Electric lamp and discharge devices: systems – Discharge device load with fluent material supply to the... – Plasma generating
Reexamination Certificate
2000-02-09
2001-05-15
Wong, Don (Department: 2821)
Electric lamp and discharge devices: systems
Discharge device load with fluent material supply to the...
Plasma generating
C315S111410, C315S111510, C313S231010, C118S72300R, C156S345420
Reexamination Certificate
active
06232723
ABSTRACT:
TECHNICAL FIELD
This invention relates to the field of direct current energy discharge techniques. More particularly, this invention relates to generating a plasma using a ceramic electrode and a direct current source.
BACKGROUND OF THE INVENTION
A plasma is a collection of charged particles, containing about equal numbers of positive ions and negative ions plus electrons. It is typically an aeroform fluid, like a gas but, unlike most gases, a plasma is a relatively good conductor of electricity and is affected by magnetic fields.
Plasmas can be formed in different ways. One method of forming a plasma is by creating an electrical potential differential between two electrodes that have a medium between them, such as a gas. As the potential increases between the plates, the positive portions of the gas are drawn toward the negatively charged electrode, and the negative portions of the gas are drawn toward the positively charged electrode. At a certain potential, the valence electrons or other negative components of certain gases are torn from the rest of the species, creating positive ions, negative ions, and free electrons. These ions and electrons tend to dissociate as described above and recombine repeatedly in the plasma. However, during the times when they exist as charged species, they tend to make the plasma very reactive.
Plasma generation devices are powered by radio frequency current sources, lower frequency alternating current sources, or direct current sources. Electrodes are fashioned from both metallic and nonmetallic materials. However, direct current sources do not tend to work reliably with metallic or nonmetallic electrodes but, rather, tend to initially arc from a somewhat random location, and then preferentially arc from that location thereafter. Thus, the combination of direct current and nonmetallic electrodes typically does not produce a uniform and well defined plasma.
A radio frequency current source can be used with nonmetallic electrodes to form a uniform plasma. However, radio frequency current sources tend to be somewhat inefficient and have other drawbacks in certain applications. For example, radio frequency current sources have a detectable radio frequency signature, which may be undesirable. They also tend to be more expensive than direct current sources. Thus, there is a need for a direct current plasma generation system that will not arc.
SUMMARY OF THE INVENTION
These and other needs are met by an apparatus for producing a plasma with a direct current. A nonmetallic first electrode, having a first surface and a second surface, has pores formed between the first and second surfaces. A conductive liquid is dispersed within the pores of the nonmetallic first electrode. The conductive liquid provides direct current pathways through the nonmetallic first electrode. The conductive liquid in a pore acts as a current—limiting resistor that suppresses arcing to that pore. A second electrode also has a first surface and a second surface. A direct current source provides a first direct current electrical potential and second direct current electrical potential.
A first conductive connector is electrically connected to the direct current source, and is disposed adjacent the first surface of the nonmetallic first electrode. The first conductive connector receives the first direct current electrical potential from the direct current source and provides the first direct current electrical potential to the nonmetallic first electrode. A second conductive connector is electrically connected to the direct current source, and is disposed adjacent the first surface of the second electrode. The second conductive connector receives the second direct current electrical potential from the direct current source and provides the second direct current electrical potential to the second electrode.
A plasma generation region is defined between the second surface of the nonmetallic first electrode and the second surface of the second electrode. The plasma generation region receives a gas that forms the plasma when the first electrical potential is applied to the second surface of the nonmetallic first electrode and the second electrical potential is applied to the second electrode. The first electrical potential is conducted by the conductive liquid through the pores of the nonmetallic first electrode to the second surface of the nonmetallic first electrode.
The apparatus disclosed herein generates a plasma using a direct current source and nonmetallic electrodes. Because the conductive liquid provides current pathways through the nonmetallic first electrode, charges do not tend to excessively accumulate at the second surface of the nonmetallic first electrode, and then suddenly discharge by arcing as occurs in other systems. Arcing is further reduced and a more uniform plasma is generated by providing pores in the nonmetallic first electrode that do not carry too much current through the nonmetallic first electrode in any one location. This is accomplished, at least in part, by pores that do not have too great a cross-sectional area, so that no one pore carries too great an amount of current. This is also accomplished by having a pore density that is not too great in any one area of the nonmetallic first electrode, so that a large portion of the current flow does not occur within a small surface area of the nonmetallic first electrode.
In a method for producing a plasma, a nonmetallic first electrode is provided, where the nonmetallic first electrode has a first surface and a second surface. The nonmetallic first electrode forms pores between the first surface of the nonmetallic first electrode and the second surface of the nonmetallic first electrode. A first conductive liquid is dispersed within the pores of the nonmetallic first electrode. The first conductive liquid provides direct current pathways from the first surface of the nonmetallic first electrode through the pores to the second surface of the nonmetallic first electrode.
A second electrode is also provided, and the second electrode also has a first surface and a second surface. A plasma generation region is formed between the second surface of the first electrode and the second surface of the second electrode. A first conductive connector is connected to the first surface of the nonmetallic first electrode, and a second conductive connector is connected to the first surface of the second electrode. A direct current source is connected to each of the first conductive connector and the second conductive connector and a gas is introduced within the plasma generation region.
A first electrical potential is applied with the direct current source to the first conductive connector, which thereby applies the first electrical potential to the nonmetallic first electrode. The first electrical potential is received at the first surface of the nonmetallic first electrode, and is conducted from the first surface of the nonmetallic first electrode via the conductive liquid through the pores of the nonmetallic first electrode to the second surface of the nonmetallic first electrode.
A second electrical potential is applied with the direct current source to the second conductive connector, which thereby applies the second electrical potential to the second electrode. A plasma is thereby formed with the gas within the plasma generation region.
REFERENCES:
patent: 4222838 (1980-09-01), Bhagat et al.
patent: 4810935 (1989-03-01), Boswell
patent: 5266146 (1993-11-01), Ohno et al.
patent: 6001431 (1999-12-01), Itoh et al.
Luedeka Neely & Graham P.C.
Vu Jimmy
Wong Don
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