HIGH-ENERGY SYNCHROTRON-RADIATION - A NEW PROBE FOR CONDENSED MATTER RESEARCH

The absorption of 150 keV synchrotron radiation in matter is weak and, as normally done with neutrons, bulk properties are studied in large samples. However, the k-space resolution obtained with a Triple Crysta l Diffractometer (TCD) for high energy synchrotron radiation is about one order of magnitude better than in high resolution neutron diffract ion. The technique has been applied to measure the structure factor S( Q) of amorphous solids up to momentum transfers of the order of 32 Ang strom(-1), to study the intermediate range Ortho-II ordering in large, high quality YBa2Cu3O6.5 single crystals and for investigations of th e defect scattering from annealed Czochralski grown silicon crystals. Magnetic superlattice reflections have been measured in MnF2 demonstra ting the potential of the technique for high resolution studies of gro und state bulk antiferromagnetism. Recently the question of two length scales in the critical scattering at the 100 K phase transition in Sr TiO3 was studied. At the PETRA storage ring, which serves as an accumu lator for the HERA electron-proton-ring at DESY and which can be opera ted up to electron energies of 12 GeV, an undulator beam line is curre ntly under construction and should be available in summer 1995. It ope ns up exciting new research opportunities for photon energies from abo ut 20 to 150 keV.