CN1213200A

CN1213200A - Pneumatic cooling electric exciting gas laser

Info

Publication number: CN1213200A
Application number: CN 97109261
Authority: CN
Inventors: 程祖海
Original assignee: Huazhong University of Science and Technology
Current assignee: Huazhong University of Science and Technology
Priority date: 1997-09-30
Filing date: 1997-09-30
Publication date: 1999-04-07
Anticipated expiration: 2017-09-30
Also published as: CN1075905C

Abstract

A pneumatically cooled, electrical excited gas laser device with downstream mixing (or premixing) is composed of gas accumulating chamber, cathode array nozzle, discharge chamber, anode array nozzle, mix-exciting chamber, resonant cavity and power supply, and features that in the condition that expensive medium He gas, laser fan and heat exchanger are not used, it can output high-power and high-quality laser beam wigh compact volume of laser head.

Description

Pneumatic cooling electric exciting gas laser

The invention belongs to laser technology field.

Along with laser processing application and development such as laser deep penetration welding, cutting and large-area laser surface peenings, demand to high power, high light beam quality laser is urgent day by day, and the major technique obstacle of restriction high power, the development of high light beam quality laser is how to obtain large volume, stable and uniform glow discharge and gain medium spatial distribution uniformity.In recent years, gas laser is in excitation power supply, and electrode structure two aspects have obtained remarkable progress, but the type of cooling of laser medium still is confined to the diffusion cooling and convection current is cooled off two kinds.Diffusion cooling laser device is owing to the restriction (generally only being several millimeters) of the spacing of being discharged, and the discharge cumulative volume is less, and the output laser power only is multikilowatt at present.The great advantage of convection current cooling laser device is to obtain large volume, stabilized uniform glow discharge and good laser medium cooling effect, laser output power can be up to tens thousand of watts, but inner necessary laser blower fan and the heat exchanger installed of laser, cause the laser structure complexity, bulky, and the spatially uniform of active medium is relatively poor in the resonant cavity.Particularly owing to the restriction of laser compressor flow and heat exchange capability of heat exchanger, this class laser output laser power further raising remains at many technical difficulties.In order to avoid the restriction of laser blower fan and heat exchanger, the H.Hara in Japan Defense Agency (JDA) first research center and A.Jujisawa just proposed the CO that mixed downstream, supersonic nozzle adiabatic expansion are cooled off as far back as 1980 ₂Laser structure, " physical magazine " (H.Hara and A.Jujisawa, " Joumalde physique ", collogue cq, Nov.1980, P.C9.203～209) have obtained 11m ^-1High small signal gain, but this experimental provision adopts two gardens tube sparking electrode, it is lower to inject discharge power.

1984, French Laserdot company adopted mixed downstream, supersonic nozzle cooling technology, has succeeded in developing 40KW electric excitation CO ₂Laser, the far field beam angle of divergence only be 1.7 times of diffraction limits " laser report " (Laser raport, July, 1,1993, P5), but this laser structure is openly reported.1993, the H.V.Blow of Germany DLR technology physics institute and E.Zeytan employing RF excited, the supersonic nozzle cooling technology, under the condition of not using cooled with liquid nitrogen, obtained 1 kilowatt of CO laser output " scientific instrument comment " (H.V.B ü lowBlow and E.Zeytang, " REV.Sci.Instrum) ", Vol.64, No.7,1993, P1764～1769).Russia LOK company adopts electron beam preionization and supersonic nozzle cooling technology, has succeeded in developing 200KW CO laser, and stream time can reach 8 hours " laser report " (Laser, report.circle, No14-16,1993).Shown mixed downstream, pneumatic cooling technology good prospects for application in gas laser.Regrettably, the laser working medium major part of all these lasers is expensive He gas, thereby operating cost is higher.

The purpose of this invention is to provide a kind of not using under expensive working medium He gas and laser blower fan and the heat exchanger condition, to improve industrial CO ₂Laser injecting electric power density and electro-optical efficiency, reduce the laser head volume and weight, improve laser output power and improve the gas laser apparatus that can realize large volume uniform glow discharge and the cooling of mixed downstream (or premixed) supersonic nozzle that beam quality is a purpose.Use apparatus of the present invention, also can under the condition of not using cooled with liquid nitrogen, obtain high power, the output of high light beam quality CO laser.

