Monte Carlo simulations of the vacuum performance of differential pumps at the Advanced Photon Source
- Experimental Facilities Division, Advanced Photon Source, Argonne National Lab, Argonne, IL 60439 (United States)
Monte Carlo computer simulations have been successfully applied in the design of vacuum systems. These simulations allow the user to check the vacuum performance without the need of making a prototype of the vacuum system. In this paper we demonstrate the effectiveness and aptitude of these simulations in the design of differential pumps for synchrotron radiation beamlines. Eventually a good number of the beamline front ends at the Advanced Photon Source (APS) will use differential pumps to protect the synchrotron storage ring vacuum. A Monte Carlo computer program is used to calculate the molecular flow transmission and pressure distribution across the differential pump. A differential pump system, which consists of two 170 l/s ion pumps with three conductance-limiting apertures, was previously tested on an APS insertion-device beamline front end. Pressure distribution measurements using controlled leaks demonstrated a pressure difference of over two decades across the differential pump. A new differential pump utilizes a fixed mask between two 170 l/s ion pumps. The fixed mask, which has a conical channel with a small cross section of 4.5{times}4.5 mm{sup 2} in the far end, is used in the beamline to confine the photon beam. Monte Carlo simulations indicate that this configuration with the fixed mask significantly improves the pressure reduction capability of the differential pump, to {approximately}3{times}10{sup {minus}5}, within the operational range from {approximately}10{sup {minus}4} to 10{sup {minus}10} Torr. The lower end of pressure is limited by outgassing from front-end components and the higher end by the pumping ability of the ion pump. {copyright} {ital 1996 American Institute of Physics.}
- Research Organization:
- Argonne National Lab. (ANL), Argonne, IL (United States)
- DOE Contract Number:
- W-31109-ENG-38
- OSTI ID:
- 389638
- Report Number(s):
- CONF-9510119-; ISSN 0034-6748; TRN: 96:028055
- Journal Information:
- Review of Scientific Instruments, Vol. 67, Issue 9; Conference: SRI `95: synchrotron radiation instrumentation symposium and the 7. users meeting for the advanced photon source (APS), Argonne, IL (United States), 16-20 Oct 1995; Other Information: PBD: Sep 1996
- Country of Publication:
- United States
- Language:
- English
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