Understanding of the pressure evolution of physical and chemical properties of hydrogen is the ultimate goal of the high pressure science. This purpose has stimulated the development of low-temperature high-pressure technique for neutron diffraction study. With benefit of high intensity neutron sources a new diamond anvil cell (DAC) has been invented by I. N. Goncharenko. This device allows us to study neutron diffraction under extreme conditions of pressures up to 50 GPa, temperatures down to 0.1K and applied magnetic fields up to 7.5 T. We describe the details of this technique in the hope that J-PARC will make an epoch in ultra-high-pressure research.
