The history of the construction of “PLANET” neutron beam line at J-PARC, which was dedicated for high-pressure research, is reviewed and performance of the completed system is introduced. The unique features of PLANET such as very strong and bright neutron beam, large sample volume, and independently controllable 6-ram press, made it possible to perform new science in many fields.
PLANET is a high-pressure neutron beamline constructed at pulsed-neutron source in Materials and Life Science Experimental Facility (MLF) in J-PARC. The six-axis multi-anvil press designed for time of flight (TOF) neutron diffraction experiments enables routine data collection at high pressures and high temperatures up to 10 GPa and 2000 K, respectively. To obtain clean data, the beamline is equipped with the incident slits and receiving collimators that eliminate parasitic scattering from the high-pressure cell. The high performance of the diffractometer for the resolution (Δd/d～0.6%) and the accessible d-spacing range (0.2-8.4 Å) together with low-parasitic scattering characteristics enables precise structure determination of crystals and liquids under high pressure and temperature conditions.
The technical development for the high-pressure and temperature neutron diffraction with six-axis large volume press, ATSUHIME, which has been installed at BL11 (PLANET) in J-PARC, is introduced. The 6-6-type assembly is one of suitable module for high-pressure neutron diffraction due to wide accessibility to the sample. In order to apply the 6-6-type assembly to the high-pressure neutron diffraction, large 6-6-type anvils (including anvils tightening by steel jacket) and the cell assembly have been designed and tested. The test compression and heating experiments demonstrated the usability of the large 6-6-type assembly. Future challenge is how high-intensity signal from sample can be ensured at high pressure.
We have developed an in situ neutron diffraction technique for observing deuterization reactions of metals at temperatures up to 1000 K and pressures up to 10 GPa. The time evolution of the diffraction profile of iron due to deuterization was collected during heating to 1000 K at a fixed pressure of 6.3 GPa and the accumulated profile of the equilibrium solid-solution state at 988 K was taken with high statistics for precise analysis of its crystal structure. The detailed analytical method as well as the developed deuterization cell will be presented in this article.
A temperature-pressure variable system for neutron scattering experiments, so called “Mito system”, was developed several years ago. The Mito system allows us (1) to control pressure up to 10 GPa, and temperature from 80 K to 473 K; (2) to control temperature with very high rate (max. 20 K min−1); (3) to control temperature stably (±0.1 K over 100 K, and ±0.3 K below 100 K, approximately). It is particularly noteworthy that pressure can be downloadable to 0 GPa even at 80 K, which is not straightforward for other systems. Here I review the background of previous situation and technical problems of neutron diffraction experiments under non-ambient conditions before the development of Mito system, and also describe how these problems were overcome. Examples of neutron diffraction experiments by using the Mito system, and the currently progressing developments for the Mito system are briefly shown.
Newly designed opposed-type anvil assemblies were developed for acquiring high signal intensity of neutron diffraction data and ruby fluorescence spectra. Ni-binded WC anvils with a wide aperture angle, which were combined with a hybrid gasket made of TiZr and Al-alloy, achieved nearly ～15 GPa at room temperature. The neutron diffraction intensity was 2.5-3.0 times greater than that using the conventional toroidal anvil assemblies. The performance test of these new anvil assemblies confirms that sufficient quality diffraction data can be obtained. Using these assemblies, high-pressure behavior of hydrogen bond in Ca(OD)2 was investigated at PLANET beamline, J-PARC.
Deuterium site positions and occupancies in the crystal structures of synthetic hydrous ringwoodite [γ-(Mg1.72Fe0.17D0.22)(Si0.97D0.12)O4] and dense hydrous magnesium silicate (DHMS) phase E [Mg2.28Si1.31O6D2.22] have been determined for the first time by high-resolution time-of-flight (TOF) neutron powder diffraction conducted at Japan Proton Accelerator Research Complex (J-PARC). These two minerals are the promised major careers of deep-mantle water. They were synthesized at pressures up to 19 GPa and at temperatures up to 1300℃ using a Kawai-type apparatus, for which we have newly designed two types of furnace assemblies to uniformly heat large masses of samples at these pressures (45 to 80 mg for each experimental run). The products were chemically uniform and free from any contamination of 1H. We successfully refined the structures of the two minerals to find the relations between their chemical bonding states and their physical properties.
In this article, we introduce our recent high-pressure study on magnetism and multiferroicity in olivine-type Mn2GeO4. This compound shows successive magnetic transitions at ambient pressure and a ferroelectric ground state driven by spin-spiral order, i.e., a multiferroic state. The multiferroicity under high pressure was taken by using a recently constructed measurement system equipped with a diamond anvil cell. The pressure evolution of the magnetic structures was investigated with powder and single-crystal neutron scattering experiments using a Paris-Edinburgh press. We found that the ferroelectricity in the lowest-temperature phase disappears at 6 GPa where an incommensurate-commensurate magnetic phase transition is observed. The origin of the pressure-induced transition is discussed. Some details of the high-pressure experimental techniques will be also presented.
The diamond anvil cells (DACs) for the neutron diffraction experiments were developed at the high-pressure diffraction instrument, the Spallation Neutrons and Pressure (SNAP) in the Spallation Neutron Source (SNS), Oak Ridge National Laboratory, USA. In the SNAP, the neutron data of ice VII were collected up to 94 GPa at room temperature. Also, the low temperature neutron experiments can be performed by using the DAC, PE-cell and gas-pressure-cell. In this article, the introduction for experimental techniques and review of the high-pressure neutron experiments on icy materials are shown.
In this article, advances on phase-transition studies of mantle minerals in the Earth's interior are reviewed. Precise phase relations of minerals and related inorganic compounds at high pressure have been determined by precise high-pressure experiments and also by thermodynamic calculations based on calorimetric measurements. Crystal-chemical studies on high-pressure analogue compounds for silicates and aluminates have been made to get insight to crystal structures and properties of the minerals stable in the deep Earth's interior. The results substantially advance our understanding of the structure and dynamics of the deep mantle.
Pb- and Bi- containing perovskites exhibit exotic properties owing to the presence of 6s electrons. High-pressure technique is promising method for synthesizing a wide variety of the perovskites. In this paper, the exotic properties of Pb- or Bi- containing perovskites, such as the origin of a large tetragonal distortion in PbVO3, structural transformation of PbMnO3 under high pressure, a large volume collapse accompanied with spin state transition in BiCoO3, polarization rotation in BiCo1−xFexO3 solid solution, and negative thermal expansion in BiNiO3 based materials are demonstrated. These properties are attributed to the correlation between 6s orbital of Pb and Bi and 3d orbital of transition metal elements.
Knowledge about transport properties of Earth-forming minerals is important to understand the formation and the evolution of solid Earth. State-of-art high-pressure techniques help us to replicate the Earth's internal conditions, and to reveal various physical properties of minerals inside of the Earth. In this article, our high-pressure experimental studies for determinations of electrical and thermal transport properties of deep inside the Earth are reviewed with focusing on the following 3 topics; (1) electrical conductivity of the Earth's lower mantle, (2) electrical and thermal conductivity of the Earth's core, (3) lattice thermal conductivity of the lower mantle.