We discuss a novel use of the Geant4 simulation toolkit to model molecular transport in a vacuum environment,in the molecular flow regime.The Geant4 toolkit was originally developed by the high energy physics communit...We discuss a novel use of the Geant4 simulation toolkit to model molecular transport in a vacuum environment,in the molecular flow regime.The Geant4 toolkit was originally developed by the high energy physics community to simulate the interactions of elemen-tary particles within complex detector systems.Here its capabilities are utilized to model molecular vacuum transport in geometries where other techniques are impractical.The techniques are verified with an application representing a simple vacuum geometry that has been studied previously both analytically and by basic Monte Carlo simulation.We discuss the use of an application with a very complicated geometry,that of the Large Synoptic Survey Telescope camera cryostat,to determine probabilities of transport of contaminant molecules to optical surfaces where control of contamination is crucial.展开更多
Nitrogen containing austenitic stainless steels(N-ASS)are widely utilized to fabricate various structural components in tokamak type fusion reactors owing to their suitable mechanical and functional proper-ties.These ...Nitrogen containing austenitic stainless steels(N-ASS)are widely utilized to fabricate various structural components in tokamak type fusion reactors owing to their suitable mechanical and functional proper-ties.These components are exposed to a range of temperatures(4-500 K)and interact closely with the magnetic fields that are used to control and contain the plasma within the tokamak systems.Nitronic-40(N40)or XM-11 stainless steel is one such N-ASS used for fabricating structural components in the mag-netic and vacuum vessel systems in tokamak devices.Fabrication of most of the larger components in the magnetic and vacuum vessel systems typically involves some type of fusion-based welding process.This study presents a double-sided friction stir welding(FSW)approach as an alternative to fusion welding processes to join 12 mm thick N40 plates to obtain joints with a low fraction ofδferrite(a detrimen-tal ferromagnetic phase),high joint efficiency,no sensitization and loss of hardness in the heat affected zone,and minimal nitrogen desorption from the weld nugget.The double-sided FSW approach yielded superior weldments when compared to similar joints accomplished by fusion welding for application in tokamak devices.展开更多
基金supported in part by the National Science Foundation through Governing Cooperative Agreement 0809409 managed by the Association of Universities for Research in Astronomy(AURA)the Department of Energy under contract DE-AC02-76-SFO0515 with the SLAC National Accelerator Laboratory.
文摘We discuss a novel use of the Geant4 simulation toolkit to model molecular transport in a vacuum environment,in the molecular flow regime.The Geant4 toolkit was originally developed by the high energy physics community to simulate the interactions of elemen-tary particles within complex detector systems.Here its capabilities are utilized to model molecular vacuum transport in geometries where other techniques are impractical.The techniques are verified with an application representing a simple vacuum geometry that has been studied previously both analytically and by basic Monte Carlo simulation.We discuss the use of an application with a very complicated geometry,that of the Large Synoptic Survey Telescope camera cryostat,to determine probabilities of transport of contaminant molecules to optical surfaces where control of contamination is crucial.
文摘Nitrogen containing austenitic stainless steels(N-ASS)are widely utilized to fabricate various structural components in tokamak type fusion reactors owing to their suitable mechanical and functional proper-ties.These components are exposed to a range of temperatures(4-500 K)and interact closely with the magnetic fields that are used to control and contain the plasma within the tokamak systems.Nitronic-40(N40)or XM-11 stainless steel is one such N-ASS used for fabricating structural components in the mag-netic and vacuum vessel systems in tokamak devices.Fabrication of most of the larger components in the magnetic and vacuum vessel systems typically involves some type of fusion-based welding process.This study presents a double-sided friction stir welding(FSW)approach as an alternative to fusion welding processes to join 12 mm thick N40 plates to obtain joints with a low fraction ofδferrite(a detrimen-tal ferromagnetic phase),high joint efficiency,no sensitization and loss of hardness in the heat affected zone,and minimal nitrogen desorption from the weld nugget.The double-sided FSW approach yielded superior weldments when compared to similar joints accomplished by fusion welding for application in tokamak devices.
