CA1038013A - Secondary-emissive electrode including a cermet - Google Patents
Secondary-emissive electrode including a cermetInfo
- Publication number
- CA1038013A CA1038013A CA241,448A CA241448A CA1038013A CA 1038013 A CA1038013 A CA 1038013A CA 241448 A CA241448 A CA 241448A CA 1038013 A CA1038013 A CA 1038013A
- Authority
- CA
- Canada
- Prior art keywords
- electrode
- metal
- cermet
- substrate
- nickel
- Prior art date
- 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
Links
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J43/00—Secondary-emission tubes; Electron-multiplier tubes
- H01J43/04—Electron multipliers
- H01J43/06—Electrode arrangements
- H01J43/18—Electrode arrangements using essentially more than one dynode
- H01J43/24—Dynodes having potential gradient along their surfaces
- H01J43/243—Dynodes consisting of a piling-up of channel-type dynode plates
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J9/00—Apparatus or processes specially adapted for the manufacture, installation, removal, maintenance of electric discharge tubes, discharge lamps, or parts thereof; Recovery of material from discharge tubes or lamps
- H01J9/02—Manufacture of electrodes or electrode systems
- H01J9/12—Manufacture of electrodes or electrode systems of photo-emissive cathodes; of secondary-emission electrodes
- H01J9/125—Manufacture of electrodes or electrode systems of photo-emissive cathodes; of secondary-emission electrodes of secondary emission electrodes
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J2201/00—Electrodes common to discharge tubes
- H01J2201/32—Secondary emission electrodes
Landscapes
- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Physical Vapour Deposition (AREA)
- Electron Tubes For Measurement (AREA)
- Common Detailed Techniques For Electron Tubes Or Discharge Tubes (AREA)
Abstract
ABSTRACT:
A substrate bearing a secondary-emissive layer which consists of a cermet consisting of a readily evaporable metal, for example Au, Ag, Cu, Ni, Cr, Al or a nickel-chromium alloy, and an alkali metal aluminium fluoride, for example cryolite. The substrate material may be, for example mild steel, or a synthetic plastics material. It is possible to make large dynodes when using mild steel substrates which are much cheaper than silver-magnesium or beryllium-coppor. The secondary-emissive layer does not require an activation treatment inside an electric discharge tube into which it is incorporated.
A substrate bearing a secondary-emissive layer which consists of a cermet consisting of a readily evaporable metal, for example Au, Ag, Cu, Ni, Cr, Al or a nickel-chromium alloy, and an alkali metal aluminium fluoride, for example cryolite. The substrate material may be, for example mild steel, or a synthetic plastics material. It is possible to make large dynodes when using mild steel substrates which are much cheaper than silver-magnesium or beryllium-coppor. The secondary-emissive layer does not require an activation treatment inside an electric discharge tube into which it is incorporated.
Description
PHB.32480 BKS/AvdV
~ .19.11.75 --~0~80~
"Electrode having a secondary-emissive layer".
. The invention relates to an electrode consistlng of at lea~t a substrate bearing a secondary-emissive layer which is composed oP several materialsl for example, a dynode in an electron multiplier tube or a 5 channel plate.
The invontion relates moreover to a method of rnanu~actu.ring such a socondary-cmls~:Lvo la~r on a ~ub~trate.
Suoh an elootrodo l~ Icnown ~rolll Br:lt:lsh Pntent Speo:Lfloation 1,211l,755 ln whi.ch a sinterod mass consisting of cryolite (Na3AlF6 or sodium alumlnium ~luoride) and a metal oxide (for example MgO, Al203 or CaO) is provided in a vapour deposition device so as to form therefrom .~ secondary-emissive layers on a substrate by vapour depositi.on.
: However, said layers are ceramic layers and insulators : ~ so that in electron(dynodes) manufactured from this material charging phenomena occur.
It is the object of the invention to avoid this drawback entirely.
. According to the invention, an electrode o~
the kind mentioned in the first paragraph is characterized in that the secondary-emissive layer cons:Lsts of a cermet comprising a readily evaporable metal and an alkali aluminium fluoride.
~ .19.11.75 --~0~80~
"Electrode having a secondary-emissive layer".
. The invention relates to an electrode consistlng of at lea~t a substrate bearing a secondary-emissive layer which is composed oP several materialsl for example, a dynode in an electron multiplier tube or a 5 channel plate.
