3,761,836
`1111
`1191
`United States Patent
` Pinsley et al. [45] Sept. 25, 1973
`
`
`[54] MAGNETICALLY COMPENSATED CROSS
`FIELD FLOWING GAS LASER
`Inventors: Edward A. Pinsley, North Palm
`Beach, Fla; Albert W. Angelbeck,
`East Hartford; Carl J. Buczek,
`Manchester. both of Conn.
`
`[75]
`
`[73] Assignee: United Aircraft Corporation, East
`Hartford. Conn.
`
`Jan. 7, 1972
`Filed:
`[22]
`[21] App]. No.: 216,302
`
`Related U.S. Application Data
`[63] Continuation of Ser. No. 877,320. Nov. 17, 1969
`abandoned.
`
`»
`
`[52] US. Cl. .............................. 331/945, 330/43
`[51]
`Int. Cl. ..................
`.. H018 3/22 H018 3/09
`
`Field of Search ..................... 331/945; 330/43;
`[58]
`315/3971
`
`[56]
`
`3,514,714
`3,577,096
`
`References Cited
`UNITED STATES PATENTS
`5/1970 Angelbeck ......................... 331/945
`5/1971
`Bridges er al. ..................... 331/945
`
`Primary Examiner—David Schonberg
`Amsm’” Emmmer—R J..Webster
`AIIorney— Anthony J. Cnso
`
`,,
`
`[57]
`
`ABSTRACT
`
`A flowing gas laser having an electric discharge plasma
`with the electric field oriented transversely with respect
`to the flow of gases therethrough is provided with a
`magnetic field which is oriented transversely with re-
`spect to both the flow and the electric field to over-
`come the forces of flowing gases thereon.
`
`2 Claims, 1 Drawing Figure
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`GILLETTE 1405
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`

