JPS5917987B2 - Cold cathode discharge tube and its manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a cold cathode laser discharge tube and a method of manufacturing the same, and more particularly to a cold cathode structure of a long-life laser discharge tube and a method of manufacturing the same.

Generally, cold cathodes are used in various types of gas lasers because they generate less heat and therefore provide a favorable thermal balance throughout the discharge tube.

Additionally, improvements in mirror coating technology and tube sealing technology are gradually increasing the lifespan of gas laser discharge tubes. The longevity of gas laser discharge tubes has been particularly impressive, and favorable results have been obtained especially for hot cathode laser discharge tubes. It has come to be clear that it is not possible to achieve such a long service life. This means that cold cathode laser discharge tubes have unique factors that limit their lifetime. In the case of a hollow cathode laser, a high current density is required, particularly on the cold cathode surface, and therefore no practical design example has yet been obtained.

During holo-cathode discharge, the atomic spectrum of the cathode material is always observed. This fact proves that despite the low equilibrium vapor pressure at the actual discharge tube temperature, a significant amount of cathode material is present in the gas phase. This phenomenon is known as so-called cathode sputtering, and is considered unavoidable with current technology.

On the other hand, if the metal vapor ions are neutralized and deposited on a cold wall, a significant amount of the inert discharge material will be incorporated into the deposited metal. This phenomenon is known as the so-called gas clean-up.

This gas clean-up can occur even if the surface current density of the cathode is low, and is particularly likely to occur if the surface of the cold cathode is processed to facilitate photoelectron emission. strong.

For such cold cathodes, when a local photoelectron γ-effect suddenly occurs, the local ionic surface current density increases in order to balance the sheath potential, resulting in local sputtering of the cathode material. It is expected that this will increase. The present invention has been made in view of the above circumstances, and provides a cold cathode laser discharge tube and a cold cathode having a cold cathode in which the gas pressure within the discharge tube hardly decreases no matter how the cleanup of the discharge body progresses. The purpose of this invention is to provide a manufacturing method for the same.

Another object of the present invention is to provide a cold cathode laser discharge tube and a method for manufacturing the same in which the photoelectron gamma effect is hardly degraded due to an increase in local ion collisions.
According to the invention, a long-life cold cathode is produced by depositing cathode material by sputter discharge at a high surface current density onto a cathode support of arbitrary shape with the cathode support as the anode.

Due to the high surface current density, the deposited layer of cathode material becomes porous and can absorb a large amount of sputter discharge material having a composition similar to the gas used in laser discharge. A small amount of oxygen gas is added into the sputter discharge body to impart a photoelectron gamma effect to the layer on which the cathode material is deposited. The preferred shape of the cathode support for Vf is such that it encloses a hollow space within which a negative glow occurs when it is used as a discharge cathode. An embodiment of the present invention will be described below with reference to the drawings.

An embodiment of the present invention applied to a He{e laser discharge tube will be described with reference to FIG.

Regarding the He-Ne laser discharge tube, the discharge tube 2 is arranged approximately along the central axis of the anode side outer tube 4. Anode side outer tube 4
One end is hermetically sealed integrally with the outer periphery of the discharge capillary tube 2, and the other end is open. A cylindrical anode 6 is hermetically sealed and connected to one end opening of the discharge capillary tube 2 extending outside the anode outer tube 4 from the sealed portion with the anode outer tube 4. The anode side extension thin tube 8 to which the first reflecting mirror 7 is airtightly attached is hermetically sealed. The other end of the discharge capillary 2 extending through the opening of the anode outer tube 4 is inserted into one insertion hole of a drum-shaped cathode support 10. This cathode side support 10
is connected to one end of a pair of cathode stems 12, 14,
Each of the cathode stems 12 and 14 extends substantially parallel to the central axis of the anode outer tube 4, passes through the anode outer tube 4, and extends to the outside of the outer tube 4. The opening of the anode side outer tube 4 is fitted with an opening of the cathode side outer tube 16 having the same shape as this opening, and they are hermetically sealed to each other by welding. A second extension capillary 18 is located along the central axis of the cathode outer tube 16, and is integrally and airtightly sealed to the anode outer tube, with one end thereof having: It is inserted into the other insertion hole of the cathode side support 10, and a second reflecting mirror 20 is attached to the other end. The anode side and cathode side outer tubes 4, 12
A container made of is filled with helium He and neon Ne at a predetermined pressure, respectively, and a large amount of sputtered discharge material having a composition similar to that of the discharge material is adsorbed on the inner surface of the cathode side support 10. A layer of cathode material 21 is formed as detailed below. The He{e laser discharge tube shown in FIG. 1 is manufactured as follows.

