5:15 PM - 7:15 PM
[SCG53-P03] Verification of Pressure Retention Stability in a Diamond Anvil Cell under Low-Pressure Conditions
Keywords:Diamond Anvil Cell, Raman spectroscopy, Quartz Raman barometer, Ruby fluorescence
A small-scale pressure device, the Diamond Anvil Cell (DAC), is used for research across a wide range of pressure conditions, from a few GPa in the crustal region to over hundreds of GPa in the mantle and core regions. Low-pressure DACs allow for a larger anvil diameter (about 1 mm), expanding the sample chamber. However, the stability of pressure retention concerning the gasket thickness, hole diameter, and pressure gradient in the sample has not been sufficiently examined. In this study, we evaluated the pressure stability inside the DAC sample chamber under low-pressure conditions by measuring the Raman shift of quartz and ruby using Raman spectroscopy to calculate the sample chamber pressure.
Quartz and ruby grains were placed inside a stainless steel gasket, and a methanol-ethanol mixture was used as the pressure-transmitting medium. The effect of different gasket hole diameters and thicknesses (0.5 mm and 0.6 mm) was examined. Additionally, the shape of the quartz samples was varied to evaluate the uniformity of applied pressure. Five different samples were tested under pressures ranging from 1.4–1.8 GPa. After maintaining the applied pressure for several days, Raman spectroscopy measurements were performed to investigate changes in pressure over time. Furthermore, pressure mapping was conducted in both the planar and depth directions to analyze the pressure distribution within the sample.
Although fluctuations in pressure over time were observed inside the DAC sample chamber, there was no indication of pressure leakage. Regarding planar pressure mapping, some samples exhibited pressure variations near the sample edges. When the sample was divided into different regions for analysis, the pressure fluctuations increased from the center to the intermediate region and then to the edge. This trend is likely due to signal detection issues at the sample-medium boundary near the sample edges. The signal strength was evaluated using the SNR (Signal-to-Noise Ratio) value. Similar to pressure, when the SNR values were mapped, it was observed that the signal strength was lower in areas where pressure fluctuations were greater, such as the edge regions. However, the maximum variation in pressure across the entire samples was only 0.01 GPa, confirming that no significant localized pressure concentration occurred, and the sample is uniformly pressurized within the DAC chamber.
Regarding depth-direction mapping, pressure variations were observed toward the edges in all samples. Similarly, when the SNR values were calculated in the depth direction, the signal intensity was found to decrease toward the edges. Additionally, planar mapping was conducted at different depths. The results showed that the average pressure distribution remained consistent across all planes, indicating uniform pressure application. Based on these findings, it was demonstrated that using a 0.5–0.6 mm gasket in a diamond anvil cell under low-pressure conditions enables uniform pressurization and stable pressure. On the other hand, since the SNR value decreases at the edges of the sample, it is desirable to measure the central region in both the planar and depth directions to obtain highly accurate data.
Quartz and ruby grains were placed inside a stainless steel gasket, and a methanol-ethanol mixture was used as the pressure-transmitting medium. The effect of different gasket hole diameters and thicknesses (0.5 mm and 0.6 mm) was examined. Additionally, the shape of the quartz samples was varied to evaluate the uniformity of applied pressure. Five different samples were tested under pressures ranging from 1.4–1.8 GPa. After maintaining the applied pressure for several days, Raman spectroscopy measurements were performed to investigate changes in pressure over time. Furthermore, pressure mapping was conducted in both the planar and depth directions to analyze the pressure distribution within the sample.
Although fluctuations in pressure over time were observed inside the DAC sample chamber, there was no indication of pressure leakage. Regarding planar pressure mapping, some samples exhibited pressure variations near the sample edges. When the sample was divided into different regions for analysis, the pressure fluctuations increased from the center to the intermediate region and then to the edge. This trend is likely due to signal detection issues at the sample-medium boundary near the sample edges. The signal strength was evaluated using the SNR (Signal-to-Noise Ratio) value. Similar to pressure, when the SNR values were mapped, it was observed that the signal strength was lower in areas where pressure fluctuations were greater, such as the edge regions. However, the maximum variation in pressure across the entire samples was only 0.01 GPa, confirming that no significant localized pressure concentration occurred, and the sample is uniformly pressurized within the DAC chamber.
Regarding depth-direction mapping, pressure variations were observed toward the edges in all samples. Similarly, when the SNR values were calculated in the depth direction, the signal intensity was found to decrease toward the edges. Additionally, planar mapping was conducted at different depths. The results showed that the average pressure distribution remained consistent across all planes, indicating uniform pressure application. Based on these findings, it was demonstrated that using a 0.5–0.6 mm gasket in a diamond anvil cell under low-pressure conditions enables uniform pressurization and stable pressure. On the other hand, since the SNR value decreases at the edges of the sample, it is desirable to measure the central region in both the planar and depth directions to obtain highly accurate data.