Abstract: A trigger apparatus and method for striking an electrical arc at the surface of a coating source material within a vapor deposition chamber is disclosed. A plunger member is mounted for axial movement in a housing configured for attachment to an inlet port of a deposition chamber. The plunger has one end adapted to carry an arc-initiating wire contact. A pneumatic drive cylinder axially reciprocates the plunger member with positive force strokes in both directions such that the wire contact alternately engages and disengages the surface of the cathode source material. Seal means are provided for maintaining a vacuum seal of the deposition chamber through the trigger apparatus. Dynamic shield means are mounted adjacent the inlet port for protecting the seal members from being coated by vapor particles within the deposition chamber. Alignment means cooperatively engage the plunger member for maintaining a positive angular position of the plunger member during reciprocal motion thereof.