Host: The Japan Society of Vacuum and Surface Science
Name : Annual Meeting of the Japan Society of Vacuum and Surface Science 2023
Location : [in Japanese]
Date : October 31, 2023 - November 02, 2023
Many of the vacuum components in accelerator-based synchrotron light sources are exposed to synchrotron radiation (SR) during operation. Hence, reducing photon-stimulated desorption (PSD) from these components could effectively shorten the commissioning time and contribute to the stable operation of the light source. One approach to limiting the desorption of gases is to cover the surfaces of these components with low-PSD materials. TiZrV alloy is a well-known non-evaporable getter (NEG) coating material and also exhibit lower PSD yields compared with Cu, Al. In a previous study, we newly found that Pd/TiZrV (Pd covered TiZrV) films further reduce the PSD yields compared to the TiZrV films. This finding indicated the possibility of applying Pd as low PSD materials. Another advantage of Pd is low resistivity of 10.9 μW・cm which is much lower than that of Ti, Zr and V metal. In the present study, dense Pd films were prepared on the inner wall of the Cu duct using magnetron sputtering. The PSD analysis and resistivity measurement were carried out. The effects of the photon dose on the desorption yields obtained from the Pd and TiZrV films are summarized in Figs. 5 (a) and (b). Compared with the TiZrV film, the Pd film showed significantly lower initial yields: factor 1/10 for H2, 1/3 for CH4 and CO, 1/5 for CO2. In all cases, the PSD yields gradually decreased over time. After a photon dose of 5 x 1022 photons/m, the yields of CH4, CO and CO2 generated by the Pd were still lower than those of the TiZrV. Following irradiation with a photon dose of 5 x 1022 photons/m, the Pd-coated tube was exposed to air then evacuated and heated, after which the PSD yield was measured. The initial H2, CO and CO2 yields from this trial were similar to the final PSD yields shown in Fig. 1. It was indicated that the air exposure had little effect on the PSD values. Resistivity data were acquired at ambient temperature using the standard four-probe technique with the applied current parallel to the film surface. The resistivities of the Pd films fabricated under Kr pressures of 0.9 and 0.4 Pa were determined to be 30 and 18 μW・cm, respectively. The latter value was approximately one order of magnitude lower than that of a TiZrV film (175 μW・cm).
