An extraction assembly may include an extraction plate for placement along a side of a plasma chamber, and having an extraction aperture, elongated along a first direction, and having an aperture height, extending along a second direction, perpendicular to the first direction. The extraction plate defines an inner surface along the extraction aperture, lying in a first plane. A beam blocker is disposed over the extraction aperture, and has an outer surface, disposed in a second plane, different than the first plane. As such, the beam blocker overlaps with the extraction plate along a first edge of the extraction aperture by a first overlap distance, and overlaps with the extraction plate along a second edge of the extraction aperture by a second overlap distance, so as to define a first extraction slit, along the first edge, and a second extraction slit along the second edge.