39. Vacuum chamber survey: Anon,Instruments and Control Systems, 38 (10), Oct 1965, 102–106

Abstract

The effect of neon glow discharge cleaning (GDC) on the reduction of water outgassing and the production of ultrahigh vacuum was studied using a 304 stainless steel chamber. Two pumping systems having different effective pumping speeds of 10 l s-1 and 182 l s-1 were used. By switching these pumping systems after GDC, the effect of GDC on the reduction of outgassing was investigated. The ion dose on the wall surface in a 2 h GDC trial at a neon gas pressure of 2 Pa was 1.25×1018 ions cm-2. During pump-down, where the pressure decrease is inversely proportional to time, the degassing effect of GDC was not so large compared to that in pump-down of the chamber at a higher pumping speed without the assistance of GDC. However, GDC in which the pressure reaches a limit after a long pump-down was very effective in reducing the pressure limit. When a cryopump that has an effective pumping speed of 274 l s-1 was used, a very low pressure of the order of 5×10-8 Pa was attained by GDC. Experimental results are discussed from the point of view of coverage reduction of adsorbed molecules on the wall surface and also using a theoretical model.