GB1605258A - Creación de Inventos y Patentes con Inteligencia Artificial

GB1605258A – Gaseous flow laser
– Google Patents

GB1605258A – Gaseous flow laser
– Google Patents
Gaseous flow laser

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Publication number
GB1605258A

GB1605258A
GB3151476A
GB3151476A
GB1605258A
GB 1605258 A
GB1605258 A
GB 1605258A
GB 3151476 A
GB3151476 A
GB 3151476A
GB 3151476 A
GB3151476 A
GB 3151476A
GB 1605258 A
GB1605258 A
GB 1605258A
Authority
GB
United Kingdom
Prior art keywords
gas
primary
flow
chamber
laser according
Prior art date
1975-09-09
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)

Expired

Application number
GB3151476A
Inventor
Bernard Lavarini
Michel Mercier
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)

Alcatel Lucent SAS

Original Assignee
Compagnie Generale dElectricite SA
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
1975-09-09
Filing date
1976-07-28
Publication date
1986-09-24

1976-07-28
Application filed by Compagnie Generale dElectricite SA
filed
Critical
Compagnie Generale dElectricite SA

1986-09-24
Publication of GB1605258A
publication
Critical
patent/GB1605258A/en

Status
Expired
legal-status
Critical
Current

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Classifications

H—ELECTRICITY

H01—ELECTRIC ELEMENTS

H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL

H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range

H01S3/09—Processes or apparatus for excitation, e.g. pumping

H01S3/097—Processes or apparatus for excitation, e.g. pumping by gas discharge of a gas laser

H01S3/0979—Gas dynamic lasers, i.e. with expansion of the laser gas medium to supersonic flow speeds

Abstract

Nitrogen, excited by an electrical discharge, is introduced into supersonic nozzles. Slits opening into the throats of these nozzles inject a mixture of carbon dioxide and helium. The mixture of the three gases expands as far as an optical cavity, and molecular excitation of the carbon dioxide produces laser emission. Application in increasing the power output of nitrogen-CO2 lasers.

