2019 年 37S 巻 p. 43-51
Understanding the behavior of water within snow cover, including its content, distribution, and movement, is essential for forecasting avalanches and for predicting the sliding of snow from the roofs of structures. We developed a high-resolution magnetic resonance imaging (MRI) system for non-destructive measurement of the distribution of water in snow cover. Our system is compact, uses a permanent magnet, and is designed for use in temperatures below 0 °C. To adapt the system to cold conditions, it was necessary to correct for inhomogeneities in the static magnetic field because a permanent magnet is strongly affected by the thermal conditions. We designed a single-layer shimming coil for this purpose. To prevent the wet snow sample from melting or freezing during scanning, we also developed a cooling system that uses a combination of liquid and air to maintain the sample at 0 °C. These improvements enabled non-destructive visualization of the water distribution in a wet snow sample, with high resolution. We therefore propose our MRI system as a powerful tool that can contribute to the understanding of wet snow physics.