JPH07111859B2 - Vacuum trigger gap device - Google Patents

Description

Description: [Object of the Invention] (Field of Industrial Application) The present invention relates to a trigger discharge type vacuum gap device, and in particular, a main trigger gap can be easily made conductive by a current trigger. The present invention relates to a vacuum trigger gap device that always gives a good and stable trigger and can be used for a long period of time.

(Prior Art) A conventional vacuum trigger gap device is formed of a high withstand voltage material such as porcelain as shown in FIG. Inside, a pair of main electrodes 2a, 2b are arranged opposite to each other. This main electrode 2a, 2b
Is formed in a flat plate shape, and the end plates 3a and 3b of the vacuum container 1 are
Are fixed to the end portions of a pair of lead shafts 4a and 4b which are introduced through the airtightly. One of the lead shafts, eg, 4a, is directly grounded to the high voltage terminal, and the other lead shaft, eg, 3b, is directly grounded. The lead shaft 4b is formed in a hollow shape, and the main electrode 2b is fixed to the shaft end.

Then, one of the main electrodes 2a and 2b described above, for example, the main electrode 2b directly grounded, is formed in a hollow shape, and the trigger space 5 is closed by an insulating member 6 at substantially the center thereof. The insulating member 6 is made of alumina (Al ₂ O ₃ ) or barium titanate (BaTiO ₃ ).

Further, one end of a needle-shaped trigger electrode 7 is arranged in the trigger space 5 surrounded by the main electrode 2b at the center of the insulating member 6. Therefore, the middle portion and the other end portion of the trigger electrode 7 are located inside the hollow portion of the lead shaft 4b. Here, as the vacuum trigger gap device, it is desirable to discharge a low voltage between the trigger electrode 7 and the main electrode 2b.
Installed very close to.

On the other hand, the magnetic field generating coil 8 is inserted inside the main electrode 2b at a position that is not destroyed by electrode melting that occurs when a current is applied between the main electrodes 2a and 2b above the trigger space 5. I have set up. For inserting the magnetic field generating coil 8, for example, a groove is formed from the outer circumference of the electrode 2b, and after inserting the magnetic field generating coil 8 from this groove, the groove is filled with the same material as the main electrode 2b. . The magnetic field generating coil 9 is supplied with power from the magnetic field generating source 9.

In the case of discharging the vacuum trigger gap device configured as described above, first, a current pulse is injected from the pulse power supply 10 between the trigger electrode 7 and the main electrode 2b near the trigger electrode 7. When this current pulse is injected, a minute discharge 5a is generated between the trigger electrode 7 and the main electrode 2b, and the plasma generated thereby is injected between the main electrodes.

(Problems to be Solved by the Invention) However, in the case of creeping discharge with the insulating member 6 interposed, the insulating performance of the insulating member 6 deteriorates due to many uses, and the trigger electrode 7 and the main electrode 2b become conductive. There is a fear. Further, when a trigger discharge is performed to bring the main electrodes 2a and 2b into a conductive state, the arc generated between the main electrodes 2a and 2b causes the minute impurities adsorbed on the surfaces and inside of the main electrodes 2a and 2b to be generated. It becomes a floating state, and finally the insulating member 6
And the deterioration of the insulating performance of the insulating member 6 is further promoted and the life of the vacuum trigger gap device is shortened.

On the other hand, in order to facilitate the discharge between the electrodes, the trigger electrode may be brought close to the main electrode to cause this direct discharge, but a considerably high voltage is required because the discharge space is a vacuum,
As a result, the trigger electrode is consumed more quickly, which is not preferable.

Therefore, an object of the present invention is to provide a vacuum trigger gap device that is easily discharged by a current trigger that can be operated at a low trigger voltage, always gives a good and stable trigger, and can be used many times over a long period of time. To do.

[Structure of the Invention] (Means for Solving Problems) The present invention is an application of a new phenomenon relating to surface field emission in vacuum, which was found by the present inventors to achieve the above object.

