An ion implantation system, comprising: an ion source configured to generate an ion beam having a plurality of ions that propagate along a beam line; a mass analyzer configured to generate a magnetic field that bends a trajectory of each of the ions within the ion beam such that ions having a first mass to charge ratio are bent more than ions having a second mass to charge ratio, wherein the second mass to charge ratio is different from the first mass to charge ratio, wherein the trajectory of each of the ions lies in a corresponding plane; a mass resolving aperture MRA, wherein the MRA has an opening; wherein the MRA is positioned such that a first portion of the ions in the ion beam as the ion beam approaches the MRA pass through the opening and are in the ion beam after the ion beam exits the MRA and the MRA alters a motion of a second portion of the ions in the ion beam as the ion beam approaches the MRA such that the second portion of the ions are not in the ion beam after the ion beam exits the MRA, characterized in that at least a portion of an edge of the opening incorporates a fin, wherein the fin has a front surface and a rear surface, wherein a normal to the front surface has a component facing the ion beam as the ion beam approaches the MRA and a normal to the rear surface has a component facing the ion beam as the ion beam exits the MRA, wherein the fin has a leading portion on the front surface closest to the oncoming ion beam that has a normal that is parallel to the direction of the beam path, wherein the front surface curves away from the leading portion in a direction away from the opening to form an outer convex section of the front surface adjacent the leading portion and an outer concave section of the front surface adjacent the outer convex section of the front surface, or wherein the front surface curves away from the leading portion in a direction away from the opening to form an outer concave section of the front surface adjacent the leading portion. an ion source configured to generate an ion beam having a plurality of ions that propagate along a beam line; a mass analyzer configured to generate a magnetic field that bends a trajectory of each of the ions within the ion beam such that ions having a first mass to charge ratio are bent more than ions having a second mass to charge ratio, wherein the second mass to charge ratio is different from the first mass to charge ratio, wherein the trajectory of each of the ions lies in a corresponding plane; a mass resolving aperture MRA, wherein the MRA has an opening; wherein the MRA is positioned such that a first portion of the ions in the ion beam as the ion beam approaches the MRA pass through the opening and are in the ion beam after the ion beam exits the MRA and the MRA alters a motion of a second portion of the ions in the ion beam as the ion beam approaches the MRA such that the second portion of the ions are not in the ion beam after the ion beam exits the MRA, characterized in that at least a portion of an edge of the opening incorporates a fin, wherein the fin has a front surface and a rear surface, wherein a normal to the front surface has a component facing the ion beam as the ion beam approaches the MRA and a normal to the rear surface has a component facing the ion beam as the ion beam exits the MRA, wherein the fin has a leading portion on the front surface closest to the oncoming ion beam that has a normal that is parallel to the direction of the beam path, wherein the front surface curves away from the leading portion in a direction away from the opening to form an outer convex section of the front surface adjacent the leading portion and an outer concave section of the front surface adjacent the outer convex section of the front surface, or wherein the front surface curves away from the leading portion in a direction away from the opening to form an outer concave section of the front surface adjacent the leading portion.