The effect of a tapered aperture on x-ray diffraction from a sample with a pressure gradient: Studies on three samples with a maximum pressure of 560 GPa

X-ray diffraction patterns were obtained using a tapered lead aperture. A detailed analysis of the effect of the tapered aperture is given. Experimental studies include results on W (423 GPa), on Pt (440 GPa, obtained using type IIa diamonds), and Mo (560 GPa). These results extend earlier studies in which we achieved for the first time static pressures greater than the pressure at the center of the earth.