First, conventional dielectric breakdown between electrodes and creepage dielectric breakdown in a vacuum will be described below. That is,
It is well known that when a strong magnetic field is applied between opposed electrodes in vacuum, so-called field emission electrons are emitted, which determines the discharge phenomenon between the electrodes.

In addition, regarding creepage breakdown in vacuum, p shown in FIG.
Electrons generated by strong field emission at a triple point consisting of a point, so-called cathode-insulator-vacuum, fly along the electric field,
It collides with the surface of the insulator and emits secondary electrons from that surface.
The secondary electrons again fly along the electric field, are accelerated, re-collide with the surface of the insulator, and emit secondary electrons again. Normally, the secondary electron emission coefficient δ on the surface of the insulator is larger than 1, so the number of electrons increases due to this repetition. In addition, the release of adsorbed gas from the surface of the insulator and electron avalanche growth in this gas cause creeping insulation. It causes destruction.

By the way, the present inventors have found out a new phenomenon of electron emission from the surface, and will be described below. When a metal coating of about μm or less is formed on the surface of the insulator, the surface resistance is about several Ω. If a current level is large when a current is applied to the metal film, a minute discharge is generated everywhere on the film surface, and this triggers discharge between the trigger electrodes. The fact that this trigger discharge causes the discharge of the main electrode was found, and another proposal is made.

The inventors performed this by lowering the level of the trigger current flowing through the metal coating, but even if the trigger current is lowered and a minute discharge is not observed on the surface of the metal coating as shown in FIG. It has been found that (region I in the figure) can be triggered.

This is because the surface of the metal film is heated to a high temperature by the trigger current flowing therethrough and a large amount of electrons are emitted beyond the work function barrier.

Regarding this electrode temperature rise and field emission, for example, the well-known data of FIG. 5 (Little et al., J. Appl. Phys.
There is Vol 34 P2430 (1963)). That is, although a normal field emission phenomenon is shown up to point S in the figure, when the electrode temperature exceeds about 800 ° C., the current sharply increases. This is because the energy of the electrons inside the metal electrode rises and the number of electrons exceeding the work function rapidly increases.

With respect to the dielectric breakdown phenomenon between the electrodes in a vacuum, the above fact was well known, but it was not known that vacuum creepage dielectric breakdown also existed.

By applying this phenomenon, the current trigger technology, which has been considered to be considerably difficult in the related art, triggers a metal or semiconductor film formed on the surface of an insulator to trigger a discharge, as in the embodiments described below. It can be seen that this is achieved by using

The present invention comprises a vacuum container, a pair of main electrodes opposed to each other with a gap provided in the vacuum container, and a trigger electrode arranged in a hollow trigger space provided in at least one of the main electrodes. As an electron emission film for generating a trigger electron beam between the trigger electrode and the main electrode, a metal or semiconductor film is formed on the surface of a member formed of an insulating material.

(Operation) When the pulse source that is the trigger source operates, the trigger current flows from the pulse source through the lead wire to the trigger section of the vacuum trigger gap. Since the trigger portion is formed of a thin coating made of metal or semiconductor, it serves as a resistor in an electric circuit and generates heat. This resistance heating causes the electron current to increase when the film temperature reaches, for example, 800 ° C., and the trigger electrode has a negative electrode control with respect to the cathode (main electrode) (see FIG. 6). Form a beam and impact heat the cathode surface. As a result, the impact-heated portion of the cathode surface by the electron beam is locally heated to a high temperature, and the locally heated electrode evaporates and spreads as a dense metal gas between the trigger electrode and the cathode. Since a voltage of several tens of volts to several hundreds of volts is generated between the cathode and the trigger electrode, a trigger discharge is generated between the cathode and the trigger electrode.
Plasma generated by this trigger discharge is injected between the main electrodes, dielectric breakdown occurs between the main electrodes to form a main discharge, and the operation of the vacuum trigger gap is completed.

Embodiment An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, FIG. 2 and FIG. 3, the main electrodes 2a and 2b are arranged in the vacuum container 1 so as to face each other in the same manner as in the conventional vacuum trigger gap device described above, and the main electrode is formed in a hollow shape. An insulating member 6 closes the trigger space 5 in the substantially central portion of the electrode 2b. This insulating member 6 is made of, for example, alumina (Al
₂ O ₃ ), which is made of a ceramic material, and has a metal or semiconductor coating 6 a on the surface facing the trigger space 5.
Are formed.

