Implementation of multi-opening orifices in the primary metrology of vacuums and small gas throughputs

Influence of gas–surface interaction on gaseous transmission probability through conical and spherical ducts

“…The conductance calculated on its basis can be different from the real one that leads to an additional uncertainty which is not included in the total uncertainty calculated in Ref. [19].…”

“…For instance, a continuous flow standard is based on gas flows through conical and spherical ducts shapes [18,19]. In the free-molecular regime, the flow rate through an aperture is expressed in terms of the transmission probability (TP) [20].…”

“…The relative variation reaches 28% for the cylinder (b ¼ 0) and it does not exceed 2.3% for the conical duct with the angle b ¼ 45 + . The typical aspect ratio of the duct used in metrology [19] is L=R ¼ 0:5. Considering the angle b ¼ 45 + , the variation of the TP reaches 1% when the momentum AC varies from 1 to 0.8 at a fixed values of the energy AC a n .…”

“…The TP was also calculated for the spherical duct used in the experimental work [19], i.e. the aspect ratio L=R ¼ 0:6 and the radii ratio R S =R ¼ 1:5.…”