AVS 62nd International Symposium & Exhibition
    Vacuum Technology Monday Sessions
       Session VT-MoM

Paper VT-MoM4
Performance Assessment of Absolute Capacitance Manometers Used in Long-term Irradiation Studies

Monday, October 19, 2015, 9:20 am, Room 230B

Session: Vacuum Measurement, Calibration, and Primary Standards
Presenter: Lily Wang, Los Alamos National Laboratory
Authors: L.L. Wang, Los Alamos National Laboratory
P.D. Honnell, Los Alamos National Laboratory
Correspondent: Click to Email
Absolute capacitance manometers (MKS121A) are used in our experiments to measure gas release of materials resulted from long-term low-dose-rate radiation exposures. The experiments involve irradiating the samples in sealed metal vessels initially under vacuum (~10-6 torr). An absolute capacitance manometer is mounted on this sealed vessel to measure the pressure of gas being accumulated from the radiolytic decomposition of the material. Recently, a set of these long-term irradiation experiments was completed. The pressure gauges had been in continuous service for almost three years (987 days) in these experiments. Of the total service time, the gauges were exposed to the Cs-137 gamma radiation for 640 days. After decommissioning these samples, the gauges were checked with a recently calibrated pressure measurement station to assess their post-irradiation measurement performance. Additionally, two gauges that exhibited an unusual behavior of measuring decreasing pressure with time during the last ~350 days are being further tested for long-term stability with this active gas. This talk will present the results of the performance assessment and the long-term stability test and discuss the pressure measurement uncertainty in this type of experiments.