Here, the coating film 6a is assumed to have the following conditions. That is, a constant relationship is required among the coating material, the film thickness, and the trigger current. As shown in FIG.
Assuming that a hollow disk having an inner system 2A and an outer diameter 2B has a trigger electrode inside and a cathode outside, and the resistance between the inner conductor X and the outer conductor Y is R, When the trigger current I _T flows through the coating 6a for τ time, that is, when the pulse width is τ, the coating temperature rise Δθ is the density of the coating 6a. If the specific heat is C The temperature rise limit Δθ _C where Δθ depends on the material, for example,
When the temperature exceeds 800 ° C, the field emission current sharply increases as shown in Fig. 5 and trigger discharge occurs, causing the main electrode to be destroyed. Therefore, from equations (1) and (2), After all, coating δ of coating 6a, specific resistance Between δ, trigger current I _T and trigger pulse width τ, However, K is a constant determined by the material and the electrode structure. Structures other than those described above are the same as those of the conventional vacuum trigger gap device described above, and therefore description thereof is omitted.

Next, a case of discharging the vacuum trigger gap device configured as described above will be described. First, the main electrode 2b
Then, a current pulse is injected from the pulse source 10 between the trigger electrode 7 which is attached to the trigger space 5 of the main electrode 2b through the insulating member 6 having the film 6a formed on the surface thereof. When the pulse is applied in this way, an electric current flows through the coating 6a formed on the surface of the insulating member 6 interposed between the main electrode 2b and the trigger electrode 7 to heat the coating 6a. When the temperature of the coating 6a rises and exceeds, for example, 800 ° C., a dominant electron current is generated by electron emission, which causes the local current 2c of the main current 2b to undergo collisional heating of the electron beam as shown in FIG. Evaporation causes a preliminary discharge 5a to be formed between the trigger electrode 7 and the main electrode 2b. The preliminary discharge 5a passes through the trigger space 5 to the space 2d between the main electrodes, and finally becomes a discharge between the main electrodes 2a and 2b.

It is ideal that there is no time delay from the start of the preliminary discharge 5a to the discharge between the main electrodes, but it usually takes several n Sec to several μSec. Then, after the main electrode is discharged, a current or voltage is applied from the magnetic field generation source 9 to the magnetic field generation coil 8 after several μsec. As a result, a magnetic field as shown by the dotted line in FIGS. 2 and 3 is generated.

However, when there is no such magnetic field generating coil 8 and a magnetic field cannot be generated, the impure gas particles adsorbed on the surface of the main electrodes due to the discharge between the main electrodes are suspended during the discharge. Part or most of it will invade into the trigger space 5, and will be adsorbed to the coating 6a formed on the surface of the insulating member 6, and the surface resistance value of this will be extremely lowered to lose the trigger function. .

On the other hand, when the magnetic field generating coil 8 is provided as in the above-mentioned embodiment, the magnetic field can be generated as described above at a position close to between the trigger space 5 and the main electrode, and the main current 2a, It is possible to prevent deterioration of the coating film 6a due to impure gas particles generated by discharge between the 2b, and it is possible to provide a vacuum trigger gap device having a longer life.

It should be noted that the present invention is not limited to the above-described embodiments, and various modifications can be implemented. That is, in the above-described embodiment, the insulating member 6 is provided between the main electrode 2b and the trigger electrode 7.
Electrons are emitted from the metal or semiconductor coating 6a formed on the surface of the electrode to cause a pre-discharge to move to the main interstitial space and finally to induce a discharge between the main electrodes 2a and 2b. Depending on the flowing current, the main electrodes 2a, 2
It is also conceivable that the electrode is melted in any one of b and the melting mark formed by this melting falls into the trigger space 5 and reaches the coating film 6a to short-circuit the trigger electrode 7 and the main electrode 2b. However, as shown in FIG. 8, the insulating member 11 has a cylindrical upper portion, a metal or semiconductor coating 11a is formed on the inner surface of the cylindrical portion, and the trigger electrode 12 also has a cylindrical upper portion. Since the portion to be discharged is laterally displaced, the problem caused by the dropping of the melting mark is eliminated. Here, the film 11a is under the same conditions as the film 6b.

