Plasma nozzle array for providing uniform scalable microwave plasma generation
View Patent ↗Microwave plasma nozzle array systems and methods for configuring the microwave plasma nozzle arrays are disclosed. The microwaves are transmitted to a microwave cavity in a specific manner and form an interference pattern that includes high-energy regions within the microwave cavity. The high-energy regions are controlled by the phases and the wavelengths of the microwaves. A plurality of nozzle elements is provided in the array. Each of the nozzle elements has a portion partially disposed in the microwave cavity and receives a gas for passing therethrough. The nozzle elements receive microwave energy from one of the high-energy regions. Each of the nozzle elements include a rod-shaped conductor having a tip that focuses the microwaves and a plasma is then generated using the received gas.
1. A method for generating plasma plumes through a microwave plasma nozzle array, comprising the steps of:
directing microwaves into a microwave cavity in opposing directions such that the microwaves interfere with each other and form a standing microwave pattern that is stationary within the microwave cavity;
adjusting a phase of at least one of the microwaves to form high-energy regions in the standing microwave pattern, the high-energy regions having a width where an amplitude of the microwaves exceeds a threshold value;
providing an array of nozzles, each of the nozzles including:
a rod-shaped conductor having a first end and a second end where the first end being a leading end of the rod-shaped conductor, and
a gas flow tube having a first end portion disposed inside the microwave cavity and a second end portion disposed outside of the microwave cavity, the first end portion is made of a substantially microwave transparent material and further the gas flow tube surrounds at least a part of the rod-shaped conductor in such a manner that the second end portion is in proximity to the first end of the rod-shaped conductor, and a portion of the gas flow tube is connected to the microwave cavity at a location where the gas flow tube surrounds the rod-shaped conductor; and
disposing the array of nozzles in the microwave cavity such that a middle portion of the rod-shaped conductor is held with respect to said gas flow tube via a holding member, at least the second end of each of the rod-shaped conductors is disposed in the microwave cavity to receive microwave energy from a corresponding one of the high-energy regions of the standing microwave pattern; the first end is being outside the microwave cavity and the second end is suspended free in the microwave cavity in such a manner that the second end is free from contact with any walls forming the microwave cavity and any members that are in contact with said walls of the microwave cavity so that plasma is formed outside of the microwave cavity.
2. A method as defined in claim 1 , wherein said step of directing microwaves includes the steps of:
transmitting microwaves to the microwave cavity; and
reflecting microwaves using a sliding short circuit operatively connected to the microwave cavity.
3. A method as defined in claim 1 , wherein said step of directing microwaves includes the step of:
transmitting microwaves generated by two microwave power heads to the microwave cavity via respective waveguides, and
introducing the microwaves into the microwave cavity directly from opposite sides of the cavity.
4. A method as defined in claim 1 , wherein said step of adjusting a phase of at least one of the microwaves includes forming the high-energy regions in a striped pattern so that the nozzles are located within the high-energy regions.
5. A method as defined claim 1 , wherein said step of providing an array of nozzles includes providing each of the conductors with a portion for collecting the microwaves and a tapered tip for focusing the microwaves to generate the plasma plumes.
6. A method for generating plasma plumes through a microwave plasma nozzle array as defined in claim 1 ,
wherein each of said nozzles includes an inner shield disposed around the inner surface of the gas flow tube to reduce microwave loss through the gas flow tube.
7. The method as defined in claim 1 , wherein one end of the gas flow tube projects externally from the microwave cavity.
