To meet a small but growing demand for low global-warming potential refrigeration technologies, a thermoacoustic-Stirling refrigerator has been developed that uses helium as the working gas. Using a new multi-stage topology [Backhaus and Keolian, “In-line stirling energy system,” US patent 7,908,856 B2 (2011)], Trillium employs a collinear stack of three linear motors driven by voltage signals phased 120 degrees apart from one another. Above each motor is a thermal core that is comprised of a pair of novel aluminum microchannel heat exchangers on either side of a rolled Kapton® regenerator. The heat exchangers have an equivalent pore size of about a thermal boundary layer thicknesses that allows high effectiveness. The linear motors drive an acoustic wave that travels along the length of the machine. Taken in isolation, each thermal core and the motor-driven piston above and below (sealed using novel plastic flexure seals) forms a single alpha-Stirling machine; taken together Trillium is three Stirling machines working together with, in principle, zero vibration due to a stationary center-of-mass as a result of the motor phasing. The talk will explain the design and present performance measurements. [Work generously sponsored the Advanced Research Project Agency—Energy (ARPA-E) under their BEETIT program.]