Ion protected linear electron beam metal evaporator
AssigneeJersey Nuclear-Avco Isotopes, Inc.
InventorHarold K. Forsen
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Abstract
A linear electron beam evaporation source for a high vapor temperature material such as uranium which is protected against filament degradation from reverse accelerated ions in the generated vapor. Electron beam evaporation is produced by the energy in a focused, cylindrical electron beam emanating from an elongate filament and impinging upon a trough shaped crucible of the material to be evaporated. A set of linear electrodes are provided adjacent to the trajectory of the focused electron beam from the filament to provide a slight deceleration voltage in the electron accelerating potential between the filament and the crucible. The decelerating voltage acts as a potential barrier to the few ions in the generated vapor.
Claims14
An ion protected linear electron beam evaporation system comprising:
- a generally trough shaped, elongated crucible containing a supply of a material to be evaporated;
- an elongate source of electrons extending in a direction parallel to the long dimension of said crucible;
- means for applying an electron accelerating potential over a portion of an arcuate trajectory for the electron beam from said source to said crucible;
- means for focusing electrons from said source of electrons on said trajectory onto the surface of the material to be evaporated in said crucible generally in a line along the long dimension of said crucible;
- the focused electron beam from said source evaporating the material within said crucible to provide a vapor of said material including a plurality of ions;
- means for providing a decelerating electrostatic field over a portion of the trajectory of said focused electron beam beyond said accelerating potential before said crucible and in a potential sufficient to generally impede the motion of the ions in the vapor from penetrating the region of said accelerating potential and striking said source.
An ion protected linear electron beam uranium evaporation system comprising:
- an elongate, water cooled crucible containing a reservoir of uranium metal;
- a filament placed to one side of said crucible and extending generally parallel to the long dimension thereof;
- a beam forming electrode extending generally parallel to said filament, having a generally L shaped cross-section member placed generally between said filament and said crucible and a further member to define a first slit above said filament;
- an accelerating electrode having a member between said beam forming electrode and said crucible and in generally nesting relationship with said beam forming electrode and a further member to define a second slit above said first slit;
- a source of high voltage connected with the positive terminal to said accelerating electrode and the negative terminal to said filament;
- a decelerating electrode electrically connected to said crucible and having members extending out above said accelerating electrode to define a third slit above said second slit;
- a low voltage source having the positive terminal thereof connected to said accelerating electrode and the negative terminal thereof connected to said decelerating electrode and said crucible;
- means for heating said filament to the point of electron emission;
- means for focusing the electrons emitted from said filament in an arcuate trajectory passing through said first, second and third slits to a generally line pattern on the surface of uranium in said crucible.
Dependencies are inferred from the claim text.