The Münster cluster-jet target for the future P̅ANDA experiment

For high precision storage ring experiments as the future P̅ANDA experiment, very sophisticated internal targets have to be used. For this purpose, a state-of-the-art cluster-jet target was developed at the University Münster. Basically, hydrogen is cooled to cryogenic temperatures and pressed through a specially shaped Laval nozzle to form a cluster-jet expanding into vacuum. Due to the stability and large mass of the clusters, a practically undisturbed flight path in vacuum of above 5 m is possible, leading to manifold possible applications, including the interaction with a storage ring beam at a distance of 2.25 m as desired for the P̅ANDA experiment. With a first prototype target, the “proof-of-principle” was delivered, and after first improvements the world record in target thickness in such large distance to the nozzle was measured. Based on this work, the final P̅ANDA cluster-jet target was developed and built up, and is presented in this article.