The disk should rotate in a vacuum at 12,000 revolutions per minute to produce the desired effect. We selected special composite bearings with ceramic balls capable of such speeds: ordinary steel ones could not cope with such conditions. To prevent bearing grease fumes from contaminating the working volume of the vacuum chamber, we selected a special grease used in spacecrafts.
There being no thermal conductivity in a vacuum, everything heated in the unit’s volume has to be forcedly cooled in a special way. At the same time, there should be no more than 60°C in the center of the disk to ensure proper operation of the bearings, the outer surface should be molten tin at about 300°C, and the temperature of the emitting EUV plasma, in general, is close to a million degrees. Our engineers selected a special titanium alloy for the disk and calculated its shape to provide the necessary strength and thermal conductivity.