Temperature control for insertable target holder for solid dopant materials
An ion source with a target holder for holding a solid dopant material is disclosed. The ion source comprises a thermocouple disposed proximate the target holder to monitor the temperature of the solid dopant material. In certain embodiments, a controller uses this temperature information to vary one or more parameters of the ion source, such as arc voltage, cathode bias voltage, extracted beam current, or the position of the target holder within the arc chamber. Various embodiments showing the connections between the controller and the thermocouple are shown. Further, embodiments showing various placement of the thermocouple on the target holder are also presented.
1. An indirectly heated cathode ion source, comprising:
an arc chamber, comprising a plurality of walls connecting a first end and a second end;
an indirectly heated cathode disposed on the first end of the arc chamber;
a shaft extending into the arc chamber; and
a target holder comprising:
a target base affixed to the shaft;
a crucible shaped as a hollow cylinder, wherein one end of the crucible is disposed proximate the target base; and
a porous plug to cover an open end of the crucible, wherein gaseous dopant material may pass through the porous plug.
2. The indirectly heated cathode ion source of claim 1 , further comprising a crucible plug to cover an opposite open end of the crucible and disposed proximate the target base.
3. The indirectly heated cathode ion source of claim 1 , further comprising a thermocouple in communication with the target holder.
4. The indirectly heated cathode ion source of claim 3 , wherein the thermocouple is affixed to an outer surface of the crucible.
5. The indirectly heated cathode ion source of claim 3 , wherein the thermocouple is disposed in a channel in a wall of the crucible.
6. The indirectly heated cathode ion source of claim 3 , further comprising a crucible plug to cover an opposite open end of the crucible and disposed proximate the target base, wherein a cavity is disposed in the target base proximate the crucible plug and the thermocouple is disposed in the cavity proximate the crucible plug.
7. The indirectly heated cathode ion source of claim 6 , wherein a channel is disposed in the target base, the channel in communication with the cavity to allow wires to be routed to the thermocouple.
8. The indirectly heated cathode ion source of claim 3 , wherein an interior of the shaft is hollow to allow wires to be routed through a hollow interior of the shaft to the thermocouple.
9. The indirectly heated cathode ion source of claim 1 , further comprising a heating element in communication with the target holder, wherein the heating element comprises resistive wires.
10. The indirectly heated cathode ion source of claim 1 , wherein the porous plug comprises graphite foam.
11. The indirectly heated cathode ion source of claim 1 , further comprising a clamp to secure the crucible to the target base.
12. The indirectly heated cathode ion source of claim 1 , further comprising an actuator in communication with the shaft to move the target holder within the arc chamber.