JPS61226984A - Sealed-off type carbon dioxide gas laser oscillating tube - Google Patents

Abstract

PURPOSE:To obtain an oscillating tube having a high output, long life and a wide output control range by respectively coating a cathode with a hollow cathode, a base material with a platinum group element or an alloy thereof and a hollow-shaped inner surface of the cathode with a conductive perovskite oxide. CONSTITUTION:The inner surface of a cathode base material 11 is coated with a perovskite oxide 12. Raw material powder is baked tentatively and crushed, and changed into a pasty shape while using a polyvinyl alcohol solution, etc. as binders, and the paste is applied onto the inner surface of the cathode base material 11, and baked mainly, thus completing a coating. When a laser oscillating tube is operated, discharge plasma 7 is introduced to the inner surface of a cathode by discharge guides 9, and CO and NOx are formed by discharge from gases CO2 and N2 encapsulated into the laser oscillating tube. Formed gases pass in and out through small holes 10 bored on its midway of the discharge guides 9 together with sealed gases, are subject to strong catalytic action by platinum in the cathode base material 11 in the outer surface of the cathode, and return to CO2 and N2, thus displaying the same effect as the inhibition of decomposition. Accordingly, long life can be kept as the oscillating tube is left as it has high performance.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a segmented carbon dioxide (CO2) laser oscillator tube that has high output, long life, and a wide output control range.

[Conventional technology]

Carbon dioxide laser oscillation tubes can be roughly divided into sealed type and gas flow type. The sealed carbon dioxide laser oscillation tube is
Gas is sealed inside the tube, and there is no need for a gas cylinder or exhaust system, which is required for gas flow type carbon dioxide laser oscillation tubes. Therefore, the device is convenient in that it can be made compact and maintenance is easy. In addition to CO2, N2. He gas is mixed in, and during discharge, toxic gases such as CO and NOx are generated according to the following reaction formula.

2C02→2CO+02 N2 +02→NO, (No, NO2, etc.) A sealed carbon dioxide laser oscillation tube is advantageous in that these toxic gases are not released outside the tube. On the other hand, it has the disadvantage that the sealed gas decomposes and accumulates each time it is discharged, resulting in a decrease in output over time and a short lifespan.

For this reason, in a sealed carbon dioxide laser oscillation tube, a catalyst is generally used in the tube to suppress the decomposition of the sealed gas. From the above reaction equation, it can be seen that a CO oxidation catalyst or a NOX reduction catalyst is suitable as the catalyst for the sealed carbon dioxide laser oscillator tube. There are various types of catalysts for sealed carbon dioxide laser oscillation tubes. For example, gas catalysts in which H2, H20, or Xe' are mixed into the gas sealed in the tube, and solid catalysts in which platinum metal elements such as platinum and their alloys are used as cathodes. There are also those that coat the inner surface of the discharge tube, and recently there are those that use conductive perovskite oxide as a cathode.

However, gas catalysts have a small catalytic effect and are adsorbed on the inner wall of the laser oscillation tube, making it difficult to control the partial pressure stably over a long period of time, so they are not suitable for achieving high output and long life. Products using conductive oxides for the cathode have a smaller catalytic effect than platinum metal elements and their alloys, which will be described below, and can have a lifespan of about 1,000 to 2,000 hours, but they require maintenance, etc. of the equipment. From a practical standpoint, a lifespan approximately 10 times longer than this is required.

Among various catalysts, platinum metal elements and their alloys have the most remarkable catalytic effect. This is because the platinum metal element and its alloy function as both a CO oxidation catalyst and a NOX reduction catalyst. In terms of catalytic effect, it is optimal as a catalyst for sealed carbon dioxide laser oscillation tubes.

