CA1194586A - Gas laser cathode and process for making same - Google Patents
Gas laser cathode and process for making sameInfo
- Publication number
- CA1194586A CA1194586A CA000406932A CA406932A CA1194586A CA 1194586 A CA1194586 A CA 1194586A CA 000406932 A CA000406932 A CA 000406932A CA 406932 A CA406932 A CA 406932A CA 1194586 A CA1194586 A CA 1194586A
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- Prior art keywords
- cathode
- layer
- gas laser
- blank
- temperature
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- 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
- H01S3/02—Constructional details
- H01S3/03—Constructional details of gas laser discharge tubes
- H01S3/038—Electrodes, e.g. special shape, configuration or composition
- H01S3/0388—Compositions, materials or coatings
-
- 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
- H01S3/02—Constructional details
- H01S3/03—Constructional details of gas laser discharge tubes
- H01S3/038—Electrodes, e.g. special shape, configuration or composition
- H01S3/0382—Cathodes or particular adaptations thereof
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- Physics & Mathematics (AREA)
- Electromagnetism (AREA)
- Engineering & Computer Science (AREA)
- Plasma & Fusion (AREA)
- Optics & Photonics (AREA)
- Carbon And Carbon Compounds (AREA)
- Lasers (AREA)
- Battery Electrode And Active Subsutance (AREA)
Abstract
GAS LASER CATHODE AND PROCESS FOR MAKING SAME
ABSTRACT
A gas laser cathode shaped at a sleeve with a three--layer wall from carbides of metals of the side subgroup of Group V of the Periodic System.
The external layers of the three-layer structure have a composition MeC0.74 to 0.95, the internal layer -MeC0.92 to 0.98 respectively or said second layer is made from a semicarbide MeC0.5. The process for producing the cathode comprises heating a graphite blank in an atmosphere of tantalum or niobium pentachloride and argon to a tempera-ture within the range of from 2,300 to 2,500°C and maintain-ing at this temperature for a period of from 5 to 8 hours.
Another embodiment of the process for making the cathode according to the present invention comprises heating a tantalum or niobium blank in the atmosphere of argon to a temperature within the range of from 2,000 to 2,200°C and maintaining at this temperature for 5 to 10 hours.
ABSTRACT
A gas laser cathode shaped at a sleeve with a three--layer wall from carbides of metals of the side subgroup of Group V of the Periodic System.
The external layers of the three-layer structure have a composition MeC0.74 to 0.95, the internal layer -MeC0.92 to 0.98 respectively or said second layer is made from a semicarbide MeC0.5. The process for producing the cathode comprises heating a graphite blank in an atmosphere of tantalum or niobium pentachloride and argon to a tempera-ture within the range of from 2,300 to 2,500°C and maintain-ing at this temperature for a period of from 5 to 8 hours.
Another embodiment of the process for making the cathode according to the present invention comprises heating a tantalum or niobium blank in the atmosphere of argon to a temperature within the range of from 2,000 to 2,200°C and maintaining at this temperature for 5 to 10 hours.
Description
GAS LASER CATHO~E AND PROCESS ~OR MAKI~G SAME
~ he present invention relate~ to quantum electronios and~ more specifical~y, it relate~ to cathode3 of ga~ e.g.
CO~=, laser~ and pro~e~s~ for making same.
It i~ known that in a ga~ laser and, in p~rticular, ~2 1~9er u~e is made of cathode~ man~actured from metal~, since met~ls (nickel~ platinum and t;he like~ ~re :re~pon-~ible for the ba3io propertie~ o~ the c~thod~s - electrical conductivity and emittivity of electrons. However~ the~e cathode~ do ~ot provida ~or long-term operation of la3er~
d~e to their sputtering un~er the ef~ect of ionio bombard-ment ~d interactio~ with the components of the workin~
ga~ mlxture.
Known in the ar~ i~ a cathode for a gas la~er ~haped a~ ~ thin-w~llad (Qbout 0.7 mm) cylindrical ~leeve from a~
electroconducting emitting materi~l - GoVar (alloy of Ni 28%, Co - 18%, Fe ~ 54%)~
This ¢athode, llke other metal cat~odes, undergoe~
~puttering under the effect o~ ion bombardment, which re-sult~ in a changed compo3ition of the working ga9 mixture, a rapid decrea2e of the radiation power~ thu~ limiting the ~ervice life OI the in~trument to a period not exceeding 500 hour~ .
Al~o known are cathode~ for electro-ion instruments :erom ¢arbide.~ of r~fractory metal~ having emis~ion proper-tie~ and a h:lgh electrical conductivity.
