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 ultapure water.
1 . A gas discharge light source comprising:
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 at or near an edge of said opening; and
a gas discharge medium in contact with the anode and the cathode.
2 . The gas discharge light source of claim 1 , wherein a ratio of said longest dimension to the dielectric thickness is at least 10 to 1.
3 . The gas discharge light source of claim 1 , wherein the uncovered surface region of the cathode comprises a slit.
4 . The gas discharge light source of claim 3 , wherein the anode extends along one side of the slit.
5 . The gas discharge light source of claim 3 , 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.
6 . The gas discharge light source of claim 1 , wherein the uncovered surface region of the cathode is substantially circular.
7 . The gas discharge light source of claim 1 , wherein the gas discharge medium is at pressure in the range from 10 Torr to 1500 Torr.
8 . The gas discharge light source of claim 1 wherein the dielectric has a thickness of 10 micrometers to 200 micrometers.
9 . The gas discharge light source of claim 1 wherein the dielectric comprises at least one material selected from the group consisting of alumina and zirconia.
10 . The gas discharge light source of claim 1 , further comprising:
a housing enclosing the anode and the cathode; and
a window covering a portion of the housing.
11 . The gas discharge light source of claim 1 , 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.
12 . The gas discharge light source of claim 1 , wherein the gas discharge medium comprises a noble gas.
13 . The gas discharge light source of claim 1 , wherein the gas discharge medium is selected from a group consisting of helium, neon, argon, krypton, xenon, and mixtures thereof.
14 . The gas discharge light source of claim 1 , wherein the gas discharge medium is a mixture comprising noble gases and electronegative gases.
15 . The gas discharge light source of claim 1 , wherein at least one of the cathode and the anode is positioned to radiate light through a light-transmitting window.
16 . The gas discharge light source of claim 1 , wherein the transmitted light has a predominant wavelength in the range of about 150-400 nm.
17 . The gas discharge light source of claim 1 , wherein the anode comprises at least one material selected from the group consisting of molybdenum, titanium and tungsten.
18 . The gas discharge light source of claim 1 , further comprising, 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.
19 . The gas discharge light source of claim 1 , wherein the cathode comprises a refractory metal.
20 . The gas discharge light source of claim 1 , wherein the cathode comprises at least one material selected from the group consisting of molybdenum, titanium and tungsten.