Micro-discharge devices and applications
A high pressure gas discharge device and methods of using the device as a UV gas discharge light source are disclosed. The device has a cathode covered partially with a dielectric layer which separates the cathode from an anode. A discharge device utilizes one or more microhollows in the uncovered part of the cathode. Methods of utilizing the discharge devise as a gas discharge light source for producing ultrapure water.
1. A system for treating a fluid comprising:
a treatment chamber coupled to a fluid inlet and a fluid outlet; and
at least one micro-discharge excimer gas discharge light source wherein the light source is configured to expose a fluid passing through the treatment chamber to radiation
wherein each light source comprises:
a cathode having a portion of its surface covered with a dielectric wherein said dielectric has an opening that forms at least one uncovered surface region of said cathode, wherein at least a longest dimension of said surface region is substantially greater than the dielectric thickness;
an anode spaced from said cathode by at least the dielectric thickness, wherein an edge of said anode is positioned adjacent to an edge of said opening; and
a gas discharge medium in contact with the anode and the cathode.
2. The system of claim 1 , further comprising:
a gas supply coupled to the light source.
3. The system of claim 1 , further comprising:
a UV detector positioned to receive light from at least one light source, the light having passed through at least a portion of the treatment chamber.
4. The system of claim 1 , wherein the gas discharge light source produces light having wavelengths in the range of 100-400 nm.
5. The system of claim 1 , wherein the gas discharge light source produces light predominantly having a wavelength of about 193 nm.
6. The system of claim 1 , wherein the gas discharge light source produces light predominantly having a wavelength of about 172 nm.
7. The system of claim 1 , wherein the fluid consists substantially of water.
8. The system of claim 1 , wherein the fluid comprises contaminants that comprise organic compounds.
9. The system of claim 8 , wherein at least a portion of the organic compounds are halogenated.
10. The system of claim 1 , wherein at least one light source forms part of a chamber seal.
11. A system for treating a fluid comprising:
a treatment chamber coupled to a fluid inlet and a fluid outlet; and
at least one micro-discharge excimer gas discharge light source wherein the light source is configured to expose a fluid passing through the treatment chamber to radiation,
wherein each light source comprises:
a cathode having a portion of its surface covered with a dielectric so as to define at least one uncovered region of the cathode, wherein at least a longest dimension of said region is substantially greater than the dielectric thickness;
one or more microhollows penetrating into the uncovered region of the cathode, wherein said microhollows are positioned within said uncovered region and have a longest dimension less than the longest dimension of said uncovered region;
an anode spaced from the cathode by at least the dielectric thickness; and
a gas discharge medium in contact with the anode and the cathode.
12. The system of claim 11 , wherein a ratio of said longest dimension to the dielectric thickness is approximately 10 to 1.
13. A method for purifying fluids of contaminants comprising:
producing light using a micro-discharge excimer gas discharge light source, the light having wavelengths in the range of 100 nm-400 nm; and
exposing a fluid to the light,
wherein the micro-discharge excimer gas discharge light source used to produce the light comprises:
a cathode having a portion of its surface covered with a dielectric so as to define at least one uncovered region of the cathode, wherein at least a longest dimension of said region is substantially greater than the dielectric thickness;
an anode spaced from the cathode by at least the dielectric thickness, wherein an edge of said anode is positioned adjacent to an edge of said opening; and
a gas discharge medium in contact with the anode and the cathode.
14. The method of claim 13 , further comprising:
flowing a cooling gas through the region of the plasma discharge.
15. The method of claim 13 , wherein the gas discharge light source produces light predominantly having a wavelength of about 193 nm.
16. The method of claim 13 , wherein the gas discharge light source produces light predominantly having a wavelength of about 172 nm.
17. The method of claim 13 , wherein the fluid consists essentially of water.
18. The method of claim 13 , wherein the fluid comprises contaminants that comprise organic compounds.
19. The method of claim 18 , wherein at least a portion of the organic compounds are halogenated.
20. The method of claim 13 , wherein the excimer gas discharge light source used to produce the light further comprises:
one or more microhollows penetrating into the uncovered portion of the cathode.
21. A gas discharge light source comprising:
a cathode having a portion of its surface covered with a dielectric so as to define at least one uncovered region of the cathode, wherein at least a longest dimension of said region is substantially greater than the dielectric thickness;
one or more microhollows penetrating into the uncovered region of the cathode, wherein said microhollows are positioned within said region and have a longest dimension less than the longest dimension of said uncovered region;
an anode spaced from the cathode by at least the dielectric thickness; and
a gas discharge medium in contact with the anode and the cathode.
22. The gas discharge light source of claim 21 , wherein a ratio of said longest dimension to the dielectric thickness is at least 10 to 1.
23. A gas discharge light source of claim 21 , wherein at least one of the microhollows penetrates completely through the uncovered portion of the cathode.
24. The gas discharge light source of claim 21 , wherein the dielectric thickness is approximately the same as the width of at least one of the microhollows.
