Reduction of water outgassing and UHV production in an unbaked vacuum chamber by neon gas discharge

✍ Scribed by K. Akaishi; K. Ezaki; Y. Kubota; O. Motojima

• Publisher: Elsevier Science
• Year: 1999
• Tongue: English
• Weight: 210 KB
• Volume: 53
• Category: Article
• ISSN: 0042-207X
• DOI: 10.1016/s0042-207x(98)00376-5

✦ Synopsis

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\ and 182 l s\ 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;10 ions cm. 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\ was used, a very low pressure of the order of 5;10\ 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.