MKS Stabil-Ion 370 Series, Инструкция по эксплуатации, Страница: 103 / 122

6 Theory of Operation and Specifications
6-3
Series 370 Stabil-Ion Instruction Manual - 370119
The amount of emission current that a B-A gauge requires for proper operation depends on many
factors such as: the size or style of the gauge, the process in which the gauge is used, the pressure
range of operation, and the desired accuracy of the indicated pressure. Emission currents are
typically in the range of 25 µA to 10 mA.
6.1.4 Degassing Bayard-Alpert Gauges
The deposition of elements or compounds on exposed gauge surfaces can result from some
processes, such as sputtering or coating operations. Water vapor is another compound that can
collect inside the gauge when a vacuum chamber is exposed to atmosphere. During normal
operation these materials will slowly come off the gauge surfaces, increasing the local pressure in
the gauge. To more rapidly get the pressure in the gauge in equilibrium with the pressure in the
chamber, "degassing" can be used to drive the molecules on the inner walls and surfaces from the
gauge back into the chamber where they can be pumped out of the system. Degassing can be done
as required or as part of a regular pumpdown sequence. Regular degassing helps prevent process
deposits from collecting and allows the gauge to provide lower and more repeatable pressure
indications by bringing the pressure in the gauge closer to equilibrium with the chamber.
Electron Bombardment (EB) degassing is accomplished by increasing the anode voltage and the
emission current to bombard the gauge with electrons of sufficient quantity and energy to displace
deposited molecules.
Cleaning a gauge with solvents is not recommended. However, if a gauge has been exposed to
silicone-based pump oil, solvent may be needed to remove the oil. If solvent is used, the gauge
must be thoroughly dried before installing it back on the system and operating or degassing it.
6.1.5 Stabil-Ion Gauge Specifications
Measuring range for N2 or Air
0.1 mA emission
4.0 mA emission (UHV)
4.0 mA emission (extended)
4x10
-9
to 2x10
-2
Torr; 5 to 3x10
-7
Pa; 5x10
-9
to 3x10
-2
mbar
2x10
-11
to 5x10
-4
Torr; 3x10
-9
to 7x10
-2
Pa; 3x10
-11
to 7x10
-4
mbar
2x10
-10
to 5x10
-4
Torr; 3x10
-8
to 7x10
-2
Pa; 3x10
-10
to 7x10
-4
mbar
X ray limit of an Extended Range
Stabil-Ion gauge 2x10
-10
Torr; 3x10
-8
Pa; 3x10
-10
mbar
X ray limit of a UHV Stabil-Ion
gauge 2x10
-11
Torr; 3x10
-9
Pa; 3x10
-11
mbar (See notes, below)
Gauge operating temperature 0
o
C to 50
o
C ambient, non-condensing
Gauge bakeout temperature 450
o
C maximum, non-operating, cable removed
Maximum gauge cable length 61 meters (200 feet)
Notes regarding x ray limit: The x ray limit is the absolute lowest indication from the
gauge. It is not practical to make repeatable measurements near the x ray limit.