This report presents the design of an undulator beamline at SPring-8 to be used for soft X-ray spectroscopy focused on radioactive materials. Photoemission spectroscopy experiments are carried out in a radioisotope (RI)-controlled area where actinide compounds as well as unsealed radioactive materials are usable. Intrusion of the radioactive materials into the electron storage ring or to the outside of the evacuated beamline components can be avoided by a specially devised RI protection/ inspection mechanism. The combination of a variably polarizing undulator and a varied-line-spacing plane-grating monochromator provides linearly or circularly polarized soft X-rays with a high resolving power in the energy range 0.28-1.5 keV. The beamline will become operational in December 1997.

Background: Fluorine is a key element for nucleosynthetic studies since it is extremely sensitive

We report measurements on high-T c YBa 2 Cu 3 O 7Ϫy ͑YBCO͒ Josephson ramp-edge junctions with different ab-plane orientation electrodes relatively rotated by 45°. The ramp-edge junctions with different crystal angles against the interface boundary are fabricated on an MgO͑100͒ substrate using a CeO 2 seed-layer technique. The Shapiro steps under microwave irradiation of 9 GHz appear qualitatively different for different crystal angles, which supports the d-wave nature of a YBCO superconductor. The magnetic-field dependence of the Josephson maximum current shows a Fraunhofer-like pattern, which is consistent with the calculated result for the d-wave junctions. The temperature dependencies of the maximum Josephson current for different angle geometry fall off rapidly with increasing temperature and deviate much from the conventional s-wave Ambegaokar-Baratoff prediction. The results are in good qualitative agreement with the calculated results based on the d-wave pairing symmetry taking the presence of the zero energy state into account. The observed angle dependencies clearly indicate that the angle-dependent Josephson current really exists.

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