Two new kinds of the standard leak elements (SLEs), with a microfluidic channel in diameter of several-micrometers and length of several-hundred-micrometers, have been developed by femtosecond (fs) laser micromachining. A technique based on the conductance modulation method can be used to accurately determine the tiny conductance (< 1×10-6 L s-1) of these SLEs.
Most leak paths of the SLEs in the literature (e.g., Nano hole, multichannel, AAO) were fabricated in a non-metallic substrate; a subsequent sealing process was hence required to attach these non-metallic leak elements to flanges for vacuum applications. Torr Seal® is the most commonly used sealant for vacuum sealing, but its outgassing rate is of order 10-7 mbar L s-1 cm-2 and a baking temperature must not exceed 120 0C. We propose a simple approach using fs laser micromachining to make the SLEs, which can be compatible with an UHV environment and can withstand higher baking temperatures.
This invention can serve to (a) calibrate the sensitivity of an ionization gauge and residual gas analyzer (RGA) for various gases, (b) calibrate the leak rate of a helium leak detector, (c) measure the pumping speed and the sorption capacity of a vacuum pump, (d) supply a precise and constant gas flow in cooperation with a low-vacuum gauge (e.g., capacitance diaphragm gauge, CDG), and (e) be a tiny differential pumping element, between which a desired pressure gradient can be attained with an appropriate pumping speed.

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