As compared to metals9 carbide~ OI mlmerou~ refracto-ry metal~ are in~ignificarltly ~pu-ttered under the oo~di-tions o~ ion bombardment and ~ub~tantially do no-t react with acti~e component~ of the gas mixture of C02 laser~
Articleæ from carbide~ ncluding cathode~, are gene-r~lly manufactured by method~ o~ powder metallurgy - com-pre~ion-moulding and ~inte:rin~ However~ the manufacture o~ relatively thi~-walled ~0.5-0~8 mm) ca.thodes f'or ga~
la~er~ by these method~ i~ hindered ~ue to brittlenes~ of carbides ~
Known in the art i~ a proce~s for the ma~u~acture of ~rticles, including cathode~ of carbides of refractory metals which comprises heating of a graphite blarlk in an atmo~phere of tantalum or niobium pentachloride and argon bs~ed on the interaction of graphite with a metal halide at a .high temperature with the formation of a carbide coat-ing. ~lowever, manufacture of cathode~ for ga~ lasers by thi~ proce~ doe~ not re~ult in a noticeable e:~tens~ on OI
the service li~e o~ la~er~, si~ce the ~raphite ~ub~trat~
actival~ interact~ with the gas medium of the laser thu~
hindering a full-~cope utili~ation of useful propertie~ of the carbide ~ e, Al~o known in the art i~ a proces~ for produci~g ar-ticle~ (cathode~, in particular) from carbides of refracto-ry metal~: compri~ing heating o:E a metal blank in a char~3e from a powder-like graphite in the atmo~ph~re of argon including tantalum and niob:lum which process is based on di~u~ion-type car~urization~ However, the manu~acture o-f cathode~ for gas la~er~ by this process is lnef~icLent due to the pre~en~e o~ an active met~l b~se a~fecting the ga~
medium compo~ition~
It i~ an object of the present inventlon to lower the rate of qputtering of the gas laser cathode und~r the ef-fect o~ ion bombar~mont, ~tabilize the lQ~ar ga~ medium com~
po~ition during lt~ operatlon and, hence, exten~ion of.the deYice ~3ervlc8 li~f9.
It is another object of the pres@nt invention to pro-vide a proce~ for the manufacture of ~uch cathade for a g~B laser.
~ he present invention resides in that in a gas laser cathode ~haped as a sleeve from an el~ctroconducting emit~
ting r.laterial, according to the present inventionl the Ye iB made three layered from ~arbide~ of metal~ of ~ide subgroup of Group V of the Periodic System ~ith e~ter-nal layer~ o~ the composition MeC0.74_0.95 layer o~ the composition ~eC0 92 0 98 re3pectiYely, or from a ~emicarbide ~leC0 5.
~ he pre~ent invention also resides in that in a pro-ce~ for m~king a cathode comprlsing heating of a graphite blank in ~n atmosphere of tantalum or niobium pentachloride, accordi~g to the pre~ent invention, the graphlte blank is heated to a temperature within the range o~ from 2 9 300 to
~ he present invention relate~ to quantum electronios and~ more specifical~y, it relate~ to cathode3 of ga~ e.g.
CO~=, laser~ and pro~e~s~ for making same.
It i~ known that in a ga~ laser and, in p~rticular, ~2 1~9er u~e is made of cathode~ man~actured from metal~, since met~ls (nickel~ platinum and t;he like~ ~re :re~pon-~ible for the ba3io propertie~ o~ the c~thod~s - electrical conductivity and emittivity of electrons. However~ the~e cathode~ do ~ot provida ~or long-term operation of la3er~
d~e to their sputtering un~er the ef~ect of ionio bombard-ment ~d interactio~ with the components of the workin~
ga~ mlxture.
Known in the ar~ i~ a cathode for a gas la~er ~haped a~ ~ thin-w~llad (Qbout 0.7 mm) cylindrical ~leeve from a~
electroconducting emitting materi~l - GoVar (alloy of Ni 28%, Co - 18%, Fe ~ 54%)~
This ¢athode, llke other metal cat~odes, undergoe~
~puttering under the effect o~ ion bombardment, which re-sult~ in a changed compo3ition of the working ga9 mixture, a rapid decrea2e of the radiation power~ thu~ limiting the ~ervice life OI the in~trument to a period not exceeding 500 hour~ .
Al~o known are cathode~ for electro-ion instruments :erom ¢arbide.~ of r~fractory metal~ having emis~ion proper-tie~ and a h:lgh electrical conductivity.
