【国外标准】 Standard Practice for Determining Vacuum Chamber Gaseous Environment Using a Cold Finger

5.1 When applied in the case in which there is no test item in the vacuum chamber (such as during bake-out operations), this procedure may be used to evaluate the performance of the vacuum chamber in relation to other data from the same or other chambers given that critical parameters (for example, length of exposure, temperature of the chamber and cold finger, anisotropy, and so forth) can be related.5.2 The procedure can be used to evaluate the effects of materials found in the residue on items placed in the vacuum chamber.5.3 The procedure can be used to describe the effect of a prior test on the residual gases within a vacuum chamber.5.4 By selecting the time at which the coolant is introduced into the cold finger, the environment present during a selected portion of a test can be characterized. This can be used to determine the relative efficacy of certain vacuum chamber procedures such as bake-out.5.5 The procedure may be used to define the outgassed products of a test item that condense on the cold finger.5.6 The procedure may be used in defining the relative cleanliness of a vacuum chamber.5.7 In applying the results of the procedure to the vacuum chamber in general, consideration must be given to the anisotropy of the molecular fluxes within the chamber.5.8 The procedure is sensitive to both the partial pressures of the gases that form the condensibles and the time of exposure of the cold finger at coolant temperatures.5.9 The procedure is sensitive to any losses of sample that may occur during the various transfer operations and during that procedure wherein the solvent is evaporated by heating it on a steam bath.NOTE 1: Reactions between solvent and condensate can occur and would affect the analysis.1.1 This practice covers a technique for collecting samples of materials that are part of the residual gas environment of an evacuated vacuum chamber. The practice uses a device designated as a “cold finger” that is placed within the environment to be sampled and is cooled so that constituents of the environment are retained on the cold-finger surface.1.2 The practice covers a method for obtaining a sample from the cold finger and determining the weight of the material removed from the cold finger.1.3 The practice contains recommendations as to ways in which the sample may be analyzed to identify the constituents that comprise the sample.1.4 By determining the species that constitute the sample, the practice may be used to assist in defining the source of the constituents and whether the sample is generally representative of samples similarly obtained from the vacuum chamber itself.1.5 This practice covers alternative approaches and usages to which the practice can be put.1.6 The degree of molecular flux anisotropy significantly affects the assurance with which one can attribute characteristics determined by this procedure to the vacuum chamber environment in general.1.7 The temperature of the cold finger significantly affects the quantity and species of materials collected.1.8 Units—The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.1.9 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. For specific warning statements, see Section 8.1.10 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.