100 keV) of neutral hydrogen 7 atoms . The design of the cesium jettarget intended to achieve the 7 following goals : - Supersonic nozzle - cooled skimmer system to increase the fraction 8 of the total nozzle flux Jn which is used as the jettarget flux Jt, 8 = Jt/Jn, from low values 8 < 10 % re- ported for sonic nozzles4 to at least 50 %.