Tunable 330 GHz Gyrotron for DNP/NMR

描述（由申请人提供）：我们提出了一个研究计划，设计，建造和操作一个可调330 GHz回旋振荡器的CW DNP/NMR研究。在世界各地的固态NMR实验室中有许多500/89磁体，这些磁体可以与330 GHz微波源一起用于执行DNP/NMR。然而，所有已知的DNP机制都需要将磁场调节到增强曲线的峰值，以优化实验的信噪比（S/N）。这需要用磁体上的扫描线圈扫描磁场，或者调整微波频率。在使用具有扫描线圈的磁体的NMR系统中，DNP/NMR研究可以用固定频率的回旋管进行。然而，现有的绝大多数NMR磁体不具有扫描线圈，并且改造这些系统是不切实际的。因此，可调谐回旋振荡器似乎是实验室选择这种类型的磁铁的方法。我们建议设计和制造一个330 GHz的回旋管，它可以在<$0.75 GHz的范围内进行调谐，这将允许覆盖，例如，克里思EPR频谱，其中增强曲线中的峰值将被分离约710 MHz。可调谐回旋管振荡器将利用一种新的磁场调谐方法的基础上激发的谐振器的高阶轴向模式。最近在麻省理工学院的250 GHz回旋振荡器上演示了<$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，适用于目前可获得宽孔磁体的600至900 MHz。

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.