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`Patented St‘pl. 25,
`
`l973
`
`3,761,836
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`1
`MAGNETICALLY COMPENSATED CROSS FIELD
`FLOWING GAS LASER
`
`3,761,836
`
`is a continuation of application Ser. No.
`This
`877,320, filed Nov. l7, I969 now abandoned.
`
`BACKGROUND OF THE INVENTION
`l. Field of Invention
`This invention relates to flowing gas lasers, and more
`particularly to means for compensating the flow field
`effects on the electric discharge plasma thereof.
`2. Description of the Prior Art
`Recently, there has been a number of advances in the
`gas laser art. Particularly,
`it has become known that
`molecular, vibrational lasers of the flow-ing type are
`capable of extremely high power density, specific
`power and total power output. These characteristics
`are further enhanced in a flowing gas laser in which the
`optical gain region (which may be an optical cavity in
`the case of an oscillator, or one or more optical gain
`paths between suitable mirrors in the case of an ampli-
`fier) is coextensive with the electric discharge plasma
`within which the population inversion of the lasing gas
`is achieved. If the plasma extends outside of are optical
`gain region, the electrical efficiency and the total out-
`put power capability are decreased. Heating of the
`gases by the plasma is mitigated when the gas flows
`across the least dimension thereof. Thus, a laser with
`the optical gain path and plasma coextensively trans-
`verse to flow has been found to be highly desirable.
`A difficulty resides in overcoming the flow field ef-
`fects which the flowing gas has upon the plasma. Spe-
`cifically, the plasma tends to be blown downstream,
`and thus out of a narrow optical gain region, or spread
`in an inefficient fashion across a broad optical gain re—
`gion. To overcome this, compensation has been pro-
`vided with RE pre-ionization means in a copending ap-
`plication of the same assignee entitled TRANSVERSE
`GAS LASER, Ser. No. 857,647, filed on Sept. 10,
`l969, by Bullis and Penney. In some instances, the RF
`pre-ionization solution is unattractive due to the need
`to provide an RF power supply, and the additional
`weight and power consumption attendant therewith.
`There arc, obviously, other situations in which RF pre-
`ionization is not perfectly suitable.
`SUMMARY OF THE INVENTION
`
`The object of the present invention is to provide im—
`proved compensation for a transverse electric dis-
`charge plasma in a flowing gas laser.
`According to the present invention, a magnetic field
`is oriented transversely with respect to both gas flow
`and the E field of a cross-field electric discharge flow-
`ing gas laser. The magnetic field exerts a force on the
`electrons drifting from the cathode to the anode to cre-
`ate a force in the direction opposite to the flow of
`gases,
`thereby compensating for
`flow field effects
`which tend to blow the electric discharge plasma down-
`stream.
`
`The present invention is capable ofsimple implemen-
`tation, not requiring additional power supplies or the
`power consumption and weight attendant therewith.
`The present invention may be implemented simply with
`permanent magnets, which are nonconsumptive.
`The foregoing and other objects, features and advan-
`tages of the present invention ,will become more appar—
`ent in the light of the following detailed description of
`
`2
`a preferred embodiment thereof, as illustrated in the
`accompanying drawing.
`
`BRIEF DESCRIPTION OF THE DRAWING
`
`The sole FIGURE herein comprises a simplified.
`schematicized, partially broken away perspective view
`ofa flowing gas laser with magnetic flow field compen-
`sation in accordance with the present invention.
`DESCRIPTION OF THE PREFERRED
`EMBODIMENT
`
`Referring to the FIGURE, a flowing gas laser incor-
`porating the present invention comprises a conduit 10
`through which lasing and other gases flow from a
`source 12 in a direction indicated by an arrow 14. The
`gas mixture may typically comprise nearly equal parts
`of carbon dioxide, nitrogen and helium, or other ratios
`or mixtures known in the art. It is important to note
`that the particular gas mixture is not really significant
`to the present invention since the invention incorpo-
`rates the force effect of a magnetic field on drifting
`electrons within an electric discharge plasma, all of
`which is independent of the particular gas mixture em-
`ployed; even though the electron drift depends in part
`on the gas mixture, the magnetic field may be adjusted
`according.
`Appended to the conduit 10 are structures which in-
`clude mirrors 15, 16 to form an optical cavity, includ-
`ing suitable output coupling capability (such as a par-
`tially reflecting mirror or a hole 17 in one of the mir-
`rors), as well as the anode 18 and cathode 19 necessary
`to establish an electric discharge plasma. The anode 18
`and cathode 19 are connected by suitable electrical
`conductors 20 to a suitable power supply 22. all as is
`known in the art. Disposed above and below the region
`between the structures 15—19 are magnetic pole pieces
`24, 26 respectively. These create a magnetic field from
`top to bottom as viewed in the FIGURE, and as indi-
`cated by the vector 28. The migration of electrons from
`the cathode to the 'anode result in a current vector (op—
`posite to electron flow) in the direction from the anode
`18 to the cathode 19 as shown by the vector 30.
`As is known, the interaction between the current and
`the magnetic field will result in an upstream force as in-
`dicated by the force vector 32. This force is exerted
`upon the electrons, and tends to maintain the electrons
`in an area between the anode and cathode. However,
`the flow field effects on the ions are much greater than
`those on the electrons since the mass of the ions is sev-
`eral orders of magnitude greater than the mass of the
`electrons. But, electrical neutrality dictates that if the
`electrons are maintained in the area between the anode
`and cathode, as the ions tend to be blown downstream,
`there is an electrical force of attraction between them
`which causes the ions to remain in the same general vi-
`cinity with the electrons. Thus, the plasma established
`by the electric field between the anode 18 and cathode
`19 is maintained in an area substantially between the
`pole pieces 24, 26.
`The magnetic field may be created by electro-
`magnets instead of the permanent magnets 24, 26 if de-
`sired. The downstream end of the conduit 10 may be
`connected to suitable exhaust means so as to vent the
`gases to ambient, or suitable flow means may be pro-
`vided so as to create a closed-loop or closed cycle sys~
`tem in which the gases are recirculated continuously
`through the conduit 10, as is known in the art. What is
`
`10
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`15
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`20
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`25
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`30
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`35
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`4O
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`45
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`50
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`55
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`6O
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`65
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`