As compared to metals9 carbide~ OI mlmerou~ refracto-ry metal~ are in~ignificarltly ~pu-ttered under the oo~di-tions o~ ion bombardment and ~ub~tantially do no-t react with acti~e component~ of the gas mixture of C02 laser~
Articleæ from carbide~ ncluding cathode~, are gene-r~lly manufactured by method~ o~ powder metallurgy - com-pre~ion-moulding and ~inte:rin~ However~ the manufacture o~ relatively thi~-walled ~0.5-0~8 mm) ca.thodes f'or ga~
la~er~ by these method~ i~ hindered ~ue to brittlenes~ of carbides ~
Known in the art i~ a proce~s for the ma~u~acture of ~rticles, including cathode~ of carbides of refractory metals which comprises heating of a graphite blarlk in an atmo~phere of tantalum or niobium pentachloride and argon bs~ed on the interaction of graphite with a metal halide at a .high temperature with the formation of a carbide coat-ing. ~lowever, manufacture of cathode~ for ga~ lasers by thi~ proce~ doe~ not re~ult in a noticeable e:~tens~ on OI
the service li~e o~ la~er~, si~ce the ~raphite ~ub~trat~
actival~ interact~ with the gas medium of the laser thu~
hindering a full-~cope utili~ation of useful propertie~ of the carbide ~ e, Al~o known in the art i~ a proces~ for produci~g ar-ticle~ (cathode~, in particular) from carbides of refracto-ry metal~: compri~ing heating o:E a metal blank in a char~3e from a powder-like graphite in the atmo~ph~re of argon including tantalum and niob:lum which process is based on di~u~ion-type car~urization~ However, the manu~acture o-f cathode~ for gas la~er~ by this process is lnef~icLent due to the pre~en~e o~ an active met~l b~se a~fecting the ga~
medium compo~ition~
It i~ an object of the present inventlon to lower the rate of qputtering of the gas laser cathode und~r the ef-fect o~ ion bombar~mont, ~tabilize the lQ~ar ga~ medium com~
po~ition during lt~ operatlon and, hence, exten~ion of.the deYice ~3ervlc8 li~f9.
It is another object of the pres@nt invention to pro-vide a proce~ for the manufacture of ~uch cathade for a g~B laser.
~ he present invention resides in that in a gas laser cathode ~haped as a sleeve from an el~ctroconducting emit~
ting r.laterial, according to the present inventionl the Ye iB made three layered from ~arbide~ of metal~ of ~ide subgroup of Group V of the Periodic System ~ith e~ter-nal layer~ o~ the composition MeC0.74_0.95 layer o~ the composition ~eC0 92 0 98 re3pectiYely, or from a ~emicarbide ~leC0 5.
~ he pre~ent invention also resides in that in a pro-ce~ for m~king a cathode comprlsing heating of a graphite blank in ~n atmosphere of tantalum or niobium pentachloride, accordi~g to the pre~ent invention, the graphlte blank is heated to a temperature within the range o~ from 2 9 300 to
2.500C and malntained ~t this temperature for a period of from 5 to 8 hour~.
In another embodiment of the pre~ent invention, in a process for the manu~acture o~ a cathode comprising heating of a tantalum or niobium blank in a charge of powder like graphite; according to the present invention, the cathode blank is heated to a temperature within the range of ~rom 29000 to 2,200C and maintained at this temperature for a period o~ from 5 to 10 hour~
A ~as laser cathode produced by the proc~ss according to the present invention ~eatures low sputtering, ~tability in a ga~ medium, hlgh mechanical ~trength, high electrical conductivity and emission characteri~tic~. These advantage~
of the cathode aGcording -to the pre~ent invention make it po~ible to extcnd the ser~ice life of ga~ lasers by as much a8 about 10 times~
:~he embodiment~ of th~ proces~ ~or the manufacture of a gas laser ¢athode according to the present inventio~ are simpla in practicing and en~ble the production o~ thi~-wal-led (005Y tO 0.7 mm) mechanically durable ~tructure~ of cathodes~
rrhe pre~ent invention will be further illu~trated by the deqcription of its embodiments and the accompanying drawingl wherein the ga~ laser cathode aocording to the prese~t invention is shown in elevatio~0 'rhe ga~ la~er cathode according to the present inven-tion is shap~d as a cylindrical sleeve with its wall~
having a three~lay~r ~ tructure and m~Lde from carbide3 of metals o.ê ~ide qubgroup OI Group V of the Periodic System.
Extern~l layers 1 have the compo~ition MeC0 7~ 0 95, ~nd inn.er layer 2 ha~3 the composition MeC0 92 o 9~3 respecti~ely or is mads OI a ~emicarbide MeC0 51 The ratio OI thickne~-~es OI the layers 1-2~ el,ected within the range o:f from 1 :1 ,1 to 1 :0025 :1 . These par~meters are e~plained by the rLeces~ity of comb:i.ning the woxking p:ropextie~ oY the cathode (low rate of sput terin,g" ~tability i:~ a gas medium, and the like) aIld its mechanical strength a3 a structurs,1 member o* the la~erO
As ha~ been shown experlmentally, the requi:red worki~g properties of the cathode a:re ensured by the compo~ition o~
0~74_0~95j herefore the composition of the extern~l carblde layer~ 1 should not go beyond the range speciI ied hereinbe:~ore .
~ he required mecha:clical strength of the cathode i~
eIl~ured ~y the inner l~yer 2 o~ a cellular ~t:ructure of ta~talum or niobium monocarbide of an approprlate compo~i-tion ~lthin the rarlge of from MeC0 92 to MeC0 9E~ or ~rolll a tantalum or niobium semicarbide MeC0 5 (at a composition of the exter~al layers of M~Co .~3 to 0 .95 ) Vi~Go~ity than monoc~rbides.
