DIELECTRIC ROD RESONATOR AT HIGH FREQUENCIES

该子项目是利用资源的许多研究子项目之一 由NIH/NCRR资助的中心赠款提供。次级项目的主要支助 子项目的主要研究者可能是由其他来源提供的， 包括其它NIH来源。 为子项目列出的总成本可能 代表子项目使用的中心基础设施的估计数量， 而不是由NCRR赠款提供给子项目或子项目工作人员的直接资金。 在95 GHz，ELDOR在缓慢翻滚/接近刚性极限的实验表明，即使B1为15 G，也有可能照射整个光谱，尽管效率降低。 增加可用的B1将改善信噪比并提高数据收集的效率。 实现这一目标的一个有前途的方法是通过使用介质加载法布里-珀罗谐振器。 对于直径等于自由空间波长和介电常数为4的介质棒，对应于毫米波长的石英，可以表明，如果将介质棒光束强度和总能量归一化为在自由空间中传播的具有相同强度和总能量的高斯光束的强度和总能量，则在介质棒中B1场比自由空间场值大大约5倍。 换句话说，与其自由空间等效物相比，介质棒谐振器可以显著增强样品处的可用B1。 与自由空间谐振器相比，介质棒的存在对毫米波场也具有显著的局部化效应，这对于尺寸受限的样品是一个优点。 我们正在探索如何将介质棒谐振器集成到适用于高功率脉冲工作的实用法布里-珀罗谐振器中。 钱德勒的早期论文对适合介质棒谐振器的耦合方案提出了有用的建议。 这种谐振器的概念也可以在170和240 GHz的低功率脉冲工作中找到应用，我们正在探索这种可能性，以期在低温下研究生物样品（如血红素铁）的饱和度。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. At 95GHz, ELDOR experiments in the slow tumbling/near rigid limit have demonstrated that even with a B1 of 15G, it is possible to irradiate the entire spectrum, although with reduced efficiency. Increasing the available B1 would improve the signal to noise and increase the efficiency of data collection. One promising method of accomplishing this goal is by the use of a dielectric-loaded Fabry-P¿rot resonator. For a dielectric rod of diameter equal to the free space wavelength and dielectric constant 4, corresponding to quartz at millimeter wavelengths, one can show that if one normalizes the dielectric rod beam intensity and total energy to that of a gaussian beam propagating in free space with the same intensity and total energy, then the B1 field is larger by approximately a factor of 5 in the dielectric rod over the free space field value. In other words, a dielectric rod resonator can significantly enhance the available B1 at a sample compared to its free space equivalent. The presence of the dielectric rod also has a significant localization effect on the millimeter wave field, compared to a free-space resonator, which is an advantage for size limited samples. We are exploring how to integrate the dielectric rod resonator into a practical Fabry-P¿rot resonator suitable for high power pulse work. The early paper by Chandler has useful suggestions for coupling schemes appropriate to a dielectric rod resonator. This resonator concept may also find applications in low power pulse work at 170 and 240GHz, and we are exploring this possibility with a view towards studying saturation in bio-samples, such as heme irons, at low temperatures.