Gas-discharge chamber electrode and electrode system using same

A gas-discharge chamber electrode is proposed, comprising a hollow metal member with an emitting portion on the gas-discharge side and with coolant pipes. The hollow metal member is coated on the outside, except for the emitting portion, with a high-temperature dielectric. The electrode system includes at least two such electrodes.

FIELD OF THE INVENTION 
The present invention relates to discharge chambers of gas-discharge, 
predominantly glow-discharge, devices, and more particularly to 
gas-discharge chamber electrodes and an electrode system using such 
electrodes. 
The invention can most advantageously be used in designing 
electric-discharge reactors for plasmochemistry, in laser engineering for 
electric-discharge lasers with transverse gas flow, as well as in 
electrophysical engineering. 
BACKGROUND OF THE INVENTION 
Known in the art is a gas-discharge chamber electrode and an electrode 
system using such electrodes. The electrode system incorporates an 
insulating plate whereon groups of electrodes are mounted. 
Each electrode extends into the gas flow and, firstly, creates a high 
aerodynamic resistance to the gas flow and, secondly, partially blocks the 
gas passage. 
The prior art electrode system is not reliable in long-term operation and 
has a low stability. 
There is also known a gas-discharge chamber electrode (cf. J. of Physic E.: 
Scientific Instruments, v. 4, No. 9, Sept., 1971, p. 708: "Electrode 
Configuration and Power Output for a Transverse Flow CO.sub.2 -Laser", N. 
Ben-Josef et al.) comprising a hollow metal member with an emitting 
portion on the gas-discharge side and coolant pipes. The electrode system 
based on such members comprises two electrodes (cathode and anode) 
wherebetween gas is blown. 
The above electrode system is intended for a gas-discharge chamber 
operating in the glow-discharge mode and is limited by a pressure of up to 
20 torr and a flow rate of 40 to 50 m/sec. When these parameters are 
exceeded, the glow discharge immediately loses its homogeneity, which is 
extremely undesirable and adversely affects the operation of the electrode 
system. 
Attempts to increase the energy content in gas involve, primarily, a 
greater number of electrodes and a higher velocity of the gas blown 
between the electrodes. Both factors impair the gas-dynamic 
characteristics of the interelectrode space and impose more stringent 
requirements on the gas pumping means. The increase in pressure and the 
associated loss in homogeneity of the glow discharge lowers the stability 
and reliability of such a system and each electrode in operation. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to improve the reliability and 
stability of electrodes in operation. 
Another object of the invention is to increase the energy content in gas. 
Still another object of the invention is to provide a reliable electrode 
system made up of interchangeable electrodes. 
The invention resides in that an electrode comprising a hollow metal member 
with an emitting portion on the gas-discharge side, provided with coolant 
pipes, is, according to the invention, coated on the outside, except for 
the emitting portion, with a high-temperature dielectric layer. 
Preferably, the high-temperature dielectric layer should be in the form of 
a film. 
It is desirable that, on the wall of the hollow metal member on the 
gas-discharge side, at least one lug be provided, and that the 
high-temperature dielectric layer be in the form of a composite shell 
comprising a body of the same configuration as the hollow metal member 
with the coolant pipes and a cover having at least one through slot in its 
bottom, the hollow metal member being accommodated in the body and covered 
by the cover so that the lug of the hollow member is received by the slot 
in the cover bottom and has its tip flush with the outer surface of the 
cover. 
The lug should preferably be in the form of a plate. 
It is expedient that a plurality of studs be made on the wall of the hollow 
metal member, arranged in longitudinal and transverse rows, while through 
holes should be made in the cover bottom to receive the studs. 
It is preferable that the hollow metal member be made as a cylinder having 
a solid end, with a lug being provided on the latter, while the 
high-temperature dielectric layer should be in the form of a solid shell 
enclosing the cylinder and having a cylindrical portion on the side of the 
cylinder's open end and a bottom with a through slot to receive the lug, 
the length of the slot exceeding the inner diameter of the shell. 
The emitting portion should preferably be coated with a layer of a 
corrosion-resistant metal. 
It is desirable that the electrode system comprise, according to the 
invention, at least two such electrodes. 
Advantages of the proposed electrodes include simple design, the 
possibility of fully controlling the quality of any electrode component in 
the course of manufacture, and higher reliability thereof in operation. 
Such electrodes can be manufactured using conventional techniques adopted 
in the electrovacuum industry. When operating in a gas-discharge chamber, 
such electrodes release insignificant amounts of gas, which is essential 
when the gas-discharge chamber operates in a closed-loop system. 
Electrode systems assembled of such electrodes feature high reliability 
because, firstly, each electrode can be tested separately, secondly, 
faulty electrodes can be easily replaced without disassembling the entire 
electrode system and, thirdly, mechanical distortions inevitable when 
pressure inside the gas-discharge chamber varies do not affect the 
high-temperature dielectric. The proposed electrodes permit assembling 
electrode systems for gas-discharge chambers of a broad power range, which 
substantially cuts down the cost of their designing and manufacture.

