Tunable 330 GHz Gyrotron for DNP/NMR

描述（由申请人提供）：我们提出一项研究计划，设计，建造和运行一个可调谐的330 GHz回旋管振荡器，用于连续波DNP/NMR研究。世界各地的固态核磁共振实验室中有许多500/89磁体，这些磁体可以与330 GHz微波源一起使用，以执行DNP/NMR。然而，所有已知的DNP机制都需要将磁场调整到增强曲线的峰值，以优化实验的信噪比（S/N）。这就需要用磁铁上的扫描线圈对磁场进行扫描，或者调整微波频率。在使用扫描线圈磁铁的核磁共振系统中，DNP/核磁共振研究可以用固定频率的回旋管进行。然而，现有的绝大多数核磁共振磁体没有扫描线圈，改造这些系统是不切实际的。因此，一个可调谐的回旋管振荡器似乎是实验室与这种类型的磁铁选择的方法。我们建议设计和制造一个330 GHz的回旋管，可以在0.75 GHz的范围内调谐，这将允许覆盖，例如，TEMPO EPR频谱，其中增强曲线中的峰值将相隔约710 MHz。可调谐回旋管振荡器将利用一种基于谐振器高阶轴向模式激发的新型磁场调谐方法。最近在麻省理工学院的250 GHz回旋加速器振荡器上演示了0.9 GHz的频率调谐。回旋管设计，原则上，可扩展到更高的频率应用到600至900兆赫，其中宽孔磁铁目前可用。

DESCRIPTION (provided by applicant): 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 gyrotron design will, in principle, be scalable to higher frequencies for application to 600 to 900 MHz where wide-bore magnets are currently available.