JP2003123621A - Indirectly heated cathode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an indirectly heated cathode that has discharge characteristics suited for large current operation and is improved in initial starting. SOLUTION: The coiled-coil 7 is fixed on the outside surface of the base metal 3 after wound several times. Aluminum foil 11 for forming aluminum layer is inserted between the base metal 3 and the coiled-coil 7. This aluminum foil 11 is in electrical conduction with the base metal 3 and the coiled-coil 7. The metallic oxide 9 is obtained by coating as an electrode material in the form of metallic carbonate (for example, barium carbonate) and by carrying out vacuum hot decomposition (thermal activation) of the coated metallic carbonate. The metallic carbonate as an electrode material is applied from the outside of the coiled-coil 7 so as to contact the base metal 3 and the aluminum foil 11, while the coiled-coil 7 is fixed to the base metal 3 by being wound and the aluminum foil 11 is inserted between the base metal 3 and the coiled-coil 7.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an indirectly heated cathode.

[0002]

2. Description of the Related Art As an indirectly heated cathode of this type, for example, one disclosed in Japanese Patent Publication No. 62-56628 is known. In the indirectly heated cathode disclosed in Japanese Patent Publication No. 62-56628, a double coil is wound a plurality of turns around an outer wall of a heat-conductive cylinder and tightly fixed, and a paste-like cathode material is double coiled. The coating is applied inside the primary spiral and between the secondary spirals to form a uniform cathode surface on the surface of the cylinder, and a heater is provided inside the cylinder.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide an indirectly heated cathode having discharge characteristics suitable for large current operation and improved initial startability.

[0004]

[Means for Solving the Problems] As a result of research and investigation, the present inventors newly found the following facts. The metal oxide as the electron-emissive substance is usually applied in the form of a metal carbonate (for example, barium carbonate, strontium carbonate, calcium carbonate, etc.) as a cathode material, and the applied metal carbonate is thermally activated (vacuum). It is obtained by thermal decomposition). When a metal carbonate (for example, barium carbonate) is applied to a holding member (for example, a multiple coil such as a double coil) that holds this metal carbonate, the metal (for example, tungsten) that is the main component of the holding member is used. ) And the metal carbonate are bound by a neutral intermolecular attractive force which is mainly Van der Waals force (W + 2BaCO ₃ ). Then, when the metal carbonate that is bound to the main component metal of the holding member is thermally activated, it is thermally decomposed as described below. W + BaOBa + 2CO ₂ ↑ + 1 / 2O ₂ ↑

In the direct heating type cathode, the holding member itself serves as a heating element (heating heater), and the contact surface temperature with BaO in the holding member reaches a high temperature of 1000 ° C. or higher, so that a thermochemical reaction occurs and a BaWOBa composition Oxygen interstitial intermetallic compounds are produced. As a result, during discharge, a discharge path (power supply path) is formed from the main component metal of the holding member, which is an electron supply source, to the Ba surface, which is the discharge surface, and thermionic emission can be started.

On the other hand, in the indirectly heated cathode, since the heat from the heating heater is indirectly transmitted to the holding member, the contact surface temperature of the holding member with BaO is the temperature at which the above-mentioned thermochemical reaction occurs. It is difficult to reach the area, W + BaOBa
The bonded state due to the neutral intermolecular attractive force continues, and the discharge path as described above is not formed. For this reason, the supply of electrons from the main component metal of the holding member to the surface of Ba becomes insufficient and the startability deteriorates.

However, even in the indirectly heated cathode, if the forced start is performed by the auxiliary lighting by short-distance discharge with the cathode or the Tesla lighting for pre-ionization by the Tesla coil for forced discharge, etc. Due to the concentration of the electric charges, the spot heating of which part becomes high temperature occurs, and an oxygen-intercalating intermetallic compound having a BaWOBa composition is generated by a thermochemical reaction. By generating the oxygen-intercalating intermetallic compound having the BaWOBa composition, a discharge path is formed from the main component metal of the holding member to the Ba surface which is the discharge surface, and the startability is improved. Then, after the start of discharge, oxygen-intercalating intermetallic compounds of BaWOBa composition are
It is formed according to the amount of discharge heat and the amount of forced heating.

As described above, the inventors of the present invention have found that the generation of the intermetallic compound (electroconductive oxygen intrusion type intermediate product) by the main component metal of the holding member and the metal contained in the metal oxide is initially started. It was newly found that it is a factor affecting sex. Further, the inventors of the present invention have once found that an oxygen interstitial intermetallic compound having a BaWOBa composition, that is, an oxygen interstitial intermetallic compound containing an intermetallic compound (Al-O-metal M) intervening oxygen (of a metal crystal of Al-metal M). A compound having oxygen interstitial solid solution at the interstitial position (hereinafter simply referred to as “oxygen interstitial intermetallic compound”) is generated, and the discharge path from the main component metal of the holding member to the Ba surface which is the discharge surface. It was also found that, after the formation of Ba, the film operates as a hot cathode until Ba disappears. In addition, when thermally activating a metal carbonate (for example, barium carbonate), excess oxygen release (overheating)
It is not a good idea because it promotes the overproduction of free barium and accelerates the consumption of Ba.

Further, the inventors of the present invention have made a research study by using the discharge surface potential as an experimental factor, focusing on the cathode drop voltage (box potential) in comparison with the conventional indirectly heated electrode (indirectly heated cathode). As a result, the following facts were newly found.

The equipotential surface, the equipotential interface, the box potential and the discharge form that will be used hereinafter are defined as follows.
The equipotential surface is defined as a state in which a discharge surface that is in a potential equipotential state is formed. The equipotential interface is defined as a structure in which a metal oxide as an electron-emissive substance is contact-coated on the equipotential surface and is in contact with a gas. The box potential is defined as a potential generated between a cathode and a terminal which is electrically insulated from the cathode near the cathode during discharge. It is a value that is similar to the cathode drop voltage used as a general term for discharge physical properties. The ionic current is defined as a current generated by an ionized gas generated by the ionization of gas molecules when electrons collide with gas molecules in a gas discharge tube. Thermionic emission is the electron emission in which when the temperature of a metal is raised, the thermal kinetic energy increases, and the electron jumps out into the space beyond the electron energy barrier (work function) of the metal. Electron emission from a metal oxide as a highly unstable electron-emitting substance. Secondary electron emission is electron emission in which electrons are pushed out from the cathode into the space when the ionized gas collides with the cathode.

