development of a cryogenic target system with optimal access to reaction detectors

a liquid hydrogen / deuterium target is used at cosy of the F Z-Juelich in the external experiments TOF, GEM and MOMO . the combination of 1mm diameter beam from COSY with the small target provides the necessary very well defined interaction vertex within few mm3. the target liquid is made on a cooled condenser and guided through a central tube assisted by gravitation into the target cell. there the liquid is kept below boiling temperature by evaporation cooling . the vapor rises up to the condenser through a very well isolated concentric center tube. this circulation provides a stable dynamic equilibrium .the target container should have as small as possible material between the reaction volume and the detectors in order to minimize secondary interactions of reaction products. in order to reduce unnecessary material , a very thin target cell is fabricated by galvanization technique