Advanced Photon Source (APS) Beamline

PCCM, through Princeton University, is a member of the Complex Materials Consortium Collaborative Access Team (CMC-CAT), which operates a pair of sophisticated x-ray beamlines at the Advanced Photon Source (APS), at Argonne National Laboratory outside of Chicago. Both are insertion device beamlines, running off an APS Undulator A, to provide an exceptionally brilliant x-ray source. Diamond crystal monochromators are used to run two beamlines (ID9B and ID9A) from a single undulator.

An example of research made possible by the CMC-CAT beamlines are the element-specific X-ray resonant experiments underway by IRG1 investigators to probe the behavior of the magnetic electrons in pyrochlores. By tuning to an absorption edge, say the Mo L-edge, one may contrast the behavior of electrons in the Mo orbitals with those on the localized Ln 4f moments. Such measurements are particularly useful in clarifying the oxidation state and local symmetry of the magnetic ion, and the origin and magnitude of the spin polarization in the semiconductor bands. These studies will be complemented by X-ray resonant magnetic scattering studies of the magnetic correlation length. These challenging experiments require a state-of-the-art synchrotron beamline, because of the very low count rates estimated (a few per second), and the need for polarization analysis.