Development of a new NEG pump using oxygen-free Pd/Ti thin film

Non-evaporable getter (NEG) pumps are widely used in synchrotron radiation facilities because they are free of oil, evaporation, sputtering, sublimation, magnetic field, and vibration as well as economical, compact, lightweight, and energy efficient. However, conventional NEG pumps have the following drawbacks: 1) decreased pumping speed after repeated venting–activating cycles; 2) relatively high activation temperature (typically 450 °C for 10 min when ZrVFe alloy is used, and typically 180 °C for 24 h when TiZrV film is used); and 3) a dedicated power supply is required. In order to overcome these disadvantages, we developed a new NEG pump with a DN 160 conflat flange using a new NEG material, i.e., oxygen-free Pd/Ti thin film, for evacuating residual H₂ and CO. After baking at 150 °C for 12 h, the pumping speeds of the NEG pump were measured with the orifice method. Pumping speeds of 500–320, 370–260, 400–300, and 310–170 L s⁻¹ were estimated for H₂ after the first, second, third, and fourth venting–activating cycles in a pumped-quantity range of 0.01–10 Pa L. On the other hand, pumping speeds of 510–440, 590–470, and 880–690 L s⁻¹ were estimated for CO after the sixth, seventh, and eighth venting–activating cycles in a pumped-quantity range of 0.003−0.03 Pa L. After baking at 150 °C for 12 h under O₂ pressure of 1.3×10^–4 Pa, pumping speeds of 680–240 L s⁻¹ and 900–470 L s⁻¹ were estimated for H₂ and CO, respectively. The advantages of the new NEG pump are as follows: 1) it does not oxidize even after repeated venting–activating cycles; 2) it can be activated by baking at 150 °C for 12 h; 3) no dedicated power supply is required; 4) it is more economical than conventional NEG pumps because no electric feedthroughs are required; and 5) the pumping speeds can be improved by baking under O₂ pressure of 1.3×10^–4 Pa. The new NEG pumps are a suitable alternative to conventional NEG pumps or titanium sublimation pumps in SR facilities.