Optical Study of Thermal conductivity of Deep Earth's Materials at High Pressure and Temperature

了解地球矿物在极端条件下的热导率和热扩散率，对于理解地球的物理和化学过程及其演化具有重要意义。通过地幔的热传输速率对地球磁场的存在和稳定至关重要。地幔内部的温度分布取决于对流、传导和辐射的传热速率。要理解这些过程，需要了解导热系数作为压力和温度的函数。在这个项目中，我们建议利用包括泵浦探针脉冲激光技术在内的DACs （Diamond Anvil Cells）光谱学来确定高P-T条件下地球关键矿物的热导率。为了确定晶格热导率，我们将使用时间和空间分辨光谱辐射测量和/或时域热反射（TDTR）测量样品的热通量及其时间历史。将采用连续激光和脉冲激光两种技术来获得热导率和扩散率。为了推测其辐射热导率，我们将研究这些地幔矿物在高P-T条件下（高达130 GPa和4000 K）的紫外-红外光谱范围内的光谱。硅酸盐钙钛矿和铁方长石，地球下地幔的两个主要阶段，将进行研究。由预合成材料生长的单晶，其成分接近于地幔中的单晶，将被用作样品。我们还将研究激光加热合成的后钙钛矿相的导热性。为了更好地了解地核-地幔边界（CMB）附近的热传输和地球温度剖面，我们将测量铁的热导率（也使用电导率和光导电性方法）。这些实验数据将给出热导率的辐射和传导部分的直接估计，因此它们可以用于地球热过程的模型计算，从而为这些模型和我们目前对地球内部的理解提供关键的测试。这项工作将通过包括研究生和本科生作为拟议研究的参与者来促进发现和理解。一系列学生，包括地区高中生、本科生、研究生和博士后助理，将受益于卡内基的科学培训，这些培训将通过参与这项工作过程中发展的尖端科学来提供。我们与美国和国外大学建立了合作关系，这使我们能够培训研究生并将其纳入我们的项目中。此外，我们通过与为这些群体服务的大学建立合作，并通过将女性和外国博士后（通过交换项目）纳入研究，扩大代表性不足群体的参与。我们的项目通过与美国和外国大学的多次卓有成效的合作，加强了研究和教育的基础设施。我们为我们的合作者提供卡内基光学设备的使用（以及nsf支持的项目，如compes和卡内基暑期实习生项目，以及能源部支持的CDAC高压中心，总部设在卡内基）。

Knowledge of thermal conductivity and thermal diffusivity of the Earth's minerals under extreme conditions is important for understanding the physical and chemical processes and their evolution in the Earth. The rate of the heat transport through the mantle is crucial for the existence and stability of the Earth's magnetic field. The temperature distribution inside the Earth's mantle depends on the rate of heat transfer by convection, conduction, and radiation. An understanding of these processes requires knowledge of the thermal conductivity as a function of pressure and temperature. In this project, we propose to determine the thermal conductivity of the Earth's key minerals under high P-T conditions by using optical spectroscopy in DACs (Diamond Anvil Cells) including pump-probe pulsed laser techniques. To determine the lattice thermal conductivity, we will measure the heat fluxes across the sample and their time history using time- and spatially resolved spectroradiometry and/or time-domain thermoreflectance (TDTR). Both continuous and pulsed laser techniques will be employed to access the thermal conductivity and diffusivity. To infer the radiative thermal conductivity, we will study the optical spectra of these mantle minerals in the ultraviolet-to-infrared spectral range at high P-T conditions (up to 130 GPa and 4000 K). Silicate perovskite and ferropericlase, the two dominant phases of the Earth's lower mantle, will be studied. Single crystals grown from pre-synthesized materials with a composition close to that in the Earth's mantle will be used as samples. We will also study the thermal conductivity of the postperovskite phase, synthesized by laser heating. To better understand the thermal transport and Earth's temperature profile near the Core-Mantle Boundary (CMB), we will measure the thermal conductivity of iron (using also electrical and optical conductivity methods). These experimental data will give a direct estimate of the radiative and conduction parts of the thermal conductivity, so they can be utilized in model calculations of the thermal processes in the Earth, thus providing a crucial test of these models and our current understanding of the Earth's interior. This work will advance discovery and understanding by including graduate and undergraduate students as participants in the proposed research. A range of students, including area high school students, undergraduates, graduate students, and postdoctoral associates, will benefit from the scientific training at Carnegie that will be provided by participation in cutting-edge science that will be developed in the course of this work. We have developed collaborations with US and foreign Universities that allow us to train and incorporate graduate student research into our project. Moreover, we broaden participation of under-represented groups by establishing collaborations with Universities serving such groups and by including women and foreign postdoctoral associates (using exchange programs) into the research. Our project enhances infrastructure for research and education through several fruitful collaborations with the US and foreign Universities. We offer the use of our Carnegie optical facilities for our collaborators (and also NSF-supported programs such as COMPRES and the Carnegie Summer Intern Program, as well as the DOE-supported CDAC high-pressure center, headquartered at Carnegie).