JP4610133B2 - Method for detecting discharge outside electrode in gas laser oscillator - Google Patents

Description

【数１】
ψ1＝arctan（ＶC1＋ＶC2）／ＶR………（１）
一方、電極外放電時には放電が前記高圧側電極９と真空容器３との間で生じ、放電電流iは真空容器３を流れて低圧側電極１１には流れないので、放電回路の等価回路は図４に示す様になる。
【００２３】
電極外放電時の放電の等価抵抗をＲ’、等価抵抗Ｒ’の両端の電圧をＶR’とすれば、前記電源電圧Ｖは、Ｖ＝ＶC1＋ＶR’となる。したがって、電源電圧Ｖ
【外２】

【数２】
ψ2＝arctanＶC1／ＶR’………（２）
上述の如く、電極外放電時には放電経路の変化に起因して、前記位相角ψ1がψ2に変化する。したがって、この位相角の変化（ψ1→ψ2）を検出することにより電極外放電を検出することができる。
【００２４】
【発明の効果】
請求項１の電極外放電検出方法によれば、レーザ発振器内部に電極外放電検出用のアンテナ電極を設けないのでアンテナ電極が焼損することがない。また、アンテナ電極により電極外放電が誘発されることもない。したがって、維持管理が容易であり従来に比較してコストダウンが可能である。また、電極外放電以外に放電抵抗が変化する異常放電である（アーク放電）も検出することができる。
【図面の簡単な説明】
【図１】本発明に係る電極外放電検出手段を備えたガスレーザ発振器の実施形態の説明図。
【図２】図１に示したガスレーザ発振器１の放電回路の等価回路。
【図３】正常放電時の等価回路における電圧のベクトル図。
【図４】電極外放電時の放電回路の等価回路。
【図５】電極外放電時の等価回路における電圧のベクトル図。
【符号の説明】
１ ガスレーザ発振器
３ 真空容器
５ 高周波電源
７a,7b,１３ 導線
９ 高圧側電極
１１ 低圧側電極
１５ 電流測定手段
Ｇ レーザガス
Ｖ 高周波電源電圧
ＶC1、高圧側電極の端子間電圧。
ＶC2 低圧側電極の端子間電圧。
ＶR,ＶR’正常および電極外放電時の等価抵抗両端の電圧[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for detecting discharge outside an electrode in a gas laser oscillator.
[0002]
[Prior art]
A typical example of a gas laser oscillator provided with means for detecting discharge outside the electrode is disclosed in Japanese Patent Application Laid-Open No. 6-252470.
[0003]
In the gas laser oscillator (1) disclosed in the above-mentioned publication, the high-voltage side dielectric electrode (5) and the ground-side dielectric electrode (7) are separated by a distance L1 in the chamber (3) of the laser oscillator. For detection to detect an out-of-electrode discharge downstream of the laser gas flowing between the high-voltage side dielectric electrode and the ground-side dielectric electrode and at a distance L2 from the high-voltage side dielectric electrode. An antenna electrode (17) is provided, and discharge outside the electrode is detected by this antenna electrode. The distance L2 is set to be larger than the distance L1, and is set to be smaller than the distance L3 between the high voltage side dielectric electrode and the chamber of the laser oscillator.
[0004]
[Problems to be solved by the invention]
In the gas laser oscillator (1) disclosed in Japanese Patent Laid-Open No. 6-252470 described above, a detection antenna electrode (17) for detecting discharge outside the electrode is provided in the vicinity of the discharge part in the chamber (3) of the laser oscillator. Since it is provided, the antenna electrode is easily burned out by the discharge outside the electrode. In addition, when an antenna electrode is provided in the laser oscillator, there is a problem that discharge outside the electrode is more likely to occur than when no antenna electrode is provided.
[0005]
The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a novel off-electrode discharge detection method in which no off-electrode discharge detection means is provided in a laser oscillator.
[0006]
[Means for Solving the Problems]
According to a first aspect of the present invention, there is provided a method for detecting discharge outside an electrode in a gas laser oscillator as a means for solving the above-mentioned problem. A discharge portion composed of a high voltage side electrode and a low voltage side electrode connected to a high frequency power source is placed in a vacuum vessel filled with laser gas. In the gas laser oscillator provided, when the voltages at both ends of the high-voltage side electrode and the low-voltage side electrode are VC1 and VC2, and the voltage at both ends of the discharge portion during normal discharge is VR, the high-frequency power supply voltage V The gist is to detect the discharge outside the electrode by previously obtaining the phase angle ψ1 with respect to the voltage VR and detecting the change (ψ1 → ψ2) of the phase angle ψ1 caused by the change in the discharge path during the discharge outside the electrode. To do .
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[0012]
FIG. 1 is an explanatory view of an embodiment of a gas laser oscillator provided with an out-electrode discharge detecting means according to the present invention.
[0013]
As shown in FIG. 1, inside the vacuum vessel 3 of the gas laser oscillator 1, a high voltage side electrode 9 and a low voltage side electrode 11 connected to a high frequency power source 5 by conducting wires 7a and 7b are provided facing each other at an appropriate interval. . Further, a laser gas G is provided between the high voltage side electrode 9 and the low voltage side electrode 11 so as to circulate from left to right by a blower (not shown).
[0014]
The high voltage side electrode 9 and the low voltage side electrode 11 are electrically insulated from the vacuum vessel 3. On the other hand, the vacuum vessel 3 is connected to the high-frequency power source 5 through conductors 7b and 13 and grounded.
[0015]
The line of the conducting wire 13 is provided with a current measuring means 15 such as an ammeter or a current transformer (CT) for measuring the current i flowing through the conducting wire 13.
[0016]
In the gas laser oscillator having the above-described configuration, when normal discharge is performed between the high-voltage side electrode 9 and the low-voltage side electrode 11, the optical axis direction (direction perpendicular to the paper surface) of the optical resonator (not shown). Laser light is output.
[0017]
When discharge outside the electrode between the high voltage side electrode 9 and the vacuum vessel 3 occurs, a large current i flows to the vacuum vessel 3, and the current i returns to the high frequency power source 5 through the conductors 7 b and 13.
[0018]
The current i flowing between the vacuum vessel 3 and the high frequency power source 5 is detected by a current measuring means 15 such as an ammeter or a current transformer, and when the current i exceeds a set threshold value, it is determined that the discharge is out of the electrode. To do. It is also possible to shut off the high-frequency power source 5 when detecting discharge outside the electrode.
[0019]
When a current transformer (Current Transformer; CT) is used for the current measuring means 15 described above, the lead wire 13 (corresponding to the primary side) through which the current i during discharge outside the electrode flows and the current measuring means 15 (to the secondary side) Equivalent) is a non-contact magnetic coupling through a transformer, so that there is an advantage that it is easy to prevent electric shock and to prevent noise in the current measuring means 15.
[0020]
FIG. 2 is an equivalent circuit 17 of the discharge circuit of the gas laser oscillator 1 shown in FIG. In the equivalent circuit 17, the high-voltage side electrode 9 and the low-voltage side electrode 11 correspond to capacitors of electrostatic capacitances C 1 and C 2, respectively, and the discharge portion corresponds to the resistance R.
[0021]
In the equivalent circuit 17, when the power supply voltage is V, the voltages between the terminals of the high-voltage side electrode 9 and the low-voltage side electrode 11 are VC1 and VC2, and the voltage across the equivalent resistance R of the discharge is VR, the power supply voltage is V V = VC1 + VC2 + VR.
[0022]
Since the phase difference between the voltages (VC1, VC2) between the high-voltage side electrode 9 and the low-voltage side electrode 11 during discharge and VR is 90 degrees, the vector diagram is as shown in FIG.

