  A new Radial Time Projection Chamber (RTPC) was developed at the Jefferson
Laboratory to track low-energy nuclear recoils for the purpose of measuring
exclusive nuclear reactions, such as coherent Deeply Virtual Compton Scattering
and coherent meson production off $^4$He. In such processes, the $^4$He nucleus
remains intact in the final state, however the CEBAF Large Acceptance
Spectrometer (CLAS) cannot track the low energy $\alpha$ particles. In 2009, we
carried out measurements using the CLAS spectrometer supplemented by the RTPC
positioned directly around a gaseous $^4$He target, allowing a detection
threshold as low as 12$\sim$MeV for $^4$He. This article discusses the design,
principle of operation, calibration methods and the performances of this RTPC.
