Discharge electrode for laser device

Details Discharge electrode for laser device Discharge electrode for laser device

2000-09-18

2003-09-30

Scott, Jr., Leon (Department: 2828)

Coherent light generators

Particular pumping means

Electrical

C372S065000

Reexamination Certificate

active

06628693

ABSTRACT:

TECHNICAL FIELD
The present invention relates to a discharge electrode for a laser device, and more particularly to the structure of the discharge electrode for the laser device.
BACKGROUND ART
A laser device which excites laser gases by electric discharge has been hitherto known and is shown, for example in U.S. Pat. No. 4,959,840.
FIG. 12
is a sectional view of an excimer laser device
101
disclosed in the aforesaid Patent.
In
FIG. 12
, a pair of discharge electrodes
104
and
105
composed of an anode
104
and a cathode
105
are disposed facing each other with a predetermined space between them at predetermined positions inside a laser chamber
102
containing laser gases. In the excimer laser device
101
, a high-voltage is applied to a space between the discharge electrodes
104
and
105
from a high-voltage power supply not illustrated to cause main discharge to occur, whereby the laser gases are excited to oscillate laser light.
A chamber opening
107
is disposed at the upper portion of the laser chamber
102
, which is sealed up with insulating members
109
and
110
made of an insulating material such as a ceramic. A space between the laser chamber
102
and the insulating member
109
is sealed by an O-ring not illustrated. A cathode supporting member
108
made of a conductive material is attached to the insulating member
109
and the cathode
105
is fixed to the cathode supporting member
108
.
A plurality of high-voltage feeder bolts
112
are screwed into the cathode supporting member
108
, penetrating through base through-holes which are disposed in the insulating members
109
and
110
at predetermined intervals in a longitudinal direction. A high-voltage current for main discharge is supplied to the cathode
105
through these high-voltage feeder bolts
112
.
FIG. 13
shows the bottom surface of the cathode supporting member
108
. As shown in
FIG. 13
, cathode bolt holes
124
, into which the high-voltage feeding bolts
112
are screwed, are disposed at predetermined intervals in the longitudinal direction in the cathode supporting member
108
. At the bottom of the cathode
105
, O-ring grooves
122
are disposed in such a manner to surround each of the cathode bolt holes
124
. O-rings not illustrated are inserted inside the O-ring grooves
122
to seal the space between the cathode supporting member
108
and the insulating member
109
.
However, the prior art disclosed in the aforesaid U.S. Pat. No. 4,959,840 has the following disadvantages.
Namely, in the prior art, as shown in FIG.
12
and
FIG. 13
, the O-ring groove
122
for scaling in the laser gases is provided to each of the high-voltage feeder bolt
112
. Therefore, the interval between the high-voltage feeder bolts
112
is not allowed to be narrower than the outer periphery of the O-ring groove
122
, and it is difficult to increase the number of the high-voltage feeder bolts
112
.
Thereby, the high-voltage current flowing to each of the high-voltage feeder bolt
112
is increased and the discharge is easy to concentrate near the high-voltage feeder bolts
112
of the cathode
105
in main discharge. As a result, main discharge may be unstable and thus causing the disadvantage of variations occurring in the pulse energy of laser light for oscillating the pulse.
SUMMARY OR THE INVENTION
The present invention is made to eliminate the disadvantages in the aforesaid art, and its object is to provide a discharge electrode for a laser device which can cause stable main discharge to occur.
To attain the aforesaid object, the discharge electrode for the laser device according to the present invention has the structure including; a cathode base made of an insulating material for sealing up a chamber opening provided in a laser chamber for containing laser gases, a cathode attached to the cathode base with a bottom surface of the cathode in contact therewith, and a plurality of high-voltage feeder rods disposed in a longitudinal direction, penetrating through the cathode base from an outside of the laser chamber and supplying a high-voltage current to the cathode, and the structure in which an O-ring groove for sealing in the laser gases is formed on the bottom surface of the cathode to surround a plurality of holes for fixing the high-voltage feeder rods disposed on the bottom surface of the cathode.
According to the aforesaid structure, for a plurality of the high-voltage feeder bolts, one O-ring groove is used for sealing in the laser gases so that the intervals between the high-voltage feeder bolts are allowed to be narrower and the number of the high-voltage feeder bolts can be increased. Therefore, the high-voltage current flowing to each of the high-voltage feeder bolt is decreased and the high-voltage current is uniformly supplied to the cathode in the longitudinal direction. Thus, discharge concentrations are decreased and variations in pulse energy of laser light are decreased.
Moreover, the discharge electrode for the laser device may have the structure further including; a cathode bar in contact with the cathode on surfaces thereof, and the structure in which the high-voltage current is supplied to the cathode by means of the high-voltage feeder rod and the cathode bar.
According to the aforesaid structure, the high-voltage current is supplied to the cathode by contacting with surfaces thereof so that the high-voltage current is supplied more uniformly to the cathode in the longitudinal direction. As a result, the discharge concentrations are further decreased and the variations in the pulse energy of laser light are further decreased.


REFERENCES:
patent: 3636472 (1972-01-01), Leonard et al.
patent: 4343040 (1982-08-01), Shibayama et al.
patent: 4488309 (1984-12-01), Tanaka et al.
patent: 4554667 (1985-11-01), Kaminski
patent: 4617668 (1986-10-01), Rudko et al.
patent: 4805182 (1989-02-01), Laakmann
patent: 4833686 (1989-05-01), Eldridge
patent: 4959840 (1990-09-01), Akins et al.
patent: 5023884 (1991-06-01), Akins et al.
patent: 5771258 (1998-06-01), Morton et al.
patent: 5875207 (1999-02-01), Osmanow
patent: 6208674 (2001-03-01), Webb et al.

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