Commissioning of OPHeLIE: The new electromagnetic crossed overlapped undulator at Super-ACO

OPHeLIE, the first electromagnetic Onuki-type undulator has been installed on the 0.8 GeV storage ring Super-ACO in February 1998. It consists in two identical 9-period crossed overlapped undulators whose magnetic fields (up to 0.12 T) are produced by conventional electromagnets. This insertion device is able to produce any kind of polarization in the VUV range with a potential polarization switching rate of 1 Hz. Measurements of focusing and closed orbit distortion show a very good agreement with magnetic measurements. A compensation scheme has been developed in order to make the operation of the insertion device as user-friendly as possible. First results obtained on photon beam are very promising. Photon energy calibration, flux optimization and polarization measurements are in progress.