FABRY PEROT RESONATOR DEVELOPMENT FOR HIGH FREQUENCY ESR

这个子项目是许多研究子项目中利用 资源由NIH/NCRR资助的中心拨款提供。子项目和 调查员(PI)可能从NIH的另一个来源获得了主要资金， 并因此可以在其他清晰的条目中表示。列出的机构是 该中心不一定是调查人员的机构。 在高场/高频ESR(HFHF-ESR)中需要使样品处的可用微波磁场B1最大化的谐振结构，因为来自大多数毫米波源的可用功率非常有限。然而，源技术的最新发展使我们能够在170 GHz时将谐振器的可用功率增加4倍，对应于在该频率下的可用B1增加一倍，在240 GHz处的可用功率增加10倍，对应于在该频率下的可用B1的三倍。假设数据采集时间与可用B1的平方成反比，这对于寿命有限的样本来说是非常重要的，例如自旋标记的活细胞。对于生物样品，还需要谐振结构和样品保持器，使水样品固有的介电损耗最小化，并利用合适的几何形状来研究宏观排列的膜样品的取向相关研究。我们已经针对95、170和250 GHz应用中的这些问题开发了一系列解决方案。最近的工作集中在开发具有可变耦合的谐振器，以获得最佳的灵敏度，并为定量温度扫描提供良好的温度控制。这些方面的进展得益于我们在HFHF-ESR频率的半共焦法布里-珀罗(FP)谐振器中使用的部分反射电感网格的内部制造技术的发展。特别是，具有连续可变反射率的耦合网的开发使我们能够关键地将谐振器耦合到各种样品，从而使可用的毫米波功率得到最佳利用。虽然这些领域的开发工作主要集中在我们的95 GHz光谱仪上，但该技术适用于我们所有的HFHF-ESR光谱仪。我们还将那些便于样品在250 GHz下开发的FP谐振器内定位的水性样品夹技术元素融入到我们用于实现最佳S/N的95 GHz FP谐振器中。我们最近还开发了灵活的探头设计，允许我们的FP谐振器工作在感应或反射模式，具体取决于实验需要。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. There is a need in high-field/high-frequency-ESR (HFHF-ESR) for resonant structures that maximize the available microwave magnetic field, B1 at the sample since the available power from most millimeter wave sources, is very limited. Recent developments in source technology, however, have allowed us to increase the available power at the resonator by a factor of 4 at 170GHz, corresponding to a doubling of the available B1 at that frequency, and a factor of 10 at 240GHz, corresponding to a trebling of the available B1 at that frequency. Given that the data acquisition time is inversely proportional to the square of available B1, this is extremely significant for samples with finite lifetimes, such as spin-labeled live cells. For biological samples there is also a need for resonant structures and sample holders that minimize the dielectric losses inherent in aqueous samples and exploit suitable geometries for orientation dependent studies of macroscopically aligned membrane samples. We have developed an array of solutions for these problems in applications at 95, 170 and 250GHz. Recent work has focused on developing resonators with variable coupling for optimum sensitivity, and good temperature control for quantitative temperature scans. Progress along these lines has been helped by the development of in-house fabrication techniques for the partially reflecting inductive meshes that we use in semi-confocal Fabry-P¿rot (FP) resonators at HFHF-ESR frequencies. In particular, the development of a coupling mesh with continuously variable reflectivity has allowed us to critically couple the resonator to a variety of samples, making the optimum use of the available millimeter wave power. Although development work in these areas has been focused primarily on our 95GHz spectrometer, the technology is applicable to all of our HFHF-ESR spectrometers. We have also incorporated those elements of our aqueous sample holder technology facilitating sample positioning within the FP resonator developed at 250GHz into the 95GHz FP resonators we use for achieving the optimum S/N. We have also recently developed flexible probe-head designs that allow our FP resonators to be operated in the induction or reflection mode, depending on the needs of the experiment.