The ratio oY thicknes~es of the layers OI fro~ 1 to 1:0.25:1, a~ it ha~ been found experimentally, en~ure~
the required mechanical strength of the cathode a~
~tructural member of the laser.
The proces~ ~or making the ~as la~er cathode accord-i~g to the pre~ent inve~tion can be per~ormed in two embo-diment~.
Accordin~ to a fir~t embodiment of the proce~ for themanufacture of a cathode 9 as a base use i~ made of a hollow graphita blank with a wall -thicknes~ ~lightly ~maller th~n the w~ hickness of the final cathocleO ~he bla~k i9 heat ed in a mixture of vapour~ o~ tantalum or niobium penta~
chloride and argon (1~5 to 2 g/l of argon) to a temper~ture within the range of from 2,300 to 2,500~C and maintained at this temperature for a period of from 5 to 8 hours. ~he pro-ces~ temperature and duration~ the starting blank thickne~s ~nd concentration of pent~ohloride are ~elected ~o as to en~ure the occurrence of the proce~s of carbidlzation with the formatio~ of a three-layer carbide ~tructure of the re-quired composition and ratio between ths layer thickne~se~
~ he t~ree-layered structure of the ~athode is ensured by thAt at the ~elected proGe~ parameter~ in the entire surface of the graphite blank there i~ ~imultaneously ~or~-ed a den~e aarbide layer ~external) and further growth of the carbide can be effect~d only through the agency of dif-fu~ion o~ carbon from the inner graphite m~trix which at a ¢~rtain proces~ ~tage i9 converted into a loo~en~d ~truc-ture and pentachloride penetrate~ thereinto along lt~ inter-grain face~ to convert thi~ structure into carbide rein-~orci~g the inner layers. At the proce~s temperature below 2,300C too den~e exter~al layer~ are formed, which hindex sharply the carbidization proces~ and make it impo~3ible to obtain the required re~ult within an acceptable time.
At a temperature exceeding 2,500C there oc¢urs formation of 100~3e c~rbide layers due to occurrence o~ the reaction i:~ bulk. The ~tar-ting thickne~s oE th}~ blank i~ ~elected by c~lculating the den~ity of carbide o~ tantalum or nio-bium and experimental corre¢tion.
Si~ce the conditions of the proce~ ~or tha manu~
tur~ of cathodes with the required parameters are lnterre lated, the time of carbidization i~ ~ound experimentally f rom the d~ta of met~llographic ~-ray structural analy~i~
of the final cathode~ and change~ in the weighk of the gra-phite blank after carbidization~ ~he above-specified time period o~ 5 to 8 hour~ ensures complete con~er~ion o~ ~ra-phite into the carbide ~tructure.
Specific condition~ of the fir~t embodiment of the proce~ according to the pre~ent invention and parameter~
of the resulti~g cathodes are shown in Table hereinbelow.
In ~nother embodiment of the proces~ ~or the manu~ac-ture o~ cathodes according to the pre~e:nt in~ention, a me-tal blank (OI tantalum or niobium respectively) with a wsll thioknes~ slightly ~maller than the wall thicknes~ o*
the final cathode i9 heated in a charge of powder-like gr~-phite in an inert medium to a temperature withi~ the range of ~rom 2,000 to 2,200C and maintained at thi3 temperature for 5 to 10 hour~. The process conditio~ nd the bl~nk thiokne~3 are ~elected ~o as to ensure occurre~ce o~ the carbidization process with the ~ormation o~ ~ three l~yered carbide ~truc-ture of the requirod composition and thicknes~
ratio.
~.~4~
~ he three~layered cathod~ st~cture in this ca3e i~
ensured by that c~rbidiæation of meta:Ls o~ the ~ide sub-~roup of Group V o~ the Periodic Sy~tem proceed~ in accord-a~ce with ~he Me-C st~te diagram~ i.e~ in extern~l layer~
contacting ~ith carbon a monocarbide MeC~ is formed7 where-in ~ can hava meanings close to the upper limit of monoge-neity of the carbide, while the inner l~yer i~ tran~formed into a semicQrbide at long residenc~ times~
~ ctual process rates depend on ~umerous parameter~ and cannot be ca].culated th~ retlcQlly with the required accu~
racy. ~or thi~ rea~on9 it is neoe~sary to carry out e~peri-mental verification of the proce~s condition~ and parame ter~ o~ the cathodes obtained. At a temperature below 2,000C the carbidization process i~ ~harply decelerated, the result bei~g a consider~bly extended carbidization time.
