X-BAND PULSE ESR SPECTROMETER FOR STUDY OF LOW-TEMPERATURE IMPURITY-HELIUM

这个子项目是许多研究子项目中利用 资源由NIH/NCRR资助的中心拨款提供。子项目和 调查员(PI)可能从NIH的另一个来源获得了主要资金， 并因此可以在其他清晰的条目中表示。列出的机构是 该中心不一定是调查人员的机构。 LASSP的低温小组目前正在积极研究杂质氦固体。杂质-氦(Im-He)固体是通过将氦气体和杂质气体或杂质气体的混合束注入超流4He[1]而形成的多孔固体。然后，来自光束的杂质或杂质簇被一层薄薄的固体氦包围。范德华力将这些成分结合成一种具有纳米级气孔的微细气凝胶结构。到目前为止，连续波ESR一直是研究Im-He固体的主要工具。脉冲ESR方法有望提供这些易碎物体结构的更多细节。例如，对于氮原子，可以检测到来自附近氮核的ESEEM，以报告距离和周围原子核的数量。这同样适用于H原子和D原子。LASSP小组在ACERT的帮助下建造了一台脉冲ESR光谱仪。ACERT提供了必要的援助，包括就分光计设计提供咨询，提供一些关键部件，如行波管放大器，并帮助建造微波桥。完成了微波脉冲桥的施工。对电桥进行了测试，发现它已经准备好与光谱仪的其余部分整合。

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. The low-temperature group at LASSP is currently actively studying impurity-helium solids. Impurity-helium (Im-He) solids are porous solids created by injecting a mixed beam of helium gas and an impurity gas or impurity gases into superfluid 4He [1]. The impurities or clusters of impurities from the beam are then surrounded by a thin layer of solid helium. Van der Waals forces bind these components into a tenuous, aerogel-like structure with nanoscale pores. So far, CW ESR has been the main tool used to study Im-He solids. Pulsed ESR methods promise to provide additional details of the structure of these fragile objects. For example, for nitrogen atoms, ESEEM from nearby nitrogen nuclei can be detected to report on distances and the number of surrounding nuclei. The same holds true for H and D atoms. The LASSP group undertook the construction of a pulse ESR spectrometer with help from ACERT. ACERT has provided the necessary level of assistance including consultation on spectrometer design, providing some critical components, such as a TWT amplifier, and helping with the construction of the microwave bridge. The microwave pulse bridge construction was completed. The bridge was tested and found to be ready for integration with the rest of the spectrometer.