Study On The Fabrication Of Conductance-controllable Leak Elements Made Of Anodic Aluminum Oxide

Vacuum technology plays a very important role in the fields of scientific research and industrial production.However,leakage exists in all the vacuum systems and it is the biggest issue in vacuum technology.One of the most important contents of vacuum metrology is the development of vacuum standard leaks.However,the commonly applied standard leaks have some shortcomings such as uncertain leak rate for different gases,uncontrollable leak channel size and complicated flow conditions,which greatly limit the application of them.Developing standard leak elements with controlled flow channel size,flow regime and conductance has become a hot area of such research in recent years.Aiming at the problems in the fabrication of the above-mentioned traditional standard leak elements,we applied a selective coating method to fabricate conductancecontrollable standard leak elements.By depositing alumina oxide films with different thicknesses on the surface of anodic aluminum oxide(AAO)and measuring the background leak rate using a helium mass spectrometer,an optimized film thickness that can seal the pores on AAO was obtained.The diameter of the pores in the AAO membrane is smaller than the average free path of helium,nitrogen and argon at atmospheric pressure so that such gases can maintain molecular flow state from vacuum to atmospheric pressure,which will greatly simplify the metrology and application procedure of the standard leak.The fabricated leak elements with different effective areas were calibrated using a homemade equipment based on difference method and dynamic constant volume method,which showed there was an excellent correspondence between the value of the conductance and the effective area.Besides,the value of the conductance of the leak elements does not change with the upstream pressure,which is another evidence of a molecular flow state in the leak element.The fabrication method proposed here can be used to simply and rapidly fabricate standard leak elements with a required value of conductance,which has a very broad application prospect.