The present invention implements by following technical measures, and it is by gas dome 3, and arc chamber 15 and mixed excitation chamber 20 3 big assemblies constitute, and described array jet pipe negative electrode 6 is divided into two separate spaces with gas dome 3 and arc chamber 15.In arc chamber, negative electrode array nozzle gas flow direction is consistent with array cathode needle course of discharge, and the discharge characteristic of every cathode needle does not disturb mutually, is easy to realize the large volume stable uniform glow discharge; Described array jet pipe anode 19 is divided into independently two spaces with arc chamber 15 and mixed excitation chamber 20.With the laser beam outbound course is reference axis, and in arc chamber 15, array cathode needle course of discharge is perpendicular to optical axis; And in mixed excitation chamber 20, the active medium flow direction is then consistent with optical axis, has realized the horizontal needle plate discharge of large volume and vertical gas flow dual purpose, can obtain high power, the output of high light beam quality laser.Described gas dome 3 is by cathode needle fixed head 1, arc chamber upper cover plate 4, and array jet pipe negative electrode 6 constitutes.Cathode needle fixed head 1 is made by resistant to elevated temperatures insulating material.Evenly distributed a plurality of apertures on fixed head, cathode needle pass aperture and are integral with fixed head is bonding, and this assembly fuses by insulating cement and arc chamber upper cover plate 4.Arc chamber upper cover plate 4 longitudinally has a plurality of nitrogen (N ₂) air admission hole 5, so that with laser working gas N ₂Introduce gas dome 3.Upper cover plate 4 also has

pressure tap

28 and 29, measures the gas-static of gas dome 3 and arc chamber 15 respectively, and is connected as a single entity by trip bolt 25 and left and

right sides wallboard

9,11; Described array jet pipe negative electrode 6 is made by resistant to elevated temperatures insulating material.Negative electrode array jet pipe is made up of garden awl (or garden post) aperture 7 of a plurality of symmetric arrays, garden awl (or garden post) aperture 7 distributes and distributes corresponding one by one with cathode needle 2, so that cathode needle 2 passes the axle center of garden awl (or garden post) aperture, between garden awl (or garden post) aperture and cathode needle, form annular expansion (or annular) jet pipe 8, gas dome gas enters arc chamber 15 through adiabatic expansion, reaching laser working gas cooling purpose in advance. negative electrode array jet pipe is connected as a single entity by trip bolt 34 and arc chamber upper cover plate 4, and by the excellent sealing between O shape circle 35 assurance gas domes 3 and the arc chamber 15.Described arc chamber 15 is by upper cover plate 4, framed

side wallboard

9,11, the cavity that array jet pipe anode 19 constitutes.Its

framed side wallboard

9,11 is made by the insulating material of anti-water logging erosion.Have bosh 13 and water-in and water-out aperture 12 on the framed side wallboard, be pasted with resistant to elevated temperatures insulating thin 10 near arc chamber one side.The upper and lower end face of framed side wallboard has

seal groove

36 and 37, and be connected as a single entity by trip bolt 27 and upper cover plate 4 and jet pipe anode 19, distance between cathode needle end points and the anode nozzle is called the discharge spacing, discharge voltage and arc chamber gas pressure by laser determine jointly, this structure makes the course of discharge of every cathode needle of arc chamber identical with gas flow direction, flash-over characteristic between pin and the pin is not disturbed mutually, have good discharge stability and uniformity, the arc chamber two ends are equipped with observation window 27.Array jet pipe anode 19 is made by oxygen-free copper or red copper, and this array jet pipe has mixed downstream and two kinds of user modes of premixed, and anode array jet pipe has two groups of separate array garden awl (or garden post) apertures 16 and 18.Array aperture 16 is the main jet pipe, and it communicates with arc chamber 15 and mixed excitation chamber 20, so that the energy carrier N that is excited by electron collision in the region of discharge ₂Gas enters mixed excitation chamber 20 after by the jet pipe adiabatic expansion.Array aperture 18 is the mixed downstream jet pipe, it and carbon dioxide (CO ₂) air inlet pipe 17 and mixed excitation chamber 20 communicate, so that laser medium CO ₂With the N that is excited ₂Gas carries out resonance energy transfer and excites (or claiming that mixed downstream excites) in the mixed excitation chamber.N ₂Gas main jet pipe and CO ₂The mixed downstream jet pipe evenly distributes along optical axis direction, and its nozzle throat diameter and number are respectively by arc chamber gas pressure, CO ₂Pipe inlet pressure and N ₂Gas and CO ₂Mixing ratio and mass flow decision.What premixed was different with the mixed downstream user mode is that 19 on array jet pipe anode uses one group of array aperture 16, does not use CO ₂(or CO) air inlet pipe 17 and array aperture 18, laser active medium CO ₂Gas and working medium N ₂Gas enters arc chamber 3 through air inlet pipe 5 together, directly is excited to excite to arc chamber 15 again after the cooling of negative electrode array jet pipe 8 adiabatic expansions.Jet pipe anode 19 has many row's cooling apertures 14, so that anode keeps favorable cooling effect.Described mixed excitation chamber 20 is made of the mixing tube 22 and the array jet pipe anode 19 of upper end open.The opening surface of mixing tube 22 is welded with adpting flange 21, and external diameter is surrounded by water jacket 23.Water jacket 23 is one with adpting flange 21 welderings, has into and out of the water hole 24 on it, so that mixing tube keeps good cooling.Be welded with aspirating chamber 33 at the mixing tube two ends.Aspirating chamber 33 is made of

