An antimatter containment field, magnetic vacuum field, magnetic bottle or magnetic containment field was a type of force field that prevented antimatter from coming into contact with matter. As such, they were a critical part of warp drive systems as antimatter provided their fuel. These fields were used in antimatter pods to store antimatter, and to contain the antimatter inside a warp core. (TNG: "Disaster"; TOS: "Obsession", "The Immunity Syndrome", "That Which Survives"; TAS: "One of Our Planets Is Missing")

The magnetic containment field was produced by the magnetic constrictor coils in the core and concentrated the antimatter to the center of the reaction chamber. It was also produced by the power transfer conduits and near the antimatter pods. The field was also utilized to propel antimatter up to the reaction chamber. If the field were to collapse or fall below 15% of its maximum integrity, the starship would be destroyed. Additionally, the magnetic field was vulnerable to quantum filaments, as they charged the vessel like a live electric wire, thus weakening the field by the inherent electromagnetic field that electricity produced. Aboard the Galaxy-class USS Enterprise-D, in the Engineering Systems Database, there was a folder titled Magnetic Containment Field Degauss Protocol. This folder contained technical manuals relevant to the topic. (TNG: "Booby Trap", okudagram; TNG: "Disaster")

In 2152, after Kuroda Lor-ehn seized control of the prison transport on which Jonathan Archer and Trip Tucker found themselves, the Starfleet captain warned Kuroda that those unfamiliar with warp ships could easily push the wrong button – such as the one operating either the plasma manifolds or the antimatter containment field. If that happened, the ship could turn into "a cloud of ionized gas". (ENT: "Canamar")

On several occasions, James T. Kirk used portable magnetic vacuum field chambers to move antimatter for use as explosives. (TOS: "Obsession", "The Immunity Syndrome") On another, Scotty was able to rig a force field box to move a large chunk antimatter they acquired from the transporter to the warp core, holding the antimatter suspended in the force field apart from matter. (TAS: "One of Our Planets Is Missing")

The USS Enterprise-D was exposed to a quantum filament in 2368. This caused a polarity shift in the antimatter containment fields of its antimatter pods, decreasing their strength. The bridge crew estimated that a strength of 15% would result in sufficient breakdown to allow the antimatter to escape, destroying the ship. (TNG: "Disaster")

In 2364, a group of Bynars caused the magnetic containment field of the USS Enterprise-D to deteriorate, resulting in an evacuation of the ship. (TNG: "11001001")

Antimatter containment fields could be deliberately breached, inducing destruction of the vessel. The USS Europa carried out this action at the Battle of the Binary Stars in 2256, in order to destroy a Klingon vessel. (DIS: "Battle at the Binary Stars")

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