MODULATION FREQUENCY-TUNE NETWORK FOR CW HIGH FIELD SPECTROSCOPY

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 C.W.目前采用的现场调制系统。高频光谱仪由一个适当改装的音频功率放大器组成，驱动一个场产生线圈。由于线圈代表高无功负载，因此当串联调谐到谐振时，磁场调制网络的运行效率最高且具有最高峰值场值。在历史上，调谐磁场调制系统需要插入一个中间网络，用于在用示波器观察由此产生的线圈电压幅度的同时，将一系列阶梯值电容器中的一个切换到调制电路中。此调整的目标是在选定的激励频率下最大化给定恒定放大器输出信号的线圈电压。然而，由于所需的大电容范围和有限的开关位置，现有网络中通过改变开关设置而获得的电容值仅是粗略相关的。因此，实际上，导致最大幅度的所选电容值可能大大偏离获得真正的谐振峰所需的值。 通过设计和建造一个替换的调谐单元，我们将其命名为(高场)调制精细调谐网络(HF-MFTN)，我们解决了调谐分辨率不足的历史问题，同时为可选的外部仪器(如示波器、频率计数器)增加了内置监控功能和电流隔离输出。我们最近建造了3个HF-MFTN单元。经过调试、测试和校准后，其中两个设备将在Acert使用，其余设备将交付给纽约州立大学奥尔巴尼分校。在Acert单元中，一个网络将安装在我们的170/240 GHz光谱仪中，另一个将安装在我们的95 GHz C.W./PULSE光谱仪中。

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. Field modulation systems currently employed in the ACERT c.w. HF spectrometers consist of an suitably-modified audio power amplifier driving a field-generating coil. Because the coil represents a highly reactive load, the field modulation network operates most efficiently and at highest peak field value when series-tuned to resonance. Historically, tuning of the field modulation systems has entailed the insertion an intermediary network for switching one of a stepped-value series of capacitors into the modulation circuit while observing with an oscilloscope the resulting coil voltage amplitude. This adjustment is made with the goal of maximizing the coil voltage for a given constant amplifier output signal at the chosen excitation frequency. However, the capacitor values available in the existing networks through variation of the switch setting are only coarsely related due to the large capacitance range required and finite number of switch positions. Therefore, a selected capacitor value that results in maximum amplitude may, in actuality, be considerably displaced from the value required for attaining the true resonance peak. With design and construction of a replacement tuning unit which we have designated the (high-field) Modulation Fine-Tuning Network (HF-MFTN), we have addressed the historical problem of inadequate field-modulation tuning resolution and at the same time added both built-in monitoring capability and galvanically-isolated outputs for optional external instrumentation (e.g., oscilloscope, frequency counter). We have recently constructed 3 HF-MFTN units. After debug, test and calibration, two of these devices will be used at ACERT and the remaining device will be delivered to SUNY Albany. Of the ACERT units, one network is to be installed in our 170/240 GHz spectrometer and the other in our 95 GHz c.w./pulse spectrometer.