Advancing neutron diffraction for accurate structural measurement of light elements at megabar pressures

Over the last 60 years, the diamond anvil cell (DAC) has emerged as the tool of choice in high pressure science because materials can be studied at megabar pressures using X-ray and spectroscopic probes. In contrast, the pressure range for neutron diffraction has been limited due to low neutron flux even at the strongest sources and the resulting large sample sizes. Here, we introduce a neutron DAC that enables break-out of the previously limited pressure range. Key elements are ball-bearing guides for improved mechanical stability, gem-quality synthetic diamonds with novel anvil support and improved in-seat collimation. We demonstrate a pressure record of 1.15 Mbar and crystallographic analysis at 1 Mbar on the example of nickel. Additionally, insights into the phase behavior of graphite to 0.5 Mbar are described. These technical and analytical developments will further allow structural studies on low-Z materials that are difficult to characterize by X-rays.

Automated summary

Over the past 60 years, the diamond anvil cell (DAC) has become the preferred tool for high pressure science due to its ability to study materials at megabar pressures using X-ray and spectroscopic probes. However, the pressure range for neutron diffraction has been limited. In this study, a neutron DAC was introduced with improved mechanical stability, gem-quality synthetic diamonds, and improved collimation, allowing for breakthroughs in the previously limited pressure range. This development enables structural studies on low-Z materials that are difficult to characterize by X-rays.