In 2012 Dubrovinsky and his colleagues have reported the generation of 620 GPa (1) using double-stage diamond anvil cell technique (ds-DAC). This technique looks to be a very promising way to generate static high pressures beyond the limit of conventional diamond anvil cell and many other groups have tried to generate high pressures using similar technique (2-4). Unfortunately, however, by now no other groups have succeeded in generating pressures beyond 500 GPa, although the first group has reported the generation of further high pressures up to 1 TPa (5). We have been working to establish a technique to achieve pressures beyond 500 GPa in a reproducible manner by adopting the concept of ds-DAC. Although we made more than 20 runs, none of them has exceeded 500 GPa. In this talk we will report various possibilities and difficulties associated with this ds-DAC technique based on the various observations obtained in our study. 

(1) L. Dubrovinsky et al., Nat. Commun. 3, 1163 (2012).
(2) T. Sakai et al., Rev. Sci. Instrum. 86, 033905 (2015).

(3) S. S. Lobanov et al, J. Appl. Phys. 118, 035905 (2015).

(4) Y. K. Vohra et al., High Pressure Res. 35, 282–288 (2015).

(5) N. Dubrovinskaia et al., Sci Adv, 2:.doi:10.1126/sciadv.1600341 (2016).