第一，这两个技术都有利于下一代低成本MRI磁体系统的运行：1）用于下一代MRI磁体的引领潮流的MgB 2磁体; 2）创新的低温设计/操作概念，在磁体外壳中引入了一定体积的固体氮。系统中固体氮的存在，由低温冷却器维持，极大地提高了磁体的热容量，使磁体能够在有限的时间内保持其工作磁场，即使其低温冷却器关闭，如停电的情况下，这种情况在农村社区和不发达国家并不罕见。只有在此关闭期间，磁体和固体氮（否则通过其低温冷却器保持在10 K的标称操作温度）将在一天的时间内升温至15 K的设计极限。这些特定温度和关闭持续时间适用于申报的演示磁体和全尺寸MRI磁体，其参考设计包含在申请中。该演示磁体系统的重要性在于，其成功运行有望刺激低成本基于MgB 2的MRI系统的商业生产（和需求）。创新的低温设计/操作概念与这种低成本磁体相结合，使MRI系统即使在比标准MRI系统默认的可靠性低得多的工作条件下也能可靠地运行。

DESCRIPTION (provided by applicant): The specific aim of this program is to demonstrate the feasibility and practicality of a low-cost, i.e., commercially viable, superconducting magnetic resonance imaging (MRI) magnet system specifically targeted for use in small hospitals, rural communities, and underdeveloped nations. The MRI system incorporates Magnesium Diboride (MgB2) composite conductor and an innovative cryogenic design/operation concept. We achieve this specific aim by building and operating a 0.5 Tesla (T)/80 cm bore demonstration magnet that, except for its lack of an MRI-grade spatial homogeneity, satisfies key operational requirements of 0.5 T/80 cm MRI magnet systems. We are confident that commercial MRI magnet manufacturers will base their design for such MRI magnets on the demonstration system proposed herein. The demonstration system introduces two important firsts to MRI superconducting magnet technology, both benefiting the operation of the next generation low-cost MRI magnet systems: 1) a trend-setting MgB2 magnet for the next-generation of MRI magnets; and 2) an innovative cryogenic design/operation concept that introduces a volume of solid nitrogen in the magnet housing. The presence of solid nitrogen in the system, maintained by a cryocooler, enhances the magnet's heat capacity enormously, enabling the magnet to maintain its operating field over a limited time period even with its cryocooler shut off as would be in case of a power outage, an event not rare in rural communities and underdeveloped nations. Only during this shut off period, the magnet and the solid nitrogen, otherwise kept at a nominal operating temperature of 10 K by its cryocooler, will warm up to a design limit of 15 K over a period of one day. These specific temperatures and shut off duration are for the proposed demonstration magnet and a full-scale MRI magnet, a reference design of which is included in the application. The significance of this proposed demonstration magnet system is that its successful operation is expected to spur commercial production (and demand) of low-cost MgB2-based MRI systems. The innovative cryogenic design/operation concept coupled to this low-cost magnet enables the MRI system to perform reliably even under working conditions much less reliable than those tacitly assumed for standard MRI systems.