Accurate Modeling of Low-Pressure, Low-Velocity Gas Flows
The Molecular Flow Module is designed to offer previously unavailable simulation capabilities for the accurate modeling of low-pressure gas flows in complex geometries. It is ideal for the simulation of vacuum systems, including those used in semiconductor processing, particle accelerators, and mass spectrometers. Small channel applications (e.g., shale gas exploration and flow in nanoporous materials) may also be addressed. The Molecular Flow Module uses the angular coefficient method to simulate steady-state free molecular flows, allowing the molecular flux, pressure, number density, and heat flux to be computed on surfaces. The number density can be reconstructed on domains, surfaces, edges, and points from the molecular flux on the surrounding surfaces. You can model isothermal and nonisothermal molecular flows and calculate the heat flux contribution from the gas molecules.
- Isothermal and nonisothermal flows using the angular coefficient method
- Reconstruction of number densities on domains, boundaries, edges, and points
- Multiple species
- Diffuse flux, evaporation, and reservoir conditions for inflow boundaries
- Total vacuum and vacuum pump conditions for outflow boundaries
- Outgassing, thermal desorption, adsorption, and deposition conditions for walls
- Additional temperature boundary conditions for nonisothermal flows
- Mesh either the entire geometry or only the surfaces
- Vacuum systems
- Semiconductor processing equipment
- Materials processing equipment
- Ultra-high vacuum chemical vapor deposition (UHV/CVD)
- Ion implantation
- Charge exchange cells
- Thermal evaporation
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This benchmark model computes the pressure in a system of outgassing pipes with a high aspect ratio. The results are compared with a 1D simulation and a Monte-Carlo simulation of the same system from the literature.
Rotating Plate in a Unidirectional Molecular Flow
This model computes the particle flux, number density and pressure on the surface of a plate that rotates in a highly directional molecular flow. The results obtained are compared with those from other, approximate, techniques for computing molecular flows.
Molecular Flow Through a Microcapillary
Computing molecular flows in arbitrary geometries produces complex integral equations that are very difficult to compute analytically. Analytic solutions are, therefore, only available for simple geometries. One of the earliest problems solved was that of gas flow through tubes of arbitrary length, which was first treated correctly by Clausing. ...
Adsorption and Desorption of Water in a Load Lock Vacuum System
This model shows how to simulate the time-dependent adsorption and desorption of water in a vacuum system at low pressures. The water is introduced into the system when a gate valve to a load lock is opened and the subsequent migration and pumping of the water is modeled.
Charge Exchange Cell Simulator
A charge exchange cell consists of a region of gas at an elevated pressure within a vacuum chamber. When an ion beam interacts with the higher-density gas, the ions undergo charge exchange reactions with the gas which then create energetic neutral particles. It is likely that only a fraction of the beam ions will undergo charge exchange ...
Molecular Flow Through an RF Coupler
This model computes the transmission probability through an RF coupler using both the angular coefficient method available in the Free Molecular Flow interface and a Monte Carlo method using the Mathematical Particle Tracing interface. The computed transmission probability determined by the two methods is in excellent agreement with less than a ...
Differentially pumped vacuum systems use a small orifice or tube to connect two parts of a vacuum system that are at very different pressures. Such systems are necessary when processes run at higher pressures and are monitored by detectors that require UHV for operation. In this model, gas flow through a narrow tube and into a high vacuum chamber ...
Molecular Flow in an Ion-Implant Vacuum System
The Ion Implanter Evaluator app considers the design of an ion implantation system. Ion implantation is used extensively in the semiconductor industry to implant dopants into wafers. Within an ion implanter, ions generated within an ion source are accelerated by an electric field to achieve the desired implant energy. Ions of the correct charge ...
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