Description

(54) GASEOUS FLOW LASER
(71) We, COMPAGNIEGENERALE D’ELECTRICITE S.A..- a French Body
Corporate, of 54, rue La Boetie, 75382 PARIS
CEDEX 08, France, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:
The present invention relates to a gaseous flow laser.
Laser generators are known in which an electric discharge is produced in a primary gas which is then mixed with a secondary gas. The electric discharge has the effect of supplying the primary gas with an excitation energy which is then transferred to the secondary gas by molecular interaction. The excitation of this second gas enables the latter to effect stimulated light emission within an optical cavity, i.e. a laser emission.
The molecules of the primary gas (e.g.
nitrogen) have three possible excitation modes: thermal, rotational and vibrational.
The relaxation periods of the first two modes are very short. Thus when nitrogen molecules mix with the molecules of the secondary gas (e.g. carbon dioxide) it is the vibrational energy of the nitrogen which produces the population reversal within the carbon dioxide which gives rise to a high-power laser pulse.
The secondary gas could, however, also be carbon monoxide CO.
The invention is concerned with the provision of such a laser with improved efficiency.
According to the present invention, there is provided a gaseous flow laser comprising: – an excitation chamber opening into an expansion chamber through primary convergent-divergent nozzles;
– means including a primary injector in the excitation chamber for introducing a primary gas at pressure into the excitation chamber to set up a turbulent flow in this chamber and to cause this gas to flow into the expansion chamber,
– means for exciting the primary gas in the excitation chamber by means of an electrical discharge which is stable and diffuse,
– means including secondary injectors in the expansion chamber which define between them the primary nozzles and which comprise injection orifices in communication with the interior of the adjacent primary nozzles at the location of the nozzle constrictions for the introduction of a secondary gas at pressure into the flow of primary gas in the divergent parts of the primary nozzles so that molecules of the secondary gas become excited by transfer of energy from molecules of the primary gas,
– optical means for enabling a stimulated emission of coherent light to be produced by the excited secondary gas, and
– discharge means for maintaining the pressure in the expansion chamber at a low level relative to that in the excitation chamber, the arrangement being such that the speed of the secondary gas in the injection orifices is sonic and the speed of the primary gas at the output of the primary nozzles is supersonic.
An embodiment of the invention will now be described by way of example with reference to the accompanying drawings in which:
Figure 1 is a schematic section view of a laser of the invention, and
Figure 2 is an enlarged view of a part of
Figure 1.
The laser illustrated comprises an excitation chamber 2 having the form of a cylinder with a diameter of 5cm and a length of 33cm.
Generally it is preferred that the length of this chamber be between 5 and 7 times its diameter.
At an upstream end of this chamber 2 are disposed two primary injectors 4 and 6 connected to a source of nitrogen under pressure SN. These two injectors are metallic and each terminates in a nozzle enabling the formation of a supersonic stream of nitrogen.
The excitation chamber 2 is connected at its downstream end to a prismatic expansion chamber 8 having a rectangular cross-section, with a height of 18mm perpendicularly to the plane of the figure and a length of 126mm in the plane of the figure.
The upstream end of the expansion chamber 8 is partly closed by 21 metallic bars such as 10 and 12, equally spaced at a spacing of 6mm and disposed perpendicularly to the plane of the figure across the whole height of the chamber. The gaps between these bars form convergent-divergent nozzles such as 14 through which the nitrogen passes from the excitation chamber 2 to the expansion chamber 8. The width of these nozzles 14 at the constriction is imam. The width at the constriction is halved for the two end nozzles situated between a side wall of the chamber 8 and a bar adjacent to this wall.The total length of these nozzles, i.e. the length of the bars 10 or 12 parallel to the flow of the nitrogen is 165mm. It will thus be seen that the bars form an assembly having a dimension measured perpendicularly both to the length of the bars and to the direction of gas flow, which is greater than the dimension of the assembly parallel to the bars.
Provided that the pressure in the expansion chamber 8 is sufficiently low, the nitrogen assumes a sonic speed at the constriction of the primary nozzles 14 and a supersonic speed in the divergent part of these nozzles. The discharge rate of the primary injectors 4 and 6 is chosen so that the pressure in the excitation chamber 2 is about one atmosphere. The high speed of the nitrogen stream which they supply, as well as the choice of the dimensions of the excitation chamber 2 and of the nozzles 14 are such that there is a turbulent flow of nitrogen in this chamber. This flow enables an electric excitation discharge to be set up between the primary injectors 4 and 6 which are connected to the positive terminal of an electric generator G via a stabilizing resistor R and the bars such as 10 and 12.The energy of this discharge is preferably between 500 and 5000 kilojoules per kilogramme of nitrogen injected, for example 1500 kJ/kg with a voltage of between 20 and 70kV.
The bars such as 10 and 12 constitute secondary injectors enabling the injection of a secondary gas into the expansion chamber 8.
The secondary gas is constituted by a mixture of carbon dioxide and helium or carbon dioxide and water vapour. These secondary injectors are disposed so that the secondary gas expands at the same time as the nitrogen and mixes with the latter in the nozzles. For this purpose, the secondary injectors are supplied in parallel under pressure from a reservoir SC and are each provided with injection orifices such as 16 and 18, extending as slots the full height of the injector on both sides of the latter and through which secondary gas reaches a sonic speed.
These slots communicate with the nozzles 14 at their constrictions and are directed downstream so that the flow of secondary gas has a component in the direction of flow of the primary gas, forming in the laser illustrated an angle of about 45″ with the direction of flow.
They have a width of 0.25mm.
All the bars 10, 12 are constructed like the injector 10 which comprises a stainless steel supply tube 30. This tube is cylindrical with an outside diameter of 4mm and a thickness of 0.2mm. It extends perpendicularly to the plane of the figures the full height of the injector, extending to the walls of the expansion chamber 8. The two ends of this tube are connected to the reservoir SC which supplies it with the secondary gas under pressure.
