The XeNA polarizer. (a) of the polarizer’s key components (the self-pressurized liquid N2 dewar that provides gas for heating and cooling of the oven and N2 gas cylinder used to operate pneumatic valves are not shown) (40). The optical path is represented by (“λ/4”) and is comprised of beam expanding optics, polarizing beam-splitter cube, quarter-wave plate, and heat sinks (see Fig. 2). For the gas cylinders, “N” and “E” designate xenon with naturally-abundant 129Xe and isotopically-enriched 129Xe, respectively (40). (b) Photograph of XeNA with open laser enclosure in its current location in a clinical MRI suite at Brigham and Womens’ Hospital, Boston, MA, USA.