A method for forming a tube-based detector for signaling when a PVD target is reduced to a predetermined quantity of the PVD target material includes providing a mold member having an inner molding member and an outer molding member defining a space therebetween, melting a desired tube material, injecting the molten tube material into the space between the inner molding member and the outer molding member, cooling the molten tube material, removing the tube from the mold member after the molten tube material has cooled and solidified into a tube, embedding the tube in the physical vapor deposition target, wherein the tube forms an enclosure of the tube-based detector.