[Expression 1]
ψ1 = arctan (VC1 + VC2) / VR (1)
On the other hand, during discharge outside the electrode, discharge occurs between the high-voltage side electrode 9 and the vacuum vessel 3, and the discharge current i flows through the vacuum vessel 3 and does not flow to the low-voltage side electrode 11. Therefore, an equivalent circuit of the discharge circuit is shown in FIG. As shown in FIG.
[0023]
If the equivalent resistance of discharge at the time of discharge outside the electrode is R ′ and the voltage across the equivalent resistance R ′ is VR ′, the power supply voltage V is V = VC1 + VR ′. Therefore, the power supply voltage V
[Outside 2]

[Expression 2]
ψ2 = arctan VC1 / VR '(2)
As described above, the phase angle ψ1 changes to ψ2 due to the change in the discharge path during discharge outside the electrode. Therefore, the discharge outside the electrode can be detected by detecting the change in the phase angle (ψ1 → ψ2).
[0024]
【The invention's effect】
According to the off-electrode discharge detection method of the first aspect, since the antenna electrode for detecting the off-electrode discharge is not provided inside the laser oscillator, the antenna electrode is not burned out. Further, no discharge outside the electrode is induced by the antenna electrode. Therefore, the maintenance management is easy and the cost can be reduced as compared with the conventional case. Further, abnormal discharge (arc discharge) in which the discharge resistance changes in addition to the discharge outside the electrode can also be detected .
[Brief description of the drawings]
FIG. 1 is an explanatory view of an embodiment of a gas laser oscillator provided with an out-of-electrode discharge detection unit according to the present invention.
2 is an equivalent circuit of a discharge circuit of the gas laser oscillator 1 shown in FIG.
FIG. 3 is a vector diagram of a voltage in an equivalent circuit during normal discharge.
FIG. 4 is an equivalent circuit of a discharge circuit during discharge outside the electrode.
FIG. 5 is a vector diagram of a voltage in an equivalent circuit during discharge outside the electrode.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Gas laser oscillator 3 Vacuum vessel 5 High frequency power supply 7a, 7b, 13 Conductor 9 High voltage side electrode 11 Low voltage side electrode 15 Current measuring means G Laser gas V High frequency power supply voltage VC1 and voltage between terminals of the high voltage side electrode.
VC2 Voltage between terminals of the low voltage side electrode.
Voltage across the equivalent resistance during VR, VR 'normal and off-electrode discharge

Claims (1)

In a gas laser oscillator in which a discharge portion consisting of a high-voltage electrode and a low-voltage electrode connected to a high-frequency power source is provided in a vacuum vessel filled with laser gas, the voltages at both ends of the high-voltage electrode and the low-voltage electrode are VC1, VC2, normal When the voltage at both ends of the discharge part at the time of discharge is VR, the phase angle ψ1 of the high-frequency power supply voltage V with respect to the voltage VR at both ends of the discharge part is obtained in advance, and this is caused by the change in the discharge path at the time of discharge outside the electrode. An off-electrode discharge detection method in a gas laser oscillator, wherein an off-electrode discharge is detected by detecting a change in the phase angle ψ1 (ψ1 → ψ2) .

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