MULTI CHANNEL TRANSMISSION LINE PROBES FOR HIGH FREQUENCY SOLID STATE NMR

用于高频固态 NMR 的多通道传输线探头

• 批准号: 6355118
• 负责人: CHAD M RIENSTRA
• 金额: $ 1.71万
• 依托单位: MASSACHUSETTS INSTITUTE OF TECHNOLOGY
• 依托单位国家: 美国
• 财政年份: 2000
• 资助国家: 美国
• 起止时间: 2000-05-01 至 2001-04-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6355118
• 关键词: biological products; biomedical resource; ear; human tissue; proteins

Probe development, as described in previous reports, has continued with the successful implementation of quadruple-resonance transmission line probes at 500 and 750 MHz. We have been extremely pleased with the efficiency of 'H operation at 750 MHz, with fields in excess of 125 kHz obtained with -100 Watts. Further development and application of triple and quadruple resonance experiments requires a high power tube amplifier that is currently being tested. We have developed transmission line MAS probes that offer significant improvements over locally tuned probes in several important areas: (1) 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 rf 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 (H) 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 element 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 that 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 room-temperature probes.

如前几次报告所述， 随着四共振传输的成功实现， 500和750 MHz的线探头。 我们非常满意 在750 MHz下的“H”操作的效率，其中场超过 在-100瓦时获得125 kHz。 进一步发展和应用 三重和四重共振实验需要高功率 电子管放大器，目前正在测试。 我们已经开发 传输线MAS探头，提供了显着的改进， 在几个重要领域的局部调谐探针：（1）效率，（2） 功率处理能力（电弧阈值和最大RF占空比）， (3)多通道可调谐性，（4）有效利用 磁体孔，以及（5）在大范围内的不受干扰的操作。 温度 两代设计已在 频率范围从200到750 MHz。 所有的设计都是基于 由McKay等人提出的RF电路拓扑，在那里， 磁体内的调谐元件是（1）螺线管采样线圈， (2)可选的串联调谐电容器。 低损耗空气介质 传输线用于以这样的方式变换阻抗， 允许以高效率和隔离度调谐多个频率。 一般拓扑在每种情况下都需要变换 采样线圈电感与高频（H）电压节点重合 其中第一物理结在磁体孔外部。 峰值 该调谐电路内的电压被最小化（对于给定的输入 功率）通过选择适当的低电感值， 调谐和匹配。 在低频方面，细节有所不同 取决于拓扑结构。 在一种情况下，集总元件陷阱用于 隔离电路 在第二种情况下，低频节点是 用于电路隔离。 为了达到高效率 在更高的频率（>500 MHz），我们已经开发了一种通用的方法， 这在高频下特别有用。 这些发展 允许设计和建造几个探头， 从200到750 MHz，大多数具有三个或四个高功率RF通道。 低温（<150 K）版本的此类探头采用射频（RF） 性能相对于 室温探头。