Further, it may be configured as shown in FIG. That is,
In FIGS. 9 and 10, in the vacuum container 1, the trigger space 5 is closed by an insulating member 6 in substantially the central portion of the main electrode 2b as in the conventional vacuum trigger gap device described above. The insulating member 6 is made of, for example, a ceramic material such as alumina (Al ₂ O ₃ ), and a metal or semiconductor coating 6b is formed on the surface facing the trigger space 5.

Here, the coating film 6b is assumed to have the following conditions. That is, a constant relationship is required among the coating material, the coating thickness, and the trigger current. When the trigger portion has a thickness δ of the coating 6b and an unevenness of the insulating member 6 is ε as shown in FIG. 10, If δ <ε (4), the coating 6b is cut by the insulating member 6 in places or is connected by a very thin layer, so that the resistance is high.

Therefore, when the trigger current I flows into this, if the current level is to some extent, a large number of minute sparks are generated on the coating surface.

Further, in practice, when the film thickness becomes about 1 μm, (4)
Even if the equation is not satisfied, a desired minute spark is generated due to the influence of the nonuniformity of the film thickness, so that δ <1 μm (5) is another condition.

This means that a large number of electron emission sources are present on the film surface, and the above-mentioned action is caused by the electrons emitted from the electron emission sources. FIG. 11 shows the trigger current and the probability of main current occurrence together with the occurrence of minute sparks in the trigger section.

The configuration other than that described above is the same as that of the conventional vacuum trigger gap device described above, and therefore description thereof is omitted.

Next, a case of discharging the vacuum trigger gap device configured as described above will be described. Also in the case of this embodiment, first, a pulse source is provided between the main electrode 2b and the trigger electrode 7 which is attached to the trigger space 5 of the main electrode 2b via the insulating member 6 having the coating 6b formed on the surface thereof. Inject voltage pulse from 10. When a pulse is applied in this way, the main electrode
An electric current flows through the coating 6b formed on the surface of the insulating member 6 interposed between the 2b and the trigger electrode 7, and countless minute sparks are generated in the coating 6b. As a result, a dominant electron current is generated, and as shown in FIG. 6, the pole portion 2c of the main electrode 2bb is subjected to collision heating of the electron beam and evaporated, and the preliminary discharge 5a is generated between the trigger electrode 7 and the main electrode 2b. It is formed. This preliminary discharge 5a
Passes through the trigger space 5 and moves to the inter-main electrode space 2d, and finally discharge occurs between the main electrodes 2a and 2b. Also in the case of this embodiment, it is ideal that there is no time delay from the start of the preliminary discharge 5a to the discharge between the main electrodes, but it is several n Se.
It usually takes c to several μSec. Then, after the main electrode is discharged, a current or voltage is applied from the magnetic field generation source 9 to the magnetic field generation coil 8 several μsec later. by this,
A magnetic field as shown by the dotted line in FIGS. 2 and 3 is generated. However, when there is no such magnetic field generating coil 8 and a magnetic field can be generated, the impure gas particles adsorbed on the surface of the main electrodes due to the discharge between the main electrodes are suspended during the discharge. A part or most of it penetrates into the trigger space 5, is adsorbed to the coating 6a formed on the surface of the insulating member 6, and extremely lowers the surface resistance value of the coating 6a to lose the trigger function.

On the other hand, when the magnetic field generating coil 8 is provided as in the above-described embodiment, the magnetic field as described above can be generated at a position close to the trigger space 5 and the main electrode, and the main electrode 2a, It is possible to prevent deterioration of the coating film 6a due to impure gas particles generated by discharge between 2b, and it is possible to provide a vacuum gap device having a further long life.

