FREQUENCY-STEPPING SYSTEM FOR 95 GHZ ESR SPECTROMETER

适用于 95 GHz ESR 光谱仪的频率步进系统

• 批准号: 7956618
• 负责人: CURT R DUNNAM
• 金额: $ 0.79万
• 依托单位: CORNELL UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-09-01 至 2010-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7956618
• 关键词: Address; Amplifiers; Biological; Computer Retrieval of Information on Scientific Projects Database; Electrons; Evaluation; Frequencies; Funding; Grant; Incentives; Institution; Investigation; Measurement; Methods; Motivation; Operative Surgical Procedures; Output; Physiologic pulse; Research; Research Personnel; Resolution; Resources; Sample Size; Sampling; Schedule; Shapes; Signal Transduction; Source; Specimen; System; Techniques; Technology; Time; United States National Institutes of Health; Work; base; design; instrument; microwave electromagnetic radiation; millimeter

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. 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.

该子项目是利用该技术的众多研究子项目之一 资源由 NIH/NCRR 资助的中心拨款提供。 研究者 (PI) 可能已从 NIH 的另一个来源获得主要资金， 因此可以出现在其他 CRISP 条目中 列出的机构是。 对于中心来说，它不一定是研究者的机构。 对于 DEER（双电子共振）和 95GHz 的扩展覆盖范围 ELDOR，需要一种双步进频率操作的方法。进行 DEER 研究的能力非常重要，因为扩展距离测量技术的开发具有重要的生物学动机。从 ACERT 的常规频率到高频范围，独特的 ACERT 2D-FT ESR 95GHz 1kW 脉冲 ESR 光谱仪有望获取各种样品，包括宏观排列的生物样本、测角的单晶和微升大小的样品，增强的高场 ESR 光谱的方向选择在结构研究中非常有价值，目前正在考虑为此目的实施 DQC 和 DEER 技术。然而，DEER 需要以两个频率顺序照射自旋系统，可以通过场跳跃或频率步进技术来实现 95GHz 的扩展覆盖范围 ELDOR。在 95GHz 进行 DEER 距离测量的愿望给了我们更多的动力来实现双频功能，以便解决这两种类型的实验工作。 对于我们的高功率 95GHz 脉冲光谱仪，现有收发器/功率放大器链的约 500 MHz 瞬时带宽促进了步进频率操作的增加，此外，我们仪器中的收发器参考振荡器部分设计有外部输入。经过检查，直接容纳外部双频源，添加用于步进频率工作的外部系统非常简单，我们的外部双频系统的实现基于固定参考PLDRO。标称 95GHz 中心频率，加上合成偏移，在 SSB 转换和乘法之后提供 95 ¿收发器输出端口处采用 10ns 微波开关来快速选择任一频率源，并在倍频定时后在收发器内执行实际毫米波脉冲整形。选择切换由我们现有 95GHz 光谱仪高分辨率 (PBHR) 定时系统的备用输出线提供。 外部双频源的设计已完成，包括特定频率 PLDRO 在内的组件已订购并接收，计划于今年夏天进行步进频率源的建设、评估和实验使用。