Tricobalt device

From Memory Alpha, the free Star Trek reference.

Tricobalt devices are a type of high yield explosive sometimes utilized by the Federation. Under certain conditions, they are capable of producing disruptions in subspace.

In 2155, Tholians of the mirror universe detonated a tricobalt device in a successful attempt to create an interphasic rift. Unwilling to explore the rift themselves, the Tholians sent a distress call through the rift. This attracted the USS Defiant of 2268 into the rift. The vessel subsequently became trapped and her crew was driven insane by the harmful effects of exposure to interphased space. The Defiant was eventually ejected from the rift into the mirror universe of 2155, where she was recovered for study by the Tholians. (ENT: "In a Mirror, Darkly")

In 2268, Arne Darvin, having traveled back in time from the year 2373, planted a tricobalt device in a tribble, which he hoped would explode near James T. Kirk, and kill him. The bomb was beamed into space by the USS Defiant, where it exploded harmlessly. (DS9: "Trials and Tribble-ations")

A pair of tricobalt devices, with a yield of 20,000 teracochranes, were used by the USS Voyager in order to destroy the Caretaker's array in 2371. The explosion destroyed the station, leaving no debris. (VOY: "Caretaker")

By 2373, the Maquis had been able to procure tricobalt weapons. In that year, Captain Benjamin Sisko theorized that they could be used in cloaked missiles that were supposedly on their way to Cardassia Prime. (DS9: "Blaze of Glory")

Tricobalt devices are relatively ineffective when used against shielded targets due to the slow expansion of energy from the explosion. It is primarily used as a demolition weapon, most notably against space stations and ground targets. (VOY: "The Voyager Conspiracy") However, when shields are weak, tricobalt devices can disable the shields. (VOY: "Blink of an Eye")

It is of note that when used under certain conditions, tricobalt explosives can cause subspace ruptures. They are however, probably not considered subspace weapons, as their effects are highly predictable and they are routinely carried by Federation vessels. Subspace weapons were banned by the second Khitomer Accords. (Star Trek: Insurrection)