Vacuum Property of Aluminum Alloy Chamber Treated with Electropolishing and Machining in Dry Atmosphere

Two aluminum alloy chambers designed to hold the magnets and electrodes of a pulse beam stretcher were manufactured. The inner surface of one chamber was treated with electropolishing. The inner surface of the other chamber was treated with machining in a dry atmosphere. The electropolished chamber contained hydrate at the surface and showed a high outgassing rate of 1×10-9 Pa·m3/ (s·m2) after a 150°C, 24-hour bakeout. The chamber machined in the dry atmospher contained less hydrate at the surface than the electropolished chamber did and showed a low outgassing rate of 1.5×10-10 Pa·m3/ (s·m2) after a 150°C, 24-hour bakeout.