The anode section 22 of the laser discharge tube is made up of the anode outer tube 4, the discharge capillary 2, the anode 6, the anode extension capillary 8, the reflector 7, the cathode stems 12, 14, and the cathode support 10.
is made by a well-known method. Next, as shown in FIG. 2, the anode section 22 is attached to the sputter discharge device 24 via the exhaust discharge vessel 26. The outer tube 28 of the sputter discharge device 24 has approximately the same shape as the cathode side outer tube 12, and has a thin tube 30 extending along its central axis and having one end that can be inserted into the other insertion hole of the cathode support 10. is present.
This thin tube 30 is integrally welded and sealed to the outer tube 28, and a conductor pin 32 having an aluminum sputtering cathode 34 at one end extends therein.
This conductor pin 32 is sealed and supported by the thin tube 30,
It extends outside the thin tube 30. An exhaust pipe 36 is connected to the exhaust discharge vessel 26, and the exhaust discharge vessel 2611
i. Anode side outer tube 4 and outer tube 2 of sputter discharge device 24
6 are each provided with an opening into which they can be fitted. As shown in FIG. 2, the anode side outer tube 4 is inserted into one opening of the exhaust discharge tube container 26, and the tightening ring 3 is inserted through the O-ring.
8 and sealed. After the sputter ring cathode 34 is placed in the cathode support 10, the outer tube of the sputter discharge device 24 is similarly inserted into the other opening of the exhaust discharge tube container 26, and the outer tube of the sputter discharge device 24 is similarly inserted through the O-ring. It is tightened and sealed by a tightening ring 40. As shown in the figure, the conductor pin 32 is connected to the negative side of a discharge voltage source 44, and the cathode stem 14 is connected to the positive side of the discharge voltage source 44 via a switch 46 for starting sputter discharge. There is. The inside of the sputter discharge container consisting of the exhaust discharge tube container 26, the anode side outer tube 4, and the outer tube 28 is evacuated via the exhaust pipe 36, and then, for example,
0.08 torr helium He, O. A gas mixture containing 0.1 Torr of neon Ne and 0.01 Torr of oxygen 02 is supplied, and the switch 46 is closed to begin sputtering discharge between the sputtering cathode 34 and the cathode support 10.

Since sputtering discharge is performed while the mixed gas continues to be supplied, a deposited layer 21 of cathode material is formed on the cathode support 10. For example, if the surface density per square meter on the surface of the cathode support 10 is 20 mA and the sputtering discharge is continued for 80 hours, the thickness of the deposited layer 21 of the cathode material will be 2 μm or more. Become. After the deposited layer 21 has been formed in this manner, the switch 46
is opened, the sputter discharge device 24 is removed from the anode side section 22, and the cathode side outer tube 16 is attached to the anode side outer tube 4.
are heat welded, and this outer tube 4, 1 and thin tube 2, 18 are bonded again.
The inner space is evacuated and helium (He) is evacuated to a predetermined pressure.
and neon (Ne) are sealed to complete a He{e laser discharge tube. He-Ne produced as above
According to the laser discharge tube, a deposited layer 21 of cathode material is formed on the cathode support 10, and this deposited layer 21VC has a large amount of discharge gas, that is, helium (He) and neon (Ne) gases adsorbed therein. There is.

