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

点击翻译按钮获取中文摘要

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.