Comparing the change in the box potential during DC operation before and after equalization, as shown in FIG.
A significant difference in box potential was confirmed. The inventor created an equipotential interface model and considered the research results of this phenomenon. The discharge form in gas discharge can be roughly expressed in three forms of ion current, thermionic emission, and secondary electron emission, and theoretically expressed by the following relational expression.
Incidentally, the discharge form of the vacuum discharge can be almost expressed only by thermionic emission, and is different from the discharge form of the gas discharge. Id = Ii + Ie = Ii (1 + γ) + Ith …… (1) Ie = Ith + γIi …… (2) Vc = Vo + {(1-Ith / Id)} / {α (γ + Ith / Id)} …… ( 3) Formula related to the Schottky effect Ie = Ithexp {(e / kT) sqr (eE / 4πεo) …… (4) Ith = SAT ^ 2 * exp (-eφ / kT) …… (5) Ise = Ith [ exp [(e / kT) sqr (eE / 4πεo)]-1] (6) where Ii: ion current Ie: emission current Ith: thermoelectron current Ise: secondary electron current Id: discharge current Vc: Cathode drop voltage γ: Coefficient (gain) related to secondary electron emission α, Vo: Parameter S: Electrode surface area A: Constant determined by material T: Cathode temperature e: Electronic load φ: Work function k: Boltzmann constant εo: Dielectric constant E in vacuum: Electric field strength at cathode drop

Next, the ion current (I
Consider the emission current (equivalent to i) and the emission current (equivalent to i). The static mass of the electron is 9.109 × 10-
Although it is 31 kg, even the lightest hydrogen among the elements is 1.675 × 10 −27 kg, which is significantly heavier than electrons. Further, while the ionized gas is attracted to the cathode and collides with it, in the case of an electron, the ionized gas is separated from the cathode, so the impact force of the ionized gas exceeds the impact force of the electron, and the ionized gas is damaged by the cathode. Is larger than an electron. From the above, the harmfulness of the ionic current to the cathode can be seen. On the other hand, from the viewpoint of the light emission and discharge phenomenon of the gas discharge tube, the ionized gas contributes as a luminescent substance, and has the effect of drawing more discharge current into the space depending on the ion current than in vacuum. . In the gas discharge tube, it is important to keep the influence on the cathode to a minimum while taking into consideration the merits and demerits of the ionic current, in order to achieve life characteristics and stability.

The box potential approximates the cathode drop voltage,
It shows the excited and ionized states of gas relatively, and serves as a guide for the amount of ionized gas generated. The lower the box potential, the smaller the amount of ionized gas produced.

As described above, there are three types of discharge in the gas discharge: ion current, thermionic emission, and secondary electron emission. Thermionic emission occurs by heating a metal oxide such as barium as an electron-emissive substance. Thermionic emission has a role of causing gas ionization at the start of discharge and starting discharge. After starting the discharge, in the case of gas discharge,
The ionized gas collides with the thermoelectrons emitted from the metal oxide as the electron-emissive substance in a form attracted to the thermoelectrons. At that time, secondary electron emission mainly occurs on the interface between the electric conductor and the metal oxide as the electron-emissive substance due to the collision with the ionized gas. In the case of gas discharge, the discharge current density per unit area is tens to hundreds of times higher than in vacuum discharge, and most of the total discharge current is formed by secondary electron emission.

Regarding the supply of secondary electrons, the electric resistivity of metal oxide as an electron-emissive substance is significantly higher than that of an electric conductor, and there is a limit to the supply of metal oxide alone as an electron-emissive substance. Most of the secondary electrons are supplied through the electric conductor and are emitted from the interface with the metal oxide as the electron-emitter. The supply of electrons, which is the basis of secondary electrons, to the electric conductor may be directly supplied from an external circuit or may be performed via a contact surface with a metal oxide as an electron-emissive substance. Thermionic emission also occurs on the metal oxide as an electron-emissive substance that does not form an interface with an electric conductor, but as described above, regarding the supply of secondary electrons, the metal oxide simple substance as an electron-emissive substance alone is used. Is limited, the secondary electron emission amount is small, and the absolute amount of the discharge current from the metal oxide simple substance as an electron-emissive substance in the gas discharge is extremely small. In summary, in the cathode in the gas discharge, the place mainly responsible for electron emission is the interface between the electric conductor and the metal oxide as the electron-emissive substance.

Next, the equipotential interface model will be described with reference to FIGS. FIG. 10 is a diagram (model diagram) in which the horizontal axis represents the heater applied voltage (Vf), that is, the axis of increase or decrease in the cathode temperature due to the amount of forced heating of the cathode, and the vertical axis represents the cathode drop voltage (box potential) (Vc). Is. Figure 11
Is a diagram (model diagram) in which the horizontal axis represents the heater applied voltage (Vf) and the vertical axis represents the discharge current (Id). However, the discharge current (Id) in FIG.
The composition ratio (region distribution) of the thermionic current, secondary electron current, and ion current is shown. The vertical axis of FIG. 10 represents height.

The constituent factor of the cathode temperature is not only the heater applied voltage (Vf), that is, the forced heating amount to the cathode, but also the so-called self-heating amount, which is commonly generated when the ionized gas collides with the cathode,
It depends on this total heat. In the region on the left side of FIG. 10 where the cathode temperature is low, that is, the amount of forced heating is small, or the area of heat dissipation is large and the amount of heat loss from the cathode is large, the amount of thermoelectrons generated is small, and the ion current is dominant in a form that compensates Then, the cathode drop voltage becomes equal to or higher than the ionization voltage, and the generation of ionized gas is accelerated. If the potential distribution on the cathode surface is non-uniform in this region, local discharge (uneven distribution of discharge positions) is likely to occur due to concentration of ion current and secondary electron current, and damage to the cathode surface due to ionized gas impact. Is large, which tends to cause scraping (sputtering) of the cathode material (metal oxide as an electron-emissive material) and stabilization (mineralization) by oxidation with a reducing metal.

On the other hand, in the region on the left side of FIG. 10 where the cathode temperature is high, that is, the amount of forced heating is large, or the heat radiation area is small and the amount of heat stored in the cathode is large, the amount of thermoelectrons generated becomes excessive. In a complementary manner, the ionic current decreases and the cathode drop voltage becomes less than the ionization voltage. However, the temperature of the cathode rises, the vapor pressure of the cathode constituent is increased, and the metal oxide as an electron-emissive substance is likely to disappear due to evaporation. Excess or shortage of the amount of heat applied to the cathode is not preferable for the reason described above. In terms of the box potential (cathode drop voltage) as an indication of the operating region, an operation near the ionization voltage is suitable.

