Method and apparatus for producing complex carbon molecules

Details Method and apparatus for producing complex carbon molecules Method and apparatus for producing complex carbon molecules

1999-09-13

2001-01-09

Mayekar, Kishor (Department: 1741)

Chemistry: electrical and wave energy

Processes and products

Electrostatic field or electrical discharge

C422S186040, C423S44500R

Reexamination Certificate

active

06171451

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention concerns a method and apparatus for producing complex carbon molecules and, in particular, a method and apparatus that utilizes the plasma within an inertial electrostatic confinement (IEC) device to convert a carbon-based gas into “buckey-balls” or fullerene C
60
and sister molecules.
The IEC was originally developed as a neutron source for activation analysis as reported in G. H. Miley, J. B. Javedani, R. Nebel, J. Nadler, Y. Gu, A. J. Satsangi, and P. Heck, “An Inertial Electrostatic Confinement Neutron/Proton Source,” Third International Conference on Dense Z-pinches, eds. Malcom Haines and Andrew Knight, AIP Conference Proceeding No. 299, AIP Press, New York, 675-689 (1994). For such application, when a gas is introduced into the chamber in the tens of mTorr pressure range, a plasma discharge is created by applying high voltage (10-100 kV) to the grid. The grid also serves to extract ions from the discharge and accelerate them toward the center of the device, where a dense, high-temperature plasma is formed. The potential surfaces are shaped such that ions are trapped and recirculated, creating a highly non-thermal plasma with energetic (kV) ions and lower-energy background electrons. The resulting plasma provides several unique opportunities for plasma processing, either using in situ methods or employing radiation emitted from the dense core region.
An inertial electrostatic confinement (IEC) particle generator is described in U.S. patent application Ser. No. 08/232,764 (Miley et al.) which was filed on Apr. 25, 1994 and is incorporated herein by reference. The inertial electrostatic confinement device disclosed therein includes a metallic vacuum vessel which is held at ground potential and contains internally and concentric to the vessel, a wire grid which acts as a cathode. The cathode may be made from a variety of metals having structural strength and appropriate secondary electron and thermionic electron coefficients. The cathode wire grid is connected to a power source to provide a high negative potential (30 kV−70 kV), while the vessel itself is conductive and maintained at a ground potential. Deuterium or a mixture of deuterium and tritium gas is introduced into the vessel. A voltage is applied to the cathode wire grid and the pressure is adjusted in order to initiate a glow discharge. To maximize the neutron yield per unit power input while maximizing grid life-time by reducing collisions with a grid, operational conditions are used to create a “star” glow discharge mode. The glow discharge generates ions which are extracted from the discharge by the electric field created by the cathode grid. These ions are accelerated through the grid openings and focused at a spot in the center of the spherical device. The resulting high energy ions interact with the background gas (beam-background collisions) and themselves (beam-beam collisions) in a small volume around the center spot, resulting in a high rate of fusion reactions. The result is a neutron generator producing neutrons as one of the D-D or D-T fusion reaction products. Where the extraction rates are high, the extracted ions may provide a deep-self generated potential well that confines trapped beam ions, creating even higher reaction rates. The device may be modified by using a field gas mixture of deuterium and helium-3 to be a source of protons rather than neutrons. One geometrical form of the device is spherical and is seen in FIG.
1
. This device is based upon the principle of an ion accelerator with a plasma target. In a neutron-generator embodiment, deuterium-deuterium fusion reactions take place in the plasma target zone and produce energetic neutrons. The device acts as a simple spherical plasma diode, having a ground potential on the outer sphere and a negative potential on a nearly geometrically transparent inner spherical grid. The spherical inertial electrostatic confinement device
10
is illustrated in
FIG. 1
where a conductive vacuum chamber
11
is connected to a ground potential at contact
17
. The device has a cathode grid
12
that defines a small sphere within the chamber and has a grid design that provides a high geometric transparency. In operation, however, this grid design has an even higher effective ion transparency, due to the effect of a concentration of ions into “microchannels”, as subsequently described. A source of power
14
is connected by a high voltage feed-through to the internal cathode grid
12
. The voltage has a negative value, thereby providing a bias between the relatively positive walls of the vacuum chamber and the central grid area. Gas is introduced into the vacuum chamber
11
by a control valve
15
and is evacuated by a pump
18
, providing a means of controlling the gas pressure in the chamber.
Upon application of a potential to the cathode grid, under certain grid-voltage, gas pressure, gas type and grid-configuration conditions, high density ions and electron beams will form within the IEC device initiating a “star” mode of operation. In this mode, high density space charged neutralized ion beams are formed into microchannels that pass through the open spaces between the grid wires. As the ions avoid contact with the wires, this mode increases the effective grid transparency to a level above the geometric value. These microchannels significantly reduce grid bombardment and erosion and increase power efficiency. For conventional star mode operation, the grid and microchannel beams are symmetric so that a convergent high-density core develops. The inertial electrostatic confinement device serves as a valuable source of neutrons or protons.
Non-thermal plasma production in the IEC leads to several other quite different but possible applications. One that has been explored to date is the production of ultraviolet (UV) radiation. The device provides a high-intensity UV-radiation source if heavy gases, such as krypton or xenon, are used. Another application is the use of the IEC to create thrust by flowing the plasma out through a channel created by an enlarged grid wire opening. A process chamber using a quartz window to contain the flowing fluid under treatment has been designed and both of the foregoing applications are disclosed in a provisional application Ser. No. 60/030,009 filed on Nov. 1, 1996 and entitled Ion Jet Thruster Using Inertial Electrostatic Confinement Discharge Plasma, and PCT Application No. PCT/US97/19306; filed on Oct. 31, 1997 and entitled “Plasma Jet Source Using an Inertial Electronstatic Confinement Discharge Plasma”, which are incorporated herein by reference. The application of the IEC structure to the production of fullerene also has been explored.
Carbon-60 was discovered in 1985 and was found to have three-dimensional, cage-like, all-carbon molecules in a gas phase carbon cluster. These even-numbered soccerball-shaped robust molecules were named “fullerenes” after R. Buckminster Fuller, the American architect who pioneered geodesic design. Since that time, there have been only a limited number of studies and papers presented on the subject of fullerene production and theory due to the relative unavailability of the all-carbon materials. Nonetheless, it was also found that in addition to the originally identified carbon-60 and carbon-70, there were hosts of other stable carbon configurations ranging from carbon-24 up to carbon-240 and beyond. Moreover, within the past 5 years, there have been modest strides in the production of carbon-60 and carbon-70 and limited yields of the higher and lower order carbon molecules.
Recently, the demand for fullerenes has been growing due to their potential applications. Many advanced materials currently in use show only a single application, but fullerenes show a series of applications, which include their use as superconductors, anti-AIDS drugs, catalysts and catalyst supports, photoconductors, optical limiters, adsorbents, precursors to synthetic diamonds, and plant growth regulators. Additionally, a major thrust of fullerene researc

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