Construction of APPLE II and in vacuum undulators at ESRF

Three helical undulators of type APPLE II have been completed and installed in the ESRF storage ring. Their interaction with the stored beam is the result of the usual residual field errors and a predictable horizontal/vertical tune shift which depends on gap and phase. The measured closed orbit distortions and tune shift induced by the ESRF Apple II undulators are presented. The observed tune shift vs. phase is very consistent with expectations. A new shimming technique has been successfully implemented which reduces the tune shift vs. phase. A noticeable improvement of the ESRF performances can be achieved with the use of in-vacuum undulators. Four 2 m long devices are being fabricated. They have been designed to provide enhanced photon fluxes in the range of 10 to 20 keV (period 17 mm, 18 mm) or at a photon energy above 30 keV (period 21 mm, 23 mm). The first results of the field measurements are presented.