By the way, among the components of this model,
The discharge area is an important factor. This can be regarded as synonymous with the electrode surface area (S) in the relational expression. As described above, in the gas discharge, the electron emission from the interface between the electric conductor and the metal oxide as the electron-emissive substance mainly constitutes the discharge. In addition to this, the discharge area changes depending not only on the temperature uniformity but also on the potential (uniform potential). That is, the discharge area is proportional to the area of the equipotential surface or the length of the equipotential surface portion, and the equipotential surface is wide,
Alternatively, the longer the electrode surface area (S: discharge area), the higher the ratio of thermionic current (Ith) from the equation (5), and the smaller the ion current amount from the equation (1). , The secondary electron current is dispersed on the equipotential surface, and the thin line portion (before equipotentialization) of the model in FIG. 11 shifts the region distribution to the thick line side (after equipotentialization) of the model, and the above (3 ), The box potential (cathode drop voltage) in FIG. 10 decreases. The reason why the equipotential interface structure between the equipotential surface and the metal oxide or gas is adopted, and the amount of thermoelectrons is increased, the amount of ion current in the discharge current is decreased and the box potential of FIG. 10 is decreased. it can.

From the above, in the gas discharge, the ionized gas amount per unit discharge area can be alleviated by reducing the amount of ion current as compared with the conventional non-potentialized cathode. As a result, It can be seen that the load on the cathode is reduced, the thermionic emission capability is less reduced, and the life characteristics are improved. As a result, the movement of the discharge position is less and the stability can be improved.

Next, the effectiveness of the equipotential surface for a gas discharge tube will be considered. As described above, the discharge form in the vacuum discharge can be almost expressed only by thermionic emission, and is different from the discharge form in the gas discharge. It can be said that the discharge area in the vacuum discharge is determined by the surface area formed by the metal oxide as the electron-emissive substance on the thermionic emission surface. Therefore, in addition to thermionic emission, the discharge area component in the gas discharge tube having a discharge form consisting of ion current and secondary electron emission and the discharge area component in vacuum discharge are different, and mainly in the cathode in gas discharge, Since the place responsible for electron emission is the interface between the electric conductor and the metal oxide as an electron-emissive substance, the equipotential surface formed from the electric conductor and having a substantially equal potential is effective for gas discharge as the discharge surface. I found that.

Further, the material used for the means for forming the equipotential surface has a thin wire structure with a plate shape including a mesh shape, a linear shape, a ribbon shape, and a foil shape, so that a surface area serving as a heat dissipation surface and a heat conducting portion are formed. The amount of heat loss is reduced as a result. The contact area between the metal oxide and the equipotential surface is increased, and as a result, the discharge area is increased. From the above, it has been found that the effect of the equipotential surface can be further enhanced by making the material used for the means of forming the equipotential surface into a mesh shape, a linear shape, or a plate and thin wire structure.

When the potential distribution on the cathode surface is non-uniform as in the prior art, the calorific value is also non-uniform accordingly, resulting in a non-uniform production density of thermions, resulting in a non-uniform ion current and secondary electron current. Local discharge (uneven distribution of discharge positions) occurs due to concentration. Then, the local discharge causes scraping (sputtering) of the cathode material (metal oxide as an electron-emissive material), stabilization by oxidation with the reducing metal (mineralization), that is, reduction of thermionic emission capability. , The discharge position moves to the next position with good thermionic emission characteristics. In this way, the surface of the cathode is deteriorated while repeating the local degradation of thermionic emission. Further, the discharge itself becomes unstable due to the movement of the discharge position described above.

Based on the results of these investigations, the indirectly heated cathode according to the present invention has a heating heater having an electrically insulating layer formed on the surface thereof, and electron emission for emitting electrons in response to heat from the heating heater. The electron emitting portion is provided with a metal oxide as an electron-emissive substance, a holding member for holding the metal oxide, and an outermost surface side portion of the electron emitting portion, and the electron emitting portion has a predetermined length. And an electric conductor made of a high melting point metal,
It is characterized in that it contains aluminum that is electrically connected to an electric conductor, and that the refractory metal and the metal oxide are bridged by the aluminum to form an oxygen intercalation type intermetallic compound.

Aluminum (Al) has an ionization potential (5.984 eV: 577 kJ / mol) and a melting point (660 ° C.) lower than that of a refractory metal, and the ionization potential is a metal (hereinafter simply referred to as “metal "M"). Therefore, in the present invention, aluminum is easily replaced with the metal M in the metal M-oxygen (O) compound formed by thermally decomposing the above compound, and the bond of the metal M-Al-O having heat resistance is formed. A compound having is formed. Further, since the refractory metal and Al are metallic bonds and the Al and the metal M are in a bond state in which electrons are easily supplied, the refractory metal and Al and the metal M are electrically conductive. There is a nature.

From the above, according to the present invention, Al serves as a bridge between the refractory metal (electric conductor) and the metal M, and an oxygen intercalating intermetallic compound is formed. Discharge electrons supplied from a power source connected to the intermetallic compound are transferred from the refractory metal to the metal M via Al.
Since a circuit that continuously and in large quantities is supplied to (a metal that becomes an electron-emissive substance), it has a discharge characteristic suitable for large-current operation and has improved initial startability. A cathode can be obtained.

Further, according to the present invention, since the equipotential surface is effectively formed in the electron emitting portion by the electric conductor,
Since thermionic emission occurs in a wide area of the formed equipotential surface, the discharge area increases, the electron emission amount per unit area (electron emission density) increases, and the load at the discharge position is reduced. . As a result, the occurrence of local discharge can be suppressed and the life of the indirectly heated electrode can be extended. Further, since the movement of the discharge position is also suppressed, stable discharge can be obtained for a long time. In addition, in connection with the increase in the discharge area, the current density is slightly increased to slightly increase the load, that is, even if the discharge current is increased, the damage can be reduced compared to the conventional one, and it is almost the same as the conventional one. With the shape, it is possible to provide an indirectly heated electrode with a large discharge current, and it is possible to realize pulse operation and large current operation.

Further, the holding member is formed by winding a refractory metal in a coil shape, and the electric conductor is in contact with the metal oxide and a plurality of the holding members are arranged along the longitudinal direction of the holding member. Is preferably provided in contact with the coil portion of the. When configured in this way, the electric conductors make the potentials on the discharge surface consisting of multiple discharge points or discharge lines approximately the same, and metal oxide spattering, which is a factor of deterioration, and stabilization by oxidation with reducing metal (mineralization) That is, it is possible to suppress the decrease in the thermoelectron emission capability and also the movement of the discharge position. As a result, with a simple configuration in which the electric conductor is provided in contact with the metal oxide,
The life of the indirectly heated electrode can be extended and stable discharge can be obtained.

The electric conductor is preferably formed in a mesh shape, a linear shape or a plate shape. With this structure, it is possible to realize an electric conductor having a structure capable of suppressing the decrease in thermionic emission ability and the movement of the discharge position at low cost and more easily. Further, since the electric conductor is a rigid body, it is easy to process and can be provided in close contact with the metal oxide. The term "plate-like" used in this specification includes ribbon-like, foil-like, and the like.

