Windowless gas target by the gas dynamic focusing of a supersonic neutral gas flow

A description is given of a target system which permits high target densities in a well-defined cylinder with a diameter of one to two millimeters with a simultaneous reduction in the secondary gas yield. The gas expands in a conical space in which a static pressure is present which is exceeded by several magnitudes by the inlet pressure of the nozzle. The supersonic beam exits this space required for the formation of the focused flow through an opening in the cone tip and is removed by pumping. The compression node can be positioned directly in the reaction plane by varying the distance of the Laval nozzle opening to the opening of the hollow cone. For the operation of a windowless gas target, a three-step differential pump system was installed concentrically around the gas beam. The most important characteristics of the system are briefly summarized