Tunable 330 GHz Gyrotron for DNP/NMR

我们提出了一项为连续波设计、制造和运行330 GHz可调回旋管振荡器的研究计划。 DNP/核磁共振研究。在固态核磁共振实验室中有许多500/89磁体 这些设备可以与330 GHz微波源一起使用来进行DNP/核磁共振。然而，所有的 已知的DNP机制要求将磁场调整到增强曲线的峰值以 优化实验的信噪比(S/N)。这就要求磁场或者是 用磁铁上的扫描线圈进行扫描，或调整微波频率。在核磁共振系统中使用 对于带有扫描线圈的磁体，可以使用固定频率的回旋管进行DNP/核磁共振研究。然而， 现有的绝大多数核磁共振磁体没有扫描线圈，改装这些磁体是不切实际的 系统。因此，可调回旋管振荡器似乎是具有以下特性的实验室的首选方法 这种类型的磁铁。我们建议设计和制造330 GHz回旋管，它可以在一系列范围内调谐 ？0.75 GHz，这将允许覆盖例如Tempo EPR频谱，其中峰值在 增强曲线将间隔约710 MHz。可调谐回旋管振荡器将利用一种新的 基于谐振器高阶轴向模激励的磁场调谐方法。频率 最近在麻省理工学院的250 GHz回旋管振荡器上演示了0.9 GHz的调谐。这个 Yrotron的设计原则上可以扩展到更高的频率，应用到600到900 MHz，其中 目前已有大口径磁铁问世。

We propose a program of research to design, build and operate a tunable 330 GHz gyrotron oscillator for CW DNP/NMR research. There are a number of 500/89 magnets in solid-state NMR laboratories around the world and these could be used with a 330 GHz microwave source to perform DNP/NMR. However, all of the known DNP mechanisms require that the magnetic field be adjusted to the peak of the enhancement curve to optimize the signal to noise ratio (S/N) of the experiment. This necessitates either that the magnetic field be swept with a sweep coil on the magnet, or that the microwave frequency be adjusted. In NMR systems using magnets with sweep coils, DNP/NMR research can be conducted with fixed frequency gyrotrons. However, the vast majority of NMR magnets in existence do not have sweep coils and it is impractical to retrofit these systems. Therefore, a tunable gyrotron oscillator appears to be the approach of choice for laboratories with this type of magnet. We propose to design and fabricate a 330 GHz gyrotron that can be tuned over a range of ¿0.75 GHz which will permit coverage, for example, of the TEMPO EPR spectrum where the peaks in the enhancement curve will be separated by about 710 MHz. The tunable gyrotron oscillator will utilize a novel magnetic field tuning approach based on the excitation of high order axial modes of the resonator. Frequency tuning of ¿0.9 GHz has been recently demonstrated on a 250 GHz gyrotron oscillator here at MIT. The yrotron design will, in principle, be scalable to higher frequencies for application to 600 to 900 MHz where wide-bore magnets are currently available.