Further, it is preferable that the aluminum is formed into a layer by covering at least a part of the surface of the electric conductor. With this configuration, aluminum is
Since at least a part of the surface of the electric conductor is coated in a layered form, the exposed surface area of Al becomes large, and a large amount of oxygen-invasion type intermetallic compounds are formed between the refractory metal (electric conductor) and the metal M. You can Further, the amount of aluminum contributing to the formation of the above-mentioned intermetallic compound can be controlled easily and appropriately.

The indirectly heated cathode according to the present invention comprises a high melting point metal wound in a coil shape, a heating heater disposed inside the high melting point metal and having an electric insulating layer formed on the surface thereof. A metal oxide as an electron-emissive substance held by a refractory metal, an electric conductor provided inside the refractory metal in contact with the refractory metal, and having a predetermined length; And aluminum that conducts to
It is characterized in that the refractory metal and the metal oxide are bridged by aluminum to form an oxygen intercalation type intermetallic compound.

As described above, according to the present invention, Al serves as a bridge between the refractory metal and the metal M, and an oxygen intercalation type intermetallic compound is formed. The intermetallic compound has a circuit in which a large number of discharge electrons supplied from a connected power source are continuously supplied from the refractory metal to the metal M (metal serving as an electron-emissive substance) via Al. Since it is formed, it is possible to obtain a sintered cathode having discharge characteristics suitable for large current operation and improved initial startability.

According to the present invention, the equipotential surface is effectively formed by the electric conductor on the back surface (the surface opposite to the discharge surface) of the refractory metal wound in a coil shape. Thermionic emission occurs in a wide area of the formed equipotential surface, the discharge area increases, the electron emission amount per unit area (electron emission density) increases, and the load at the discharge position is reduced. Thereby, the occurrence of local discharge can be suppressed, and the life of the electrode can be extended. Further, since the movement of the discharge position is also suppressed, stable discharge can be obtained for a long time. In addition, in connection with the increase in the discharge area, the current density is slightly increased to slightly increase the load, that is, even if the discharge current is increased, the damage can be reduced compared to the conventional one, and it is almost the same as the conventional one. In shape, it can provide indirectly heated electrodes with high discharge current, pulse operation,
A large current operation can be realized.

It is preferable that the electric conductor is provided in contact with the metal oxide and also with the plurality of coil portions of the refractory metal. When configured in this way, the electrical conductors make the potentials of the discharge surfaces consisting of multiple discharge points or discharge lines almost equal, and the deterioration of metal oxides due to spattering and oxidation with reducing metal (mineralization) ) That is, it is possible to suppress the decrease in the thermoelectron emission capability and also the movement of the discharge position. As a result, with a simple structure in which the electric conductor is provided in contact with the metal oxide, the life of the electrode can be extended and stable discharge can be obtained.

Further, it is preferable that the metal oxide is in contact with the heater for heating via the electrically insulating layer. With this configuration, the heat of the heating heater is directly transferred to the metal oxide, and the heat of the heating heater can be reliably and efficiently transferred to the metal oxide during preheating. Further, it is possible to suppress the loss of the amount of heat required for the operation of the hot cathode, as compared with the prior art having a cylinder. For this reason,
It becomes possible to operate the electrode without increasing the amount of heat supplied to the electrode from the outside and the forced overheating.

The refractory metal is preferably in contact with the heating heater via the electric insulating layer. With this structure, the heat of the heating heater is directly transferred to the high melting point metal, and the heat of the heating heater can be transferred to the high melting point metal reliably and efficiently at the time of preheating. Further, it is possible to suppress the loss of the amount of heat required for the operation of the hot cathode, as compared with the prior art having a cylinder. For this reason,
It becomes possible to operate the electrode without increasing the amount of heat supplied to the electrode from the outside and the forced overheating.

Further, the electric conductor is preferably a refractory metal formed in a mesh shape, a linear shape or a plate shape. With this structure, it is possible to realize an electric conductor having a structure capable of suppressing the decrease in thermionic emission ability and the movement of the discharge position at low cost and more easily. Further, since the electric conductor is a rigid body, it is easy to process and can be provided in close contact with the metal oxide.

Further, it is preferable that the aluminum is formed into a layer by covering at least a part of the surface of the refractory metal. In this case, since aluminum covers at least a part of the surface of the refractory metal in a layered form, the exposed surface area of Al becomes large, and the oxygen-invasion type intermetallic compound reacts with the refractory metal and the metal M. More can be formed during Further, the amount of aluminum contributing to the formation of the above-mentioned intermetallic compound can be controlled easily and appropriately.

Aluminum is preferably formed into a layer by vapor deposition.

The refractory metal is composed of a single metal of tungsten, tantalum, molybdenum, rhenium, niobium, osmium, iridium, iron, nickel, cobalt, titanium, zirconium, manganese, chromium, vanadium, rhodium or an alloy thereof. It is preferable. As a result, the work function is lowered, and good thermionic emission becomes possible. In addition, good heat resistance and heat dissipation will be exhibited.

The refractory metal is preferably made of a simple metal such as tungsten, tantalum or molybdenum or an alloy thereof. As a result, the practicability is excellent in terms of cost and handling. Further, the melting point of these refractory metals is 2500 ° C. or higher,
Sintering can be performed at a high temperature of 0 ° C. or higher, and a large amount of intermetallic compounds can be formed reliably.

The metal oxide preferably contains an oxide of any one of barium, strontium and calcium, a mixture of these oxides or an oxide of a rare earth metal. With this configuration,
The work function can be effectively reduced, and thermionic emission becomes easy.

The indirectly heated cathode according to the present invention has a heater for heating having an electrically insulating layer formed on the surface thereof, and an electron emitter for receiving electrons from the heater for heating to emit electrons. The radiating portion is a metal oxide as an electron-emissive substance, a refractory metal, and a layer formed by coating at least a part of the surface of the refractory metal in a layered form, and aluminum that is electrically conductive with the refractory metal. , And a high melting point metal and a metal oxide are bridged by aluminum to form an oxygen intercalation type intermetallic compound.

[0044]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the indirectly heated cathode according to the present invention will be described below in detail with reference to the drawings. In the description, the same elements or elements having the same function will be denoted by the same reference symbols, without redundant description. In this embodiment, the present invention is applied to a cathode for a gas discharge tube.

(First Embodiment) First, a cathode for a gas discharge tube according to a first embodiment of the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 is a schematic sectional view showing a gas discharge tube cathode according to the first embodiment, and FIG. 2 is a schematic front view showing the gas discharge tube cathode.

