| AVS 62nd International Symposium & Exhibition | |
| Vacuum Technology | Tuesday Sessions |
| Session VT-TuA |
| Session: | Gas Dynamics and Modeling, Pumping and Outgassing |
| Presenter: | Fabrizio Siviero, SAES Getters, Italy |
| Authors: | F. Siviero, SAES Getters, Italy T. Porcelli, SAES Getters, Italy G. Bongiorno, SAES Getters, Italy M. Urbano, SAES Getters, Italy E. Maccallini, SAES Getters, Italy P. Manini, SAES Getters, Italy |
| Correspondent: | Click to Email |
The use of analytical and numerical tools for the simulation of several physical quantities in complex vacuum systems is becoming a well-established practice. Applications range from large machines like particle accelerators to smaller systems, for example analytical instrumentation or special processing chambers. The computational approach is essential whenever an accurate estimation of pressure profiles or effective pumping speeds is needed for vacuum systems that do not present a very simple geometry. This is very often the case of real UHV systems, where NEG pumps are increasingly employed to improve the performances of the pumping system in terms of base pressure, size, weight or power consumption.
Two main approaches are currently used in the field, i.e. the test-particle Monte Carlo (TPMC) and the Angular Coefficients (AC) methods. At SAES labs both these methods are being used, the former by means of the MOLFLOW+ code, the latter with an interface developed internally in MATLAB and ANSYS environment. The simulation work has two main aims: first as a tool to support the development of NEG products, then more and more frequently to help customers in taking full advantage of the use of getter technology in their systems. Indeed, the use of NEG pumps in the vacuum layout may allow redesigning the complete system, for example enabling the improvement of other important parts in the design of the machine.
The case of NEG pumps simulation presents some peculiar features, since it is not always possible to model the pump as a simple absorbing surface, i.e. the flange inlet, but the complete device must be modelled. Thus it becomes important to properly set the characteristics of the pumping surface in terms of geometry and sticking probability. Some examples will be presented about:
i) the NEG characterization in terms of pumping speed for different gases;
ii) the design of new systems and the upgrade of existing facilities, where NEG pumps, including combination pumps (NEXTorr®) and custom solutions, are used to improve the vacuum level or solve practical issues related to the size and weight of the conventional pumping system.
Results show that vacuum modeling of NEG pumps is an helpful tool to system design and optimization.