Isothermal ion source with auxiliary heaters
An ion source includes a chamber having a first end, a second end opposite the first end, a first wall extending from the first end to the second end, and a second wall opposite the first wall. The ion source also includes a source filament at the first end of the chamber and configured to emit electrons and a first amount of heat, a beam aperture at the second wall of the chamber, and one or more heaters positioned within the chamber and between the second end and the beam aperture and operable to provide a second amount of heat. The one or more heaters are positioned and operable such that the second amount of heat balances the first amount of heat to reduce or eliminate a temperature gradient in the chamber.
1 . An ion source comprising:
a chamber having a first end, a second end opposite the first end, a first wall extending from the first end to the second end, and a second wall opposite the first wall;
a source filament at the first end of the chamber and configured to emit electrons and a first amount of heat;
a beam aperture at the second wall of the chamber; and
one or more heaters positioned within the chamber and between the second end and the beam aperture and operable to provide a second amount of heat;
wherein the one or more heaters are positioned and operable such that the second amount of heat balances the first amount of heat to reduce or eliminate a temperature gradient in the chamber.
2 . The ion source of claim 1 , further comprising:
a plurality of thermocouples distributed in the chamber; and
a controller configured to provide closed-loop control of the one or more heaters based on output from the plurality of thermocouples.
3 . The ion source of claim 1 , further comprising a reflector electrode at the second end of the chamber and configured to reflect the electrons away from the second end.
4 . The ion source of claim 3 , wherein operation of the one or more heaters reduces or eliminates condensation on an insulator of the reflector electrode.
5 . The ion source of claim 1 , further comprising a gas inlet at the second wall of the chamber, wherein the gas inlet is aligned with the beam aperture.
6 . The ion source of claim 1 , wherein the one or more heaters comprise a first cylindrical heater extending from the second end of the chamber and along the first wall of the chamber.
7 . The ion source of claim 6 , wherein the one or more heaters comprise a second cylindrical heater extending from the second end of the chamber and along the first wall of the chamber, wherein the second cylindrical heater is spaced apart from the first cylindrical heater.
8 . The ion source of claim 1 , further comprising a plurality of support posts coupled to the first wall of the chamber and extending away from the chamber, wherein the plurality of support posts provide uniform pathways for heat transfer out of the chamber.
9 . The ion source of claim 8 , further comprising a water-cooling system, wherein:
the plurality of support posts extend from the chamber to the water-cooling system; and
the water-cooling system is configured to remove heat from the plurality of support posts.
10 . The ion source of claim 9 , wherein the water-cooling system is further configured to measure the heat removed from the plurality of support posts by the water-cooling system.
11 . The ion source of claim 1 , further comprising an oven configured to provide an Ytterbium gas into the chamber via an inlet in the first wall.
12 . The ion source of claim 1 , further comprising a test device configured to measure a plasma uniformity of an ion beam emitted from the beam aperture, wherein control for the one or more heaters is tuned based on the plasma uniformity.
13 . The ion source of claim 1 , wherein the second amount of heat is substantially equal to the first amount of heat.
14 . The ion source of claim 1 , wherein reducing or eliminating the temperature gradient in the chamber causes a reduction or elimination of a non-uniform current in an ion beam emitted from the beam aperture.
15 . A method, comprising:
providing a metallic gas into a chamber;
ionizing the metallic gas by providing power to a filament to cause the filament to emit electrons in the chamber, wherein providing power to the filament causes the filament to add heat to the chamber proximate a first end of the chamber;
reducing or eliminating a temperature gradient in the chamber by operating one or more heaters positioned in the chamber, the one or more heaters positioned inside the chamber and extending from a second end of the chamber opposite the first end; and
extracting an ion beam from the chamber via an aperture positioned between the filament and the one or more heaters.
16 . The method of claim 15 , wherein operating the one or more heaters comprises causing the one or more heaters to balance the heat added to the chamber by the filament.
17 . The method of claim 15 , further comprising measuring temperatures at a plurality of positions in the chamber; and
wherein operating the one or more heaters comprises controlling the one or more heaters based on the temperatures at the plurality of positions in the chamber.
18 . The method of claim 17 , further comprising:
measuring a plasma uniformity of the ion beam extracted through the aperture; and
determining setpoints for the temperatures at the plurality of positions in the chamber based on measurements of the plasma uniformity, wherein the setpoints are associated with optimal plasma uniformity.
19 . The method of claim 18 , comprising controlling the one or more heaters to drive the temperatures at the plurality of positions to the setpoints.
20 . The method of claim 15 , further comprising removing heat from the chamber by operating a water cooling system thermally coupled to the chamber by a plurality of support posts.