Capacitively coupled devices and oscillators
Certain embodiments described herein are directed to devices that can be used to sustain a capacitively coupled plasma. In some examples, a capacitive device can be used to sustain a capacitively coupled plasma in a torch in the absence of any substantial inductive coupling. In certain embodiments, a helium gas flow can be used with the capacitive device to sustain a capacitively coupled plasma.
1. A method of sustaining a capacitively coupled plasma comprising:
introducing a gas flow into a torch body comprising alumina, wherein the gas flow comprises helium gas; and
providing radio frequency energy to the torch body using a capacitive device configured to sustain the capacitively coupled plasma in the torch body comprising the alumina, in which the capacitive device contacts an external surface of the torch body, wherein the capacitive device comprises a wire coil comprising a plurality of coils coupled to each other and positioned external to and coiled around the torch body with the wire coils forming an aperture that receives the torch body, in which the wire coil is configured to couple to an oscillator at a first end of the wire coil to provide the radio frequency energy and contacts the external surface of the torch at a second terminal end of the wire coil to provide capacitive coupling to the torch.
2. The method of claim 1 , further comprising sustaining the capacitively coupled plasma in the absence of any substantial inductive coupling.
3. The method of claim 1 , further comprising configuring the helium gas flow at a flow rate of about 0.5 Liters/minute or less.
4. The method of claim 1 , further comprising configuring the plurality of coils to comprise a plurality of wires each of which is coupled to adjacent wires and each of which contacts the external surface of the torch.
5. The method of claim 1 , further comprising sustaining the capacitively coupled plasma in the absence of an injector.
6. The method of claim 1 , further comprising configuring the capacitive device as a substantially cylindrical wire coil that surrounds at least a portion of the torch.
7. The method of claim 6 , further comprising cooling the oscillator using ambient air.
8. The method of claim 1 , further comprising using a portable power source to power the capacitive device.
9. The method of claim 1 , further comprising using a battery to power the capacitive device.
10. The method of claim 1 , further comprising using a power source of about 500 Watts or less to power the capacitive device.
11. The method of claim 1 , further comprising using a 110-120 Volts alternating current source to power the capacitive device.
12. The method of claim 1 , further comprising using an additional capacitive device to provide radio frequency energy to the torch.
13. The method of claim 12 , further comprising configuring the additional capacitive device as a wire coil comprising a plurality of coils coupled to each other.
14. The method of claim 12 , further comprising configuring the additional capacitive device as a plate electrode.
15. The method of claim 12 , further comprising electrically coupling the capacitive device and the additional capacitive device to the same oscillator.
16. The method of claim 12 , further comprising electrically coupling each of the capacitive device and the additional capacitive device to a different oscillator.
17. The method of claim 1 , further comprising configuring the torch as an alumina torch comprising a hollow cylindrical body, and configuring the gas flow as a helium gas flow.
18. The method of claim 1 , further comprising configuring the capacitive device to sustain the capacitively coupled plasma in the torch when it is present by itself and without any inductive device comprising an induction coil or a plate electrode.