MechanismEditA.T. Fields are normally invisible barriers but become visible to the naked eye when colliding with other things. They are mainly used as an almost impenetrable shield; only the most powerful weapons are capable of breaching an A.T. Field. and even then, damage to the Angel is generally minimal. Through most of the series, the only thing that can reliably penetrate an A.T. Field is another A.T. Field, as seen in Episode 02 when the Evangelion Unit-01 "corrodes" Sachiel's A.T. Field.
The Lance of Longinus, an ancient, extraterrestrial weapon, as well as its duplicates, is able to penetrate any A.T. Field, no matter how strong it is.
Some Angels are sophisticated enough to use A.T. Fields as a method of attack or movement. Sachiel, Israfel and Bardiel can be seen making jumps assisted by their A.T. Fields, while Sahaquiel and Zeruel use theirs to attack, with Sahaquiel using it to destroy satellites and Zeruel in the Rebuild to shove attackers away.
It is revealed later in the series that every living thing possesses an A.T. Field: Angels and Evangelions just have A.T. Fields so strong that they are easily detectable and can even stop physical attacks.
The A.T. Fields appear usually as octagonal or hexagonal fields. They are often orange, though pastel purple and red ones have also been used. Rather than traditional force-fields, A.T. Fields appear to behave more like membranes and twist and tear as such when they are penetrated.
Rebuild of EvangelionEdit
In the Rebuilds, the A.T. Fields present all of the same properties so far, and are once again used as weapons by the Evas.
In the same battle with Zeruel, Unit-01 creates an artificial arm with its A.T. Field, and uses it as a weapon, taking the form of a ring of geometric shapes which blast the Angel back.