A CO2 laser heating system for in situ high pressure-temperature experiments at HPCAT

Abstract

We present a CO laser heating setup for synchrotron x-ray diffraction inside a diamond anvil cell, situated at HPCAT (Sector 16, Advanced Photon Source, Argonne National Lab, Illinois, USA), which is modular and portable between the HPCAT experiment hutches. The system allows direct laser heating of wide bandgap insulating materials to thousands of degrees at static high pressures up to the Mbar regime. Alignment of the focused CO laser spot is performed using a mid-infrared microscope, which addressed past difficulties with aligning the invisible radiation. The implementation of the mid-infrared microscope alongside a mirror pinhole spatial filter system allows precise alignment of the heating laser spot and optical pyrometry measurement location to the x-ray probe. A comparatively large heating spot (∼50 m) relative to the x-ray beam (<10 m) reduces the risk of temperature gradients across the probed area. Each component of the heating system and its diagnostics have been designed with portability in mind and compatibility with the various experimental hutches at the HPCAT beamlines. We present measurements on ZrO at 5.5 GPa which demonstrate the improved room-temperature diffraction data quality afforded by annealing with the CO laser. We also present measurements at 5.5 GPa up to 2800 K in which we do not observe the postulated fluorite ZrO structure, in agreement with recent findings.

Pressure‐Tuneable Visible‐Range Band Gap in the Ionic Spinel Tin Nitride

“…EXAFS measurements were performed on samples which were CO 2 laser annealed with in situ XRD confirming the complete and homogeneous structural change. [37] Note that while the calculated ground state structure above 97 GPa is I4 3d,w ee xperimentally observe R3 c up to 125 GPa. Kinetic barriers were not considered and most likely conditions that permit access to I4 3d were not met.…”

“…While XRD signal strength varies with atomic number, reducing information gained on smaller atoms when in the presence of heavier nuclei, XAS (particularly extended X‐ray absorption fine structure, EXAFS) probes nearest‐neighbour distances, allowing the locations of N atoms to be refined (Figure c), and complete crystallographic information to be extracted (Supporting Information, Table S11). EXAFS measurements were performed on samples which were CO 2 laser annealed with in situ XRD confirming the complete and homogeneous structural change …”

Oxidation of High Yield Strength Metals Tungsten and Rhenium in High-Pressure High-Temperature Experiments of Carbon Dioxide and Carbonates

“…This wavelength equates to a photon energy of the same order of magnitude as lattice phonons in covalent crystals, and it is usually absorbed by minerals and transparent oxides [52]. Note, however, that the focal size of the laser spot in this case is larger than in the case of solid-state lasers [12], making the heating of the gasket metal more likely.…”

From Molecules to Carbon Materials—High Pressure Induced Polymerization and Bonding Mechanisms of Unsaturated Compounds

“…There are several ways to apply high temperature to the sample in DAC, mainly including laser and resistance heating [27]. Laser heating is achieved by focusing Nd: YAG or CO 2 lasers on the sample [28,29]. The temperature is determined by measuring the thermal radiation intensity and fitting the Planck blackbody radiation equation [30,31].…”