[M-IS26] ガスハイドレートと地球環境・資源科学

[MIS26-09] 天然メタンハイドレートの三次元非破壊観察

*竹谷 敏¹、八久保 晶弘²、山下 聡²、南 尚嗣²、坂上 寛敏²、兵藤 一行³、米山 明男⁴ (1.産業技術総合研究所、2.北見工業大学、3.高エネルギー加速器研究機構、4.九州シンクロトロン光研究センター)

キーワード：クラスレートハイドレート、天然ガスハイドレート、ハイドレート堆積物、Ｘ線ＣＴ

The density of gas hydrates varies depending on the type of guest spices encapsulated in the hydrate crystal, but is generally about the same as ice or water (0.9~1.1 g/cm³). A material with such a relatively small density has a small absorption rate of X-rays. For this reason, it is difficult to visualize the internal structure using the X-ray absorption contrast caused by the slight difference in density within the material, which is the visualization principle of medical and industrial X-ray computed tomography (CT) systems. On the other hand, the phase of X-rays shifts significantly even in materials with small density. Therefore, if we can detect the phase shift of X-rays in a material, it is possible to observe the small density difference in the material with high sensitivity 1).

In this study, we used diffraction contrast (DEI) method2) as a method to detect the phase shift; the DEI method can detect density differences of about 0.01 g/cm³. The DEI method can detect a density difference of about 0.01 g/cm³ and has a relatively wide dynamic range of density (density difference: ~1 g/cm³).3) It is also effective for high-sensitivity measurement of samples with coexisting gas (voids) in addition to gas hydrate and ice (water).3) We also performed absorption-contrast X-ray CT measurements on a sample of natural sediment. The results will be reported.