DETAILED DESCRIPTION OF THE INVENTION 
Consider a gas-discharge chamber electrode used in laser engineering, e.g., 
in electric-discharge transverse gas flow lasers. The electrode comprises 
a hollow metal member 1 (FIG. 1) with an emitting portion 2 on the side of 
the gas-discharge zone (not shown) and provided with coolant pipes 3 and 
4. On the outside, the hollow metal member 1 is coated, with the exception 
of the emitting portion, with a high-temperature dielectric layer 5. The 
layer 5 is applied on the metal member 1 as a film, using conventional 
techniques. Used for the purpose may be, for example, glass enamel or 
oxide coats based on aluminum or another metal. The emitting portion 2 of 
the metal member 1 is coated with a layer 6 of a corrosion-resistant 
metal, such as niobium or titanium. 
In another embodiment, a lug 7 (FIG. 2) is made on the wall of the hollow 
metal member 1. The lug surface facing the gas-discharge zone serves as 
the emitting portion 2. The high-temperature dielectric layer 5 is made as 
a composite shell comprising a body 8 of the same configuration as the 
hollow metal member 1 with the cooling pipes, and a cover 9 having a 
through slot in its bottom 10. The metal member 1 is accommodated in the 
body 8 and covered by the cover 9 so that the lug 7 of the metal member 1 
is received by the slot in the bottom 10 of the cover 9 and has its tip 
flush with the outer surface of the cover. 
According to still another embodiment, a gas-discharge chamber electrode 
may be made having a plurality of studs 7 provided on the wall of the 
metal member 1 and arranged in longitudinal and transverse rows. In the 
bottom 10 of the cover 9 through holes 11 (FIG. 3) are made to receive the 
studs 7. The latter enter the holes 11 in the bottom 10 of the cover 9 so 
that their tips are flush with its outer surface and the end faces of the 
studs 7 serve as the emitting surface 2. 
The high-temperature dielectric layer 5 may be made as a solid shell 12 
(FIG. 4). In this case, the hollow metal member 1 is essentially a 
cylinder with a solid end on which a lug 7 is provided. The cylinder 
houses coolant pipes 3 and 4 arranged coaxially with the cylinder. The 
solid shell 12 has a cylindrical portion on the side of the open end of 
the metal member 1, and a bottom in which a through slot is made to 
receive the lug 7, the length of the slot exceeding the inner diameter of 
the shell 12. 
Composite or solid shells from a high-temperature dielectric are made using 
any conventional technique, for example, hot slip forming of a 
high-temperature dielectric based on alumina. 
In all embodiments, the emitting surface 2 may be coated with a layer of a 
corrosion-resistant metal. 
Two or more electrodes 13 (FIG. 5) mounted on a base plate 14 (the mounting 
is not shown) make up an electrode system. Gas flows between the electrode 
system having a charge of one sign and an electrode 15 with a charge of 
the opposite sign. The arrangement of the electrode system relative to the 
electrode 15 is determined by the discharge gap. The electrode (FIG. 1) 
having a film coating is made by applying a layer of, e.g. glass enamel or 
an oxide coat based on aluminium or another metal, on a hollow metal 
member. 
The electrodes (FIGS. 2 and 3) whose protective coating is the 
high-temperature dielectric layer 5 are assembled by bonding, the 
adhesive, e.g., an epoxy compound with a filler, being applied in advance 
on the mating surfaces. 
In the case where the protection of the electrode (FIG. 4) is in the form 
of the solid shell 12, the electrode is assembled by, e.g., soldering the 
lug 7 to the hollow member 1, both being preinserted into respective 
cavities of the solid shell 12. The sealing of the lug 7 in the slot is 
achieved by soldering with a metallic or nonmetallic solder. When the 
electrode system (FIG. 5) is assembled, the electrodes 13 are fixed on the 
base plate 14 with the aid of nuts screwed on the threaded ends (not 
shown) of pipes with elastic gaskets being used to seal the pipes.