end cap

31,32 and exhaust tube 30, end cap 31 respectively with ring flange 21, mixing tube 22 weldering is one.End cap 32 will connect with laserresonator, to form laser generation output.The mixed excitation chamber component links to each other with the arc chamber assembly with anode array jet pipe by trip bolt 27, and guarantees sealing by O shape circle 38.

Compared with prior art, the most outstanding advantage of the present invention is:

1. it is pre-cooled to have adopted negative electrode array jet pipe adiabatic expansion technology that the region of discharge working gas is carried out, and helps reducing the arc chamber working gas temperature.And place the axle center of negative electrode array jet pipe owing to every cathode needle, not only cathode needle itself obtains good cooling effect, and the gas flow direction consistent (the cathodic discharge direction and the airflow direction quadrature of existing horizontal needle plate discharge technology) of the course of discharge of having guaranteed every pin and negative electrode array jet pipe, flash-over characteristic between pin and the pin is separate, does not disturb (the upstream cathode needle of existing horizontal needle plate discharge technology has stronger preionization effect to the downstream cathode needle) mutually.Increase row, the number of columns of cathode needle,, be easy to realize that the stable and uniform glow discharge and tens of ultra-large volume is to hundreds of kilowatt ultra high power laser output the discharge stability and the not influence of uniformity of arc chamber.

2. the ingenious application of two groups of separate array jet pipe anode apertures can be used apparatus of the present invention under mixed downstream and two kinds of working conditions of premixed.This anode array jet pipe is two separate spaces with the region of discharge and the laser excitation vibration region separation of gas laser, is reference axis with the laser beam outbound course, and in arc chamber, array cathodic discharge direction is perpendicular to optical axis; And it is indoor at mixed excitation, the active medium flow direction is then consistent with optical axis, it not only makes the mixed downstream technology become possibility, also successfully solved the technical barrier of horizontal spininess plate large volume uniform glow discharge and vertical gas flow, make apparatus of the present invention have cross-flow laser output laser power height, the measured two-fold advantage of vertical stream Laser Output Beam matter simultaneously concurrently.

3. owing to the adiabatic expansion effect of negative electrode and anode two-stage array jet pipe, the gas temperature of mixed excitation chamber can reach utmost point low value.The operating pressure of choose reasonable gas dome Working medium gas and the pumping speed of aspirating chamber pump, can make apparatus of the present invention under the condition of not using cooled with liquid nitrogen, realize the output of CO laser, also can not have expensive working medium He gas and do not use the laser blower fan and the heat exchanger condition under, obtain high-gain, the CO of high electro-optical efficiency ₂Light laser output has significantly reduced CO ₂The volume and weight of laser head helps industrial CO ₂The miniaturization of laser.

Fig. 1 is apparatus of the present invention cross section view.

Fig. 2 is apparatus of the present invention longitudinal section cutaway view.

Claims

1. Pneumatic cooling electric exciting gas laser, it is by gas dome (3), and arc chamber (15) and mixed excitation chamber (20) three big assemblies constitute, and it is characterized by:

(1) described array jet pipe negative electrode (6) is divided into two separate spaces with gas dome (3) and arc chamber (15), in arc chamber, negative electrode array nozzle gas flow direction is consistent with array cathode needle course of discharge, the discharge characteristic of every cathode needle does not disturb mutually, is easy to realize the large volume stable uniform glow discharge; Described array jet pipe anode (19) is divided into independently two spaces with arc chamber (15) and mixed excitation chamber (20), is reference axis with the laser beam outbound course, and in arc chamber (15), array cathode needle course of discharge is perpendicular to optical axis; And in mixed excitation chamber (20), the active medium flow direction is then consistent with optical axis, has realized the horizontal needle plate discharge of large volume and vertical gas flow dual purpose, can obtain high power, the output of high light beam quality laser;

