A workpiece support has a vessel having a top interior wall and a bottom interior wall. An interior cavity is defined between the top interior wall and bottom interior wall, wherein a support surface configured to support a workpiece. A plate is positioned within the interior cavity, dividing the interior cavity into a top cavity and a bottom cavity. The top and bottom cavities are fluidly coupled about a periphery of the plate. A first taper defined in one or more of the top interior wall and a top portion of the plate provides a substantially constant volume across a radial cross-section of the top cavity. A second taper defined in one or more of the bottom interior wall and a bottom portion of the plate provides a substantially constant volume across a radial cross-section of the bottom cavity. First and second ports fluidly couple the top and bottom cavities to respective first and second fluid channels.