A dual magnetron particularly useful for RF plasma sputtering includes a radially stationary open-loop magnetron comprising opposed magnetic poles and rotating about a central axis to scan an outer region of a sputter target and a radially movable open-loop magnetron comprising opposed magnetic poles and rotating together with the stationary magnetron. During processing, the movable magnetron is radially positioned in the outer region with an open end abutting an open end of the stationary magnetron to form a single open-loop magnetron. During cleaning, part of the movable magnetron is moved radially inwardly to scan and clean an inner region of the target not scanned by the stationary magnetron. The movable magnetron can be mounted on an arm pivoting about an axis at periphery of a rotating disk-shaped plate mounting the stationary magnetron so the arm centrifugally moves between radial positions dependent upon the rotation rate or direction.