The invontion relates moreover to a method of rnanu~actu.ring such a socondary-cmls~:Lvo la~r on a ~ub~trate.
Suoh an elootrodo l~ Icnown ~rolll Br:lt:lsh Pntent Speo:Lfloation 1,211l,755 ln whi.ch a sinterod mass consisting of cryolite (Na3AlF6 or sodium alumlnium ~luoride) and a metal oxide (for example MgO, Al203 or CaO) is provided in a vapour deposition device so as to form therefrom .~ secondary-emissive layers on a substrate by vapour depositi.on.
: However, said layers are ceramic layers and insulators : ~ so that in electron(dynodes) manufactured from this material charging phenomena occur.
It is the object of the invention to avoid this drawback entirely.
. According to the invention, an electrode o~
the kind mentioned in the first paragraph is characterized in that the secondary-emissive layer cons:Lsts of a cermet comprising a readily evaporable metal and an alkali aluminium fluoride.
-2-, ~381~3 lhe cermet may contain in addition magnesium fluoride, preferably less than 18% by weight of the overall quantity of fluoride. If as a matter of fact less than approximately 18% by weight of magnesium fluoride is present, a homogeneous crystal with the alkali aluminium fluoride is still formed. However, this is not required to obtain a good secondary emission.
The dynodes of a discrete dynode channel plate and of an electron multiplier are also made frequently o beryllium-copper ~BeCu) or o silver magnesium (AgMg), which materials can be activated so that a surface having a high secondary-emission factor (~ = 4-6) is obtained. However, these materials are expensive and beryllium-copper has the addition drawback of being very poisonous so that many precautions in processing said material have to be taken. Mild steel is not considered as a secondary emitter because it has too low a secondary-emission factor ~ ~ approx. 2).
According to the invention the roadily cvaporablo motal proeorably is a metal from the group gold, silver, copper, nickel, chromium or a nickel-chromium alloy. Preferably the cermet contains from lO to 60% by weight of this readily evaporable metal.
According to the invention the substrate may be manufactured from an electrically conductive material, for example mild steel, or an insulator, for example a synthetic plastics material (for example the material PHB.3Z480 19.11.75 ~038~ L3 known by the trade name "Kapton", manufactured by Dupont de Nemours and Co~.
A method of manufacturing such a secondary-emis~ive layer on a substrate comprises the s-tep of evaporatlng a thin fllm o~.-the readily evaporable metal on the substrate. Said metal deposition is then continued but an alkali aluminium fluoride is simultaneously vapour-deposited. The vapour deposition o~ the metal ancl the alkali alumin:Lum fluoride is d:iscont:Lnued substantia:lly simultaneously.
It ha~s bo or! :round that the sdcondary-olll:l~s:Lve layers accord:Ln~ to the lnvQntlon have stable secondary-emission properties :Lf the substrates comprising said layers are stored in dry air. (This may be done, for example, in a dessica-tor withsilica gel.) It has also been found that the value of~(secondary-emission factor) ,, does substantially not decrease after the layers had been exposed to the ambie~t atmosphere for 30 to 60 minutes.
. Mo,reover, the assembly process of t~e dynodes and the 20--, electron discharge tubes in which the dynodes are mounted has proved to have no detrimental influence on the quality of said electron discharge tubes.
Dependent on their application, secondary-emiss:ive lQyers must have a di~ferent electrlc conductivity.
Z5 In application with electrically conductive dynodes having secondary-emissive layers, the layers,need be 7~J~ ~rk , 4 , PHB.32480 19.-11.75 ~.~3~0~;~
capable of transporting only so much charge from the metal substrate to the emissive surface that the charge which is dissipated from said surface by secondary emission is replenished. Examples of suoh applications are elcctron multlplier~ of the so-called l~Venetian-blind~type for the detection of :individual particles and channel plates of the laminated type which can be used for imaging and display purposes.
The invontion will now be doscrlbed in groater detail with re~erenoe to a ~iguro~ in wh:lch Flgure 1 i~ a diagramlllatlc ropro~ontcltlon o~
a part o~ an cleotroclo, Figures Z and 3 5how a channcl plate of the laminated type, ~ Figure 4 shows a dynode made of two halves, and Figure 5 shows a channel plate having a continuous dynode.
Figure ~ shows diagrammatically a part of an electrode. The mild steel substrate 1 is covered with a 1-2 /um thick nickel layer 2. Provided on the nickel layer 2 is a nickel chromium layer 3 (200-300 ~ thick) - whioh serves as a basis for the cermet layer 4 (200 ~ thick).
