First experiments with a 100 period superconductive undulator with a   period length of 3.8 mm
  A prototype of a novel superconductive undulator with a period length of 3.8 mm is described. The undulator is 100 periods long. In the first tests described in this paper the undulator was cooled in a helium bath and it was shown that it can be operated as expected with a maximum current of 1400 A. Afterwards the undulator field was measured with a miniature Hall probe with an active area of (100x100)x10^-6 m^2. Calculated and measured field distributions are in good agreement. A cryostat for a beam test at Mainz microtron MAMI was built in which liquid helium cools indirectly the in-vacuum undulator. At the moment the cryostat is tested and optimized. 
M. Fritz, T. Hezel, M. Homscheidt, H.O. Moser, R. Rossmanith, Th.   Schneider, H. Backe, S. Dambach, F. Hagenbuck, K.-H. Kai...