The cathode C1 for a gas discharge tube is an indirectly heated cathode, and is a glass bulb in which deuterium gas, a rare gas such as argon, or a rare gas such as argon and mercury are hermetically sealed (see FIG. (Not shown) is hermetically sealed so as to face both inner ends thereof. As shown in FIGS. 1 and 2, the gas discharge tube cathode C1 includes a heating heater 1, a base metal 3, and an electron emitting portion 5.

The heater 1 for heating has a diameter of 0.03 to 0.1.
It consists of a filament coil in which a tungsten element wire of mm, for example, 0.07 mm is double wound. The surface of the tungsten filament coil is coated with an electric insulating material (for example, alumina, zirconia, magnesia, silica, etc.) by an electrodeposition method or the like to form an electric insulating layer 2.

The base metal 3 is formed in a cylindrical shape, and is made of a medium-high melting point metal, such as molybdenum, which has conductivity and has a melting point higher than the cathode temperature during operation. The heater 1 for heating is inserted and arranged inside the base metal 3. The base metal 3 is connected to the lead rod 4 and grounded. Further, one end of the heater 1 for heating is also connected to the lead rod 4 and grounded. As the base metal 3, a cylindrical tubular member is generally used, but an arcuate (opened) tubular member having a cutout portion may be used.

The electron emitting portion 5 receives heat from the heating heater 1 and emits electrons, and includes a double coil 7 (holding member) and a metal oxide 9 as an electron-emissive substance. I'm out. The double coil 7 is a multiple coil composed of a coil wound in a coil shape. Double coil 7
Is a rigid body (metal conductor) having conductivity, and is II in the periodic table.
High melting point of tungsten, tantalum, molybdenum, rhenium, niobium, osmium, iridium, iron, nickel, cobalt, titanium, zirconium, manganese, chromium, vanadium, rhodium, etc. It is composed of a single metal (melting point of 1000 ° C. or higher) or an alloy thereof. When the double coil 7 is made of the above-mentioned material, the work function of the double coil 7 is lowered, and good thermoelectron emission from the electron emitting portion 5 is possible. Further, it exhibits good heat resistance and heat dissipation.

The double coil 7 is preferably made of a single metal of tungsten, tantalum, molybdenum, or an alloy thereof. Double coil 7 is tungsten,
By using a single metal of tantalum or molybdenum or an alloy thereof, the practicability is excellent in terms of cost, handling and the like. In this embodiment, as the double coil 7, a tungsten (W) wire having a diameter of 0.091 mm is formed in a primary coil having a diameter of 0.25 mm and a pitch of 0.146 mm, and the primary coil has a diameter of 1.7 m.
A double coil with m and a pitch of 0.6 mm is used. Instead of using the double coil 7, a triple coil, a single coil or the like may be used as the holding member. Further, instead of using the coil-shaped member, a mesh-shaped member may be used.
As described above, by using the coil or mesh member, the heat radiation area as the holding member can be reduced.

The double coil 7 is wound and fixed on the outer surface of the base metal 3 a plurality of times. An aluminum foil 11 for forming an aluminum layer is inserted between the base metal 3 and the double coil 7. Aluminum foil 1
The thickness of 1 is about 0.005 mm. The aluminum foil 11 is electrically connected to the base metal 3 and the double coil 7. As a result, the double coil 7 passes through the base metal 3 and the aluminum foil 11,
It will be electrically connected to the lead rod 4.

The metal oxide 9 is held by the double coil 7. The surface portion of the double coil 7 and the metal oxide 9 are exposed to the outside of the gas discharge tube cathode C1 such that the surface of the metal oxide 9 and the surface portion of the double coil 7 serve as a discharge surface. The surface portion of the oxide 9 is brought into contact with the surface portion of the double coil 7.

As the metal oxide 9, barium (B
a), an oxide of any one of strontium (Sr) and calcium (Ca), or a mixture of these oxides, an oxide of a rare earth metal containing scandium and yttrium (IIIa in the periodic table), or A mixture of these oxides, or an oxide of a simple substance selected from barium, strontium, and calcium as the main constituent, or a mixture of these oxides and a minor constituent of which includes scandium and yttrium (periodic III of the table
The oxide which is a) is used. Rare earth metals including barium, strontium, calcium, scandium, and yttrium have a small work function, can easily emit thermoelectrons, and can increase the thermoelectron supply amount. In addition, rare earth metals (II in the periodic table
When Ia) is added, the amount of supplied thermoelectrons can be further increased and the sputtering resistance can be improved.

The metal oxide 9 is a metal carbonate (eg barium carbonate, strontium carbonate,
It is obtained by subjecting the applied metal carbonate to vacuum heating decomposition (thermal activation) at about 1,000 ° C. The metal oxide 9 thus obtained finally becomes an electron-emissive substance. In the metal carbonate as the electrode material, the double coil 7 is fixed by being wound around the outer surface of the base metal 3 multiple times, and the aluminum foil 11 is inserted between the base metal 3 and the double coil 7. In this state, the double coil 7 is applied so as to come into contact with the base metal 3 and the aluminum foil 11.

When the applied metal carbonate is decomposed by heating under vacuum (thermal activation), aluminum is a metal having a relatively low ionization potential and melting point. Therefore, the metal contained in the aluminum foil 11 and the metal oxide 9 (for example, B
Between a) and the tungsten (W) forming the double coil 7, an oxygen interstitial compound of BaWOBa composition, that is, an oxygen interstitial intermetallic compound is formed. The metal oxide 9 is used as the base metal 3 and the aluminum foil 11.
And is electrically connected to the lead rod 4 via. The first ionization energy of aluminum is 57
It is 7 KJ / mol.

From the above, the cathode C1 for gas discharge tube of the first embodiment includes the metal oxide 9, the aluminum foil 11 (aluminum layer), and the double coil 7 made of a refractory metal, and the aluminum foil 11 and double coil 7
Are electrically connected to each other, so that between the aluminum foil 11, the metal oxide 9 and the double coil 7, BaWO
Oxygen interstitial intermetallic compounds having a Ba composition can be easily produced.

In the cathode C1 for gas discharge tube of the first embodiment, since the aluminum foil 11 and the double coil 7 are electrically connected to each other, the double coil 7 serving as an electron source and the metal oxide are oxidized. The metal contained in the substance 9 is electrically conducted through the aluminum foil 11 and the intermetallic compound described above, and a discharge path is formed in the gas discharge tube cathode C1. In the gas discharge tube cathode C1, the double coil 7 and the metal contained in the metal oxide 9 are electrically conducted through the intermetallic compound, and a discharge path is formed in the gas discharge tube cathode C1. It will also be done.

As a result, the cathode C1 for gas discharge tube is
Decomposition (thermal activation) of metal carbonate under vacuum (metal activation)
In this state, thermionic emission can be started, and the initial startability can be improved.

