AVS2001 Session VST3-ThP: Vacuum System Modeling Poster Session
Thursday, November 1, 2001 5:30 PM in Room 134/135
Thursday Afternoon
Time Period ThP Sessions | Topic VST Sessions | Time Periods | Topics | AVS2001 Schedule
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VST3-ThP-1 Pressure Distribution Modeling for Cyclotron's Vacuum Chambers and Ion Beam Guidelines
A.V. Tikhomirov (Joint Institute for Nuclear Research, Russia); M.N. El-Shazly, G.G. Gulbekian (JINR, FLNR, Russia) The simulation method for determination of the pressure distribution inside the vacuum chamber of any geometrical configuration for a cyclotron's vacuum system is described. The results of the simulation program codes tested on the base of the data obtained at the FLNR heavy ion cyclotrons are presented. The developed simulation method practically allows optimizing any configuration of the vacuum system from the point of view of the pumping speed and pump's location. In conjunction with another program code, developed by the authors for an evaluation of the ion charge changing cross section, this simulation method allows to forecast the ion beam loss due to the charge exchange with the residual gas molecules. |
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VST3-ThP-2 Pressure Field in a Tube with General and Arbitrary Time- and Position-Dependent Degassing
F.T. Degasperi (Faculdade de Tecnologia de São Paulo FATEC-SP, Brazil); S.L.L. Verardi (Universidade de São Paulo, Brazil); J. Takahashi, M.N. Martins (Instituto de Fisica da USP, São Paulo, Brazil) We present in this paper analytical and numerical results for the pressure profile in a tube with general and arbitrary time- and position-dependent degassing. The time evolution of the pressure profile is discussed. We also study the time evolution of the pressure along the tube in situations commonly found in vacuum technology, like particle accelerators, colliders, storage rings, and synchroton light sources. |
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VST3-ThP-4 Mathematic Simulation of Processes in Flow Parts of Hybrid Turbomolecular Vacuum Pumps
M.G. Sapeshinsky (Bauman Moscow State Technical University, Russia) Results on 3-dimensional mathematic simulation of processes in flow parts of hybrid turbomolecular pumps (TMP) are presented. Description of algorithms and of a calculation programs complex for characteristics of hybrid turbomolecular pumps with molecular and drum forcing channels is given. The influence of geometric parameters of a flow part on an operation rate and a maximal compression degree of pump channels is investigated. The concept of optimisation of hybrid pumps under restrictions of controlled parameters is developed.The optimal variants of a flow part are given. Rated and experimental data are compared. There is developed an algorithm of optimization of a TMP flow part with axial and axial-radial gas flow under functional restrictions on controlled parameters, ensuring the desired TMP operation rate at fixed suction pressure for a chosen gas, and also the desired operation rate for several gases using the algorithm of slipping access and the absolute penalty functions metod. It is found out, that within the investigated operation rate's range an axial-radial scheme has better mass-size characteristics compared to that of an axial scheme. Decrease in volume of a flow part with optimal geometric parameters makes from 36 % (S=0.5 m3/sec) to 53 % (S=20 m3/sec) due to decreasing the axial rotors number. Here the external diameter of axial rotors increased from 35 % (S=0.5m3/sec) to 5 % (S=20m3/sec). More preferable is the axial-radial scheme with periphery-center flow direction. It is found out, that if ensuring the desired raised evacuation characteristic for light gases, the flow part volume of all the three schemes increases due to increase in axial rotors number and smoother changing of geometric parameters over rotors, and mass-size characterictics of axial-radial schemes come worse. Decrease in the flow part volume comparing to that of an axial scheme makes for the scheme with periphery-center flow 24 % (S=20m3/sec, P=10-5 Pa, S=15 m3/sec and P=10-3 Pa). The volume of an axial scheme raised on 93 %, of axial-radial schemes - on 163 % and 150 % compared to the computation results when ensuring the desired operation rate only for nitrogen. |
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VST3-ThP-5 Developing of Calculation Methods of Diffusion Vacuum Pumps' Characteristics
M.G. Sapeshinsky (Bauman Moscow State Technical University, Russia); B.N. Kemenov (Npk Intelvac, Russia) Results on 3-dimensional mathematic simulations of processes in an inlet chamber of diffusion vacuum pumps, of interaction between pumped out gas and steam molecules are presented. Description of algorithmus and of a calculation programs complex for characteristics of diffusion vacuum pumps is given. Using the developed calculation programs the influence of parameters and form of a steam flow, geometry of a body, as well as of an oil reflector and protecting screens, on operation rate and on reverse oil flow of diffusion pumps is investigated. Rated and experimental data are compared. The concept of optimisation of an inlet chamber of diffusion pumps is developed |
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VST3-ThP-6 Pressure Field Calculations in Vacuum Systems
F.T. Degasperi (Faculdade de Tecnologia de São Paulo FATEC-SP, Brazil); S.L.L. Verardi (IBILCE, UNESP, São José do Rio Preto., Brazil); V. Baranauskas (UNICAMP, Brazil) The traditional and usual vacuum technology approach to the description of vacuum systems considers them made up of discrete elements. This approach is very useful, but it delivers only the average pressure, not allowing the evaluation of the pressure at each point of the vacuum system. In other words, the detailed pressure distribuition is not determined. In this article we study and describe a powerful method to deal with vacuum problems in the pressure field framework. It uses anlytical and computational tools based on the Finite Elements Method. Details of the mathematical formulation and modeling are given. In special, a detailed discussion about the boundary conditions is also presented. In this article we also calculate and show the pressure distribuition of complex geometries, considering degassing effects from the surfaces. |
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VST3-ThP-7 Computer Applications in Vacuum Measurement
D. Tian (Lanzhou Institute of Physics, P.R.China) Study of vacuum measurement has been developed in our laboratory for over thirty years. Measurement standard apparatus of total pressure, partial pressure and flow (leak rate) were constructed successively. They are used to calibrate the vacuum gage, mass spectrometer, leak and flowmeter. Computer technology is used widely in these fields. With the aid of computer, these projects can proceed successfully and efficiently. Some application examples are introduced in this article. Computer simulation was used to solve some theoretical problems in vacuum measurement. By means of Monte-Carlo method and view-factor method the computer simulations were accomplished in nonuniform molecular flow field of dynamic flow method calibration system and relative calibration system. Computer can complete complicate scientific calculation easily. Static expansion apparatus is an absolute vacuum standard and needs a great deal of formula calculations for the correction of pressure, volume, and temperature. Computer can provide a real-time value of actual pressure so as to find measurement problems in time. In order to improve control accuracy, manual operation has been replaced by computer automatic control gradually. According to the principle of negative feedback and algorithm of proportional integral differential (PID) control, the fluctuation of pressure in variable chamber was controlled within ±0.01% by a computer adjusting the piston displacement. This technology enabled us to manufacture a high precise constant pressure flowmeter. Computer can not only control and safeguard vacuum pumps, valves and gauges, but also acquire and manage measurement data. Comparison method apparatus calibrates vacuum gages automatically with high efficiency by using interface communication and logical control. With further application of computer technology, vacuum measurement technology will progress rapidly in the future. |