  A new radial time projection chamber based on Gas Electron Multiplier
amplification layers was developed for the BONuS12 experiment in Hall B at
Jefferson Lab. This device represents a significant evolutionary development
over similar devices constructed for previous experiments, including
cylindrical amplification layers constructed from single continuous GEM foils
with less than 1\% dead area. Particular attention had been paid to producing
excellent geometric uniformity of all electrodes, including the very thin
metalized polyester film of the cylindrical cathode. This manuscript describes
the design, construction, and performance of this new detector.