Said cermet consists of nickel-chromium and cryolite.
~`igures 2 and 3 show a chah~el plate of the laminated type in a plan vlew (Figure 3) and in a perpendicular cross-sectional vlew (Pigure 3).
_5_ ' '.
PHB.32480 19.11-75 ~380~3 Th1s laminated type differs from the usual channel plate in that this channel plate has a construction consisting of plates 5 and 6 having holes 7 pro-;ided in~a matrix form.
. It is composed of alterna;tely conductive plates 5 and spacing plates 6 so that the :Lnner wall o~ each channel is formed by the inner walls of a number of holes of aIternatively conductive and spacing material situated one behind the other. As a result of this the inner wall consist~ o~ a numbor of discreto cl~nodes. The holes of`
-the 9UCCegSiVe clynodes shou]d be su~ Lciont:l.y alignecl to ~orm un:Lntorruptocl chal1no:Lfl th~ou~rh the c1-lann~:l plate 9truoture. Tho :Lnnor wa:Ll Or tho holcs irl tho conduot:Lve plates 5 are covered with the cermet 3 according to the invention. During operation, all successive conductive 1S plates (dynodes) are fed with increasing potentials by a divided direct current source which is denoted dia-grammatically by Bm. In one channel the direction of the electron amplification in the channel is denoted by arrows.
The cross-sectional view of Figure 4 shows a dynode having indented aperture as described in Bri-tish Patent Application 16541/73, (Netherlands Patent Application or~ bC.~ q'~y 7,l~o~,439 laid open to public inspection\), in which the dynode is made from two matching halves 8 and 9.
The inncr wall is again covered with the cermot 3.
The invention may also be used in photo-multipliers having continuous dynodes, for examp:le, . .
.
" PHB.32480 .. . - 19.11.75 ' ~31~ 3 the channel pla~e described in British Patent Application 2842/73 (Netherlands Patent Appli(cation JLl.ne. a3,~ 195~y 7,400,76~ laid open to publlc inspection\), and shown in Figure 5. In such a channQl plate, each channel is open and may hav~ a very open conical or py:ramidal shape.
For devices having continuous dynodes the degree of conductivity which is required for -the secondary-emissive layers 3 in th~ channels ls based on considerations which dlI`fQr :~rom thoso which clete:rm:LnQ.
10 ' the design of l:he above-tnent:Lonecl lam.Lnatod channe:l. plat~.
In part~.cular, tho :Layor on eaoll channo:L wn.Ll o~ tho open chann~l wlll have to be capable o~ passin~ current A from an,input electrodo 11 on the input side of th~plate to an output electrode 12 on the output side so a~ to 15 obtatn in,this manner a potential gradient along the wal3s of the channels. In addition it will have to be possible to also r~plenish the charge lost as a result of secondary emission. Moreover, in contrast with the above-described specimens, the secondary-emissive layers which are electrically conductive are provided on a substrate 13 of insulation material (for example glass, plastics?'instead of on a substrate o~ a conductive material.
The invention will now be ~urther described with re~erence to two examples.
Example 1 A mild steel substrate ~or a dynode was de~reas~d and~was~then covered with a 1'to'2 ~um thick liick'e~"lay0r;
~7~
.~ , ' .
PHB.32480 19.11.75 - 1~3~)~3 The mild steel may in addition be decarburised by heating at 900C in a mixturc of 90% nitrogen and 10~ hydrogen which hQs been made moist by passing it t~rough water at ro~m temperature.
The mild steel substrate was then placed in a vacuum deposition de~ice and the pressure was reduced to between 3x10 and 2x10 5 Torr. The substrate was then heated to 300C and maintained at this temper~ture.
The vacuum depos:ltion o~ ~ chromium-niokel alloy con-sistlng of` ~0~ by welght o~ nickel and 20~ by Wo:igtlt o~
chromium was startecl 10 m:lnutos a~tor I;ho substrato had reached sald temperaturo. ~tor the dopo~:lt:Lon o~ 200 to 300 ~ of the nlckel-chromium alloy, thc evaporation o~
the cryolite was started. In the collective vapour deposition of the nickel-chromium alloy and the cryolite the quantity by woight of deposited cryolite was twice as large as the quantity by weight of the nickel-chromium alloy. The vapour deposition of the nickel-chromium .