Therefore, when the He-+Je laser discharge tube is operated, the discharge body will displace the cathode material layer 21 on the cathode support 10.
Even if the discharge material is absorbed by the laser discharge tube, the same amount of the discharge material will be released, and the pressure of the discharge material within the laser discharge tube will continue to be kept substantially constant. As a result, the life of the laser waste tube can be extended. Furthermore, since the cathode discharge surface in this laser discharge tube is a cathode material layer 21 newly formed by sputter discharge during the manufacturing process, it is more durable than when a plate-shaped raw material whose manufacturing process is unknown is used. The photoelectron emission γ effect can be maintained for a long time. Next, a He{d positive column laser discharge tube to which the present invention is applied will be explained with reference to FIGS. 2 and 3. As shown in the figure, the discharge capillary 48 is arranged on the central axis of the metal outer tube 50.
One end of the tube 8 extends outside the coaxial double cylindrical cathode support 52 inserted into the outer tube 50, and includes a first ceramic sealing tube 54, a sealing metal piece 56, It is located within a cathode side sealing section 62 consisting of a metal circular tube 58 and a sealing cover 60 made of ceramic. This cathode side. Sealing part 6
An outflow gap 64 is provided in the discharge capillary tube 48 in the discharge tube 2 to allow the cadmium (Cd) vapor to flow out into the sealing part 62.
Further, this discharge capillary 48 passes through a sealing cover 60, and its opening is sealed by a first reflective optical system 66. A return discharge tube 68 made of a coaxial circular box-shaped member is provided between the cathode support 52 and the sealing cover 60, and the discharge capillary 48 is connected to the cathode support 5 through this return discharge tube 68.
It communicates with the interior space of 2. The other end of the discharge capillary 48 is
The anode-side sealing section 70 extends into the anode-side sealing section 70 consisting of second and third ceramic sealing tubes 72 and 74 connected to the outer tube 50, a sealing metal piece 76, and the like. The opening passes through the inner oven 78 and is sealed by a second optical system 80. The oven 78 includes a heater (not shown), this heater is connected to heater electrodes 81 and 82 provided on the second sealed tube 72, and cadmium (Cd) is stored in the oven 78. At the same time, a gap 84 for the inflow of cadmium vapor is bored in the discharge capillary tube 48 in the oven 78. Third sealed tube 7
4 has a discharge capillary 48! f- A communicating space is provided;
A discharge anode 86 is located within this space. As in the first embodiment already described, on the inner surface of the cathode support 52,
The cathode material layer 88 is formed by the method described below. The above-mentioned He{d positive column laser discharge tube has a fourth
As shown in the figure, from the cathode side sealing part 62 to the metal circular tube 58
, a ceramic sealing cover 60, a reflective optical system 66, etc. are only provided.

A sputter discharge vessel 90 is attached to such an unfinished discharge tube as shown in the figure. That is, the rod-shaped aluminum plate supported by this sputter discharge container 90
A sputter electrode 92 is inserted into the cathode support 52, and the sputter discharge vessel 90 is vacuum-tightly attached to the ceramic sealed tube 54 by an L-ring 94. A metal-ceramic enclosure 94 connected to a sputter electrode 92 is connected to the negative side of a discharge voltage source 96, and an outer tube 50 connected to a cathode support 52, which serves as an anode for sputter discharge, is connected to a discharge voltage via a switch 100. connected to the positive side of source 96. On the outer periphery of the cathode support 52 outside the outer tube 50, there is a solenoid coil 1 for generating an axial magnetic field of the discharge tube.
00 is placed. The airtight space within the unfinished discharge tube and sputter discharge vessel 90 is evacuated via an exhaust pipe 102 attached to the outer tube 98 and then filled with, for example, 0.04 Torr of helium He and 0.01 Torr of oxygen 02. A gas mixture containing the above is supplied. Solenoid coil 100 is energized to create an axial magnetic field of, for example, 1200 Gauss and switch 100 is closed to create a uniform spatter discharge between aluminum electrode 92 and cathode support 52. If the mixed gas is continued to be supplied while cleanup is generated by sputter discharge, a deposited layer 88 made of aluminum with helium He adsorbed is formed on the inner surface of the cathode support 52. This deposited layer 88 has a thickness of approximately 2.5 μm when a discharge with a surface current density of 25 mA per 1 d of the surface of the cathode support 24 is continued for 80 hours.
m or more. After the deposited layer 88 has been formed, the sputter discharge container 90 is removed, and the metal cylinder 58 and the sealing cover 6 are removed.
0 and a reflective optical system 66 are attached to the sealed tube 54 to complete the discharge lamp. In this laser discharge tube, helium (He) filled in the discharge tube and cadmium (Cd) vapor generated in the oven, flowing into the metal circular tube 58 through the discharge capillary 48, and depositing on the inner surface of the metal tube are used. A pure helium discharge and a coupled helium-cadmium discharge thus occur between the anode 86 and the deposited layer 88 of the cathode support 52. In this laser discharge tube, even if a clean-up phenomenon occurs in the deposited layer 88 of the cathode support 52, helium is generated from the deposited layer 88 as described above, so the helium pressure inside the discharge tube can be kept approximately constant. As a result, a longer life of the laser discharge tube is achieved. Furthermore, with reference to FIGS. 5 and 6, a hollow cathode He to which the present invention is applied
{'d The laser discharge tube will be explained.

