Kunz Martin, Yan Jinyuan, Cornell Earl, Domning Edward E, Yen C Ethan, Doran Andrew, Beavers Christine M, Treger Aaron, Williams Quentin, MacDowell Alastair A
Advanced Light Source, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
Earth and Planetary Sciences Department, University of California, Santa Cruz, California 95064, USA.
Rev Sci Instrum. 2018 Aug;89(8):083903. doi: 10.1063/1.5028276.
A new design for a double-sided high-pressure diamond anvil cell laser heating set-up is described. The prototype is deployed at beamline 12.2.2 of the Advanced Light Source at Lawrence Berkeley National Lab. Our compact design features shortened mechanical lever arms, which results in more stable imaging optics, and thus more user friendly and more reliable temperature measurements based on pyrometry. A modification of the peak scaling method was implemented for pyrometry, including an iterative method to determine the absolute peak temperature, thus allowing for quasi-real time temperature mapping of the actual hotspot within a laser-heated diamond anvil cell without any assumptions on shape, size, and symmetry of the hotspot and without any assumptions to the relationship between fitted temperature and peak temperature. This is important since we show that the relationship between peak temperature and temperature obtained by fitting the Planck function against the thermal emission spectrum averaged over the entire hotspot is not constant but depends on variable fitting parameters (in particular, the size and position of the fitting window). The accuracy of the method is confirmed through measuring melting points of metal wires at ambient pressure. Having absolute temperature maps in real time allows for more differentiated analyses of laser heating experiments. We present such an example of the pressure variations within a heated hotspot of AgI at a loaded base pressure of 3.8 GPa.
本文描述了一种用于双面高压金刚石砧室激光加热装置的新设计。该原型已部署在劳伦斯伯克利国家实验室先进光源的12.2.2光束线上。我们的紧凑设计特点是缩短了机械杠杆臂，这使得成像光学系统更加稳定，从而基于高温测定法实现了更用户友好、更可靠的温度测量。对高温测定法实施了峰值缩放方法的改进，包括一种确定绝对峰值温度的迭代方法，从而能够在不假设热点形状、大小和对称性以及不假设拟合温度与峰值温度之间关系的情况下，对激光加热金刚石砧室内的实际热点进行准实时温度映射。这很重要，因为我们表明，通过将普朗克函数拟合到整个热点平均热发射光谱而获得的峰值温度与温度之间的关系不是恒定的，而是取决于可变的拟合参数（特别是拟合窗口的大小和位置）。通过测量常压下金属丝的熔点，证实了该方法的准确性。实时获取绝对温度图有助于对激光加热实验进行更细致的分析。我们给出了一个在3.8 GPa加载基础压力下，AgI加热热点内压力变化的示例。