Each secondary injector comprises, moreover, an upstream part 32 made of brass on the upstream side of the slots 16 and 18 and mounted on the tube 30. The upstream part is semi-cylindrical and is concentric with the tube 30. The diameter of the semi-circular cross-section of this part is 5 mm. The slots 16 and 18 all communicate with the expansion chamber 8 substantially in a single plane which passes through the axes of all the tubes 30.
The edges of the upstream parts 32 are in the shape of knife-edges i.e. they are sharp. They are perpendicular to the plane of the figures and the two sides of the edge form an angle of about 45″.
The secondary injector 10 further comprises a downstream part 34 made of brass. The upstream edges of this part 34 constitute part of the walls of the slots 16 and 18.
The width of the downstream part 34 is the largest in the plane passing through the axes of all the tubes such as 30. This largest width is the distance which separates the lateral ends of the downstream part 34, these lateral ends constituting the inside edge of the opening of the slots 16 and 18. This opening has a width of about 0.35mm and is situated substantially in the plane passing through the axes of all the tubes 30, whereas the width of the slots 16 and 18, measured perpendicularly to these slots is about 0.25mm.
The width of the downstream part 34 then decreases progressively downstream to a knife-edge shaped downstream end, whose sharp edge is parallel to the axis of the tube 30 situated at a distance of 14mm from the latter, the plane passing through each downstream edge and the axis of the corresponding tube 30 being parallel to the direction of gas flow.
Between the lateral and downstream ends of the downstream part 34, the walls of these latter are plane and each forms one of the walls of the divergent part of a nozzle such as 14.
This disposition results in the secondary gas leaving the slots 16 and 18 and passing into an empty space 0.35mm wide along the divergent walls of the nozzles 14. It mixes with the primary gas while expanding with it. The pressures of the primary gas and secondary gas are chosen to be substantially equal at the constriction of the nozzles. The pressure in the tubes such as 30 is about 0.7 or 0.8 bars, with a proportion of 16% of CO2 and 84% of helium, by volume. This in conjunction with the relatively low pressure in the expansion chamber ensures that the secondary gas reaches the speed of sound in the injection orifices.
The flow of nitrogen is 20% of the total gas flow, by volume. The partial pressure in the expansion chamber 8 is 8 torr for the nitrogen and 32 torr for the CO2 + He mixture.
Immediately downstream from the secondary injectors such as 10 and 12, the two lateral walls of the expansion chamber 8 perpendicular to the plane of the figure are replaced by two metallic mirrors 20 and 22, having a rectangular shape 8 cm in length parallel to the gas flow.
The mirror 20 is concave and solid. The mirror 22 is plane and has a central opening 12mm in diameter closed by a window 24 made of sodium chloride. Thus, a resonant optical cavity is formed enabling a stimulated emission of light from the excitation energy supplied by the nitrogen to the carbon dioxide to be produced, the light thus produced being able to leave through the window 24. The space inside this cavity has previously been called the emission zone. The position of this zone remains the same if the mirrors 20 and 22 are replaced by windows for using the device described as a laser amplifier.
The expansion chamber 8 is continued by a discharge tube 26 which is also prismatic and has the same cross-section and which communicates with an evacuated enclosure 28 communicating with a pumping assembly 29.
WHAT WE CLAIM IS:
1. A gaseous flow laser comprising: – an excitation chamber opening into an expansion chamber through primary convergent-divergent nozzles, – means including a primary injector in the excitation chamber for introducing a primary gas at pressure into the excitation chamber to set up a turbulent flow in this chamber and to cause this gas to flow into the expansion chamber, – means for exciting the primary gas in the excitation chamber by means of an electrical discharge which is stable and diffuse, – means including secondary injectors in the expansion chamber, which define between them the primary nozzles and which comprise injection orifices in communication with the interior of the adjacent primary nozzles at the location of the nozzle constrictions for the introduction of a secondary gas at pressure into the flow of primary gas in the divergent parts of the primary nozzles so that molecules of the secondary gas become excited by transfer of energy from molecules of the primary gas, – optical means for enabling a stimulated emission of coherent light to be produced by
the excited secondary gas, and
– discharge means for maintaining the
pressure in the expansion chamber at a low
level relative to that in the excitation chamber,
the arrangement being such that the speed of
the secondary gas in the injection orifices is
sonic and the speed of the primary gas at the
output of the primary nozzles is supersonic.
2. A laser according to Claim 1, wherein the injection orifices are directed so that the flow of secondary gas therethrough has a component in the direction of the flow of the primary gas.
3. A laser according to Claim 1 or 2, wherein the secondary injectors are in the form of parallel bars and the injection orifices comprise slots extending along the length of these bars.
4. A laser according to Claim 3, wherein the bars form an assembly having a dimension measured perpendicularly both to the length of the bars and to the direction of gas flow, which is greater than the dimension of the assembly parallel to the bars.
5. A laser according to Claim 3 or 4, wherein each of the secondary injectors comprises an upstream part situated upstream from the injection orifices and a downstream part situated downstream from the orifices, the upstream part being of larger dimension than the downstream part, measured perpendicularly to the length of the bars and to the direction of gas flow.
6. A laser according to Claim 5, wherein the downstream part terminates in a knife-edge at the downstream end.
7. A laser according to Claim 5 or 6, wherein the injection orifices are each defined partly by a knife-edge at the downstream end of the upstream part, the outside face of which knife-edge forms a wall of a primary nozzle.
8. A laser according to any one of claims 4 to 7, wherein each of the secondary injectors incorporates a feed tube having a circular cross-section extending along the length of the injector and arranged to receive the secondary gas under pressure, the upstream part of the injector forming a projection which is substantially semi-cylindrical and is concentric with this tube.
9. A laser according to any preceding claim, and in use, wherein the primary gas is nitrogen and the secondary gas is carbon dioxide.
10. A laser according to any preceding claim, wherein the excitation means comprise
**WARNING** end of DESC field may overlap start of CLMS **.

