A magnet bar assembly for a rotary target cathode, the magnet bar assembly comprising: a support structure; a magnet bar structure movably attached to the support structure, the magnet bar structure including a plurality of magnets; and a positioning mechanism operatively coupled to the support structure and the magnet bar structure, the positioning mechanism configured to move the magnet bar structure between a retracted position and a deployed position, the positioning mechanism comprising a bladder assembly coupled to the support structure and the magnet bar structure, wherein the bladder assembly comprises: a retraction bladder positioned on a side of the support structure opposite from the magnet bar structure; and a magnet bar actuation plate located to sandwich the retraction bladder between the magnet bar actuation plate and the support structure, the magnet bar actuation plate coupled to the magnet bar structure by a plurality of bolts that pass through the support structure; wherein the positioning mechanism is configured such that, when the magnet bar assembly is inserted into a target cylinder or removed from a target cylinder, the magnet bar structure is in the retracted position, which substantially reduces a magnetic force between the magnets and a magnetic target material of the target cylinder; and wherein the positioning mechanism is configured such that, when the magnet bar assembly is in the target cylinder, the magnet bar structure is in the deployed position, which substantially increases the magnetic force between the magnets and the magnetic target material, and which allows a magnetic field from the magnet bar structure to penetrate through the magnetic target material. a support structure; a magnet bar structure movably attached to the support structure, the magnet bar structure including a plurality of magnets; and a positioning mechanism operatively coupled to the support structure and the magnet bar structure, the positioning mechanism configured to move the magnet bar structure between a retracted position and a deployed position, the positioning mechanism comprising a bladder assembly coupled to the support structure and the magnet bar structure, wherein the bladder assembly comprises: a retraction bladder positioned on a side of the support structure opposite from the magnet bar structure; and a magnet bar actuation plate located to sandwich the retraction bladder between the magnet bar actuation plate and the support structure, the magnet bar actuation plate coupled to the magnet bar structure by a plurality of bolts that pass through the support structure; wherein the positioning mechanism is configured such that, when the magnet bar assembly is inserted into a target cylinder or removed from a target cylinder, the magnet bar structure is in the retracted position, which substantially reduces a magnetic force between the magnets and a magnetic target material of the target cylinder; and wherein the positioning mechanism is configured such that, when the magnet bar assembly is in the target cylinder, the magnet bar structure is in the deployed position, which substantially increases the magnetic force between the magnets and the magnetic target material, and which allows a magnetic field from the magnet bar structure to penetrate through the magnetic target material. a retraction bladder positioned on a side of the support structure opposite from the magnet bar structure; and a magnet bar actuation plate located to sandwich the retraction bladder between the magnet bar actuation plate and the support structure, the magnet bar actuation plate coupled to the magnet bar structure by a plurality of bolts that pass through the support structure; wherein the positioning mechanism is configured such that, when the magnet bar assembly is inserted into a target cylinder or removed from a target cylinder, the magnet bar structure is in the retracted position, which substantially reduces a magnetic force between the magnets and a magnetic target material of the target cylinder; and wherein the positioning mechanism is configured such that, when the magnet bar assembly is in the target cylinder, the magnet bar structure is in the deployed position, which substantially increases the magnetic force between the magnets and the magnetic target material, and which allows a magnetic field from the magnet bar structure to penetrate through the magnetic target material.