AVS 64th International Symposium & Exhibition
    Vacuum Technology Division Monday Sessions
       Session VT+MN-MoM

Paper VT+MN-MoM5
Cold Cathode Gauge Improvements Extend Performance into UHV Pressure Range

Monday, October 30, 2017, 9:40 am, Room 7 & 8

Session: Progress with Measurement in Vacuum
Presenter: Timothy Swinney, MKS Instruments, Inc., Pressure and Vacuum Measurement Group
Authors: T. Swinney, MKS Instruments, Inc., Pressure and Vacuum Measurement Group
G. Brucker, MKS Instruments, Inc., Pressure and Vacuum Measurement Group
Correspondent: Click to Email
Cold cathode gauges (CCG) of inverted magnetron design are routinely used to measure pressure in industrial high vacuum chambers. Reduced internal outgassing, compared to hot cathode gauges, also makes CCGs well suited for accurate ultra-high vacuum (UHV) measurement in applications such as high-energy physics, surface science experiments and ultrahigh resolution mass spectrometers. In order to provide accurate and repeatable pressure measurements extending into deeper UHV levels, it is important to design CCGs that provide a consistent linear response to pressure over the entire measurement range. Our latest research efforts have focused on the understanding of gauge signal response to pressure with particular emphasis on the displacement of the magnetron knee and discharge sustain issues to lower pressures through systematic design changes. In this presentation, the linear response of CCGs to pressure is explained based on a simple pure electron plasma model. Pressure readings below the magnetron knee are described in terms of a pressure-dependent plasma model controlled by design parameters. The effect of magnetic strength, electric field and plasma boundary conditions on the onset of the magnetron knee and the ability to sustain a stable discharge into UHV levels is described. A patent-pending modification to the CCG internal electrode design is presented that extends the operational pressure of the gauge into deeper UHV levels by controlling the location of the pure electron plasma inside the ionization volume. This new understanding of CCG signal response to pressure has led to the development of enhanced sensor designs that operate at pressures one to two decades lower than legacy designs.