17:15 〜 18:30
[SIT18-P04] GHz ultrasonic velocity measurements of iron beyond the bcc-hcp transition Ⅱ: sample thickness determination using X-ray imaging method
キーワード：GHz超音波測定、鉄、高圧
The sound velocity of iron (Fe) at high pressure is an important physical property for estimating the structure of planetary interiors. We have developed the GHz ultrasonic travel time technique using a diamond anvil cell (DAC). This technique utilize ultrasonic interferometry to determine the travel time of a sample in DAC. The ultrasonic waves travelling through the DAC are reflected at the front and back of the sample and produce interference. The travel time is determined by varying the frequency of the ultrasonic waves and examining the periodicity of the intensity changes in the interference region.
In this poster, we will report
1. the results of travel time measurements on iron (Fe) and the sound velocity estimated by thickness measurements on recovered samples
2. preliminary results of in-situ measurements of sample length using X-ray imaging measurements.
A symmetrical DAC with a culet diameter of 600 um was used. The generated pressure was determined by the ruby fluorescence method. The pressure was increased up to 15 GPa and travel time measurements have been carried out during the decompression process. The sample thickness was determined from scanning electron microscopy (SEM) images of cross sections of the recovered samples. Based on the thickness of the recovered sample and the travel time measurement at 6.7 GPa, the P-wave sound velocity was determined to be 6.68(8) km/s. This value is about 6% higher than of previous studies (Decremps et al., 2014). This is probably due to the preferred orientation of the samples in the non-hydrostatic experiments, or the hcp-Fe remaining in the samples.
In addition, we performed X-ray imaging measurement for future in-situ measurements. Kapton was used as an X-ray transparent gasket. Incident X-rays were applied from a direction perpendicular to the DAC compression axis. Preliminary result shows that the method can be used to determine the thickness of the sample with an accuracy of ~5 μm.
In this poster, we will report
1. the results of travel time measurements on iron (Fe) and the sound velocity estimated by thickness measurements on recovered samples
2. preliminary results of in-situ measurements of sample length using X-ray imaging measurements.
A symmetrical DAC with a culet diameter of 600 um was used. The generated pressure was determined by the ruby fluorescence method. The pressure was increased up to 15 GPa and travel time measurements have been carried out during the decompression process. The sample thickness was determined from scanning electron microscopy (SEM) images of cross sections of the recovered samples. Based on the thickness of the recovered sample and the travel time measurement at 6.7 GPa, the P-wave sound velocity was determined to be 6.68(8) km/s. This value is about 6% higher than of previous studies (Decremps et al., 2014). This is probably due to the preferred orientation of the samples in the non-hydrostatic experiments, or the hcp-Fe remaining in the samples.
In addition, we performed X-ray imaging measurement for future in-situ measurements. Kapton was used as an X-ray transparent gasket. Incident X-rays were applied from a direction perpendicular to the DAC compression axis. Preliminary result shows that the method can be used to determine the thickness of the sample with an accuracy of ~5 μm.