(Second Embodiment) Next, based on FIG.
The gas discharge tube cathode C2 according to the second embodiment will be described.
FIG. 3 is a schematic sectional view showing a cathode for a gas discharge tube according to the second embodiment.

The gas discharge tube cathode C2 is an indirectly heated cathode similar to the gas discharge tube cathode C1 of the first embodiment. As shown in FIG. 3, the heating heater 1 and the electron emitting portion 5 are provided.
And a linear member (electrical conductor) 21 and an aluminum wire 23 for forming an aluminum layer.

The linear member 21 formed in a linear shape is a rigid body (metal conductor) having conductivity, and is IIIa to VII of the periodic table.
a, VIII, Ib group, specifically, tungsten, tantalum, molybdenum, rhenium, niobium, osmium,
It is made of a simple metal such as iridium, iron, nickel, cobalt, titanium, zirconium, manganese, chromium, vanadium, rhodium, or a rare earth metal (melting point 1000 ° C. or higher), or an alloy thereof. In this embodiment, a linear member made of tungsten is used. The diameter of the linear member 21 is set to about 0.1 mm. The linear member 21 is arranged outside the double coil over the longitudinal direction of the double coil 7 so as to be substantially orthogonal to the discharge direction. The linear member 21 is grounded by connecting one end to the lead rod 4.

The aluminum wire 23 has one end connected to the other end of the linear member 21 via the nickel plate member 25, and the other end connected to the lead rod 4. In this way, the linear member 21 is inserted through the nickel plate member 25.
By connecting the aluminum wire 23 with the aluminum wire 23, the bondability between the linear member 21 and the aluminum wire 23 can be improved. Alternatively, the linear member 21 and the aluminum wire 23 may be directly joined to each other to be connected.

The diameter of the aluminum wire 23 is 0.1 mm.
It is set to a degree. The aluminum wire 23 is arranged inside the double coil 7 over the longitudinal direction of the double coil 7 so as to be substantially orthogonal to the discharge direction and in contact with the double coil 7. As a result, the aluminum wire 23
It is in a state of being electrically connected to the double coil 7.

Next, based on FIG. 4, an example of a process of manufacturing the cathode C2 for a gas discharge tube (the heater 1 for heating, the linear member 21, and the aluminum wire 23 are provided for the double coil 7) Will be explained.

First, the tungsten wire 22 is cut and bent into a hairpin shape. The cut tungsten wire 22 constitutes the linear member 21. Next, a pair of aluminum wires 23 are connected to the ends of the tungsten wire 22 bent into a hairpin shape through a nickel plate member 25 by welding. Then, as shown in FIG. 4A, the bent portion of the wire 22 made of tungsten is welded and connected to the lead rod 4.

Next, a pair of aluminum wires 23 are passed through the inside of the double coil 7, and the double coil 7 is sandwiched between the tungsten wire 22 and the aluminum wire 23 as shown in FIG. 4B. After that, the heater 1 for heating is inserted inside the double coil 7, and the aluminum wire 23 and the end of the heater 1 for heating are welded and connected. Through the above steps, the heater 1 for heating and the aluminum wire 23 are arranged inside the double coil 7, and the linear member 21 (the wire 22 made of tungsten) is arranged outside the double coil 7. Can be obtained.

Next, based on FIG. 5, an example of a process of manufacturing the cathode C2 for a gas discharge tube (the heater 1 for heating, the linear member 21 and the aluminum wire 23 is provided for the double coil 7) Will be explained.

First, one tungsten wire 22 is cut and bent into a hairpin shape, and as shown in FIG. 5, the end portion of the hairpin bent tungsten wire 22 is welded to the lead rod 4. Connect with. Next, the central portion of the aluminum wire 23 is directly joined to the bent portion of the tungsten wire 22 by welding. As the aluminum wire 23, "A" manufactured by Niraco Co., Ltd.
l Chrome-O "(Fe: 70%, Cr: 25
%, Al: 15%) can be used.

Then, similarly to the step shown in FIG. 4, the aluminum wire 23 is passed through the inside of the double coil 7, and the double coil 7 is sandwiched between the tungsten wire 22 and the aluminum wire 23. Then, the heater 1 for heating is inserted inside the double coil 7, and the aluminum wire 23 and the end of the heater 1 for heating are welded and connected.

Further, based on FIG. 6, an example of a process of manufacturing the cathode C2 for a gas discharge tube (where the heater 1 for heating, the linear member 21 and the aluminum wire 23 are arranged for the double coil 7) explain.

First, one tungsten wire 22 is cut and bent into a W shape, and as shown in FIG.
The end portion and the bent portion of the tungsten wire 22 bent into a W shape are connected to the nickel plate member 27 by welding. Next, the aluminum wire 23 is directly joined to each of the bent portions of the tungsten wire 22 by welding.

Then, after the nickel plate member 27 is connected to the lead rod 4 by welding, the aluminum wire 23 is passed through the inside of the double coil 7 as in the step shown in FIG.
The double coil 7 is sandwiched between the tungsten wire 22 and the aluminum wire 23. Then, the heater 1 for heating is inserted inside the double coil 7, and the aluminum wire 23 and the end of the heater 1 for heating are welded and connected.

Referring again to FIG. The metal oxide 9 is
It is held by the double coil 7 and is provided in contact with the linear member 21 and the aluminum wire 23. The metal oxide 9 and the linear member 21 are the surface of the metal oxide 9 and the linear member 21.
Is exposed to the outside of the gas discharge tube cathode C2 so that the surface of the wire becomes a discharge surface, and the linear member 21 comes into contact with the surface portion of the metal oxide 9. The metal oxide 9 is
A metal carbonate (for example, barium carbonate, strontium carbonate, calcium carbonate, etc.) is used as an electrode material, the heating heater 1 is arranged inside the double coil 7, and the linear member 21 is arranged outside the double coil 7. Is provided, the aluminum wire 23 is provided inside the double coil 7, and is applied from the linear member 21 side, and the applied metal carbonate is vacuum-heat decomposed to be provided.

When the applied metal carbonate is decomposed by heating under vacuum (thermal activation), since aluminum is a metal having a relatively low ionization potential and melting point, the metal contained in the aluminum wire 23 and the metal oxide 9 (for example, B
Between a) and the tungsten (W) forming the double coil 7, an oxygen interstitial compound having a BaWOBa composition, that is, an oxygen interstitial intermetallic compound is formed. The metal oxide 9 is electrically connected to the lead rod 4 via the double coil 7, the linear member 21, and the aluminum wire 23.

From the above, the cathode C2 for gas discharge tube of the second embodiment includes the metal oxide 9, the aluminum wire 23 (aluminum layer), and the double coil 7 made of a refractory metal, and the aluminum wire 23 and double coil 7
, And are electrically connected to each other, the BaWOB is provided between the aluminum wire 23, the metal oxide 9 and the double coil 7.
Oxygen interstitial intermetallic compounds of a composition can be easily produced.

