CONSTRUCTION OF NEW 170 & 250GHZ CW- ESR SPECTROMETER

本子项目是利用由NIH/NCRR资助的中心赠款提供的资源的众多研究子项目之一。子项目和研究者（PI）可能已经从另一个NIH来源获得了主要资金，因此可以在其他CRISP条目中表示。列出的机构是中心的，不一定是研究者的机构。我们用改进的、低损耗的、宽带准光学元件构建了我们的新型HFHF-ESR连续波光谱仪，并将其集成到从Magnex购买的新型9T磁铁中。从这些升级中观察到的信号噪声比的改善，很大程度上是由于准光桥的插入损耗减少和新装置的机械稳定性提高，这对我们研究的水介质中各种生物样品至关重要。新配置的桥的灵活性对于我们正在进行的圆二色ESR （CD-ESR）的开发工作也很重要。我们正在实施的升级也将提高我们用于单晶旋转研究的测角仪的性能，因为新磁铁的热孔中准光学的横截面积减少了。增加的可达井眼横截面积允许更强大的机械控制机制以及更有效的低温控制系统，我们最近进行了测试。今年实施的桥梁的主要改进是安装了更强大、更可靠的毫米波源，这是基于最先进的高频乘法器的进步。与我们的旧源相比，我们已经能够将170GHz的可用功率提高4倍。在240GHz，我们已经实现了一个数量级的改进，在可用功率相比，我们的旧源。此外，功率电平可以方便地由操作员控制，频率也是如此。此外，为实现CD-ESR或其他先进概念而修改源将更容易受到影响，因为在毫米波频率上没有锁相环。这种锁相环是我们旧源的一个组成部分，这使得修改和维修非常困难。

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. We have built our new HFHF-ESR cw spectrometer with improved, low-loss, broadband quasioptical components and incorporated it into the new 9T magnet purchased from Magnex. The observed improvements in signal to noise accruing from these upgrades, due in large part to the reduced insertion loss of the quasioptical bridge and higher mechanical stability of the new setup, are crucially important for the wide variety of biological samples in aqueous media that we study. The flexibility of the newly configured bridge is also important for the development work on circular dichroism ESR (CD-ESR) that we are undertaking. The upgrades that we are implementing will also improve the performance of our goniometer for single crystal rotation studies, because of the reduced cross-sectional area of the quasioptics in the wam bore of the new magnet. The increased accessible bore cross-sectional area allows a more robust mechanical control mechanism as well as a more efficient cryogenic control system which we have recently tested. The major improvement to the bridge implemented this year has been the installation of more powerful and reliable millimeter wave sources based on advances in the state-of-the-art for high-frequency multipliers. We have been able to increase the available power at 170GHz by a factor of 4 compared to our old source. At 240GHz we have achieved an improvement by an order of magnitude in the available power compared to our old source. In addition, the power level is conveniently controllable by the operator, as is the frequency. Furthermore, modifications to the source for implementation of CD-ESR or other advanced concepts will be much easier to affect as there is no phase-locked loop at the millimeter wave frequency. Such a phase-lock loop was an integral part of our old sources which made modification and servicing very difficult.