CONSTRUCTION OF NEW 170 & 250GHZ CW- ESR SPECTROMETER

这个子项目是利用由NIH/NCRR资助的中心拨款提供的资源的许多研究子项目之一。子项目和调查员(PI)可能从另一个NIH来源获得了主要资金，因此可能会出现在其他CRISE条目中。列出的机构是针对中心的，而不一定是针对调查员的机构。我们用改进的、低损耗、宽带准光学元件建造了我们的新HFHF-ESR CW光谱仪，并将其集成到从MagneX购买的新9T磁体中。从这些升级中观察到的信噪比改善，在很大程度上是由于准光桥的插入损耗的减少和新装置的更高的机械稳定性，对于我们研究的水介质中的各种生物样品至关重要。新配置的电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，因为新磁体的WAM孔中的准光学元件的横截面积减少了。增加的可接近钻孔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，我们最近测试了这一系统。今年对电桥进行的主要改进是安装了更强大、更可靠的毫米波源，这是基于高频倍增器的最先进技术。与我们的旧电源相比，我们已经能够将170 GHz的可用功率增加4倍。在240 GHz，我们已经实现了一个数量级的改善，在可用的功率与我们的旧来源。此外，功率水平和频率都可以由操作员方便地控制。此外，为了实现CD-ESR或其他先进概念而对信号源进行的修改将更容易受到影响，因为在毫米波频率上没有锁相环。这种锁相环是我们旧电源的组成部分，这使得修改和维修变得非常困难。

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.