(2) described gas dome (3) is by cathode needle fixed head (1), arc chamber upper cover plate (4), the cavity that array jet pipe negative electrode (6) constitutes, its cathode needle fixed head (1) is made by resistant to elevated temperatures insulating material, evenly distributed a plurality of apertures on fixed head, cathode needle passes aperture and is integral with fixed head is bonding, and this assembly fuses by insulating cement and arc chamber upper cover plate (4), and arc chamber upper cover plate (4) longitudinally has a plurality of nitrogen (N ₂) air admission hole (5), so that with laser working gas N ₂Introduce gas dome (3), upper cover plate (4) also has pressure tap (28) and (29), measures the gas-static of gas dome (3) and arc chamber (15) respectively, and by trip bolt (25) and left and right sides wallboard (9), (11) are connected as a single entity;

(3) described array jet pipe negative electrode (6) is made by resistant to elevated temperatures insulating material, negative electrode array jet pipe is made up of garden awl (or the garden post) aperture (7) of a plurality of symmetric arrays, garden awl (or garden post) aperture (7) distributes and distributes corresponding one by one with cathode needle (2), so that cathode needle (2) passes the axle center of garden awl (or garden post) aperture, between garden awl (or garden post) aperture and cathode needle, form annular expansion (or annular) jet pipe (8), gas dome gas enters arc chamber (15) through adiabatic expansion, reach laser working gas cooling purpose in advance, negative electrode array jet pipe is connected as a single entity by trip bolt (34) and arc chamber upper cover plate (4), and by the excellent sealing between O shape circle (35) assurance gas dome (3) and the arc chamber (15);

(4) described arc chamber (15) is by upper cover plate (4), framed side wallboard (9), (11), the cavity that array jet pipe anode (19) constitutes, its framed side wallboard (9), (11) make by the insulating material of anti-water logging erosion, have bosh (13) on the framed side wallboard and advance, ostium excurrens (12), be pasted with resistant to elevated temperatures insulating thin (10) near arc chamber one side, on the framed side wallboard, the lower surface has seal groove (36) and (37), and be connected as a single entity by trip bolt (27) and upper cover plate (4) and jet pipe anode (19), the arc chamber two ends are equipped with observation window (27), array jet pipe anode (19) is made by oxygen-free copper or red copper, this array jet pipe has mixed downstream and two kinds of user modes of premixed, anode array jet pipe has two groups of separate array garden awl (or garden post) apertures (16) and (18), array aperture (16) is the main jet pipe, it communicates with arc chamber (15) and mixed excitation chamber (20), so that the energy carrier N that is excited by electron collision in the region of discharge ₂Gas enters mixed excitation chamber (20) after by the jet pipe adiabatic expansion, and array aperture (18) is the mixed downstream jet pipe, it and carbon dioxide (CO ₂) air inlet pipe (17) and mixed excitation chamber (20) communicate, so that laser medium CO ₂With the N that is excited ₂Gas carries out resonance energy transfer and excites (or claiming that mixed downstream excites), N in the mixed excitation chamber ₂Gas main jet pipe and CO ₂The mixed downstream jet pipe evenly distributes along optical axis direction, and its nozzle throat diameter and number are respectively by arc chamber gas pressure, CO ₂Pipe inlet pressure and N ₂Gas and CO ₂Mixing ratio and mass flow decision, what premixed was different with the mixed downstream user mode is that array jet pipe anode (19) only uses one group of array aperture (16), does not use CO ₂(or CO) air inlet pipe (17) and array aperture (18), laser active medium CO ₂Gas and working medium N ₂Gas enters arc chamber (3) through air inlet pipe (5) together, directly is excited to excite to arc chamber (15) again after the cooling of negative electrode array jet pipe (8) adiabatic expansion, and jet pipe anode (19) has many row's cooling apertures (14), so that anode keeps favorable cooling effect;

(5) described mixed excitation chamber (20) is made of the mixing tube (22) and the array jet pipe anode (19) of upper end open, the opening surface of mixing tube (22) is welded with adpting flange (21), external diameter is surrounded by water jacket (23), water jacket (23) is one with adpting flange (21) weldering, have on it into, apopore (24), so that mixing tube keeps good cooling, be welded with aspirating chamber (33) at the mixing tube two ends, aspirating chamber (33) is by end cap (31), (32) and exhaust tube (30) constitute, end cap (31) respectively with ring flange (21), mixing tube (22) weldering is one, end cap (32) will connect with laserresonator, to form laser generation output, the mixed excitation chamber component links to each other with the arc chamber assembly with anode array jet pipe by trip bolt (27), and guarantees sealing by O shape circle (38).