Further, in the above-described embodiment, the pre-discharge is performed between the main electrode 2b and the trigger electrode 7 by the electron emission from the metal or the semiconductor coating 6b formed on the surface of the insulating member 6, and the main gap space is transferred. Eventually, a discharge between the main electrodes 2a, 2b is induced, but the current flowing due to this discharge between the main electrodes causes melting of the electrode in either of the main electrodes 2a, 2b, and a melting mark formed by this melting triggers. It is also conceivable that the trigger electrode 7 and the main electrode 2b are short-circuited by dropping into the space 5 and reaching the coating film 6b. However, as shown in FIG. 12, the upper portion of the insulating member 11 is formed into a cylindrical shape, and the metal or semiconductor coating 11b is formed on the inner surface of the cylindrical portion, and the trigger electrode 1
Also in the case of 2 as well, by making the upper part a cylindrical shape, the part for performing the preliminary discharge is laterally displaced, so that there is no problem due to the drop of the melting mark. Here, the coating 11b is the coating 6
Under the same conditions as b.

EFFECTS OF THE INVENTION The present invention forms a metal or semiconductor coating on the surface of the insulating member of the trigger portion as described above, and causes a trigger spark flowing in the coating on the surface of the insulating member to cause a minute spark or to change the coating temperature. As a result, an increase in electron current and beam formation due to this rise, and a trigger discharge between the trigger electrode and one of the main electrodes due to local heating of the electrodes cause discharge between the main electrodes, which enables good current triggering. ,
Moreover, the coating is not damaged by the trigger current. Further, since a magnetic field generating coil is provided in a portion of the trigger space close to the space between the main electrodes to generate a magnetic field,
It is possible to prevent the impure gas particles generated by the main gap discharge from entering the trigger space, prevent the deterioration of the insulating member, and provide a long-life vacuum trigger gap device.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention, and FIG.
FIG. 3 is an enlarged sectional view showing the trigger portion of the figure, FIG. 3 is a plan view of FIG. 2, FIG. 4 is an explanatory view showing the operation of one embodiment of the present invention, and FIG. 5 is a vacuum related to the present invention. 6 is an explanatory view showing the temperature dependence of the electron current under a strong electric field, FIG. 6 is an explanatory view showing the operation of the trigger unit related to the present invention, and FIG. 7 is a graph showing the trigger current and the trigger probability related to the present invention. FIG. 8 is an explanatory view showing a relationship, FIG. 8 is a sectional view showing an essential part of another embodiment of the present invention,
FIG. 9 is a sectional view of still another embodiment of the present invention,
FIG. 10 is an enlarged cross-sectional view of an essential part of the embodiment shown in FIG. 9, FIG. 11 is an explanatory view showing a relationship between trigger current and trigger probability related to the present invention, and FIG. 12 is another different embodiment of the present invention. FIG. 13 is a sectional view showing a main part of the embodiment, and FIG. 13 is a sectional view showing a conventional vacuum trigger gap device. 1 ... Vacuum container, 2a, 2b ... Main electrode 5 ... Trigger space, 6 ... Insulating member 6a ... Coating, 7 ... Trigger electrode 8 ... Magnetic field generating coil

Claims (4)

[Claims] 1. A vacuum container, a pair of main electrodes opposed to each other with a gap provided in the vacuum container, and a trigger electrode arranged in a hollow trigger space provided in at least one of the main electrodes. As an electron emission film for generating a trigger electron beam between the trigger electrode and the main electrode, a metal or semiconductor film is formed on the surface of a member formed of an insulating material. Vacuum trigger gap device. 2. The thickness of the coating is δ, and the specific resistance is And the trigger current I _T and the trigger pulse current width τ, However, the relational expression of C: a constant determined by the material and the electrode structure is satisfied.
The vacuum trigger gap device according to the paragraph. 3. The invention according to claim 1, wherein the relation of δ <ε or δ <1 μm is established, where δ is the thickness of the coating and ε is the irregularity of the surface of the member formed of an insulating material. The vacuum trigger gap device described. 4. The vacuum trigger gap device according to any one of claims 1 to 3, wherein a magnetic field generating coil is arranged on the main electrode on the opening side of the trigger space.