Thermionics e-Gun™, an electron beam evaporation source,
is used to produce uniform high-purity films and optical coatings. The compact
design and ease of maintenance make it useful in practically all vacuum
systems and for many varied applications. It has been used to evaporate
refractory and dielectric materials, as well as the more common conductive
and semiconductor materials. e-Gun evaporation sources are reliable and
simple to operate. They are equally suited for research or production applications.
Theory of Operation
Custom Installation: Twin HM
2 e-guns Mounted on a Single Flange-Inside View
Custom Installation: Twin HM
2 e-guns Mounted on a Single Flange-Outside View
Electron beam heating is an efficient way of achieving temperatures in
excess of 3,500°C (6,300°F) for uniform thin film, optical coating
and vacuum metallurgic processes. The all-metal-sealed models are bakeable
to 230°C (446°F). The e-Gun source and companion control power
supply have been designed to be part of any high or ultra-high vacuum
system.
The e-Gun source is a self-accelerated
electron beam device. A beam of electrons, held at a high negative potential,
is produced by the hot tungsten filament. The beam of electrons leaving
the filament is magnetically focused and then deflected 270° by the
integral permanent magnet. The electron beam is accelerated into the evaporant
material contained within the water-cooled, grounded crucible. The beam
strikes the evaporant material with a spot of approximately 1/8”
diameter and an intensity of approximately 25 kW/cm2. Sweeping
the electron beam across the evaporant material contained in the crucible
is performed by an electro-magnetic system, with either manual or automatic
controls.
The rate at which source materials
may be evaporated is dependent upon power input, charge size, charge shape,
and the characteristics of the material to be evaporated. The highest
evaporation rates are obtained with materials that have low evaporation
temperatures and low thermal conductivity.
The evaporant vapor cannot become contaminated because the focused electron
beam strikes only the evaporant source material in the crucible. The beam
deflection and effective shielding keeps the filament hidden from the evaporant
vapor. The crucible is cooled so efficiently that its surface never gets warm
enough to react with the evaporant material.
The e-Gun source will operate
in a system base pressure as low as 5 x 10-11 Torr. The magnitude
of pressure, which normally increases during evaporation, depends on the
pumping capacity of the system and the cleanliness of the evaporant material.
This pressure increase is minimized by the high thermal efficiency of
the source. There is minimal outgassing of surrounding surfaces because
only the evaporant is heated.
All of Thermionics’ single,
linear motion, three and five position e-Guns are 100% metal-sealed, thus
eliminating “O” ring outgassing. Outgassing could require additional
pumping capacity and sometimes result in sample contamination.
Mounting Configurations
Each e-Gun is available in three standard mounting configurations:
- e-Gun mounted on a PyraFlat
or ConFlat metal-seal type flange, which uses a standard OFE copper
gasket
- e-Gun with a 1” diameter
bolt-type mount, which mount through a 1” diameter hole, and is
sealed by a compression O-ring
- e-Gun alone with no mounting
flange
Ordering Information
Please specify the mounting configuration at the time the order is placed,
the prices listed
may not include the bolt-type or flange-type mount.
Other mounting flanges, configurations
and geometries are routinely supplied, please call the factory for further
information.
Custom e-Guns
Any e-Gun can be designed and manufactured to fit existing or new systems.
Please consult the factory with your special requirements.
Hanks HM2 e-Guns are manufactured and protected
under one or more of the following patents:
Patent No. 4,835,789
Patent No. 4,891,821
Patent No. 4,947,404