An internal target should be so thin that it doesn't
affect the beam significantly, on the other hand it should
be thick enough to reach a reasonable number of the
These requirements can be fulfilled with a cluster target
where cooled gas (e.g. hydrogen) is pressed through a
Inside the nozzle the gas is cooled by the expansion and
molecules freeze together forming clusters.
Using skimmers free gas molecules are peeled off the
So the rest gas pressure in the target chamber is very low
(the COSY beam isn't affected), only in the beam-target
interaction region the target density is high enough.
After traversing the target chamber the clusters warm
up and are pumped away.
of the cluster target just before installation
about the cluster target including some instructive
thesis of C.Quentmeier, University of Münster (german)
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Last updated: 15-December-1997 by