The cathode body 102 of this laser discharge tube forms part of the discharge vessel, and the cathode body 102 has a cathode hole 1 along its axis.
04 is drilled, and anode cavities 106, 108, 110 are drilled parallel to the axis and circularly symmetrically. Each of the anode cavities 106, 108, 110 and the cathode hole 104
are in communication with each other via cutout grooves 112, 114, and 116 provided in each of the anode cavities 106, 108, and 110, respectively. Anodes 118, 120, 122 are inserted into each anode cavity 106, 108, 110, respectively, and the anode cavity 10 corresponding to each of the anodes 118, 120, 122 is inserted into each anode cavity 106, 108, 110.
A gap is provided between the anode 6, 108, and the wall surface of the anode cavity 110 to have a cathode dark section such that no glow discharge is generated between the anode and the anode cavity wall surface. each anode 118,
120 and 122 have convex portions 124, 126, and 12, respectively.
8 is provided, and this convex portion is projected into the cathode hole 104 via grooves 112, 114, and 116. Cathode body 102
Further, holes 130, 132, and 134 are formed to increase the volume of stored helium gas communicating with the cathode hole 102. As shown in FIG. 5, the cathode body 102 and the anodes 118, 120, 122 have a laser beam passing through their center.
Ceramic sealing ring 136 with hole 139 for
, 138. That is, the anode 118 is inserted into a hole 140 provided in the sealing ring 136 and connected to an anode pin 142 that is hermetically fixed to the sealing ring 136, and one side of the sealing ring 136 is provided with a sealing piece. 144 and is sealed to the welding piece 146 of the cathode body 102 by welding. A variable reflector holder 145 is sealed to the other side of the sealed tube 136, and a reflector 148 is attached to the variable reflector holder 145 by a metal piece 150 sealed with glass frit. It is sealed by welding. A Cd metal source container 152 opening into a hole in the sealing ring 136 is held between the sealing ring 136 and the variable reflector holder 46, which is later destroyed. In the embodiment shown in FIG.
As is clear from the drawing, the left and right sides of the sealing ring 138 are symmetrical, and the two are connected to complete a laser discharge tube. A layer of cathode material 154 is deposited on the inner surface of cathode hole 104 of cathode body 102 by a method similar to that previously described.

