In some embodiments, substrate processing apparatus may include a chamber body; a lid disposed atop the chamber body; a target assembly coupled to the lid, the target assembly including a target of material to be deposited on a substrate; an annular dark space shield having an inner wall disposed about an outer edge of the target; a seal ring disposed adjacent to an outer edge of the dark space shield; and a support member coupled to the lid proximate an outer end of the support member and extending radially inward such that the support member supports the seal ring and the annular dark space shield, wherein the support member provides sufficient compression when coupled to the lid such that a seal is formed between the support member and the seal ring and the seal ring and the target assembly.