(covers information from several alternate timelines)
An antiproton beam was a confined beam of antiprotons.
Encountered in 2267, the "planet killer" used a beam of "pure" antiprotons (an incredible scientific concept, at the time) as its primary weapon, capable of destroying whole planets. (TOS: "The Doomsday Machine")
When she was undercover with the Maquis, Seska developed a tactic by which she disabled the computer core of a Cardassian frigate above Bajor with a modified antiproton beam that penetrated its shields and hull. In 2372, Chakotay attempted to use the same tactic against Maje Culluh's Kazon raider, but Seska anticipated his plans and captured him. (VOY: "Maneuvers")
In 2371 two Jem'hadar fighters used a type of antiproton beam to detect the USS Defiant through its Romulan cloaking device. (DS9: "The Search, Part I") The Cardassians later used this technique when the Defiant was hijacked by the Maquis in 2371. However, Thomas Riker, commanding the captured starship, was able to negate the beam by adjusting the resonance frequency of the cloaking device. (DS9: "Defiant") Later, when Enabran Tain led a fleet of twenty Romulan Tal Shiar and Cardassian Obsidian Order ships into the Gamma Quadrant to attack the Founders' homeworld, they modified their cloaks so the Jem'Hadar couldn't detect their approach. In order for this to succeed, the ships had to limit their speed to warp six, so that their warp signatures wouldn't be detected through their cloaking devices. (DS9: "The Die is Cast")
A Federation starship could increase its shields by a factor of ten by taking the warp drive offline, remodulating its shields to emit a beta-tachyon pulse, and then emitting a series of focused antiproton beams to the shield bubble. According to B'Elanna Torres, though, this procedure entailed significant risk of the shield bubble igniting and "burning [them] all to a crisp". (VOY: "The Q and the Grey")
|Cloaking penetration technology|
|Antiproton beam • Gravitic sensor net • Long-range tachyon scanner • Metaphasic sweep • Quantum beacon • Tachyon detection grid|