Development of Magnetic Resonance Imaging Technique for Ultra Low Temperature Physics

We have developed a Magnetic Resonance Imaging (MRI) technique applicable for ultra low temperature physics. In contrast to conventional MRI for general use where a pulsed-field gradient method is commonly used, we used a steady-field gradient method to avoid an eddy current heating due to metallic parts around the sample cell. We applied the MRI for3He-4He mixture liquid with a critical concentration below 1 K and visualized the shape of the phase-separated boundary. We obtained two-dimensional space resolution of a few 10 μm. We extracted the interfacial tension of the boundary which was in good agreement with reported values. The contact angle of the boundary to the cell wall was small at low temperature and increased toward 90° near the critical temperature.