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

0132270萨克森为了获得地核和地幔物理条件下的高质量数据，我们需要修改现有设备，并开发在超高压下加热样品和测量温度和压力的新技术。 这笔赠款的资金将充分利用金刚石砧技术来研究在高压至超高压和高温下具有地球物理重要性的材料。我们将研究激光加热中的问题的性质，这些问题与大的温度梯度（冷金刚石到热样品），色差（使用折射光学元件，即使经过色差校正，也会导致严重的温度误差，这些误差会随着光谱区域的选择位置而显著变化）和发射率知识不足（波长相关发射率，需要使用普朗克函数）有关。将探索激光加热系统、光学系统和测定几种金属和氧化物发射率的方法的组合。 还将测试一种使用数字成像相机确定温度的新方法。其他发展将包括：i）在高压下使用碳硅石（SiC）砧（~ 50 GPa）以达到接近2000 K的温度，ii）设计电池，该电池为电引线提供容易接近样品的途径，并且仍然保持Mao-Bell设计的所有优点，并且容易在金刚石周围的良好惰性气氛下冷却，和iii）构建可以电加热和激光加热的单元，在一巴或几巴的压力下对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。我们将试图提供一个解决的关键问题，同时测量的压力和温度。***

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. ***