Pomeranchuk cell for hyperpolarized $^{3}$He based on the brute force method

MRI (Magnetic Resonance Imaging) has been used for the medical diagnosis as a radiation-free imaging equipment. Since the proton has been mainly used for medical MRI, usefulness has been rather restrictive. As an example for expanding the range of applicability, MRI with hyperpolarized $^{3}$He gas has been used for the lung disease. Here, ``hyperpolarized'' means ``polarized higher than the thermal equilibrium polarization.'' For producing a large amount of hyperpolarized $^{3}$He gas at a time, we have been developing a hyperpolarization technique based on the brute force method which uses an ultralow temperature of a few mK and a strong magnetic field around 17 T in combination with the principle of the Pomeranchuk cooling. The Pomeranchuk cell made with non-metallic materials of small heat capacity is attached to the $^{3}$He/$^{4}$He dilution refrigerator using a sintered silver allowing large heat conduction. After the sensors to monitor the temperature and pressure of $^{3}$He are calibrated and the Pomeranchuk cell is constructed, the system is tested. Then, the solidification of $^{3}$He and the measurement of NMR (Nuclear Magnetic Resonance) signals of $^{3}$He under the magnetic field of 17 T are carried out. The current status is reported in this talk.