NSLS-II Seminar

In synchrotron radiation sources, Planar Polarized Undulators (PPUs) and Elliptically Polarized Undulators (EPUs) produce high energy photon beams with controlled polarization.
As far as PPUs are concerned, In Vacuum Undulator is the existing technology to build small period high field undulator. In such devices, Neodymium-Iron-Boron (NdFeB) or Samarium Cobalt (SmCo) permanent magnets maintained at ambient temperature are enclosed in the vacuum where the multi GeV electron beam is stored. IVU requires the use of magnets with high resistance against demagnetization. This constraint limits the use of magnets with a remanence below 1.3T. In particular NdFeB magnets with remanence higher than 1.4T cannot be used. However below 150K these magnets have similar resistance to SmCo magnet. Thus since 2004, several Cryogenic Permanent Magnet Undulators (CPMU) are under development in radiation sources. A first CPMU was installed in the storage ring at the ESRF in 2008. Two other CPMU are under development at the ESRF and SOLEIL, there are planned to be installed in 2010. Specificities relevant to such devices such as the operation temperature, the impact of thermal gradient will be presented. In-vacuum magnetic measurement bench developed at the ESRF and SOLEIL are discussed.
Among EPUs, Advanced Planar Polarized Light Emitter-II (APPLE-II) is the device which produces the strongest helical field. APPLE-II consists in two planar undulators side by side; the adjustable shift between girders sets the polarization. At SOLEIL, 9 APPLE-II with period ranging from 80 mm down to 44 mm have been successfully assembled and installed in the storage ring. An APPLE-II with 36 mm period and 0.8 T peak field is under development. At such low period and high field, magnetic force introduces mechanical deformation leading finally to systematic error in the undulator field. The investigations done to point out the deformation are presented. Solutions to minimize systematic errors are dis