Beta-tachyon

From Memory Alpha, the free Star Trek reference.

The beta-tachyon is a type of subatomic particle, a form of the tachyon particle. Beta-tachyons can be used to increase the strength of Federation starship shields by a factor of ten. The ship must remodulate its shields to emit a beta-tachyon pulse, and then project a series of antiproton beams into the shield bubble. (VOY: "The Q and the Grey")