Establishing highly conductive path in gas by thermal guidance of discharge

Claim 3

The method as set forth in claim 1, including the further step of triggering the discharge of high potential between said points when the heated rarefaction trail has been established in the gas.

Claim 4

The method as set forth in claim 1, wherein the ratio of the gas density Rho 2 in the established rarefaction trail to the ambient gas density Rho o for a pulsed laser beam lies substantially within the range of 0.1 to 0.9 and is expressed as ( Rho 2/ Rho o)Pulse (1+ (107E exp(-x/Lao)/ pi r21 Lao Cv Rho o To)) 1/ where r1 is the radius of the laser beam in centimeters, Lao is the absorption length in centimeters of the gas at the wavelength of the laser, E is the energy in Joules emitted by the laser, x is distance along the beam from its point of origin, gamma is the specific heat ratio of the gas, cv is the specific heat of the gas at constant volume, and To is the ambient temperature of the gas.

Claim 5

The method as set forth in claim 2, wherein the discharge of the high voltage is initiated after the laser beam is pulsed on and within the lifetime tc of the low density trail as determined by thermal conduction, in which tc r22 cp Rho 2/2K where K is the thermal conductivity of the gas, cp is the specific heat of the gas at constant pressure, r2 is the radius of the established trail, and Rho 2 is the density of the gas in the trail.

Claim 6

The method as set forth in claim 1, wherein the laser means is pulsed ''''on'''' to provide a beam of high peak power and of duration which does not exceed the acoustic transit time of a compressional wave across the radius of the beam as expressed by r1/Vs, where r1 is the radius of the laser beam and Vs is the velocity of sound in the heated gas trail, whereby to minimize the tendency of a gas to change its index of refraction and defocus the beam.

Claim 7

The method as set forth in claim 1, wherein the ratio of the density Rho 1 of the gas within the established laser beam trail to the ambient gas density Rho o for a continuous-wave (CW) lasEr beam lies substantially within the range of 0.1 to 0.9 and is expressed as ( Rho 1/ Rho o)CW ( 1 + (E(t)/ pi r21 Lao Cp Rho o To)) 1 where r1 is the radius of the laser beam in centimeters, Lao is the absorption length in centimeters of the gas at the wavelength of the laser, E(t) is the total energy in Joules emitted by the laser in a given time interval, Cp is the specific heat of the gas at constant pressure, and To is the ambient temperature of the gas.

Claim 8

The method as set forth in claim 1, wherein as a part of the selecting of said laser beam, the step of doping the gas medium to add it to other components selected to alter its absorption length for radiation at the wavelength of the selected laser for the purpose of adjusting the absorption length of the medium to more closely match the distance between said discharge points.

Claim 9

The method as set forth in claim 1, wherein said laser means selecting step includes the selecting of two lasers of differing absorption wavelengths in said gas medium wherein the first laser has a beam having the shorter absorption length and the second laser has a beam having the longer absorption length; and said radiating and focusing step includes radiating the beams along the same trail such that the first laser beam produces a rarefaction trail extending partially from one point toward the other point and making the gas medium more transparent to the second laser beam, and the second laser beam passes through said more-transparent trail portion and produces a rarefaction trail completing said path to the other point.

Claim 10

The method as set forth in claim 1, wherein said laser means selecting and radiating steps include selecting two lasers, and focusing their beams from different initiating locations to respectively pass through said discharge points and substantially intersect in the vicinity of a third point.

Claim 11

Apparatus for establishing a heated rarefaction trail for the purpose of guiding the discharge of high potential electrical energy comprising a path of known discharge distance extending between spaced points through a gas medium of substantial ambient pressure, laser means having a beam wavelength which when passed through said gas medium experiences an absorption length of the same order as said discharge distance, the laser means including means for focusing said beam along said path between said points, the dimensions of the focused beam along the path and the energy of the laser beam which is delivered to the gas medium in the path being adjusted to raise the energy of the medium by an amount falling substantially within the range of 20 percent to 800 percent but below the level at which substantial thermal ionization of the gas takes place, thereby to produce a rarefaction trail along said path between said spaced points.

Claim 12

Apparatus for establishing a heated rarefaction trail for the purpose of guiding the discharge of high potential electrical energy comprising a path of known discharge distance extending between spaced points through a gas medium of substantial ambient pressure, laser means having a beam wavelength which when passed through said gas medium experiences an absorption length of the same order as said discharge distance, the laser means including means for focusing said beam along said path between said points, the dimensions of the focused beam along the path and the energy of the laser beam which is delivered to the gas medium in the path being adjusted to raise the energy of the medium by an amount falling substantially within the range of 20 percent to 800 percent but below the level at which substantial thermal ionization of the gas takes place, thereby to produce a rarefaction trail along said path between said spaced points.

Claim 13

Apparatus as set forth in claim 10, wherein said spaced points comprise electrodes across which a high potential is connected, and said means for focusing said beam comprises means for directing the beam between two selected electrodes, thereby establishing the discharge therebetween to the exclusion of other paths.

Claim 14

Apparatus as set forth in claim 10, wherein said spaced points comprise electrodes; a source of high potential coupled between said electrodes; and trigger control means coupled to said laser means and to said source and operative to trigger the laser ''''on'''' and then to trigger the source ''''on'''' to discharge the high-potential through the rarefaction trail when the latter has been established by the laser means.

Claim 15

Apparatus as set forth in claim 10, wherein said supply comprises a pulse discharge direct-current supply with an alternating current ripple superimposed upon the direct-current pulse.

Claim 16

Apparatus as set forth in claim 10, wherein sAid laser means comprises two lasers having means for focusing their beams to substantially intersect each other in the vicinity of a third point to form a rarefaction trail including said spaced points and said third point; electrodes at said spaced points and intersecting said beams; and a source of high potential coupled between said electrodes.

Claim 17

Apparatus as set forth in claim 10, wherein said laser means comprises two lasers having different wavelengths, including a first laser having a shorter absorption length in said medium and a second laser having a longer absorption length in said medium, and the lasers including means for focusing their beams along the same trail such that the first laser beam produces a rarefaction trail extending from one point less than all the way toward the other point and making the medium more transparent to the second laser beam; and the second laser passing through said more-transparent trail and producing a rarefaction trail completing said path to the other point.

Claim 18

Apparatus as set forth in claim 15, wherein said two lasers have their focusing means colinearly disposed to radiate along the same path between said spaced points.

Claim 19

Apparatus as set forth in claim 10, wherein said path of known distance comprises an antenna radiation path including an electrode at a lower point therealong and an upper point comprising the top of the antenna radiator, the wavelength of the laser being selected such that the absorption length in the medium substantially equals the length of the radiator; a high-voltage high-energy source coupled between ground and said electrode and having energy limited to propagate a streamer tip along said trail which extends only over the length of the desired radiator; and means operative to discharge the source along the trail while the laser beam is present.

Claim 20

Apparatus as set forth in claim 10, wherein the laser means is pulse operated and has its energy and its time duration proportioned such that said trail energy level will be reached in a time which does not exceed the acoustic transit time of a compressional wave across the radius of the beam.