Oxygen-free Pd/Ti deposition applied for the first mirror test chamber of a new soft X-ray beamline BL-11 in Photon Factory

Abstract Soft X-ray beamlines require a hydrocarbon-free ultrahigh vacuum (UHV) to prevent carbon contamination of the optical elements. In addition, dry pumps and turbomolecular pumps (TMPs) should be stopped during user operation to suppress vibration of the optical elements. For these reasons, the UHV of soft X-ray beamlines is usually maintained by sputter ion pumps and non-evaporable getter (NEG) pumps. However, conventional sputter ion pumps and NEG pumps scarcely pump hydrocarbons. Recently, we developed oxygen-free Pd/Ti as a new NEG that can reduce hydrocarbons in UHV. During baking oxygen-free Pd/Ti oxidize residual hydrocarbons through the catalytic action of Pd forming CO and CO 2 those can be easily pumped by TMP. Furthermore, oxygen-free Pd/Ti works as an excellent NEG with an activation temperature of 75–150 °C for residual H 2 and CO. We applied oxygen-free Pd/Ti deposition for the first mirror (M1) test chamber of a new soft X-ray beamline BL-11 in the Photon Factory 2.5 GeV ring (Tsukuba, Japan). Then the mirror and mirror holder system was installed in the M1 test chamber. After pumping and baking at 90–110 °C for 52 hours, the pressure in the M1 test chamber reached 6.0 × 10 – 8 Pa. When the M1 test chamber was isolated from TMP the pressure was maintained at ca. 5 × 10 –7 Pa. These results suggest that the oxygen-free Pd/Ti deposited film is activated by baking and works as NEG. After white synchrotron radiation irradiation slight carbon contamination on the mirror was observed. When oxygen is introduced the carbon contamination was removed to some extent.