A cryocooler/solid-Ne cooled 500MHz/20cm MRI magnet

描述（由申请人提供）： 本项目的具体目标是：1）将新的设计/操作概念应用于MRI超导磁体，使这些磁体能够实现在某些方面类似于基于低场永磁体的磁体的操作特征; 2）通过完成500 MHz/20 cm超导MRI磁体，证明该概念对高场MRI（500 MHz及以上）磁体的适用性。完整的系统将安装在FBML中，供一组MRI和脑科学研究人员使用。我们坚信，这种新的设计/操作概念将及时被商业磁体制造商采用，用于下一代MRI磁体。这些功能包括：1）无液体系; 2）如果用户要求，在特定时间段（本系统中为12小时）内安静、无噪音/无振动的系统运行; 3）即使在停电或制冷机定期维护的情况下，也能在此时间段内保持恒定的操作场。也就是说，所提出的MRI磁体将几乎与基于低场永磁体的系统一样容易操作。 这项拟议工作的意义是一个创新的设计/操作概念的实际应用，最近开发的FBML创建“干”MRI磁体的功能，将极大地受益于用户。系统中的固体氖的体积使该干磁体能够比其湿对应物更稳定地保持其4.2K的标称操作温度，其中液体饱和温度是压力敏感的。该系统的另一个特点是磁体的工作温度范围，特意选择将其扩展到6.0 K。与固体氖一起，这个“大”的工作温度范围极大地增加了系统的热容量，使其能够在关闭制冷机和热解耦的情况下运行12小时。“无低温冷却器”操作，虽然在这个有限的时间内，不仅可以为用户提供一个无噪声/振动的测量环境，如果这种环境是实验所需要的，而且还将允许系统保持其操作领域，即使在停电的情况下或在其低温冷却器维护期间。

DESCRIPTION (provided by applicant): The specific aims of this project are to: 1) apply a new design/operation concept for MRI superconducting magnets that enable these magnets to achieve operational features that in some respect resemble those of low-field permanent-magnet based counterparts; and 2) demonstrate applicability of this concept to high-field MRI (500 MHz and above) magnets by completing a 500 MHz/20 cm superconducting MRI magnet. The completed system will be installed in the FBML for a group of MRI and brain science researchers. We strongly believe that this new design/operational concept will in time be adopted by the commercial magnet manufacturers for the next generation MRI magnets. These features include: 1) liquid-free system; 2) if required by the user, a quiet, noise/vibration-free system operation over a specific time period (12 h in this system); 3) ability to maintain a constant operating field, over this time period, even in the event of a power outage or while the cryocooler is under scheduled maintenance. That is, the proposed MRI magnet will be almost as easy to operate as a low-field permanent-magnet based system. The significance of this proposed work is a practical application of an innovative design/operation concept recently developed at the FBML for creation of "dry" MRI magnets with features that would immensely benefit the user. A volume of solid neon in the system enables this dry magnet to keep its nominal operating temperature of 4.2 K much more stably than its wet counterpart, in which liquid saturation temperature is pressure sensitive. An added feature of this proposed system is the magnet's operating temperature range, which is purposely chosen to extend to 6.0 K. Together with solid neon, this "large" operating temperature range increases the system's heat capacity enormously, enabling it to operate over a period of 12 h with its cryocooler turned-off and thermally decoupled. "Cryocoolerless" operation, though over this limited period, not only could provide the user a noise/vibration-free measurement environment, if such an environment is required by the experiment, but also would permit the system to maintain its operating field even in the event of power outage or during its cryocooler maintenance.