Tachyon collectors are used to catch tachyons emitted from high-speed particle collisions (or other sources) and convert them into energy.
When particles collide at high speed, they emit energy-dense tachyons. The higher the collision energy, the more energy is ejected with the tachyons. They also fly farther, and there are more of them at higher speeds.
Tachyons will always exit in random directions at the collision point. Surrounding the entire area in collectors ensures you'll catch them all. If all tachyons are collected, you can get up to 4x the amount of energy that was used to accelerate the particles.
For detailed information on particle acceleration and tachyon mechanics, see the particle accelerator guide.