Miniature vacuum leak element made with porous nickel sheet

Small characteristic sizes (<1 μm) for vacuum leak elements are essential to achieve low conductances and high operating pressures in the free molecular flow regime. In this study, a miniature vacuum leak element is fabricated using a porous nickel sheet with pore size of less than 1 μm and a vacuum coupling radius seal (VCR) type gasket. One side of the porous nickel sheet is well sealed for restricting conductance by the simple polishing and sintering method, and a hole with diameter of about 100 μm is drilled with a laser in the sealing film for conducting gas. In the molecular flow regime, the typical conductance of the leak element is ∼10−9 m3/s, and the operation pressure can be up to about 5.0 × 104 Pa for Ar, and 1.0 × 105 Pa for He. Other advantages are: (1) the 4-VCR type leak element is very small, and can be easily fabricated; (2) the proper sintering process significantly improve the strength of porous material, and the presented leak is very robust; (3) the sheet shape for porous nickel is conducive to releasing the adsorbed gas; (4) technically, the porous nickel and the VCR nickel gasket can be welded together. Thus, the all-metal type leak is feasible.