  During the last years several attempts were undertaken to decrease the period
length of undulators to the mm range. In this paper, a novel type of an
in-vacuum undulator is described which is built with superconductive wires. The
period length of this special device is 3.8 mm. In principle, it is possible to
decrease this period length even further. A 100 period long undulator has been
built and will be tested with beam in the near future.