At a temper~ture above ~9200C the prooes~ of carbidization i~ accompa~ied by the formation of defect~ in the growing carbide la~er~ and by changes in the cathode ~hape due to inter~l stresse~ and pla3tic deforn~tion. In the manu~ac-ture of cathodes ~rom niobium oarbide the process tempera-ture i3 maintained within the range of from 2~000 to 2,100~C, in the case of tantalu~ carbide the proce~ tempe-rature i~ maintained within the range of from 2,100 to 2,200~. Since all the conditions of the procc~ for the manufacture of cathode~ with the required parameter~ are interrelated, the proce~s duration i~ an overall factor and its value~ are found experimentally on the basi~ of me-tallographic ana].yqis. ~he process d~ration increa~e3 wi-th lowering o~ the temperature and decreasing thicknes~
of the ilmer layer of the composition llleG10 5. Since ~emicar-bides of tan-talum and niobium have a very .n~rrow range o-~homogeneity and a hexagonal lattice, variations in -the semi-carbide composition could not be establi~hed from the X-ray an~lysi~ data~
Particular condition~ of the second embodiment of the proce~ accordi.~g to the pre~ent inventionL and parameter~
of -the re~ulting cathodes are shown in Table 2 h.ereinbelo~.
~ est3 were carried out of sealed C02 lasers with dif~
derent cathodes produced according to the present invention and having the parame-ter3 sho~n in Tables 1 and 2, For the purpo~e of comparison a ~ealed C02 laser with a metallic (covar) cathode o~ a ~imilar s~ape was a1~o tested.
~ he tests have shown that the use o~ cathode~ produced f~om tantalum or niobium carbide by the proce~ according to the present invention make~ it possible to e~tend the service li~e of sealed C02 lasers ~rom 500 (for covar cathode) to 10,000 hours and over.
At the same -time, the obtaining a maximum po~ible value of a unit power of radiation per unit wa~elength and maintaining it substantially constant with time are ensured. It ha~ also been found that limitation to the service li~e is impo~ed not by the ini~luence o~ the catho-de, but o~ ot;her factors, the elimination of which must bring about i.'urther exten~ion of the 3er~ice li~e of gas laser~ .
- ~0 -T a b 1 e NoO Blank Proce~s Parameters of -the obtained matsrial parameter~ ca~hode~
Tempe Dura- Penta- Layer E~ter~al Inner rature~tion, ~hlorlda thick~ layer layer ~C hours concen- ~e~s compo~i- compo~i-tration, ratio tion tion g/l OI
argon 1 G.raphite 2~500 5 2 1 0.5:1 TaC~07~ TaC0~92 2Ditto 2,300 8 2 1:1:1 T~Co 9~TaC0 98 3Dit~o 29400 .6 1.5 1:0.5:1 ~bCoo74~bC0.92 4Dltto 2,300 8 1.5 1:1:1 NbCo.92~C0.98 T ~a~ b l e 2 ___ 1Niobium 2,000 4 - 1:0,5:1 ~bC0.95~bC0.5 2 ~ant~lum 2,200 8 _ 1:0.25:1 TaCa 8 TaC0 5
In another embodiment of the pre~ent invention, in a process for the manu~acture o~ a cathode comprising heating of a tantalum or niobium blank in a charge of powder like graphite; according to the present invention, the cathode blank is heated to a temperature within the range of ~rom 29000 to 2,200C and maintained at this temperature for a period o~ from 5 to 10 hour~
A ~as laser cathode produced by the proc~ss according to the present invention ~eatures low sputtering, ~tability in a ga~ medium, hlgh mechanical ~trength, high electrical conductivity and emission characteri~tic~. These advantage~
of the cathode aGcording -to the pre~ent invention make it po~ible to extcnd the ser~ice life of ga~ lasers by as much a8 about 10 times~
:~he embodiment~ of th~ proces~ ~or the manufacture of a gas laser ¢athode according to the present inventio~ are simpla in practicing and en~ble the production o~ thi~-wal-led (005Y tO 0.7 mm) mechanically durable ~tructure~ of cathodes~
rrhe pre~ent invention will be further illu~trated by the deqcription of its embodiments and the accompanying drawingl wherein the ga~ laser cathode aocording to the prese~t invention is shown in elevatio~0 'rhe ga~ la~er cathode according to the present inven-tion is shap~d as a cylindrical sleeve with its wall~
having a three~lay~r ~ tructure and m~Lde from carbide3 of metals o.ê ~ide qubgroup OI Group V of the Periodic System.
Extern~l layers 1 have the compo~ition MeC0 7~ 0 95, ~nd inn.er layer 2 ha~3 the composition MeC0 92 o 9~3 respecti~ely or is mads OI a ~emicarbide MeC0 51 The ratio OI thickne~-~es OI the layers 1-2~ el,ected within the range o:f from 1 :1 ,1 to 1 :0025 :1 . These par~meters are e~plained by the rLeces~ity of comb:i.ning the woxking p:ropextie~ oY the cathode (low rate of sput terin,g" ~tability i:~ a gas medium, and the like) aIld its mechanical strength a3 a structurs,1 member o* the la~erO
As ha~ been shown experlmentally, the requi:red worki~g properties of the cathode a:re ensured by the compo~ition o~
0~74_0~95j herefore the composition of the extern~l carblde layer~ 1 should not go beyond the range speciI ied hereinbe:~ore .
