[the_seraphim]

couple it with some double walled carbon nanotubes and you can get upto 700 GPa

https://www.nextbigfuture.com/2019/01/fabrication-of-ultrast...

[DiseasedBadger]

I wonder if one could just stuff the tubes with hydrogen, then lanthanum powder, then just let them expand? They might auto-heat from the pressure, and assemble themselves, if you just unfroze them.