MKS Stabil-Ion 370 Series, Инструкция по эксплуатации, Страница: 101 / 122

6-1
Series 370 Stabil-Ion Instruction Manual - 370119
Chapter 6
6 Theory of Operation and
Specifications
This chapter provides a brief explanation of the theory of operation and the general specifications
for Stabil-Ion gauges and Convectron gauges.
6.1 Stabil-Ion Gauge Theory of Operation
6.1.1 Operating Principles of Bayard-Alpert Ionization Gauges
A Bayard-Alpert (B-A) gauge is a hot-filament style ionization gauge. It is called such because a
heated filament (cathode) is used to emit electrons toward a grid (anode).
The pressure indication of a B-A vacuum gauge is based on the ionization of the gas molecules by a
constant flow of electrons. The negative electrons are emitted at a well-controlled, selectable rate
from a heated filament (cathode) and are accelerated toward a positively-charged wire grid (anode).
Electrons pass into the space enclosed by the grid. In this space the electrons collide with the gas
molecules that are in the vacuum system, and produce positive ions. The positive ions are then
collected by the ion collector that is located along the axis of the cylindrical grid. The ion collector
is at nearly ground potential, which is negative with respect to the grid. At a constant filament-to-
grid voltage and electron emission current, the rate that positive ions are formed is directly
Figure 6-1 Stabil-Ion Gauge Illustrations and Principle of Operation
Ion collector
Precision-wound,
stress-relieved grid
Grid support,
3 places
Tensioned
filaments
Stabil-Ion Gauge illustration
shown with part of the stainless
steel cover and heat shield
removed.
Stabil-Ion Gauge shown with
the stainless steel cover
removed for clarity.
Principle of Operation: Electrons
are created by a hot filament and
accelerated to the grid. The
current is actively controlled by
the electronics.