Plasma generator using dielectric resonator

• US 9,491,841 B2
• Filed: 03/12/2014
• Issued: 11/08/2016
• Est. Priority Date: 03/13/2013
• Status: Active Grant

• Current Assignee: Radom Corporation
• Original Assignee: Radom Corporation
• Inventors: Jevtic, Jovan, Menon, Ashok, Pikelja, Velibor
• Primary Examiner(s): Vanore, David A
• Application Number:
  US14/775,492
• Publication Number:
  US 20160029472A1
• Time in Patent Office: 972 Days
• Field of Search: 250/288, 250/215, 250/423.R, 250/424, 219/121.48, 219/121.52, 219/121.44, 315/111.21, 315/111.81, 315/39, 324/318, 324/633
• US Class Current: 1/1
• CPC Class Codes: G01N 21/718 Laser microanalysis, i.e. with formation of sample plasma
• CPC Class Codes: G01N 22/00 Investigating or analysing materials by the use of microwaves or radio waves, i.e. electromagnetic waves with a wavelength of one millimetre or more G01N3/00 - G01N17/00, G01N24/00 take precedence
• CPC Class Codes: G21B 1/057 Tokamaks
• CPC Class Codes: H01J 2237/002 Cooling arrangements of objects being observed or treated H01J2237/2001
• CPC Class Codes: H01J 37/321 the radio frequency energy being inductively coupled to the plasma
• CPC Class Codes: H01J 37/3244 Gas supply means
• CPC Class Codes: H01J 37/32467 Material
• CPC Class Codes: H01J 49/10 Ion sources; Ion guns
• CPC Class Codes: H01J 49/105 using high-frequency excitation, e.g. microwave excitation, Inductively Coupled Plasma [ICP]
• CPC Class Codes: H01S 3/0975 using inductive or capacitive excitation
• CPC Class Codes: H05H 1/30 using applied electromagnetic fields, e.g. high frequency or microwave energy H05H1/28 takes precedence
• CPC Class Codes: H05H 1/46 using applied electromagnetic fields, e.g. high frequency or microwave energy H05H1/26 takes precedence
• CPC Class Codes: H05H 1/4652 using inductive coupling means, e.g. coils
• CPC Class Codes: H05H 2242/24 Radiofrequency or microwave generators
• CPC Class Codes: Y02E 30/10 Nuclear fusion reactors

Abstract

A dielectric resonator is excited at its natural resonant frequency to produce highly uniform electric field for the generation of plasma. The plasma may be used optical or mass spectrometer.

Claims

1. A plasma generator comprising:

a dielectric resonator structure having a central axis;

a radiofrequency power source electrically coupled to the dielectric resonator structure to promote an alternating polarization current flow at a natural resonant frequency of the dielectric resonator structure about the axis to generate plasma in an adjacent gas.

2. The plasma generator of claim 1 wherein the dielectric resonator has a quality factor of greater than 100.

3. The plasma generator of claim 1 wherein the dielectric resonator has electrical resistivity greater than 1×

10¹⁰ Ω

·

cm.

4. The plasma generator of claim 1 wherein the dielectric resonator has a melting point greater than a melting point of copper.

5. The plasma generator of claim 1 wherein dielectric resonator has a dielectric constant with a loss tangent of less than 0.01.

6. The plasma generator of claim 1 wherein the dielectric resonator has a dielectric constant of greater than five.

7. The plasma generator of claim 1 wherein the material of the dielectric resonator is selected from the group consisting of alumina (Al₂O₃) and calcium titanate (CaTiO₃).

8. The plasma generator of claim 1 wherein the dielectric resonator is a ring having a central opening along the axis.

9. The plasma generator of claim 8 wherein the ring has a central opening of at least one millimeter in diameter or at least one half inch in diameter.

10. The plasma generator of claim 8 further including a gas port introducing gas into the ring along an axis of the ring.

11. The plasma generator of claim 1 further including a feedback system wherein the radiofrequency power source communicates with the feedback system to automatically seek the natural resonant frequency of the dielectric resonator structure to output radiofrequency power at the natural resonant frequency of the dielectric resonator structure.

12. The plasma generator of claim 1 wherein the radiofrequency power source is a magnetron.

13. The plasma generator of claim 1 wherein the radiofrequency power source output power in a range from 20 to 1000 megahertz.

14. The plasma generator of claim 1 wherein the radiofrequency power source outputs power in a range including at least one frequency selected from the group consisting of 13.56 MHz, 27 MHz, 40 MHz, 60 MHz, 430 MHz, 915 MHz, 2450 MHz.

15. The plasma generator of any of the preceding claims incorporated into of the structure of any single device in the group consisting of:

an optical laser, a plasma torch, a rocket engine, an electron-cyclotron plasma or ion source, an inductively coupled plasma source for semiconductor processing, and an ion cyclotron plasma heater.

17. The plasma generator of claim 1 wherein the dielectric resonator is adapted in shape and material to primarily couple energy to the plasma inductively.

18. The spectrometer of claim 2 wherein axial surfaces of the dielectric resonator are substantially free from electrical shielding.

19. The plasma generator of claim 1 wherein the dielectric resonator and the radiofrequency power source are placed within a waveguide and the radiofrequency power source is electrically coupled to the dielectric resonator structure by radiation through the waveguide.

16. A method of generating plasma using a plasma generator including a dielectric resonator structure having a central axis and a radiofrequency power source electrically coupled to the dielectric resonator structure to promote an alternating polarization current flow at a natural resonant frequency of the dielectric resonator structure about the axis to generate plasma in an adjacent gas, the method comprising the steps of

(a) introducing a gas into a region adjacent to the dielectric resonator structure;

and

(b) exciting the dielectric resonator structure at a natural resonant frequency to generate plasma in the introduced gas.