|AVS 57th International Symposium & Exhibition|
|Vacuum Technology||Tuesday Sessions|
|Session:||Vacuum Technology Poster Session and Student Posters|
|Presenter:||H. Yoshida, National Institute of Advanced Industrial Science and Technology (AIST), Japan|
|Authors:||H. Yoshida, National Institute of Advanced Industrial Science and Technology (AIST), Japan
K. Arai, National Institute of Advanced Industrial Science and Technology (AIST), Japan
M. Hirata, National Institute of Advanced Industrial Science and Technology (AIST), Japan
H. Akimichi, National Institute of Advanced Industrial Science and Technology (AIST), Japan
|Correspondent:||Click to Email|
A new two-stage flow dividing system has been developed for the calibration of ultrahigh vacuum gauges from 10–9 Pa to 10–5 Pa for N2, Ar, and H2. This system is designed based on the techniques of the calibration system in high vacuum region from 10–7 Pa to 10–2 Pa .
The system consists of four chambers: an initial chamber V0, a flow divider V1, a calibration chamber V2, and an evacuation chamber V3. Chambers between V0 and V1 and chambers between V1 and V2 are connected to each other with a capillary and a sintered filter, respectively. The chamber V2 is evacuated by a turbo molecular pump (1100 L/s for N2) through an orifice of 30 mm in diameter. The flow divider V1 is evacuated by a subsidiary turbo molecular pump (220 L/s for N2). The pressure P0 in the initial chamber is changed in 12 steps using a pressure controller in the range from 102 Pa to 105 Pa. The time interval for each step is 600 seconds. Following the change in the P0, the pressure P1 in the flow divider and the pressure P2 in the calibration chamber similarly change from 10-4 Pa to 10 Pa and from 10-9 Pa to 10-5 Pa, respectively. The pressure P2 is determined from the pressure P1 using a pressure ratio of P2 to P1. The ratio is pressure independent because the conductances of sintered filter C1 and the effective pumping speed of the turbo molecular pump though the orifice Cmain are pressure independent at molecular flow region.
The modifications of this system from the previous one are listed below. (1) TiN coated stainless steel vacuum chambers are used as V2 and V3 to decrease outgassing from the chambers . (2) The conductance of the sintered filter is 1000 times smaller than that of previous system to control the pressure in the range from 10-9 Pa to 10-5 Pa. (3) The ratio P2/P1 is measured using a calibrated ionization gauge and a calibrated spinning rotor gauge. The ratio for N2, Ar, and H2 is obtained to be 6.41 x10–7, 6.26 x10–7, and 8.36 x10–7, respectively.
The pressure P2 is measured by an Extractor gauge (EXG) and an Axial-Symmetric Transmission gauge (ATG). The typical background pressure was (2-4)x10-9 Pa. These gauges were calibrated from 10–9 to 10–5 Pa for N2, Ar, and H2 with an uncertainty of about 5% with the confidence level of 95% (k=2). The linearities of these gauges were within ±2%. The fluctuations of pressure indications were within ±2% for 1 hour.
 H. Yoshida, K. Arai, H. Akimichi, M.Hirata, J. Vac. Sci. Technol. A 26 128 (2008)
 H. Akimichi, M Hirata, Metrologia 42 S184 (2005)