`H11
`H91
`United States Patent
` Pinsley et al. [45 1 Sept, 25, 1973
`
`
`[54] MAGNETHCALLY 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] Appl. No.: 216,302
`
`Related U_S_ Application Data
`'
`_
`. 877
`'
`] Commuamn of Ser No
`’320' NOV
`abandoned.
`
`63
`
`[
`
`. 17
`
`’ 1969’
`
`[52] us CL ............................... N 331/945 330/43
`[51]
`Int CL ................ U
`Hols 3/22’ Hols 3/09
`
`Field of Search ................... .. 331/94.5; 330/4.3;
`[58]
`315/39.71
`
`[56]
`
`3,514,714
`3.577.096
`
`References Cited
`UNITED sTATEs PATEN1-5
`5/1970 Angclbcck ....................... .. 331/94.5
`5/197]
`Bridges et al. ................... .. 331/94.5
`
`Primary E.taminer—David Schonberg
`A”l5"’”’ E-"“""'"9"—R J-_web5‘°"
`Aiiurne_v— Anthony J. Criso
`
`7
`
`[57]
`
`ABSTRACT
`
`A flowing gas laser having an electric discharge plasma
`with the electric field oriented transversely with respect
`.
`.
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`to the flow of gases therethrough is provided with a
`_
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`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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`A
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`TSMC-12
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`TSMC v. Zond, In
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`TSMC-1205
`TSMC v. Zond, Inc.
`Page 1 of 6
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`Patented Scpl. 25, 1973
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`3.76l,836
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`TSMC-1205 I Page 2 of 6
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`TSMC-1205 / Page 2 of 6
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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. 17, 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,
`I969, by Bullis and Penney. ln 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 are, obviously, other situations in which RF pre-
`ionization is not perfectly suitable.
`SUMMARY OF THE INVENTION
`
`10
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`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 of simple 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
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`55
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`60
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`65
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`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
`of a 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
`
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`TSMC-1205 I Page 3 of 6
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`TSMC-1205 / Page 3 of 6
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`4
`3
`tical gain region, the comprising comprising:
`important to the present invention is that the magnetic
`means for establishing an optical gain region which
`field be capable of generating a force on the electrons
`has an optical axis therethrough;
`as a result of the J—cross-B product which is opposite to
`means for providing a flow of a gas mixture including
`the flow of gases through the electric discharge plasma.
`‘Typical parameters for a small, laboratory model of
`a lasing gas through said optical gain region in a di-
`the present invention include a conduit having a width
`rection transverse to,the axis;
`of six inches, a depth of one-half inch, with a flow of
`means_for establishing an electric discharge plasma
`gases therein having a mixture of l:3:6 CO2, N2 and He,
`within said optical gain region, the electric field of
`respectively, at a total pressure of 25 Torr and a flow
`said plasma being transverse to the flow of gases
`velocity of 30 M/sec. The magnetic pole pieces 24, 26 10
`through said optical gain region; and
`provided 300 gauss, and the electric field comprised
`means for establishing a magnetic field in said optical
`approximately 100-150 volts per centimeter.
`gain region, the flux lines of the magnetic field
`Although the invention has been shown and de-
`being transverse with respect to both said flow of
`scribed with respect
`to a preferred embodiment
`gasezénd wgh Fetpect to Said elect“? field‘ and ion‘
`thereof, it should be understood by those skilled in the 15
`eme _m‘:
`1ireCn0:t_%,genferate 1? OrC:‘:n e elf-
`art that the foregoing and various other changes and
`trons m ‘ _e p,asma Y,‘ mg r°m_t 6 ,cat 0 6 to t e
`omissions in the form and detail thereof may be made
`anode wlmfh 15 °Pp°S"e_t° the? dlrecnon of gas fl_°w
`therein without departing from the spirit and scope of
`through said optical gain region for compensating
`the invention
`for flow field effects which tend to blow the electric
`Having thus described a typical embodiment of our 20
`dlscharge Plasma d°V_V"5tTe3m-_
`_
`_
`invention, that which we claim as new and desire to se-
`2- The 235 laser 3CC0Td1“g to C_13"1'f 1 Whefieln the '31‘
`cure by Letters Patent of the United States is:
`menslon Of Said Oimcal gal" T3310" 1"_th€ direction f3f
`1. In a flowing gas laser of the type in which electrical
`said €i€CtI‘iC
`field IS greater than the dimension Of Sald
`power is coupled into the gag flowing through an opti-
`cal gain region through electron collisions within an 25 optical gain region in the direction of said magnetic
`electric discharge plasma established in the optical gain
`field.
`region, an optical output power is coupled from the op-
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`3,761,836
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`D UNITED STATES ?ATENT OFFICE
`CERTIFICATE OF CORRECTION
`
`Patent No.
`
`3 761 836
`
`_
`
`Dated Segtember-25, 1973
`
`Inventor(s)
`
`EDWARD A. PINSLEY ET AL
`
`it is certified that error appears in the above-identified patent
`and that said Letters Patent are hereby corrected as shown below:
`
`-Column 1,_line 15,
`
`"flow-ing” should read -- flowing --
`
`line 24,
`
`"are" should read -- the --
`
`line 37,
`line 1,
`
`Column 4,
`
`"RE" should read -- RF --
`b*”delete “comprising” first occurrence"
`afid ineert -- combinatien --
`
`Signed and_sea1ed this 25th day of Decemfier 1973.
`
`(SEAL)
`Attest:
`
`EDWARD M.ELETCHER,JR.
`Attesting Officer» T
`
`'
`
`.
`
`V
`
`b
`RENE D. TEGTMEYER
`' Acting Comissioner of Patents
`
`L
`
`TSMC-1205 I Page 5 of 6
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`TSMC-1205 / Page 5 of 6
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`UNTTED STATES TATENT oTTTcE
`CEWMNCATE OF CORRECTEON
`
`Dated Segtember-25, 1973
`
`Inventor(s)
`
`EDWARD A. PINSLEY ET AL
`
`appears in the above—identified patent
`it is certified that error
`hown below:
`and that said Letters Fatent are hereby corrected as s
`
`gan-
`E
`
`Column 1,
`
`line 15,
`
`"flow-ing" should read 4- flowing --
`
`line 24,
`
`line 37,
`
`”are” should read -5 the --
`
`“RE” should read -- RF -r
`
`Column 4, line 1,
`
`delete "comprising" first occurrence
`
`--
`
`and insert -— combinatio
`
`Signed and S
`
`ealed this 25th day of Decemter 1973.
`
`(SEAL)
`Attest:
`
`EDWARD M.ELETCHER,JR.
`Attesting Officer
`
`_
`RENE D- TEGTMYER
`Acting Comissioner of Patents
`
`4TSMC-1205 I Page 6 of 6
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`TSMC-1205 / Page 6 of 6