That is, the anodes 118, 120, 122 are connected to three-phase AC power supplies 156, 158, 160 connected in delta, and the neutral point is connected to the negative side of the DC power supply 162 by the switch 16.
4, and the positive side of the DC power supply 162 is connected to the cathode body 102. Helium (He) gas, for example, 0.1 Torr, is supplied to the cathode hole 104 and the anode cavities 106, 108, 110, and the switch 16 is turned on.
4 is closed, the anodes 118, 120, 122 are used as cathodes and the cathode body 102 is used as an anode, and the power supplies 156, 158, 160 are connected.
, 164, a three-phase pulsating current voltage is supplied between the two. Therefore, spatter discharge occurs between the protrusions 124, 126, 128 of the anode and the wall surface of the cathode hole. During approximately one quarter of one cycle of the supplied three-phase pulsating voltage, the cathode hole wall surface is maintained at a negative potential with respect to the convex portion, so spatter discharge is temporarily interrupted. Ru. While spatter discharge occurs intermittently, the inside of the discharge vessel is filled with 0.1 Torr of helium (He).
As it continues to be filled with gas, the Cd metal source vessel 152 continues to be heated by sputter discharge to a temperature capable of providing approximately 5 x 10-3 Torr of Cd metal vapor. If the sputter discharge is continued in this manner, for example, for about 80 hours, a cathode material layer in which helium gas is adsorbed, ie, a cadmium layer 154, is deposited on the wall surface of the cathode hole. The Cd metal source container 152 has the Cd metal therein dissipated by sputter discharge, and then the container 152
is destroyed to ensure a laser optical path between the pair of reflecting mirrors 148. The hollow cathode He{d laser discharge tube as described above can produce 400 ml of Cd without externally replenishing Cd metal.
It has been confirmed that it continues to operate for 000 hours.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view showing a He-+Je laser discharge tube according to an embodiment of the present invention, and FIG. 2 is a longitudinal sectional view showing an assembly during the manufacturing process of the laser discharge tube shown in FIG. 1. , FIG. 3 is a vertical cross-sectional view showing a He{d positive column laser discharge tube according to another embodiment of the present invention, and FIG. 4 is a diagram showing an assembly during the manufacturing process of the laser discharge tube shown in FIG. 5 is a longitudinal sectional view showing an assembly during the manufacturing process of a hollow cathode He{'d laser discharge tube according to still another embodiment of the present invention, and FIG. It is a V-line sectional view. 2... Discharge capillary, 4... Anode side capillary, 6... Anode, 7, 20... Reflector, 8... Anode side extension tubule,
DESCRIPTION OF SYMBOLS 10... Cathode side support body, 12, 14... Cathode stem, 16... Cathode side outer tube, 18... Extension part thin tube, 21
...Deposition layer, 22...Anode side section, 24...
・Spatsuta discharge equipment, 26... Exhaust discharge container, 28
... Outer tube, 30 ... Thin tube, 32 ... Conductor pin, 3
4... Sputtering cathode, 36... Exhaust pipe, 38
, 40... Tightening ring, 42... Voltage source for discharge, 4
6...Switch, 48...Discharge capillary tube, 50...Outer tube, 52...Rinpoku support body, 54...Sealing tube, 56...
Metal piece for sealing, 58... Metal circular tube, 60... Sealing cover, 62... Cathode side sealing part, 64... Outflow gap, 6
6... Reflection optical system, 68... Return discharge tube, 70.
...Anode side sealing part, 72, 74...Sealing tube, 76...
- Metal piece, 78... Oven, 80... Second optical system, 81, 82... Zeta electrode, 84... Gap, 86
. . . Anode, 88 . . . Cathode, 90 . . . Sputter discharge container, 92 .・・・
・Switch, 102...Cathode body, 104...Rinpoku hole,
106, 108, 110...Anode cavity, 112, 11
4, 16... Notch groove, 118, 120, 122...
Anode, 24, 126, 128... Convex portion, 130, 13
234, 140... Hole, 136, 138... Sealing ring, 42... Anode pin, 144... Sealing piece, 145...
...Variable reflection retainer, 146...Welded piece, 148...
・Reflector, 150...Metal piece, 152...Cd metal source container, 154...Rinkyoku material layer, 156, 158, 160
, 162...power supply, 164...switch.

Claims (1)

[Claims] 1. A cold cathode discharge tube comprising a pair of reflecting mirrors constituting an optical cavity, a discharge vessel housing a laser discharge electric body, and an anode and a cathode for generating a discharge in the discharge vessel on the optical axis of the optical cavity, in which the above-mentioned Cold cathode discharge tube 2, characterized in that the cathode consists of a cathode material active layer on which the discharge material is adsorbed and an active layer support electrode on which the cathode material active layer is deposited.The cathode material active layer has a photoelectronic effect. Cold cathode discharge tube 3 according to claim 1, characterized in that the cathode material active layer contains metal as a laser active medium and supplies metal vapor during laser discharge. The cold cathode discharge tube 4 according to claim 1. The cold cathode discharge tube 5 according to claim 1, wherein the cathode has a shape that surrounds a space in which a negative glow discharge occurs. Generating sputter discharge on a supporting electrode placed in an airtight container containing a gas having a composition similar to that of the laser discharge material to form a cathode material active layer in which the discharge material is adsorbed on the surface of the supporting electrode. A method for manufacturing a cold cathode discharge tube 6, characterized in that the gas having a similar composition contains a component that imparts a photoelectric effect to the active layer through sputter discharge. Manufacturing method 7 of cold cathode discharge tube
8. Method for manufacturing a cold cathode discharge tube according to claim 6, wherein the component giving the photoelectric effect is oxygen. 9. Method 9 of manufacturing a cold cathode discharge tube according to claim 5, wherein the supporting electrode is used as an anode, the sputter discharge electrode is used as a cathode, and sputter discharge is generated between the two. Claim 5, characterized in that sputter discharge electrode material is deposited on the support electrode and the sputter discharge electrode is subsequently removed.
Method for manufacturing a cold cathode discharge tube described in section