A gas-jet target for cluster fragmentation experiments has been studied in the inlet pressure range of 0.1-5.5 Torr corresponding to a target thickness range of 10 1 3 -1.2 x 10 1 5 at. cm - 2 . The total flow has been found to be in quantitative agreement with the Poiseuille formula in the pressure range of 1.0-5.5 Torr. The profile of the jet is in good agreement with the (cos φ) 5 2 law expected in the viscous flow regime in the inlet pressure (P 0 ) range of 0.1-5.5 Torr. From cross section measurements using the inlet pressure range of 1.5-5.5 Torr, the target thickness has been found to be proportional to P 0 2 as expected. The target thickness characterization has been extended in the range 10 1 3 to 10 1 4 at. cm - 2 from measurements with cluster beams.