~ he required mecha:clical strength of the cathode i~
eIl~ured ~y the inner l~yer 2 o~ a cellular ~t:ructure of ta~talum or niobium monocarbide of an approprlate compo~i-tion ~lthin the rarlge of from MeC0 92 to MeC0 9E~ or ~rolll a tantalum or niobium semicarbide MeC0 5 (at a composition of the exter~al layers of M~Co .~3 to 0 .95 ) Vi~Go~ity than monoc~rbides.
The ratio oY thicknes~es of the layers OI fro~ 1 to 1:0.25:1, a~ it ha~ been found experimentally, en~ure~
the required mechanical strength of the cathode a~
~tructural member of the laser.
The proces~ ~or making the ~as la~er cathode accord-i~g to the pre~ent inve~tion can be per~ormed in two embo-diment~.
Accordin~ to a fir~t embodiment of the proce~ for themanufacture of a cathode 9 as a base use i~ made of a hollow graphita blank with a wall -thicknes~ ~lightly ~maller th~n the w~ hickness of the final cathocleO ~he bla~k i9 heat ed in a mixture of vapour~ o~ tantalum or niobium penta~
chloride and argon (1~5 to 2 g/l of argon) to a temper~ture within the range of from 2,300 to 2,500~C and maintained at this temperature for a period of from 5 to 8 hours. ~he pro-ces~ temperature and duration~ the starting blank thickne~s ~nd concentration of pent~ohloride are ~elected ~o as to en~ure the occurrence of the proce~s of carbidlzation with the formatio~ of a three-layer carbide ~tructure of the re-quired composition and ratio between ths layer thickne~se~
~ he t~ree-layered structure of the ~athode is ensured by thAt at the ~elected proGe~ parameter~ in the entire surface of the graphite blank there i~ ~imultaneously ~or~-ed a den~e aarbide layer ~external) and further growth of the carbide can be effect~d only through the agency of dif-fu~ion o~ carbon from the inner graphite m~trix which at a ¢~rtain proces~ ~tage i9 converted into a loo~en~d ~truc-ture and pentachloride penetrate~ thereinto along lt~ inter-grain face~ to convert thi~ structure into carbide rein-~orci~g the inner layers. At the proce~s temperature below 2,300C too den~e exter~al layer~ are formed, which hindex sharply the carbidization proces~ and make it impo~3ible to obtain the required re~ult within an acceptable time.
At a temperature exceeding 2,500C there oc¢urs formation of 100~3e c~rbide layers due to occurrence o~ the reaction i:~ bulk. The ~tar-ting thickne~s oE th}~ blank i~ ~elected by c~lculating the den~ity of carbide o~ tantalum or nio-bium and experimental corre¢tion.
Si~ce the conditions of the proce~ ~or tha manu~
tur~ of cathodes with the required parameters are lnterre lated, the time of carbidization i~ ~ound experimentally f rom the d~ta of met~llographic ~-ray structural analy~i~
of the final cathode~ and change~ in the weighk of the gra-phite blank after carbidization~ ~he above-specified time period o~ 5 to 8 hour~ ensures complete con~er~ion o~ ~ra-phite into the carbide ~tructure.
Specific condition~ of the fir~t embodiment of the proce~ according to the pre~ent invention and parameter~
of the resulti~g cathodes are shown in Table hereinbelow.
In ~nother embodiment of the proces~ ~or the manu~ac-ture o~ cathodes according to the pre~e:nt in~ention, a me-tal blank (OI tantalum or niobium respectively) with a wsll thioknes~ slightly ~maller than the wall thicknes~ o*
the final cathode i9 heated in a charge of powder-like gr~-phite in an inert medium to a temperature withi~ the range of ~rom 2,000 to 2,200C and maintained at thi3 temperature for 5 to 10 hour~. The process conditio~ nd the bl~nk thiokne~3 are ~elected ~o as to ensure occurre~ce o~ the carbidization process with the ~ormation o~ ~ three l~yered carbide ~truc-ture of the requirod composition and thicknes~
ratio.
~.~4~
~ he three~layered cathod~ st~cture in this ca3e i~
ensured by that c~rbidiæation of meta:Ls o~ the ~ide sub-~roup of Group V o~ the Periodic Sy~tem proceed~ in accord-a~ce with ~he Me-C st~te diagram~ i.e~ in extern~l layer~
contacting ~ith carbon a monocarbide MeC~ is formed7 where-in ~ can hava meanings close to the upper limit of monoge-neity of the carbide, while the inner l~yer i~ tran~formed into a semicQrbide at long residenc~ times~
~ ctual process rates depend on ~umerous parameter~ and cannot be ca].culated th~ retlcQlly with the required accu~
racy. ~or thi~ rea~on9 it is neoe~sary to carry out e~peri-mental verification of the proce~s condition~ and parame ter~ o~ the cathodes obtained. At a temperature below 2,000C the carbidization process i~ ~harply decelerated, the result bei~g a consider~bly extended carbidization time.
