Power source

The two men were standing in a small nexus chamber overlooking the eight radiating particle accelerator tubes designed to feed the super-laser beam. The walls were covered with readout meters, fluctuating bar graph monitors, banks of controls, and other equipment. Much of it was beyond CPO Tenn Graneet's knowledge, but that was all right. He didn't need to know everything about how it worked. He just had to be able to work it.

(...)

Star Wars: Death Star Part 1 Chapter 33