The higher the temperature, the better the catalytic effect of platinum metal elements and their alloys, and for this reason they are generally used as cathodes. At this time, a problem arises in that platinum metal elements and their alloys are more prone to sputtering than other metals. That is, sputtering deposits in the vicinity of the cathode accompanying sputtering adsorb the filler gas, and as a result, the filler gas pressure and gas composition within the laser oscillation tube move away from the optimal conditions for laser oscillation tube operation over time. As a result, the output of the laser oscillation tube decreases, resulting in a shortened lifespan. In addition, sputtering deposits are conductive because they are of the same quality as the cathode material, and in severe cases, abnormal discharge can occur through the sputtering deposits, which is one of the factors that limits the life of the laser oscillator tube. Become. Cathode sputtering is highly dependent on discharge current. That is, if the discharge current is increased in order to increase the laser output, sputtering will also increase and the life of the laser oscillation tube will be shortened, so the high output of the sealed carbon dioxide laser oscillation tube has been forced to be limited.

Another difficulty in using platinum metal elements and their alloys as cathodes is their high work function. In addition to the need to maintain maximum output for a long period of time in a laser device, it is also desirable to be able to vary the output over a wide range. In a carbon dioxide laser oscillator tube, when the discharge current is reduced, it is desirable that the minimum output that can be controlled is as small as possible.If the discharge current is made extremely small to reduce the output, the cathode has a high work function. Discharge at minute currents becomes unstable, resulting in intermittent discharge or pulsed discharge. Therefore, it becomes impossible to narrow down the output. When platinum metal elements and their alloys are used for the cathode, the output control is limited to a maximum output of about 1720.

[Problem that the invention seeks to solve]

The present invention eliminates these drawbacks of conventional sealed carbon dioxide laser oscillation tubes and provides a practical sealed carbon dioxide laser oscillation tube that has high output, long life, and a wide output control range.

[Means for solving problems]

In order to solve the above problems, a sealed carbon dioxide laser oscillation tube of the present invention will be explained with reference to FIGS. 1 and 2, which correspond to embodiments.

The cathode 1 is a hollow cathode, and the base material 11 is a platinum metal element or an alloy thereof. cathode 1
The hollow inner surface of the conductive perovskite oxide 12
It is covered with.

[Effect]

The platinum metal element or its alloy in the cathode base material 11 functions as both a CO oxidation catalyst and a NOx reduction catalyst. Also, the conductive perovskite oxide 1 on the surface of the cathode
2 has the effect of suppressing sputtering, and at the same time,
Since the work function is low, discharge becomes stable at minute currents.

〔Example〕 The present invention will be explained in detail below based on the drawings.

FIG. 1 is a schematic cross-sectional view showing an embodiment of a sealed carbon dioxide laser oscillation tube to which the present invention is applied, and FIG. 2 is an enlarged cross-sectional view of the cathode and its vicinity, which is the main part thereof. In Figure 1, 1
is a cylindrical hollow cathode, 2 is an anode, 3 is a total reflection mirror, 4 is an output mirror, 5 is the inside of the discharge tube, 6 is an outer tube (jacket) with a cooling water inlet and outlet, and 7 is the discharge plasma generated by discharge. , 8 is laser output light. In Figure 2,
9 is a discharge guide for uniformly guiding the discharge plasma into the cathode at the same time as determining the position of the cathode; 10 is a pore for the circulation of gas sealed inside and outside the cathode; 11 is a hollow cathode base material made of platinum; 12 is a discharge guide for uniformly guiding discharge plasma into the cathode; Hollow cathode base material 1
This is a conductive perovskite oxide coated on the inner surface of the cylinder. Perovskite oxide is a substance represented by the molecular formula ABO3 and has a unique crystal structure. The fired body exhibits piezoelectricity or metal-type conductivity depending on the composition. For example, La+-xsrXGo03 or La+-
xsrxMno3 and the like exhibit remarkable electrical conductivity.

The inner surface of the cathode base material 11 can be coated with perovskite oxide 12 by the following method in the same way as ordinary ceramic baking.