At a temper~ture above ~9200C the prooes~ of carbidization i~ accompa~ied by the formation of defect~ in the growing carbide la~er~ and by changes in the cathode ~hape due to inter~l stresse~ and pla3tic deforn~tion. In the manu~ac-ture of cathodes ~rom niobium oarbide the process tempera-ture i3 maintained within the range of from 2~000 to 2,100~C, in the case of tantalu~ carbide the proce~ tempe-rature i~ maintained within the range of from 2,100 to 2,200~. Since all the conditions of the procc~ for the manufacture of cathode~ with the required parameter~ are interrelated, the proce~s duration i~ an overall factor and its value~ are found experimentally on the basi~ of me-tallographic ana].yqis. ~he process d~ration increa~e3 wi-th lowering o~ the temperature and decreasing thicknes~
of the ilmer layer of the composition llleG10 5. Since ~emicar-bides of tan-talum and niobium have a very .n~rrow range o-~homogeneity and a hexagonal lattice, variations in -the semi-carbide composition could not be establi~hed from the X-ray an~lysi~ data~
Particular condition~ of the second embodiment of the proce~ accordi.~g to the pre~ent inventionL and parameter~
of -the re~ulting cathodes are shown in Table 2 h.ereinbelo~.
~ est3 were carried out of sealed C02 lasers with dif~
derent cathodes produced according to the present invention and having the parame-ter3 sho~n in Tables 1 and 2, For the purpo~e of comparison a ~ealed C02 laser with a metallic (covar) cathode o~ a ~imilar s~ape was a1~o tested.
~ he tests have shown that the use o~ cathode~ produced f~om tantalum or niobium carbide by the proce~ according to the present invention make~ it possible to e~tend the service li~e of sealed C02 lasers ~rom 500 (for covar cathode) to 10,000 hours and over.
At the same -time, the obtaining a maximum po~ible value of a unit power of radiation per unit wa~elength and maintaining it substantially constant with time are ensured. It ha~ also been found that limitation to the service li~e is impo~ed not by the ini~luence o~ the catho-de, but o~ ot;her factors, the elimination of which must bring about i.'urther exten~ion of the 3er~ice li~e of gas laser~ .
- ~0 -T a b 1 e NoO Blank Proce~s Parameters of -the obtained matsrial parameter~ ca~hode~
Tempe Dura- Penta- Layer E~ter~al Inner rature~tion, ~hlorlda thick~ layer layer ~C hours concen- ~e~s compo~i- compo~i-tration, ratio tion tion g/l OI
argon 1 G.raphite 2~500 5 2 1 0.5:1 TaC~07~ TaC0~92 2Ditto 2,300 8 2 1:1:1 T~Co 9~TaC0 98 3Dit~o 29400 .6 1.5 1:0.5:1 ~bCoo74~bC0.92 4Dltto 2,300 8 1.5 1:1:1 NbCo.92~C0.98 T ~a~ b l e 2 ___ 1Niobium 2,000 4 - 1:0,5:1 ~bC0.95~bC0.5 2 ~ant~lum 2,200 8 _ 1:0.25:1 TaCa 8 TaC0 5
3 ~iobium 2,100 5 - 1:0,3:1 ~bCo 9~bCo 5
4 ~antalum 2~100 10 - 1Ø5:1 TaCo.85 TaaOo5 Th~s, the advantage o~ t~e gaa la~er cathode produ¢e~
by the proce~ according to the pre~ent invention reside~
in an e~ten~ion by a~ much a~ ~everal times of the servi~e life of ga~ la~ers. Thls applie~ not only to C02 lasers~
but to many other g~9 la~ers in which ~puttering of the cathc)de i~ o~` princ.ipal importance, for example, to C0 la~ers~ helium-neon la~er3, and the like.
by the proce~ according to the pre~ent invention reside~
in an e~ten~ion by a~ much a~ ~everal times of the servi~e life of ga~ la~ers. Thls applie~ not only to C02 lasers~
but to many other g~9 la~ers in which ~puttering of the cathc)de i~ o~` princ.ipal importance, for example, to C0 la~ers~ helium-neon la~er3, and the like.
Claims (4)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A gas laser cathode shaped as a sleeve from carbi-des of metals of the side subgroup of Group V of the Perio-dic System; said sleeve having three layers across its wall thickness: a first layer - outer, a second layer - inner and a third layer - outer; said first and third outer layers having a composition MeC0.74 to 0.95; said second inner layer having a composition MeC0.92 to 0.98 respecti-vely.
