Development of High-Temperature Technique with Diamond Anvil Window Cells for use in Geophysical Sciences

为了在地核和地幔的物理条件下获得高质量的数据，我们需要改进我们现有的设备，并开发在超高压下加热我们的样品以及测量温度和压力的新技术。这笔赠款的资金将充分利用钻石砧子技术，在高压到超高压和温度下研究具有地球物理意义的材料。我们将研究激光加热问题的本质，因为这些问题与大的温度梯度(热样品的冷钻石)、色差(使用折射光学元件，即使是色校正的，也会导致严重的温度误差，该误差随光谱区域的所选位置而显著变化)以及对发射率(使用普朗克函数所需的依赖于波长的发射率)的知识贫乏有关。将探索几种金属和氧化物的发射率测定的激光加热系统、光学系统和方法的组合。还将测试一种使用数字成像相机测定温度的新方法。其他开发将包括：i)在高压(~50 Gpa)下使用碳化硅(碳化硅)顶锤以达到接近2000K的温度；ii)设计一种电池，使其能够方便地接触到电导线样品，并且仍然保持MAO-Bell设计的所有优点，并且在钻石周围良好的惰性气氛下很容易进行冷却；iii)建立可以进行电加热和激光加热的电池，对在1巴或几巴压力下加热的样品进行原位x射线衍射，以测量固体的热膨胀和熔化温度。我们将试图为同时测量压力和温度这一关键问题提供解决方案。***

0132270SaxenaTo obtain high quality data at physical conditions of Earth's core and mantle, we need to modify our present equipment and develop new techniques of heating our samples at ultra-high pressures and for measuring the temperature and pressure. Funds from this grant will fully exploit the diamond-anvil techniques to study materials of geophysical importance at high to ultra-high pressures and temperatures. We will study the nature of the problems in laser heating as related to large temperature gradients (cool diamond to the hot sample), chromatic aberration (use of refractive optical elements, even chromatically corrected, results in the severe temperature errors that vary significantly with the chosen position of a spectral region) and poor knowledge of emissivity (wavelength dependent emissivity, needed for use of the Planck function). A combination of laser-heating systems, optical systems and methods for the determination of emissivity of several metals and oxides will be explored. A new method of temperature determination using a digital imaging camera will also be tested. Additional developments will include: i) the use of moissanite (SiC) anvils at high pressures (~ 50 GPa) to reach temperatures close to 2000 K, ii) design of a cell that provides easy access to the sample for the electrical leads and still maintains all the benefits of the Mao- Bell design and is easily cooled with a good inert atmosphere around the diamonds, and iii) building of cells which can be both electrically and laser heated with in-situ x-ray diffraction of the heated sample at one bar or few bars of pressure to measure thermal expansion and melting temperatures of solids. We will attempt to provide a solution to the key problem of simultaneous measurement of pressure and temperature. ***