For example, La1-xsrxcoo3 is 0.7,
Raw material powders mixed at a molar ratio with an Sr content of 0.3 are calcined and then ground to form a paste using a polyvinyl alcohol solution or the like as a binder. After applying the paste to the inner surface of the cathode base material 11, main firing is performed to complete the coating. In order to increase the mechanical bonding strength between the sword base material 11 and the conductive perovskite oxide 12, 1 to 1 portion of vitreous material mainly composed of 5i02 is added to the paste described above.
It is effective when about 0% by weight is mixed. As the amount of vitreous mixed in increases, the specific resistance increases, but since the impedance of a normal carbon dioxide laser oscillation tube is relatively high at 10 OKΩ to LMΩ, the increase in resistance value caused by the inclusion of about 1 to 10% of vitreous substance ( 100Ω to IKΩ) does not pose a problem when used as a cathode.

When the laser tube operates, discharge plasma 7 is guided to the inner surface of the cathode by discharge guide 9. At this time, CO1N OX is generated by discharge from the gas (CO2, N2) sealed in the laser oscillation tube. The generated gas enters and exits together with the sealed gas through a pore 10 formed in the middle of the discharge guide 9, and is subjected to a strong catalytic action by the platinum of the cathode base material 11 on the outer surface of the cathode, resulting in CO2, N2
Return to The result is the same effect as suppressing decomposition.

Further, when the laser oscillation tube is operated, the conductive perovskite oxide 12 on the inner surface of the cathode is exposed to the discharge plasma 7. In general, oxides are less prone to sputtering than metals, and conductive perovskite oxides are less likely to cause sputtering than conventional platinum metal elements or their alloys as cathodes. The problem becomes negligible.

In the sealed carbon dioxide laser oscillator tube of the above embodiment, it is possible to obtain 65 W per meter of discharge length, and the lifespan is 10,000.
I was able to make it on time.

Furthermore, the cathode of the sealed carbon dioxide laser oscillator tube with the above configuration has been found to be able to maintain an extremely stable discharge even when the current is small.The so-called hollow cathode in the form of a cylinder has a conventionally known configuration, but There is no so-called hollow cathode effect when current is applied. To obtain the hollow cathode effect, the cathode material must have a low work function. Table 1 shows the work functions of typical platinum metal elements and conductive perovskite oxide constituent elements. As shown in the same table, it can be seen that the conductive perovskite oxide constituent elements have a lower work function when compared with the platinum metal element. Furthermore, oxides generally have a lower work function than elemental metals. Taking all of these into consideration, it is believed that the cathode of the sealed carbon dioxide laser oscillator tube having the above structure has high discharge stability when a small current is applied.

Table 1 Work functions of metals In the above embodiment, the hollow cathode base material 11 was made of platinum (p
t), but in addition to that, Pd, Rh, Os, Ir
The hollow cathode base material 11 may be made of other metal such as copper, and the surface may be plated with platinum or the like.

〔Effect of the invention〕

As explained above, the sealed carbon dioxide laser oscillation tube of the present invention has a high catalytic effect because the platinum metal element or its alloy used in the cathode base material has a high catalytic effect, and no harmful gases accumulate. Long lifespan can be maintained due to performance. The conductive perovskite oxide 12 on the inner surface of the cathode is
Since it exhibits great resistance to sputtering, it also becomes possible to achieve high output and long life.

Furthermore, because the discharge stability is good when the current is small, the output control range is wide, making it possible to continuously vary the output from zero to maximum output.

[Brief explanation of drawings]

FIG. 1 is a side sectional view of a laser oscillation tube to which the present invention is applied, and FIG. 2 is an enlarged view of the main parts thereof. l... Cathode, 2... 7 nodes, 3... Total reflection mirror, 4... Output mirror,
5...Discharge section inner tube, 6...Outer tube, 7...
...Discharge plasma, 8... Laser output light, 9°81. discharge guide, 10. ,,, Pore, 11,,
,,,Cathode substrate, 12,,,,Conductive perovskite oxide.

Claims (1)

[Claims] 1. A sealed carbon dioxide laser oscillation tube, characterized in that the cathode is a hollow cathode made of a single metal of a platinum metal element or an alloy of a platinum metal element, and the inner surface of the cathode is coated with a conductive perovskite oxide.