FREQUENCY-STEPPING SYSTEM FOR 95 GHZ ESR SPECTROMETER

这个子项目是许多利用资源的研究子项目之一 由NIH/NCRR资助的中心拨款提供。子项目的主要支持 而子项目的主要调查员可能是由其他来源提供的， 包括其它NIH来源。 列出的子项目总成本可能 代表子项目使用的中心基础设施的估计数量， 而不是由NCRR赠款提供给子项目或子项目工作人员的直接资金。 对于两个DEER（双电子？电子共振）和95 GHz下的扩展覆盖ELDOR，需要双步进频率操作的方法。进行DEER调查的能力是重要的，因为有显着的生物动机，在扩展距离测量技术开发的常规频率在ACERT的高频制度。 独特的ACERT 2D-FT ESR 95 GHz 1 kW脉冲ESR光谱仪有望获得广泛的样品，包括宏观对齐的生物样品，具有测角功能的单晶和微升大小的样品。 高场ESR谱的增强取向选择在结构研究中是有价值的，DQC和DEER技术目前正在考虑用于此目的。然而，DEER的实现需要以两个频率顺序地照射自旋系统。在95 GHz的扩展覆盖ELDOR可以通过场跳变或频率步进技术来实现，但是在95 GHz进行DEER距离测量的愿望给了我们额外的激励来实现双频能力，以解决这两种类型的实验工作。 对于我们的高功率95 GHz脉冲频谱仪，增加步进频率操作是由现有的收发器/功率放大器链的约500 MHz的瞬时带宽促进。此外，我们的仪器中的收发器参考振荡器部分设计有外部输入，直接容纳外部双频源。因此，为步进频率工作添加外部系统是简单的。我们的外部双频系统的实现基于标称95 GHz中心频率的固定参考PLDRO，加上合成偏移，在SSB转换和乘法之后，在收发器的输出端口提供95 <$GHz至0.4 GHz的信号。在频率参考模块中采用10 ns微波开关以快速选择任一频率源，在频率倍增之后在收发器内执行实际毫米波脉冲的整形。频率选择开关的定时由我们现有的95 GHz频谱仪高分辨率（PBHR）定时系统的备用输出线提供。 外部双频源的设计已经完成，包括特定频率PLDRO在内的组件已经订购并收到。步进频率源的建造、评估和实验使用定于今年夏天进行。

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. For both DEER (double electron?electron resonance) and extended-coverage ELDOR at 95GHz, a method of dual-stepped-frequency operation is desired. The ability to conduct DEER investigations is important because there is significant biological motivation in expanding distance measurement techniques developed at conventional frequencies at ACERT to the high frequency regime. The unique ACERT 2D-FT ESR 95GHz 1kW pulse ESR spectrometer holds the promise of being able to access a wide range of samples including macroscopically-aligned biological specimens, single-crystals with goniometry, and microliter-sized samples. The enhanced orientation selection of high-field ESR spectrum is valuable in structural studies, with both DQC and DEER techniques presently under consideration for this purpose. The implementation of DEER requires, however, irradiating spin systems sequentially at two frequencies. Extended-coverage ELDOR at 95GHz may be accomplished by either field-jump or frequency-stepping techniques, but the desirability of making DEER distance measurements at 95GHz gives us added incentive to implement a dual-frequency capability in order to address both types of experimental work. For our high-power 95GHz pulse spectrometer, the addition of stepped-frequency operation is facilitated by the ca 500 MHz instantaneous bandwidth of the existing transceiver/power amplifier chain. Moreover, the transceiver reference oscillator section in our instrument was designed with an external input which directly accommodates an external dual-frequency source. Consequently, adding an external system for stepped-frequency work is straightforward. Our realization of the external dual-frequency system is based on a fixed reference PLDRO at the nominal 95GHz center frequency, plus a synthesized offset providing, after SSB conversion and multiplication, a 95 ¿ up to 0.4 GHz signal at the transceiver's output port. A 10ns microwave switch is employed in the frequency reference module to rapidly select either frequency source, with shaping of the actual millimeter-wave pulses performed within the transceiver following frequency multiplication. Timing for the frequency selection switching is provided by a spare output line from our existing 95GHz spectrometer high-resolution (PBHR) timing system. Design of the external dual-frequency source is complete and the components, including the frequency-specific PLDRO, have been ordered and received. Construction, evaluation and experimental use of the step-frequency source is scheduled for this summer.