8. A method for generating plasma plumes through a microwave plasma nozzle array, comprising the steps of:
directing a first pair of microwaves into a microwave cavity in opposing directions along a first axis;
directing a second pair of microwaves into the microwave cavity in opposing directions along a second axis, the first axis being normal to the second axis such that the first and the second pairs of microwaves cross and interfere with each other to form high-energy regions that are arranged in a matrix pattern and are stationary within the microwave cavity;
adjusting a phase of at least one of the microwaves to control the high-energy regions, the high-energy regions having a width where an amplitude of the microwaves exceeds a threshold value;
providing a plurality of nozzles, each of the nozzles including:
a rod-shaped conductor having a first end and a second end where the first end being a leading end of the rod-shaped conductor, and
a gas flow tube having a first end portion disposed inside the microwave cavity and a second end portion
disposed outside of the microwave cavity, the first end portion is made of a material which is substantially transparent to microwaves and further the gas flow tube surrounds at least part of the rod-shaped conductor in such a manner that the second end portion is in proximity to the first end of the rod-shaped conductor, and a portion of the gas flow tube is connected to the microwave cavity at a location where the gas flow tube surrounds the rod-shaped conductor; and
disposing a plurality of nozzle arrays in the microwave cavity such that a middle portion of the rod-shaped conductor is held with respect to said gas flow tube via a holding member, at least the second end of each of the rod-shaped conductors in each nozzle is disposed in the microwave cavity so that each nozzle element of the nozzle arrays is configured to receive microwave energy from a corresponding one of the high-energy regions; the first end is being outside the microwave cavity and the second end is suspended free in the microwave cavity in such a manner that the second end is free from contact with any walls forming the microwave cavity and any members that are in contact with said walls of the microwave cavity so that plasma is formed outside of the microwave cavity.
9. A method as defined in claim 8 , wherein said step of directing the first pair of microwaves includes the steps of:
transmitting microwaves to the microwave cavity; and
reflecting microwaves using a sliding short circuit operatively connected to the microwave cavity.
10. A method as defined in claim 8 , wherein each of said step of directing the first pair of microwaves and said step of directing the second pair of microwaves includes the step of:
transmitting microwaves generated by two microwave power heads to the microwave cavity, via respective waveguides, and
introducing the microwaves into the microwave cavity directly from opposite sides of the cavity.
11. A method as defined in claim 8 , further comprising the steps of:
generating the microwaves by a microwave power head; and
providing a power splitter connected to the microwave power head.
12. A method as defined in claim 8 , wherein said step of adjusting a phase of at least one of the microwaves includes adjusting phases of the first pair of microwaves.
13. A method as defined in claim 8 , wherein said step of adjusting a phase of at least one of the microwaves includes adjusting phases of the second pair of microwaves.
14. A method as defined in claim 8 , wherein said step of adjusting a phase of at least one of the microwaves includes adjusting phases of both the first pair and the second pair of microwaves.
15. A method for generating plasma plumes through a microwave plasma nozzle array as defined in claim 8 ,
wherein each of said nozzles includes an inner shield disposed around the inner surface of the gas flow tube to reduce microwave loss through the gas flow tube.
16. The method as defined in claim 8 , wherein one end of the gas flow tube projects externally from the microwave cavity.
17. A method for generating plasma plumes through a microwave plasma nozzle array, comprising the steps of:
directing microwaves into a microwave cavity in opposing directions through separate waveguides such that the microwaves are injected into the microwave cavity via two opposite openings formed on a wall of the microwave cavity, interfere and form a standing microwave pattern that is stationary within the microwave cavity;
adjusting a phase of at least one of the microwaves to control high-energy regions generated by the standing microwave pattern, the high-energy regions having a width where an amplitude of the microwaves exceeds a threshold value;
providing a plurality of nozzles, each of the nozzles including:
a rod-shaped conductor having a first end and a second end where the first end being a leading end of the rod-shaped conductor, and
a gas flow tube having a first end portion disposed inside the microwave cavity and a second end portion disposed outside of the microwave cavity, the first end portion is made of a material substantially transparent to microwaves and further the gas flow tube surrounds at least part of the rod-shaped conductor in such a manner that the second end portion is in proximity to the first end of the rod-shaped conductor, and a portion of the gas flow tube is connected to the microwave cavity at a location where the gas flow tube surrounds the rod-shaped conductor; and
disposing the nozzle array at least partially in the microwave cavity so that a middle portion of the rod-shaped conductor is held with respect to said gas flow tube via a holding member, at least the second end of the rod-shaped conductor is disposed in the microwave cavity to receive microwave energy from a corresponding one of the high-energy regions of the standing microwave pattern; the first end is being outside the microwave cavity and the second end is suspended free in the microwave cavity in such a manner that the second end is free from contact with any walls forming the microwave cavity and any members that are in contact with said walls of the microwave cavity so that plasma is formed outside of the microwave cavity.
18. A method for generating plasma plumes through a microwave plasma nozzle array as defined in claim 17 ,
wherein each of said nozzles includes an inner shield disposed around the inner surface of the gas flow tube to reduce microwave loss through the gas flow tube.
19. The method as defined in claim 17 , wherein one end of the gas flow tube projects externally from the microwave cavity.