(a) The white ring is a ceramic helical insert on which the screw sample holder is placed. The scale bar is 10 mm. (b) The body of the growth cell is made of quartz glass (orange). Two capillaries of quartz glass with rubber stoppers (yellow) are fixed to the body with an adhesive. Tubes of elastomer (red) are attached to each capillary. After the growth cell is filled with the growth solution (light blue), the tubes are closed with metal wires (arrows). (c) Schematic illustration of the growth cell.