In the cathode C2 for gas discharge tube of the second embodiment, since the aluminum wire 23 and the double coil 7 are electrically connected to each other, the double coil 7 serving as an electron supply source and the metal oxide are oxidized. The metal contained in the substance 9 is electrically conducted through the aluminum wire 23 and the above-mentioned intermetallic compound, and a discharge path is formed in the cathode C2 for gas discharge tube. Also, the cathode C2 for gas discharge tube
In, the double coil 7 and the metal contained in the metal oxide 9 are electrically conducted through the above-mentioned intermetallic compound,
A discharge path is also formed in the gas discharge tube cathode C2.

As a result, the cathode C2 for gas discharge tube is
Decomposition (thermal activation) of metal carbonate under vacuum (metal activation)
In this state, thermionic emission can be started, and the initial startability can be improved.

Further, the cathode C for gas discharge tube of the second embodiment
In 2, the linear member 21 is provided in contact with the metal oxide 9 and the equipotential surface is effectively formed by the linear member 21, so that thermionic emission is performed in a wide area of the formed equipotential surface. As a result, the discharge area increases, the electron emission amount (electron emission density) per unit area increases, and the load at the discharge position is reduced. It is possible to suppress stabilization (mineralization) due to oxidation with a metal, that is, a decrease in thermionic emission capability. As a result, it is possible to suppress the occurrence of local discharge,
The life of the gas discharge tube cathode C2 can be extended.
Further, since the movement of the discharge position is also suppressed, stable discharge can be obtained for a long time.

Further, the cathode C for gas discharge tube of the second embodiment
In No. 2, in connection with the increase in the discharge area, the current density is slightly increased to slightly increase the load, that is, even if the discharge current is increased, the damage can be reduced as compared with the conventional one.
This makes it possible to provide an indirectly heated electrode having a large discharge current and having substantially the same shape as the conventional one, and it is possible to realize pulse operation and large current operation.

Further, the cathode C for gas discharge tube of the second embodiment
In the case of No. 2, since the linear member 21 is used, it is possible to realize an electric conductor having a configuration capable of suppressing a decrease in thermionic emission capability and a movement of the discharge position at low cost and more easily. Further, since the linear member 21 (electrical conductor) is a rigid body, it is easy to process and can be provided in close contact with the metal oxide 9.

Further, the cathode C for gas discharge tube of the second embodiment
In the second aspect, the heater 1 for heating is used as a nucleus, and the double coil 7 holding the metal oxide 9 is arranged outside the heater 1 as a core, and the surface portion of the metal oxide 9 held by the double coil 7 is arranged. By arranging the linear member 21 so as to be in contact with the
Can be prevented from falling. Further, a large amount of metal oxide 9 is held between the pitches of the double coil 7, which has an effect of replenishing the amount of metal oxide lost due to deterioration over time during discharge.

(Third Embodiment) Next, based on FIG.
The gas discharge tube cathode C3 according to the third embodiment will be described.
FIG. 7 is a schematic sectional view showing a cathode for a gas discharge tube according to the third embodiment.

As shown in FIG. 7, the gas discharge tube cathode C3 includes a heater 1 for heating, a double coil 33 as a holding member, a linear member 35 as an electric conductor, and an electron emitting substance (cathode). And a metal oxide 9 as a substance. Here, the double coil 33 and the metal oxide 9 as the electron-emissive substance form an electron emission unit that receives heat from the heating heater 1 and emits electrons.

The double coil 33, like the double coil 7 in the first embodiment, is a multiple coil composed of a coil wound in a coil shape and has a mandrel 34. Inside the double coil 33, the heater 1 for heating is inserted and arranged. Here, the mandrel is a core wire that plays a role of a mold that determines a winding diameter when the filament coil is formed. As the material of the mandrel, molybdenum is used, for example. As described above, since the double coil 33 has the mandrel 34, it is possible to further prevent the double coil 33 from being deformed during processing.

The linear member 35 formed in a linear shape is a rigid body (metal conductor) having conductivity, and is IIIa to VII in the periodic table.
a, VIII, Ib group, specifically, tungsten, tantalum, molybdenum, rhenium, niobium, osmium,
It is made of a simple metal such as iridium, iron, nickel, cobalt, titanium, zirconium, manganese, chromium, vanadium, rhodium, or a rare earth metal (melting point 1000 ° C. or higher), or an alloy thereof. In this embodiment, a linear member made of tungsten is used. The diameter of the linear member 35 is set to about 0.1 mm. The linear member 35 is preferably made of a single metal of tungsten, tantalum, molybdenum, or an alloy thereof. When the linear member 35 is a single metal of tungsten, tantalum, molybdenum, or an alloy thereof, it is excellent in practicality in terms of cost, handling, and the like.

The linear member 35 has a predetermined length,
It is arranged outside the double coil 33 over the longitudinal direction of the double coil 33 so as to be substantially orthogonal to the discharge direction.
As shown in FIG. 7, the linear member 35 is provided in electrical contact with a plurality of coil portions of the double coil 33 along the longitudinal direction of the double coil 33. Preferably, the double coil 33 may be provided in electrical contact over the entire length in the longitudinal direction. This linear member 35 is
Double coil 33 and metal oxide 9 as an electron emitting substance
It is provided on the outermost surface side portion of the electron emitting portion including and.

The linear member 35 is connected via the lead rod 4 to
It is grounded (GND) by being connected to the grounding side terminal of the heating heater 1. As a result, the double coil 33 is grounded, and the metal oxide 9 as the electron-emissive substance becomes the ground potential. The number of linear members 35 is not limited to one, and may be two or more. Moreover, you may weld each contact point of the linear member 35 and the double coil 33.

Further, the linear member 35 is formed with an aluminum layer covering at least a part of the surface thereof. This aluminum layer is formed by vapor deposition (physical vapor deposition (PVD) method, chemical vapor deposition (CVD) method), plating or the like of aluminum (Al) on the surface of the linear member 35, and is electrically connected to the linear member 35. It is in the state of doing. The vacuum deposition method and the ion plating method in the PVD method are particularly effective for forming the aluminum layer. The aluminum layer does not have to be formed on the entire surface of the linear member 35, and may be formed on at least a part of the surface of the linear member 35.

In place of the linear member 35, a plate-shaped member having a conductive rigid body (metal conductor) formed in a plate shape, a mesh-shaped member obtained by knitting a metal conductor in a mesh shape, or the like may be used. Good. In this case, the aluminum layer is formed so as to cover at least a part of the surface of the plate member, the mesh member, or the like.

