FREQUENCY MODULATION STUDY AND DEVELOPMENT FOR HF CW SPECTROMETERY

高频连续波谱仪的调频研究与开发

• 批准号: 7602688
• 负责人: CURT R DUNNAM
• 金额: $ 1.79万
• 依托单位: CORNELL UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-09-01 至 2008-08-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7602688
• 关键词: Biological; Circular Dichroism; Computer Retrieval of Information on Scientific Projects Database; Detection; Development; Frequencies; Funding; Grant; Heating; Institution; Literature; Methods; Motion; Noise; Operative Surgical Procedures; Performance; Proteins; Reading; Research; Research Personnel; Resources; Sampling; Scheme; Solutions; Source; Spin Labels; System; Techniques; United States National Institutes of Health; Width; design; detector; improved; magnetic field

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. All ACERT c.w. spectrometers currently utilize conventional ca 100KHz magnetic field modulation for ESR spectral line detection. However, for high-field detection of moderately broad spectral linewidths the utility of this detection technique is severely constrained. Detection of moderately broad HF spectra corresponding to, e.g., spin-labeled proteins in the intermediate slow-motion regime, becomes relatively inefficient when Bmod << Hpp, necessitating operation of field modulation components at the extreme limit of power input capability, corresponding to a maximum field modulation of only 5 - 10Gpp. At field values exceeding this modulation level, coil-induced Lorentz forces become an increasingly significant microphonic noise source, and the coil power dissipation rapidly becomes a significantly perturbing heat source. Ideally, modulation widths of ca 100G would be available for a majority of HF samples, in particular biological samples at low concentrations,; however, this value is clearly out of reach of conventional direct magnetic field modulation techniques. An alternative modulation solution we have previously investigated is the circular-dichroism scheme described in the 2006 ACERT grant renewal proposal, Core Project III, at (F). For spectra that are not too broad, however, source frequency modulation (FM), a simpler and more easily implemented method of broad ESR line detection, seems possible (Hyde et al., 2007). Our initial task will be to evaluate the performance of a wide-band FM line detection system of at least 280 MHzpp (100Gpp) maximum modulation capability which may be adapted to our existing 170/240 GHz c.w. spectrometer. Because this HF spectrometer utilizes a bolometer power detector rather than a typical hetrodyne conversion and detection scheme as described elsewhere in the literature, our FM line detection system will differ in key design aspects with respect to FM systems described elsewhere. We believe, for example, that it is likely FM detection SNR in a bolometer (or other baseband power detection) system can be greatly enhanced by subtracting out the frequency- (i.e., field-) dependent baseline prior to synchronous demodulation. We have assigned this project a very high priority since improved HF c.w. ESR sensitivity is a critical factor in reading biological samples of low concentration.

该副本是利用众多研究子项目之一 由NIH/NCRR资助的中心赠款提供的资源。子弹和 调查员（PI）可能已经从其他NIH来源获得了主要资金， 因此可以在其他清晰的条目中代表。列出的机构是 对于中心，这不一定是调查员的机构。 所有Acert C.W.光谱仪当前利用常规CA 100KHz磁场调制来进行ESR光谱线检测。但是，对于中等广泛的光谱线宽的高视野检测，该检测技术的效用受到了严格的限制。当BMOD << hpp << HPP时，检测中间慢动作状态中的自旋标记的蛋白的中等宽HF光谱的检测变得相对较低，需要在电源输入能力极限下进行场调制成分的运行，与仅5-10GPP的最大现场调制相对应。在超过此调制水平的场值时，线圈诱导的洛伦兹力成为越来越重要的显微节噪声源，并且线圈功率耗散迅速成为一种显着的扰动热源。 理想情况下，大多数HF样品，特别是低浓度的生物样品，CA 100G的调节宽度将可用；但是，该值显然是传统直接磁场调制技术的范围。 我们先前研究过的替代调制解决方案是2006年ACERT授予续签建议，核心项目III，at（f）中描述的循环分解方案。然而，对于不太宽的光谱，源频率调制（FM）似乎是一种更简单，更容易实现的广泛ESR线检测方法（Hyde等，2007）。 我们的最初任务是评估至少280 MHzpp（100GPP）的最大调制能力的宽频FM线路检测系统的性能，该系统可以适应我们现有的170/240 GHz C.W.光谱仪。因为该HF光谱仪使用了验量计功率检测器，而不是文献中其他地方所述的典型的Hetrodyne转换和检测方案，所以我们的FM线检测系统在关键设计方面在其他位置所述的FM系统方面会有所不同。例如，我们认为，可以通过在同步解调之前减去频率（即（即）依赖性基线的频率 - （即）依赖性基线，可以大大增强FM检测SNR。自HF C.W.改进以来，我们将该项目分配给了很高的优先级。 ESR敏感性是阅读低浓度的生物学样品的关键因素。