AUTOMATIC FREQUENCY CONTROL (AFC) SYSTEM FOR HIGH-FIELD BRIDGE

这个子项目是利用资源的许多研究子项目之一。 由NIH/NCRR资助的中心拨款提供。对子项目的主要支持 子项目的首席调查员可能是由其他来源提供的， 包括美国国立卫生研究院的其他来源。为子项目列出的总成本可能 表示该子项目使用的中心基础设施的估计数量， 不是由NCRR赠款提供给次级项目或次级项目工作人员的直接资金。 ACERT设施目前包括一台用于C.W.的170/240 GHz准光桥式光谱仪。EPR研究。在过去的一年里，光谱仪桥架进行了实质性的升级，例如更换了C.W.毫米波源和安装新设计的参照臂。此外，光谱仪谐振器还得益于一系列机械改进，显著提高了隔振和调谐精度。我们致力于制造和实施这些设备的目标是创造一种性能出众的仪器，同时为经验较少的操作员保持相对易用性。 考虑到这一目标，我们打算继续开发用于170/240 GHz C.W.的自动频率控制(AFC)系统。适用于最近获得的两种毫米波源之一的分光计。与传统C.W.中常见的AFC系统相同对于微波EPR仪器，我们建议的高场AFC系统将提供传统的源频率跟踪能力，从而消除实验过程中谐振器或源频率漂移的不利影响。在我们的概念设计中，还可以配置AFC系统，通过允许调整样品位置而简化法布里-珀罗谐振器的调整，而不会因样品介电负载的相应变化导致的失谐效应而导致操作员混乱。 对AFC环路进行了初步的设计测量和研究，并完成了概念设计。我们已初步计划在今年晚些时候建造、测试和最终实施这一光谱仪升级。

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. ACERT facilities presently include a 170/240GHz quasioptical-bridge spectrometer for c.w. EPR studies. During the past year, the spectrometer bridge has been substantially upgraded, e.g., with replacement of the c.w. millimeter-wave sources and installation of a newly-designed reference arm. Additionally, the spectrometer resonator has benefited from a series of mechanical improvements which have significantly improved vibration isolation and tuning accuracy. Our goal in pursuing the fabrication and implementation of these items is to create an instrument of exceptional capability while maintaining relative ease of use for less-experienced operators. With that objective in mind, we intend to continue our development of an automatic frequency control (AFC) system for the 170/240GHz c.w. spectrometer suitable for use with either of the recently-acquired millimeter-wave sources. In common with familiar AFC systems found in conventional c.w. microwave EPR instruments, our proposed high-field AFC systems will provide conventional source frequency-tracking capability, thereby eliminating detrimental effects of resonator or source frequency drift during the course of an experiment. In our conceptual design, it will also be possible to configure the AFC system in a way which simplifies adjustment of the Fabry-Perot resonator by allowing adjustment of sample position without the potential for operator confusion due to detuning effects caused by corresponding variation in the sample's dielectric loading. Preliminary design measurements and studies of the AFC loop have been made and a conceptual design completed. We have tentatively scheduled construction, test and final implementation of this spectrometer upgrade for later this year.