Thermionics manufactures a full line
of sputter ion pumps.
These are:
Each pump is:
- Designed for a specific application
- Able to provide continuous and contaminant free pumping
- Reliable from one micron to 2 x 10-11 Torr (measured)
- Free from backstreaming
- Bakeable to 300°C assembled
- Bakeable to 450°C magnets removed
- Able to act as its own vacuum gauge
All pumps are manufactured to exacting UHV standards. Pump bodies, flanges
and element anodes are made of 304 stainless steel, bakeable to 450°C.
Double re-entrant electrical insulators are made of high-quality aluminum
oxide, bakeable to 450°C, and are equipped with sputter shields. Pump
magnets are high-strength ferrites bakeable to 300°C.
Choosing the Right Pump for Your Application
As a full line vacuum manufacturer, TLI can recommend the best pump for
your job without reservation or bias. We cover the full line of ion pumps.
The table below gives a comparison between pumps for different pumping applications.
Standard Diode Pumps use two titanium
cathodes in each pumping element. They are the pump of choice for most
applications for their long life, reliability and high speed per unit
price. These pumps are not recommended when significant amounts of hydrogen
or noble gases are to be pumped or where frequent high starting loads
are encountered.
Noble Diode Pumps use one titanium
and one tantalum cathode to increase pumping speed for noble gases. Increased
speed eliminates the pressure and speed instabilities shown by standard
diodes when pumping against a prolonged air leak while retaining the long
life and reliability of the standard diode. These are the most stable
pump for noble gas loads.
Noble diodes were developed to pump noble gases. In every instance but
one they are identical to a standard diode. The difference is the use
of one tantalum cathode in place of one of the two titanium cathodes in
the standard pump. The tantalum, because of its larger atomic number,
produces a greater number of energetic neutrals which can bury themselves
in locations which are less subject to resputtering.
Tantalum is somewhat less effective than titanium as a getter. Therefore
the speed of the noble diode is approximately 5% lower than the standard
diode. Another fact of note is the lessened solubility of hydrogen in
tantalum at elevated temperatures. Since elevated temperatures will be
encountered during prolonged starting, it would be wise to avoid applications
which require this pump to handle large amounts of hydrogen. Naturally,
applications differ. Should you have any questions about the applicability
of a pump for your use, please give us a call at 209-586-7890. We have
a wide variety of prior applications to draw upon.
Hydrogen Diode Pumps are also similar
to standard diodes. There are two differences in construction. The first
is a thicker cathode. Because hydrogen diffuses into titanium like water
into a sponge, the more titanium, the more capacity for hydrogen the pump
has. This absorption of hydrogen can lead to a structural problem, however.
Titanium swells and distorts as it absorbs large amounts of hydrogen.
Therefore, hydrogen pumps have special structural modifications to prevent
distortion from causing electrical shorts.
These extra construction details make the hydrogen diode a good choice
for long pump life applications. Examples might be pumps operating in
radioactive environments or operation at remote locations. Recommended
when the major gas load is hydrogen or hydrogen-containing gases such
as water vapor. It also pumps other non-noble gases.
Triode Pumps use reverse electrical
polarity and a radically different cathode design to achieve two important
advantages over the diode pumps: (1) an electrically isolated cathode
allows the starting glow discharge to be confined at significantly higher
pressures, resulting in shorter starting times; (2) the sputter cathode
design allows noble and non-noble gases sputtering. Triodes have the highest
speeds for noble gases and freedom from argon instability in the event
of an air leak. Disadvantage: because of the sputter cathode design, the
triode pumps requires more frequent service.