;~ alloy and the cryolite was discontinued simultaneously w~en the overall thickness of the depositcd cermet layer was approximately 2000 ~. The extra nlcke}-chromium alloy layer serves as an extra barrier layer between the material o~ the cermet and the mild steel so that the decrease o~ the secondary-em:issive properbie9 o~ tho cermet material durlng :its li~e is restricted.
, ' PHB.32480 , 19.11.75 ~38i)~3 The ~econdary-emission coefficient ~ of the above-described nickel-chromium alloy-cryolite cermet clecreased initially upon irradiating ~ith electrons . having an energy of 300~V but recovered to a c~nstant g ' value of 3-4 subsequently. Depe~dent on the way of`
activating, the & for a boryllium-copper surface would in'the same circumstances be 4 to 5 and for a silver-magnesium surface which was irradiated with 200 eV
electrons it would be more than 5.
' 10 Example 2 ~ qual wei~hts of cr~olite and mngrles:lum :~:Luor:Ld~
were mlxed and placed in an evaporation boat. The boat WAS then heated so as to melt this,mixture and the contents of the boat were allowed to solidify.
~ mild steel dynode substrate which had been degreased was nickel-plated with 2 /um of nickel.
The nickel-plated mild steel substrate was then placed in a vacuum ev,aporation apparatus, and the pressure was reduced to between 3 x 10 and 2 x 10 5 Torr. The substrate was then heated to 300C and was maintained at this ' temperature. Vacuum evaporation of gold was commerced 10 minutes after the substrate had reached this temperature.
After 200-300 ~ of gold had been deposited, evaporation of the m:Lxture of cryolitc and magnesium fluoride was commenced, the rate of deposition of -the cryolite plus magnesium fluoride being four times the rate of cleposition (in terms of mass) of the gold. When thc tatal thickness PHB.32480 19.11.75 ~L~38013 of the deposited film had reached 2000 A, evaporation of the gold and of the cryolite plus magn~sium fluoride was stopped simultaneously.
' When the resulting cermet film was irradiated with 300 eV electrons, the S of the layer was initially 4.1, but after l~ minutes ~ had fallen to 2.25.
The electron beam used to irradiate the cermet had a current density of 25 /uA/sq. cm. on the cermet surface.
After llo minutes of irradiat:lon, ~n had recovered to a value of ? and after 1300 minutos it wa3 round that had reached a ~te~dy va:Lue of ~.9. The pn ~rn o~` the change in values of` ~ ~or tho nLolcol chroml~lm cryolLte ccrmet prepared by t,he mothod described ln ~xatnple 1 was similar to the pattern obser~ed with this gold~cryolite-magnesium fluorlde cermet.
'Although the suitability of the cermet according to the invention has been mainly described with reference to examples relating to dynodes o~
channel plates, it will be obvious to those skilled in the art that such a cermet can successfully be used in all electrodes which have to be provided with a 9 econdary-emi 9 S ive layer. Hence the invention is by no means restricted to channel plates.
, - ' ' '
The dynodes of a discrete dynode channel plate and of an electron multiplier are also made frequently o beryllium-copper ~BeCu) or o silver magnesium (AgMg), which materials can be activated so that a surface having a high secondary-emission factor (~ = 4-6) is obtained. However, these materials are expensive and beryllium-copper has the addition drawback of being very poisonous so that many precautions in processing said material have to be taken. Mild steel is not considered as a secondary emitter because it has too low a secondary-emission factor ~ ~ approx. 2).
According to the invention the roadily cvaporablo motal proeorably is a metal from the group gold, silver, copper, nickel, chromium or a nickel-chromium alloy. Preferably the cermet contains from lO to 60% by weight of this readily evaporable metal.
According to the invention the substrate may be manufactured from an electrically conductive material, for example mild steel, or an insulator, for example a synthetic plastics material (for example the material PHB.3Z480 19.11.75 ~038~ L3 known by the trade name "Kapton", manufactured by Dupont de Nemours and Co~.
A method of manufacturing such a secondary-emis~ive layer on a substrate comprises the s-tep of evaporatlng a thin fllm o~.-the readily evaporable metal on the substrate. Said metal deposition is then continued but an alkali aluminium fluoride is simultaneously vapour-deposited. The vapour deposition o~ the metal ancl the alkali alumin:Lum fluoride is d:iscont:Lnued substantia:lly simultaneously.