`

`3
`
`3,761,836
`
`4
`
`tical gain region, the comprising comprising:
`means for establishing an optical gain region which
`has an optical axis therethrough;
`means for providing a flow ofa gas mixture including
`a lasing gas through said optical gain region in a di-
`rection transverse tothe axis;
`means_for establishing an electric discharge plasma
`'within' said optical gain region, the electric field of
`said plasma being transverse to the flow of gases
`through said optical gain region; and
`means for establishing a magnetic field in said optical
`gain region, the flux lines of the magnetic field
`being transverse with respect to both said flow of
`gases and with respect to said electric field, and ori-
`ented in a direction to generate a force, on elec-
`trons in the plasma drifting from the cathode to the
`anode which is opposite to the direction of gas flow
`through said optical gain region for compensating
`for flow field effects which tend to blow the electric
`discharge plasma downstream.
`2. The gas laser according to claim 1 wherein the di-
`mension of said optical gain region in the direction of
`said electric field is greater than the dimension of said
`optical gain region in the direction of said magnetic
`field.
`*
`*
`*
`*
`3k
`
`' "
`
`~
`
`5
`
`important to the present invention is that the magnetic
`field be capable of generating a force on the electrons
`as a result of the J-cross-B product which is opposite to
`the flow of gases through the electric discharge plasma.
`'Typical parameters for a small, laboratory model of
`the present invention include a conduit having a width
`of six inches, a depth of one-half inch, with a flow of
`gases therein having a mixture of 1:3:6 C02, N2 and He,
`respectively, at a total pressure of 25 Torr and a flow
`velocity of 30 M/sec. The magnetic pole pieces 24, 26 10
`provided 300 gauss, and the electric field comprised
`approximately 100—150 volts per centimeter.
`Although the invention has been shown and de—
`scribed with respect
`to a preferred embodiment
`thereof, it should be understood by those skilled in the 15
`art that the foregoing and various other changes and
`omissions in the form and detail thereof may be made
`therein without departing from the spirit and scope of
`the invention.
`
`Having thus described a typical embodiment of our
`invention, that which we claim as new and desire to se-
`cure by Letters Patent of the United States is:
`1. In a flowing gas laser of the type in which electrical
`power is coupled into the gas flowing through an opti-
`cal gain region through electron collisions within an
`electric discharge plasma established in the optical gain
`(
`region, an optical output power is coupled from the op-
`
`20
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`25
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`30
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`

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`PO-WSO
`W
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`,
`
`T UNITED STATES TATENT OFFICE
`CERTIFICATE OF CORRECTION
`
`PatmuzNo.
`
`3 761 336
`
`.
`
`Dated segtemberrzs, 1973
`
`Inventofls)
`
`EDWARD A. PINSLEY ET AL
`
`it is certified that error appears in the above—identified patent
`and that said Letters Eaten? are hereby corrected as shown below:
`
`T E”- Coklumni‘1,_line 15,
`
`V'iflow-ing” should read: F-- flowing --
`
`“E
`
`line 24,
`
`"are” Should read -- the --
`
`Column 4,
`
`line 37,-
`lihe’Jl,
`
`”RE" should read —- RF --
`deiecel'romprising.” first occurrence I
`ahd inéert ,_- combination --
`
`Signed andsealed this 25th day of December 1973.
`
`(SEAL)
`Attest:
`‘
`EDWARD M.ELETCHEE,JE.
`Attesting Officer, 7
`
`-
`
`,
`
`,
`
`,
`RENE D. TEGTMEYER
`Acting Commissioner of Patents
`
`
`
`

`

`mg?
`
`a
`
`UNITED STATES TATENT OFFECE '
`CEETEWCATE OF CORRECTEON
`
`3 761 836
`
`,
`
`,
`
`Dated SeEtember-ZS, 1973
`
`Inventor(s)
`
`EDWARD A. PINSLEY ET AL
`
`identified patent
`It is certified that error appears in the above— shown belOw:
`and that said Letters Eatent are hereby corrected as
`'.
`E”
`.
`.
`"flow-ing" should read -- flowing --
`
`Column 1,
`
`line 15,
`
`"l
`
`line 24,
`
`”are” should read -— the --
`
`line 37,
`
`”RE” should read -- RF --
`
`Column 4, line 1,
`
`‘delete "comprising” first occurrence
`
`and insert -- combinatio —-
`
`Signed and sealed this 25th day of Deoember 1973.
`
`(SEAL)
`Attest:
`
`EDWARD M.ELETCHER,JR.
`Attesting Officer_
`
`RENE D..TEGTMEYER
`Acting Commissioner of Patents
`
`
`
`