An adapter for a deposition chamber includes an adapter body extending longitudinally about a central axis between an upper side and lower side opposite the upper side. The adapter body has a central opening about the central axis. The adapter body has a radially outer portion having a connection surface on the lower side and a radially inner portion having a coolant channel and a stepped surface on the lower side. At least a portion of the coolant channel is spaced radially inwardly from a radially inner end of the connection surface. At least the portion of the coolant channel is disposed longitudinally below the connection surface between the connection surface and the stepped surface.