25. A gas discharge light source of claim 21 , wherein the uncovered portion of the cathode comprises a slit.
26. A gas discharge light source of claim 25 , wherein the anode extends along one side of the slit.
27. A gas discharge light source of claim 25 , wherein a first portion of the anode extends from one end of the slit and a second portion of the anode extends from the opposite end of the slit.
28. A gas discharge light source of claim 21 , wherein the uncovered portion of the cathode is substantially circular.
29. The gas discharge light source of claim 21 , wherein the anode and the cathode are coupled to a source of direct current.
30. The gas discharge light source of claim 21 , wherein the anode and the cathode are coupled to a source of alternating current.
31. The gas discharge light source of claim 21 , wherein the anode and the cathode are coupled to a source of pulsed electrical current.
32. The gas discharge light source of the claim 21 , wherein the gas is at pressure in the range from 10 Torr to 1500 Torr.
33. The gas discharge light source of claim 21 , further comprising:
a housing enclosing the anode and the cathode; and
a window covering a portion of the housing.
34. The gas discharge light source of claim 33 , further comprising:
a gas inlet; and
a gas outlet.
35. The gas discharge light source of claim 21 , wherein the gas comprises a noble gas.
36. The gas discharge light source of claim 21 , wherein the gas is selected from a group consisting of helium, neon, argon, krypton, xenon, and mixtures thereof.
37. The gas discharge light source of claim 21 , wherein the gas is a mixture comprising noble gases and electronegative gases.
38. The gas discharge light source of claim 21 , wherein the gas comprises atmospheric air.
39. The gas discharge light source of claim 21 , wherein the cathode comprises a refractory metal.
40. The gas discharge light source of claim 21 , wherein the cathode comprises at least one material selected from the group consisting of molybdenum, titanium and tungsten.
41. The gas discharge light source of claim 21 , wherein the dielectric comprises a heat resistant dielectric.
42. The gas discharge light source of claim 21 , wherein the dielectric comprises at least one material selected from the group consisting of alumina and zirconia.
43. The gas discharge light source of claim 21 , wherein the dielectric has a thickness of 10 micrometers to 200 micrometers.
44. The gas discharge light source of claim 21 , wherein the dielectric comprises a coating applied to the cathode.
45. The gas discharge light source of claim 21 , wherein the anode comprises a refractory metal.
46. The gas discharge light source of claim 21 , wherein the anode comprises at least one material selected from the group consisting of molybdenum, titanium and tungsten.
47. The gas discharge light source of claim 21 , wherein the anode comprises at least one plate.
48. The gas discharge light source of claim 21 , wherein the anode comprises a metal layer covering at least a portion of the dielectric.
49. A gas discharge device according to claim 21 , wherein at least one of the anode and the cathode is thermally coupled to a heat sink.
50. The gas discharge light source of claim 21 , further comprising
gas-tight passages transverse to the anode and the cathode;
a gas input port coupled to each passage; and
a gas exhaust port coupled to each passage.
51. The gas discharge light source of claim 21 , wherein at least one of the cathode and the anode is positioned to radiate light through a light-transmitting window comprising an inside surface exposed to an excimer-forming gas, and an exterior surface exposed to a target fluid.
52. A gas discharge device according to claim 51 , wherein the inside surface is compatible with exposure to the excimer gas and its excited component species.
53. A gas discharge device according to claim 51 , wherein the outside surface is compatible with high purity water contact.
54. A gas discharge device according to claim 51 , wherein there is a light-transmitting window proximal to both the anode and cathode sides of the device.
55. A gas discharge device according to claim 51 , wherein the transmitted light has a predominant wavelength in the range of about 150-400 nm.
56. A gas discharge light source comprising:
a first and second electrode, the first electrode comprising a base electrode material and having a portion of its surface covered with a dielectric so as to define at least one uncovered region of the first electrode, wherein at least a longest dimension of said region is substantially greater than the dielectric thickness,
said second electrode comprising a base electrode material and spaced from the first electrode by at least the dielectric thickness
a gas discharge medium in contact with the first electrode and the second electrode; and
a plurality of microhollows penetrating into at least one electrode wherein an electrode surface material in at least one of the microhollows is a different material than the base electrode material.
57. The gas discharge light source of claim 56 , wherein said surface material comprises a refractory metal.
58. The gas discharge light source of claim 56 , wherein said surface material comprises at least one material selected from the group consisting of tungsten, molybdenum, and titanium.
59. The gas discharge light source of claim 56 , wherein said surface material comprises at least one low work function material.
60. The gas discharge light source of claim 56 , wherein said surface material comprises a material selected from the group consisting of barium and cesium.
61. The gas discharge light source of claim 56 , wherein said surface material comprises a dispenser cathode material.
62. The gas discharge light source of claim 61 , wherein the dispenser cathode material comprises a mixture of a low work function material and a refractory metal base.
63. The gas discharge light source of claim 56 , wherein at least one electrode has a fusible link configured to cease conducting electrical current if the current through the fusible link exceeds a specified level for a specified amount of time.
64. The gas discharge light source of claim 56 , wherein at least one of the microhollows is surrounded by circumferential gap penetrating a portion of at least one electrode to a thickness of electrode wherein the thickness is selected to form a fusible link.