It ha~s bo or! :round that the sdcondary-olll:l~s:Lve layers accord:Ln~ to the lnvQntlon have stable secondary-emission properties :Lf the substrates comprising said layers are stored in dry air. (This may be done, for example, in a dessica-tor withsilica gel.) It has also been found that the value of~(secondary-emission factor) ,, does substantially not decrease after the layers had been exposed to the ambie~t atmosphere for 30 to 60 minutes.
. Mo,reover, the assembly process of t~e dynodes and the 20--, electron discharge tubes in which the dynodes are mounted has proved to have no detrimental influence on the quality of said electron discharge tubes.
Dependent on their application, secondary-emiss:ive lQyers must have a di~ferent electrlc conductivity.
Z5 In application with electrically conductive dynodes having secondary-emissive layers, the layers,need be 7~J~ ~rk , 4 , PHB.32480 19.-11.75 ~.~3~0~;~
capable of transporting only so much charge from the metal substrate to the emissive surface that the charge which is dissipated from said surface by secondary emission is replenished. Examples of suoh applications are elcctron multlplier~ of the so-called l~Venetian-blind~type for the detection of :individual particles and channel plates of the laminated type which can be used for imaging and display purposes.
The invontion will now be doscrlbed in groater detail with re~erenoe to a ~iguro~ in wh:lch Flgure 1 i~ a diagramlllatlc ropro~ontcltlon o~
a part o~ an cleotroclo, Figures Z and 3 5how a channcl plate of the laminated type, ~ Figure 4 shows a dynode made of two halves, and Figure 5 shows a channel plate having a continuous dynode.
Figure ~ shows diagrammatically a part of an electrode. The mild steel substrate 1 is covered with a 1-2 /um thick nickel layer 2. Provided on the nickel layer 2 is a nickel chromium layer 3 (200-300 ~ thick) - whioh serves as a basis for the cermet layer 4 (200 ~ thick).
Said cermet consists of nickel-chromium and cryolite.
~`igures 2 and 3 show a chah~el plate of the laminated type in a plan vlew (Figure 3) and in a perpendicular cross-sectional vlew (Pigure 3).
_5_ ' '.
PHB.32480 19.11-75 ~380~3 Th1s laminated type differs from the usual channel plate in that this channel plate has a construction consisting of plates 5 and 6 having holes 7 pro-;ided in~a matrix form.
. It is composed of alterna;tely conductive plates 5 and spacing plates 6 so that the :Lnner wall o~ each channel is formed by the inner walls of a number of holes of aIternatively conductive and spacing material situated one behind the other. As a result of this the inner wall consist~ o~ a numbor of discreto cl~nodes. The holes of`
-the 9UCCegSiVe clynodes shou]d be su~ Lciont:l.y alignecl to ~orm un:Lntorruptocl chal1no:Lfl th~ou~rh the c1-lann~:l plate 9truoture. Tho :Lnnor wa:Ll Or tho holcs irl tho conduot:Lve plates 5 are covered with the cermet 3 according to the invention. During operation, all successive conductive 1S plates (dynodes) are fed with increasing potentials by a divided direct current source which is denoted dia-grammatically by Bm. In one channel the direction of the electron amplification in the channel is denoted by arrows.
The cross-sectional view of Figure 4 shows a dynode having indented aperture as described in Bri-tish Patent Application 16541/73, (Netherlands Patent Application or~ bC.~ q'~y 7,l~o~,439 laid open to public inspection\), in which the dynode is made from two matching halves 8 and 9.
The inncr wall is again covered with the cermot 3.
The invention may also be used in photo-multipliers having continuous dynodes, for examp:le, . .
.
" PHB.32480 .. . - 19.11.75 ' ~31~ 3 the channel pla~e described in British Patent Application 2842/73 (Netherlands Patent Appli(cation JLl.ne. a3,~ 195~y 7,400,76~ laid open to publlc inspection\), and shown in Figure 5. In such a channQl plate, each channel is open and may hav~ a very open conical or py:ramidal shape.
For devices having continuous dynodes the degree of conductivity which is required for -the secondary-emissive layers 3 in th~ channels ls based on considerations which dlI`fQr :~rom thoso which clete:rm:LnQ.
10 ' the design of l:he above-tnent:Lonecl lam.Lnatod channe:l. plat~.