Claims (11)

**WARNING** start of CLMS field may overlap end of DESC **. proportion of 16% of CO2 and 84% of helium, by volume. This in conjunction with the relatively low pressure in the expansion chamber ensures that the secondary gas reaches the speed of sound in the injection orifices. The flow of nitrogen is 20% of the total gas flow, by volume. The partial pressure in the expansion chamber 8 is 8 torr for the nitrogen and 32 torr for the CO2 + He mixture. Immediately downstream from the secondary injectors such as 10 and 12, the two lateral walls of the expansion chamber 8 perpendicular to the plane of the figure are replaced by two metallic mirrors 20 and 22, having a rectangular shape 8 cm in length parallel to the gas flow. The mirror 20 is concave and solid. The mirror 22 is plane and has a central opening 12mm in diameter closed by a window 24 made of sodium chloride. Thus, a resonant optical cavity is formed enabling a stimulated emission of light from the excitation energy supplied by the nitrogen to the carbon dioxide to be produced, the light thus produced being able to leave through the window 24. The space inside this cavity has previously been called the emission zone. The position of this zone remains the same if the mirrors 20 and 22 are replaced by windows for using the device described as a laser amplifier. The expansion chamber 8 is continued by a discharge tube 26 which is also prismatic and has the same cross-section and which communicates with an evacuated enclosure 28 communicating with a pumping assembly 29. WHAT WE CLAIM IS:

1. A gaseous flow laser comprising: – an excitation chamber opening into an expansion chamber through primary convergent-divergent nozzles, – means including a primary injector in the excitation chamber for introducing a primary gas at pressure into the excitation chamber to set up a turbulent flow in this chamber and to cause this gas to flow into the expansion chamber, – means for exciting the primary gas in the excitation chamber by means of an electrical discharge which is stable and diffuse, – means including secondary injectors in the expansion chamber, which define between them the primary nozzles and which comprise injection orifices in communication with the interior of the adjacent primary nozzles at the location of the nozzle constrictions for the introduction of a secondary gas at pressure into the flow of primary gas in the divergent parts of the primary nozzles so that molecules of the secondary gas become excited by transfer of energy from molecules of the primary gas, – optical means for enabling a stimulated emission of coherent light to be produced by
the excited secondary gas, and
– discharge means for maintaining the
pressure in the expansion chamber at a low
level relative to that in the excitation chamber,
the arrangement being such that the speed of
the secondary gas in the injection orifices is
sonic and the speed of the primary gas at the
output of the primary nozzles is supersonic.

