The outgassing rate of a small test chamber made of type 304 stainless steel has been measured as a function of pumping speed in the range from 0.3 to 200 ℓ/s. The chamber was first exposed to air and then pumped with different pumping speeds for three days at 20 °C without baking. Typical outgassing rates of the chamber are determined from the measurement of steady pressures at the pumping time of 72 h. It is found, as a result, that measured outgassing rates q obey a set of power laws of and , where S/A is the ratio of pumping speed S to the surface area A of the chamber, C1 and C2 are constants, the exponents m1 and m2 are 0.8282 for S/A⩾10−3 ℓ/s cm2 and 0.4655 for S/A⩽10−3 ℓ/s cm−2. It is shown that the observed power law can be derived from theoretical consideration and is useful to estimate the ultimate pressure of an unbaked vacuum system.
Experimental study on the scaling law of the outgassing rate with a pumping parameter
K. Akaishi, Y. Kubota, O. Motojima, M. Nakasuga, Y. Funato, M. Mushiaki; Experimental study on the scaling law of the outgassing rate with a pumping parameter. J. Vac. Sci. Technol. A 1 March 1997; 15 (2): 258–264. https://doi.org/10.1116/1.580522
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