Improvement of Pumping Characteristics of Oxygen-Free Palladium/Titanium Non-Evaporable Getter (NEG) Coating Based on Removal of Carbon Contamination

Abstract

Non-evaporable getter (NEG) coating is widely used in accelerators for maintaining ultrahigh vacuum. We developed a new oxygen-free Pd/Ti NEG coating, whose pumping speed does not decline even after repeated vent-activation cycles with an activation temperature of about 150°C. However, it is known that the pumping speed is suppressed when carbon contaminants cover the Pd film surface. Here, we report that carbon contamination can be removed by baking under O₂ pressure 1.3×10^-4 Pa, and the pumping speed can be improved several times.