Miniature diamond anvils for X‐ray Raman scattering spectroscopy experiments at high pressure

X‐ray Raman scattering (XRS) spectroscopy is an inelastic scattering method that uses hard X‐rays of the order of 10 keV to measure energy‐loss spectra at absorption edges of light elements (Si, Mg, O etc .), with an energy resolution below 1 eV. The high‐energy X‐rays employed with this technique can penetrate thick or dense sample containers such as the diamond anvils employed in high‐pressure cells. Here, we describe the use of custom‐made conical miniature diamond anvils of less than 500 µm thickness which allow pressure generation of up to 70 GPa. This set‐up overcomes the limitations of the XRS technique in very high‐pressure measurements (>10 GPa) by drastically improving the signal‐to‐noise ratio. The conical shape of the base of the diamonds gives a 70° opening angle, enabling measurements in both low‐ and high‐angle scattering geometry. This reduction of the diamond thickness to one‐third of the classical diamond anvils considerably lowers the attenuation of the incoming and the scattered beams and thus enhances the signal‐to‐noise ratio significantly. A further improvement of the signal‐to‐background ratio is obtained by a recess of ∼20 µm that is milled in the culet of the miniature anvils. This recess increases the sample scattering volume by a factor of three at a pressure of 60 GPa. Examples of X‐ray Raman spectra collected at the O K ‐edge and Si L ‐edge in SiO 2 glass at high pressures up to 47 GPa demonstrate the significant improvement and potential for spectroscopic studies of low‐ Z elements at high pressure.