CONSTRUCTION OF NEW 170 & 250GHZ CW- ESR SPECTROMETER

该子项目是利用NIH/NCRR资助的中心赠款提供的资源的许多研究子项目之一。子项目和研究者（PI）可能从另一个NIH来源获得主要资金，因此可以在其他CRISP条目中表示。所列机构为中心，不一定是研究者所在机构。我们已经建立了我们的新HFHF-ESR连续波光谱仪与改进的，低损耗，宽带准光学元件，并将其纳入新的9 T磁铁购买的Magrex。从这些升级中获得的信噪比的改善，在很大程度上是由于准光桥的插入损耗降低和新设置的机械稳定性更高，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孔中准光学器件的横截面积减小。增加的可接近孔横截面积允许更鲁棒的机械控制机构以及我们最近测试的更有效的低温控制系统。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，这是基于最先进的高频乘法器的进步。与旧源相比，我们能够将170 GHz的可用功率提高4倍。在240 GHz时，与旧源相比，我们的可用功率提高了一个数量级。此外，功率水平和频率都可由操作者方便地控制。此外，对用于实现CD-ESR或其他先进概念的源的修改将更容易受到影响，因为在毫米波频率处没有锁相环。这样的锁相环是我们的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.