Tunable 330 GHz Gyrotron for DNP/NMR

描述(由申请人提供)：我们提出了一项研究计划，设计、制造和运行一个可调谐的330 GHz回旋振荡器，用于CW DNP/核磁共振研究。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微波源一起使用来执行DNP/核磁共振。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扫描磁场，或者调整微波频率。在使用带有扫描线圈的磁体的核磁共振系统中，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，因此对这些系统进行改造是不切实际的。因此，可调谐回旋管振荡器似乎是具有这种类型磁体的实验室的首选方法。我们建议设计和制造一个330 GHz的回旋管，它可以在0.75 GHz的范围内调谐，这将允许覆盖例如Tempo EPR谱，其中增强曲线中的峰将被分离约710 MHz。可调谐回旋管振荡器将利用一种新的磁场调谐方法，该方法基于谐振器的高阶轴向模的激励。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的频率调谐。回旋管的设计原则上可以扩展到更高的频率，适用于目前有大口径磁铁的600到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.