2. A laser according to Claim 1, wherein the injection orifices are directed so that the flow of secondary gas therethrough has a component in the direction of the flow of the primary gas.

3. A laser according to Claim 1 or 2, wherein the secondary injectors are in the form of parallel bars and the injection orifices comprise slots extending along the length of these bars.

4. A laser according to Claim 3, wherein the bars form an assembly having a dimension measured perpendicularly both to the length of the bars and to the direction of gas flow, which is greater than the dimension of the assembly parallel to the bars.

5. A laser according to Claim 3 or 4, wherein each of the secondary injectors comprises an upstream part situated upstream from the injection orifices and a downstream part situated downstream from the orifices, the upstream part being of larger dimension than the downstream part, measured perpendicularly to the length of the bars and to the direction of gas flow.

6. A laser according to Claim 5, wherein the downstream part terminates in a knife-edge at the downstream end.

7. A laser according to Claim 5 or 6, wherein the injection orifices are each defined partly by a knife-edge at the downstream end of the upstream part, the outside face of which knife-edge forms a wall of a primary nozzle.

8. A laser according to any one of claims 4 to 7, wherein each of the secondary injectors incorporates a feed tube having a circular cross-section extending along the length of the injector and arranged to receive the secondary gas under pressure, the upstream part of the injector forming a projection which is substantially semi-cylindrical and is concentric with this tube.

9. A laser according to any preceding claim, and in use, wherein the primary gas is nitrogen and the secondary gas is carbon dioxide.

10. A laser according to any preceding claim, wherein the excitation means comprise
two electrodes, one constituted by the primary injector and the other by the secondary injectors, the excitation chamber having the form of a cylinder, the length of which is between 5 and 7 times its diameter.

11. A laser substantially as herein described with reference to the accompanying drawings.

GB3151476A
1975-09-09
1976-07-28
Gaseous flow laser

Expired

GB1605258A
(en)

Applications Claiming Priority (1)

Application Number
Priority Date
Filing Date
Title

FR7527598A

FR2569062A1
(en)

1975-09-09
1975-09-09
Gas laser device

Publications (1)

Publication Number
Publication Date

GB1605258A
true

GB1605258A
(en)

1986-09-24

Family
ID=9159758
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Application Number
Title
Priority Date
Filing Date

GB3151476A
Expired

GB1605258A
(en)

1975-09-09
1976-07-28
Gaseous flow laser

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DK
(1)

DK373776A
(en)

FR
(1)

FR2569062A1
(en)

GB
(1)

GB1605258A
(en)

PT
(1)

PT65500A
(en)

TR
(1)

TR19075A
(en)

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* Cited by examiner, † Cited by third party

Publication number
Priority date
Publication date
Assignee
Title

US3688215A
(en)

1970-09-21
1972-08-29
Us Air Force
Continuous-wave chemical laser

US3760294A
(en)

1971-09-27
1973-09-18
Us Army
Thermal mixing gas laser

FR2180547B1
(en)

1972-04-20
1977-01-14
Comp Generale Electricite

1975

1975-09-09
FR
FR7527598A
patent/FR2569062A1/en
not_active
Withdrawn

1976

1976-07-28
GB
GB3151476A
patent/GB1605258A/en
not_active
Expired

1976-08-10
TR
TR61907576A
patent/TR19075A/en
unknown

1976-08-19
DK
DK373776A
patent/DK373776A/en
unknown

1976-08-20
PT
PT6550076A
patent/PT65500A/en
unknown

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Publication number
Publication date

FR2569062A1
(en)

1986-02-14

TR19075A
(en)

1985-09-13

DK373776A
(en)

1985-03-05

PT65500A
(en)

1976-09-01

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