In part~.cular, tho :Layor on eaoll channo:L wn.Ll o~ tho open chann~l wlll have to be capable o~ passin~ current A from an,input electrodo 11 on the input side of th~plate to an output electrode 12 on the output side so a~ to 15 obtatn in,this manner a potential gradient along the wal3s of the channels. In addition it will have to be possible to also r~plenish the charge lost as a result of secondary emission. Moreover, in contrast with the above-described specimens, the secondary-emissive layers which are electrically conductive are provided on a substrate 13 of insulation material (for example glass, plastics?'instead of on a substrate o~ a conductive material.
The invention will now be ~urther described with re~erence to two examples.
Example 1 A mild steel substrate ~or a dynode was de~reas~d and~was~then covered with a 1'to'2 ~um thick liick'e~"lay0r;
~7~
.~ , ' .
PHB.32480 19.11.75 - 1~3~)~3 The mild steel may in addition be decarburised by heating at 900C in a mixturc of 90% nitrogen and 10~ hydrogen which hQs been made moist by passing it t~rough water at ro~m temperature.
The mild steel substrate was then placed in a vacuum deposition de~ice and the pressure was reduced to between 3x10 and 2x10 5 Torr. The substrate was then heated to 300C and maintained at this temper~ture.
The vacuum depos:ltion o~ ~ chromium-niokel alloy con-sistlng of` ~0~ by welght o~ nickel and 20~ by Wo:igtlt o~
chromium was startecl 10 m:lnutos a~tor I;ho substrato had reached sald temperaturo. ~tor the dopo~:lt:Lon o~ 200 to 300 ~ of the nlckel-chromium alloy, thc evaporation o~
the cryolite was started. In the collective vapour deposition of the nickel-chromium alloy and the cryolite the quantity by woight of deposited cryolite was twice as large as the quantity by weight of the nickel-chromium alloy. The vapour deposition of the nickel-chromium .
;~ alloy and the cryolite was discontinued simultaneously w~en the overall thickness of the depositcd cermet layer was approximately 2000 ~. The extra nlcke}-chromium alloy layer serves as an extra barrier layer between the material o~ the cermet and the mild steel so that the decrease o~ the secondary-em:issive properbie9 o~ tho cermet material durlng :its li~e is restricted.
, ' PHB.32480 , 19.11.75 ~38i)~3 The ~econdary-emission coefficient ~ of the above-described nickel-chromium alloy-cryolite cermet clecreased initially upon irradiating ~ith electrons . having an energy of 300~V but recovered to a c~nstant g ' value of 3-4 subsequently. Depe~dent on the way of`
activating, the & for a boryllium-copper surface would in'the same circumstances be 4 to 5 and for a silver-magnesium surface which was irradiated with 200 eV
electrons it would be more than 5.
' 10 Example 2 ~ qual wei~hts of cr~olite and mngrles:lum :~:Luor:Ld~
were mlxed and placed in an evaporation boat. The boat WAS then heated so as to melt this,mixture and the contents of the boat were allowed to solidify.
~ mild steel dynode substrate which had been degreased was nickel-plated with 2 /um of nickel.
The nickel-plated mild steel substrate was then placed in a vacuum ev,aporation apparatus, and the pressure was reduced to between 3 x 10 and 2 x 10 5 Torr. The substrate was then heated to 300C and was maintained at this ' temperature. Vacuum evaporation of gold was commerced 10 minutes after the substrate had reached this temperature.
After 200-300 ~ of gold had been deposited, evaporation of the m:Lxture of cryolitc and magnesium fluoride was commenced, the rate of deposition of -the cryolite plus magnesium fluoride being four times the rate of cleposition (in terms of mass) of the gold. When thc tatal thickness PHB.32480 19.11.75 ~L~38013 of the deposited film had reached 2000 A, evaporation of the gold and of the cryolite plus magn~sium fluoride was stopped simultaneously.
' When the resulting cermet film was irradiated with 300 eV electrons, the S of the layer was initially 4.1, but after l~ minutes ~ had fallen to 2.25.
The electron beam used to irradiate the cermet had a current density of 25 /uA/sq. cm. on the cermet surface.
After llo minutes of irradiat:lon, ~n had recovered to a value of ? and after 1300 minutos it wa3 round that had reached a ~te~dy va:Lue of ~.9. The pn ~rn o~` the change in values of` ~ ~or tho nLolcol chroml~lm cryolLte ccrmet prepared by t,he mothod described ln ~xatnple 1 was similar to the pattern obser~ed with this gold~cryolite-magnesium fluorlde cermet.
