MULTI CHANNEL TRANSMISSION LINE PROBE FOR HIGH FREQUENCY SOLID STATE NMR

用于高频固态核磁共振的多通道传输线探头

• 批准号: 6279720
• 负责人: CHAD M RIENSTRA
• 金额: $ 2.37万
• 依托单位: MASSACHUSETTS INSTITUTE OF TECHNOLOGY
• 依托单位国家: 美国
• 财政年份: 1998
• 资助国家: 美国
• 起止时间: 1998-05-01 至 1999-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6279720
• 关键词: biological products; biomedical resource; human tissue; nucleic acids; proteins

We have developed transmission line MAS probes which offer significant improvements over locally tuned probes in several important areas: (I) efficiency, (2) power-handling capability (arc threshold and maximum rf duty cycle), (3) multi-channel tunability, (4) efficient use of space within the magnet bore, and (5) unperturbed operation over a large range of temperatures. Two generations of designs have been implemented at frequencies ranging from 200 to 750 MHz. All designs are based on the if circuit topology proposed by McKay et al. where the only lumped tuning elements within the magnet are (1) the solenoid sample coil and (2) an optional series tuning capacitor. Low loss air-dielectric transmission line is used to transform impedance in a manner that allows tuning several frequencies with high efficiency and isolation. The general topology in every case requires transformation of the sample coil inductance to a high frequency (1H) voltage node coincident with the first physical junction outside the magnet bore. Peak voltages within this tuning circuit are minimized (for a given input power) by choosing appropriately low values of inductance before tuning and matching. On the low-frequency side, details differ depending on topology. In one case, lumped ~lement traps are used for isolation circuits. In the second case, low frequency nodes are exploited for circuit isolation. In order to achieve high efficiency at higher (>500 MHz) frequencies, we have developed a general approach which is particularly useful at high frequencies. These developments have permitted the design and construction of several probes ranging from 200 to 750 MHz, most with three or four high-power rf channels. Low-temperature (<150 K) versions of such probes operate with rf performance which is not significantly compromised relative to the roomtemperature probes.

我们开发了传输线MAS探头， 在几个方面， 重要方面：（1）效率，（2）功率处理能力（电弧 阈值和最大RF占空比），（3）多信道可调谐性， (4)有效利用磁体孔内的空间，以及（5）不受干扰 在很大的温度范围内运行。 两代 已经在200到750的频率范围内实现了设计 MHz. 所有的设计都是基于的中频电路拓扑结构提出的 McKay等人，其中磁体内仅有的集总调谐元件 是（1）螺线管采样线圈和（2）可选的串联调谐 电容器 低损耗空气介质传输线用于 以允许调谐多个频率的方式变换阻抗 具有高效率和隔离性。 在每一个 这种情况下，需要将采样线圈电感转换为高 频率（1H）电压节点与第一物理电压节点重合， 磁孔外的结。 此调谐范围内的峰值电压 电路最小化（对于给定的输入功率），通过选择 在调谐和匹配之前适当地降低电感值。 对 低频侧，细节根据拓扑而不同。 在一个 在这种情况下，集总元件陷阱用于隔离电路。 在 第二种情况，利用低频节点进行电路隔离。 为了在更高（>500 MHz）频率下实现高效率， 我们已经制定了一个通用的方法， 高频率 这些发展使设计和 几个探头的构造，范围从200到750 MHz，大多数 三个或四个高功率RF信道。 低温（<150 K） 这种探针的版本以RF性能工作， 相对于室温探针而言，这是显著受损的。