Electronics &
Communication Technologies -
Bayard-Alpert Gauges For UHV Systems
Sealed and nude types
Useful to measure vacuum in the range of 10-4 to10-9
torr
Wide applications in mass spectrometers, surface
analytical instruments, thin film deposition units,
accelerators and other equipments operational in UHV
systems.
Introduction
Bayard Alpert gauges (both sealed and nude types) are
used for measurement of low pressure in the range of
10-4 to 10-9 torr. This is achieved by measuring the
ionisation current, which decreases with the decrease
in the pressure and is also dependent on the type of
the gas species present in the vacuum system. These
gauges come under the category of hot ionisation vacuum
gauges. It consists of a filament, an ion collector
and a grid. In sealed type gauges they are supported
on a glass wafer base having a number of glass to metal
(GM) seals. The metal pins apart from supporting the
above components are also used to provide electrical
connections. The whole assembly is housed in a glass
envelope with wafer base fused at one end. In nude type
gauges, a tubular Kovar metal to glass seal is welded
to a standard SS flange. The tungsten filament, molybdenum
grid and the tungsten ion collector are spot welded
to the Kovar pins of the GM seal as in sealed type gauges.
This assembly is protected by a removable transparent
(acrylic) cover.
Technical Specification
Filament
:
Tungsten
Filament voltage
:
4.2 V
Filament current
:
3.2 A
Filament potential
:
+ 100 V DC
Collector
:
Tungsten
Collector potential
:
0 V DC
Grid and Supports
:
Molybdenum
Grid potential
:
+ 200 V DC
Degass power for grid
:
30 to 40 Watts
Pressure range
:
10 -4 to10 -9 torr
Sensitivity
:
~ 12/ torr for Nitrogen
Leakage current
:
~ 10 -12 A
Envelope and tubulation material (For Sealed
Gauge)
:
Kodial sealing glass
Baking temperature: nude gauge/ sealed gauge
:
400 0 C/ 350 0 C
Flange size for nude gauge
:
CF 35 (70 mm OD Conflat)
Flange material
:
SS 304
Protection (For Nude gauge)
:
Perspex cover
Application
These gauges are required for the measurement of vacuum
in the range 10-4 to10-9 torr. Such gauges are needed
for mass spectrometers, surface analytical instruments,
thin film deposition units, accelerators and all other
equipments/ processes needing ultra high vacuum. Apart
from DAE, research institutions/ universities and some
of industrial units using UHV systems may find these
vacuum gauges very useful.
For
further information please contact :
Head,
Technology Transfer & Collaboration Division,
Bhabha Atomic Research Centre,
Trombay, Mumbai - 400 085
Tel : 091-022-25505337/25593897
Fax : 091-022-25505151
E-mail : headttcd@barc.gov.in
