  The JENSA gas-jet target was designed for experiments with radioactive beams
provided by the rare isotope re-accelerator ReA3 at the National
Superconducting Cyclotron Laboratory. The gas jet will be the main target for
the Separator for Capture Reactions SECAR at the Facility for Rare Isotope
Beams on the campus of Michigan State University, USA. In this work, we
describe the advantages of a gas-jet target, detail the current recirculating
gas system, and report recent measurements of helium jet thicknesses of up to
about $10^{19}$ atoms/cm$^2$. Finally a comparison with other supersonic
gas-jet targets is presented.
