[en] This paper describes experimental results and operating experiences with an apparatus to produce a jet of Cs as a charge-exchange target for the formation of negative hydrogen ions. The nozzle throat was slit 2 x 60 mm², and the nominal exit Mach number M = 5 was obtained with a 50 mm long wedge-like supersonic section. Compared to the sonic slit nozzle used in other alkali jet target systems, the supersonic section reduces the circulating cesium by a factor of 3 for the same line density and flow divergence. Cs loss through the target aperture openings is monitored with a surface ionization detector located 41 cm away from the jet axis. The measurements of the spatial distribution of the Cs loss and its time-dependence when turning the Cs jet on and off show that the observed Cs is mostly coming from Cs scattered and/or evaporated from surfaces seen by the Cs jet. The intensity depends on temperature and surface condition of the inner walls of the jet-target assembly, but changes little with jet intensity. The lowest flux measured with the detector in the central position was 4.10¹² atoms cm^-2s^-1, compared with 1,2.10¹⁹ in the jettarget