'Although the suitability of the cermet according to the invention has been mainly described with reference to examples relating to dynodes o~
channel plates, it will be obvious to those skilled in the art that such a cermet can successfully be used in all electrodes which have to be provided with a 9 econdary-emi 9 S ive layer. Hence the invention is by no means restricted to channel plates.
, - ' ' '
Claims (10)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. An electrode at least consisting of at least a substrate bearing a secondary-emissive layer composed of several materials, characterized in that said layer consists of a cermet which contains a readily-evaporable, metal and an alkali aluminium fluoride.
2. An electrode as claimed in Claim 1, characterized in that the cermet contains in addition magnesium fluoride.
3. An electrode as claimed in Claim 1, characterized in that the readily-evaporable metal is a metal from the group gold, silver, copper, nickel, chromium or a nickel-chromium alloy.
4. An electrode as claimed in Claim 3, characterised in that the readily-evaporable metal occupies 10 to 60% by weight of the cermet.
5. An electrode as claimed in Claim 1, characterized in that the substrate consists of mild steel.
6. An electrode as claimed in Claim 5, characterized in that the substrate is covered with a layer of nickel or a nickel-chromium alloy on which the said emissive layer is provided.
7. An electrode as claimed in Claim 1, characterized in that the substrate consists of a synthetic plastics material.
8. An electrode as claimed in Claim 2, characterized in that the magnesium fluoride occupies less than 18% by weight of the overall quantity by weight of alkali aluminium fluoride and magnesium fluoride.
9. A method of manufacturing an electrode as claimed in Claim l, characterized in that a thin film of readily-evaporable metal is deposited on the substrate and that the readily-evaporable metal is then deposited together with an alkali aluminium fluoride, after which the deposition of metal and the fluoride is discontinued simultaneously.
10. A method as claimed in Claim 9, characterized in that simultaneous ly with the metal and the alkali aluminium fluoride, magnesium fluoride is also vapour deposited.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB5400674A GB1523730A (en) | 1974-12-13 | 1974-12-13 | Secondaryemissive layers |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1038013A true CA1038013A (en) | 1978-09-05 |
Family
ID=10469661
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA241,448A Expired CA1038013A (en) | 1974-12-13 | 1975-12-10 | Secondary-emissive electrode including a cermet |
Country Status (5)
| Country | Link |
|---|---|
| JP (1) | JPS5835337B2 (en) |
| CA (1) | CA1038013A (en) |
| DE (1) | DE2554030C2 (en) |
| FR (1) | FR2294542A1 (en) |
| GB (1) | GB1523730A (en) |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2023333B (en) * | 1978-06-14 | 1982-09-08 | Philips Electronic Associated | Electron multipliers |
| GB2023332B (en) * | 1978-06-14 | 1982-10-27 | Philips Electronic Associated | Electron multipliers |
| GB2048561B (en) | 1979-04-02 | 1983-02-23 | Philips Electronic Associated | Method of forming a secondary emissive coating on a dynode |
| EP0490154A3 (en) * | 1990-12-07 | 1992-09-30 | Siemens Aktiengesellschaft | Method for determining the charge of a sample region |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3672989A (en) * | 1968-08-03 | 1972-06-27 | Japan Broadcasting Corp | Porous layer of a secondary electron multiplier and a method of manufacturing the same |
| JPS4833348A (en) * | 1971-08-31 | 1973-05-09 |
-
1974
- 1974-12-13 GB GB5400674A patent/GB1523730A/en not_active Expired
-
1975
- 1975-12-02 DE DE19752554030 patent/DE2554030C2/en not_active Expired
- 1975-12-10 JP JP50146488A patent/JPS5835337B2/en not_active Expired
- 1975-12-10 CA CA241,448A patent/CA1038013A/en not_active Expired
- 1975-12-12 FR FR7538122A patent/FR2294542A1/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| DE2554030C2 (en) | 1982-10-28 |
| JPS5835337B2 (en) | 1983-08-02 |
| FR2294542A1 (en) | 1976-07-09 |
| GB1523730A (en) | 1978-09-06 |
| DE2554030A1 (en) | 1976-06-16 |
| FR2294542B1 (en) | 1980-06-13 |
| JPS5177167A (en) | 1976-07-03 |
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