Synchrotron radiation instrumentation collaborative access team SRI-CAT sector 4

The research objective for this sector of the Advanced Photon Source (APS) is the development of sources and applications of polarized x-rays covering the energy range from 0.5 to 50 keV. Both linearly and circularly polarized x-rays have been very successfully applied to the study of magnetic properties of materials. However, the applications have been limited due primarily to the lack of energy-tunable, high-brilliance x-ray beams with adjustable polarization properties. It is the authors` intention that this sector will to some extent ameliorate that situation. They are confident that optics can be fabricated to simultaneously provide a high-quality beam with adjustable polarization in the energy range above 5 keV using the standard undulator A as a source. That is not the case below 5 keV, and hence they are planning to develop and install a helical undulator that can generate beams of variable (linear or circular) polarization in this lower energy range. Magnetic circular dichroism, resonant and non-resonant magnetic x-ray scattering, and other polarization-dependent phenomena will be investigated using hard x-rays. Techniques similar to those described for the hard x-rays plus spatially resolved, spin-polarized photoemission studies will be developed and used with the intermediate energy x-rays. They have incorporated some features not directly related to polarization studies, which were not available elsewhere on SRI-CAT beamlines. One of those features is a large vacuum tank immediately downstream of the ratchet wall into which high heat load beamline components can be installed and tested. A second feature is a mirror capable of focusing the white beam for high heat flux optical-component development and other uses. The insertion-device development, polarization programs, and beamline component testing all fall well within the existing scope of the SRI CAT programs