2. A process for making a gas laser cathode comprising:
heating a graphite blank of said cathode in the atmosphere of tantalum or niobium pentachloride and argon to a tempe-rature within the range of from 2,300 to 2,500°C and main-taining said blank at this temperature for 5 to 8 hours.
heating a graphite blank of said cathode in the atmosphere of tantalum or niobium pentachloride and argon to a tempe-rature within the range of from 2,300 to 2,500°C and main-taining said blank at this temperature for 5 to 8 hours.
3. A gas laser cathode shaped as a sleeve from carbi-des of metals of the side subgroup of Group V of the Perio-dic System; said sleeve having three layers across its wall thickness: a first outer layer, a second inner layer and a third outer layer; said first and third outer layers having a composition MeC0.8 to 0.95, said second inner layer being made from a semicarbide MeC0.5.
4. A process for making a gas laser cathode comprising:
heating a blank of said cathode from tantalum or niobium in a charge of powder-like graphite in the atmosphere of argon to a temperature within the range of from 2,000 to 2,200°C;
maintaining said blank at this temperature for a period of from 5 to 10 hours.
heating a blank of said cathode from tantalum or niobium in a charge of powder-like graphite in the atmosphere of argon to a temperature within the range of from 2,000 to 2,200°C;
maintaining said blank at this temperature for a period of from 5 to 10 hours.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19823224644 DE3224644A1 (en) | 1982-07-01 | 1982-07-01 | Cathode for gas lasers and method for producing it |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1194586A true CA1194586A (en) | 1985-10-01 |
Family
ID=6167373
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000406932A Expired CA1194586A (en) | 1982-07-01 | 1982-07-08 | Gas laser cathode and process for making same |
Country Status (5)
| Country | Link |
|---|---|
| JP (1) | JPS5914686A (en) |
| CA (1) | CA1194586A (en) |
| DE (1) | DE3224644A1 (en) |
| FR (1) | FR2530088A1 (en) |
| SE (1) | SE453033B (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE3642749A1 (en) * | 1986-12-15 | 1988-06-23 | Eltro Gmbh | SURFACES FOR ELECTRICAL DISCHARGE |
| CA1272504A (en) * | 1986-11-18 | 1990-08-07 | Franz Prein | Surface for electric discharge |
| US5282332A (en) * | 1991-02-01 | 1994-02-01 | Elizabeth Philips | Stun gun |
| AU7937198A (en) * | 1997-07-03 | 1999-01-25 | Hamamatsu Photonics K.K. | Discharge tube and method of calibrating laser wavelength by using the same |
Family Cites Families (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB974447A (en) * | 1962-02-13 | 1964-11-04 | High Temperature Materials Inc | Metallic carbides and a process of producing the same |
| DE1250796B (en) * | 1963-08-13 | 1967-09-28 | Ciba Aktiengesellschaft, Basel (Schweiz) | Process for the production of finely divided, non-pyrophoric carbides of metals or metalloids of III., IV., V. or VI. Group of the periodic table |
| US3399980A (en) * | 1965-12-28 | 1968-09-03 | Union Carbide Corp | Metallic carbides and a process of producing the same |
| GB1396455A (en) * | 1972-05-04 | 1975-06-04 | Toyoda Chuo Kenkyusho Kk | Method of forming a carbide layer |
| DE2303358A1 (en) * | 1973-01-24 | 1974-07-25 | Patra Patent Treuhand | COLD CATHODE LASER |
| CA1017531A (en) * | 1973-05-02 | 1977-09-20 | Ppg Industries, Inc. | Preparation of finely-divided refractory powders |
| US3991385A (en) * | 1975-02-03 | 1976-11-09 | Owens-Illinois, Inc. | Gas laser with sputter-resistant cathode |
| US4017808A (en) * | 1975-02-10 | 1977-04-12 | Owens-Illinois, Inc. | Gas laser with sputter-resistant cathode |
| US4085385A (en) * | 1975-03-21 | 1978-04-18 | Owens-Illinois, Inc. | Gaseous laser device with damage-resistant cathode |
| GB1579249A (en) * | 1977-05-18 | 1980-11-19 | Denki Kagaku Kogyo Kk | Thermionic cathodes |
-
1982
- 1982-07-01 DE DE19823224644 patent/DE3224644A1/en active Granted
- 1982-07-02 SE SE8204124A patent/SE453033B/en not_active IP Right Cessation
- 1982-07-08 FR FR8212007A patent/FR2530088A1/en active Granted
- 1982-07-08 CA CA000406932A patent/CA1194586A/en not_active Expired
- 1982-07-13 JP JP12071982A patent/JPS5914686A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| FR2530088A1 (en) | 1984-01-13 |
| SE453033B (en) | 1988-01-04 |
| FR2530088B1 (en) | 1985-02-01 |
| JPS5914686A (en) | 1984-01-25 |
| DE3224644A1 (en) | 1984-01-05 |
| SE8204124L (en) | 1984-01-03 |
| JPS643350B2 (en) | 1989-01-20 |
| SE8204124D0 (en) | 1982-07-02 |
| DE3224644C2 (en) | 1989-05-24 |
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