Returning to FIG. 7, the gas discharge tube cathode C3 is
It has a metal oxide 9 as an electron-emissive substance. The metal oxide 9 is held by the double coil 33, and the linear member 3
5 is provided in contact with. The metal oxide 9 and the linear member 35 are exposed to the outside of the gas discharge tube cathode C3 so that the surface of the metal oxide 9 and the surface of the linear member 35 serve as a discharge surface. The linear member 35 on the surface
Are in contact with each other.

The metal oxide 9 is a metal carbonate (eg barium carbonate, strontium carbonate,
It is obtained by subjecting the applied metal carbonate to thermal decomposition under vacuum. When performing vacuum thermal decomposition by energizing the heating heater, AC thermal decomposition is preferable to DC thermal decomposition. The metal oxide 9 thus obtained finally becomes an electron-emissive substance. As shown in FIG. 7, the metal carbonate serving as the cathode material is provided with the heater 1 for heating inside the double coil 33 and the linear member 35 provided on the double coil 33. In the state, it is applied from the linear member 35 side.

Further, metal carbonate as a cathode material is applied to the double coil 33 (the linear member 35) in a state where the heater 1 for heating is not provided inside the double coil 33, and then the two The heating heater 1 may be inserted inside the heavy coil 33. In this way, the heater 1 for heating is inserted and disposed after the application of the metal carbonate so that the heater 1 for heating has a small hole when the electric insulating layer 2 formed on the heater 1 for heating has small holes.
When the metal carbonate is applied in the state where the metal carbonate is provided, the applied metal carbonate is prevented from entering into the small holes and short-circuiting the metal oxide 9 obtained from the metal carbonate and the heater 1 for heating. This is because.

As shown in FIG. 7, the heater 1 for heating is in contact with the metal oxide 9 via the electric insulating layer 2. Therefore, the heat of the heater 1 for heating can be transferred to the metal oxide 9 reliably and efficiently during preheating. Further, compared with the indirectly heated cathode for a gas discharge tube having a heat-conductive cylinder disclosed in Japanese Patent Publication No. 62-56628, the heat radiation area is smaller, which is necessary for hot cathode operation. The loss of heat quantity can be suppressed. Therefore, it is possible to design the electrode so that the electrode operates only by the amount of heat generated by self-heating, without the need to supply the amount of heat to the electrode from the outside or forced overheating. Here, self-heating means that when electrons are emitted from the electrode in the gas discharge tube, ionized gas molecules in the discharge space collide and are electrically neutralized, but due to the impact of the gas molecules colliding with the electrode, It means that heat is generated.

In addition to the above-mentioned metal oxides, it is also conceivable to use metal borides such as lanthanum boride, metal carbides, metal nitrides, etc. as a source of thermionic electrons. Carbides, metal nitrides, and the like have a poor track record as a thermoelectron supply source as a hot cathode for gas discharge tubes, and are meaningless to be added as main and sub constituent requirements. However, it may be used in the peripheral part of the cathode for the purpose other than the thermionic supply source, for example, for improving the insulating effect for suppressing the amount of heat dissipation other than the discharge part.

By the way, when the applied metal carbonate (for example, barium carbonate) is vacuum-heat decomposed (thermally activated), aluminum layered on the surface of the linear member 35 and the metal oxide 9 are contained. Barium oxide (BaO) is formed between the metal (for example, barium) to be formed, and aluminum (Al) is formed between the barium oxide and the refractory metal (tungsten (W)) forming the linear member 35.
Serves as a bridge between tungsten and barium, etc., and is an oxygen interstitial type, that is, an oxygen interstitial type intermetallic compound (WAlO
Ba) will be formed. In intermetallic compounds,
A covalent bond and an ionic bond are mixed, and free barium (Ba) is present as described above.

Aluminum (Al) has a lower ionization potential and melting point than tungsten, and has the same ionization potential as barium. The ionization potential of aluminum is 5.984 eV (577 kJ / m).
ol), and the melting point is 660 ° C. Therefore, barium in the Ba-oxygen (O) compound formed by thermally decomposing barium carbonate is easily replaced by aluminum,
A compound having a Ba—Al—O bond having heat resistance is formed. Further, since tungsten and aluminum are metallic bonds and aluminum and barium are in a bond state in which electrons are easily supplied, there is conductivity between tungsten, aluminum and barium.

From the above, according to the third embodiment, aluminum becomes a bridge, and between the aluminum layer formed on the surface of the linear member 35, the linear member 35, and the metal oxide 9, Oxygen interstitial intermetallic compounds having a WAlOBa composition can be easily produced. This intermetallic compound is a circuit in which discharge electrons supplied from a connected power source are continuously and in large quantities supplied from the linear member 35 to a metal (barium or the like) which becomes an electron-emissive substance through Al. Is formed, the cathode C3 for gas discharge tube is formed.
In the thermally activated state, thermionic emission can be started, and the initial startability is improved.

Further, in the third embodiment, aluminum is formed in layers by covering at least a part of the surface of the linear member 35. As a result, aluminum coats at least a part of the surface of the linear member 35 in a layered manner, so that the exposed surface area of Al becomes large, and the oxygen-intrusion type intermetallic compound is absorbed between the linear member 35 and the electron-emissive substance. It is possible to form a large amount between the metal and the metal. Further, the amount of aluminum contributing to the formation of the above-mentioned intermetallic compound can be controlled easily and appropriately.

Further, the cathode C for gas discharge tube of the third embodiment
3, the linear member 35 is provided in contact with the metal oxide 9, and the linear member 35 makes electrical contact with the double coil 33 at a plurality of locations, so that the linear member 35 provides an equipotential surface. Since it is formed effectively, thermionic emission occurs in a wide area of the formed equipotential surface, so that the discharge area increases, the electron emission amount per unit area (electron emission density) increases, and Since the load is reduced, it is possible to suppress the deterioration of the thermionic emission capability, that is, the stabilization (mineralization) due to the sputtering of the metal oxide 9 and the oxidation with the reducing metal, which are deterioration factors. As a result, the occurrence of local discharge can be suppressed and the life of the cathode can be extended. Further, since the movement of the discharge position is also suppressed, stable discharge can be obtained for a long time.

Further, in the cathode C3 for gas discharge tube,
In connection with the increase in the discharge area, the current density is slightly increased to slightly increase the load, that is, even if the discharge current is increased,
Damage can be reduced compared to the conventional one. This makes it possible to provide an indirectly heated cathode for a gas discharge tube with a large discharge current, which has substantially the same shape as the conventional one, and can realize pulse operation and large current operation.

Further, since the linear member 35 is used as the electric conductor, the electric conductor having a structure capable of suppressing the decrease of the thermoelectron emission ability and the movement of the discharge position can be realized at low cost and more easily. . Further, since the linear member 35 (electric conductor) is a rigid body, it is easy to process and can be provided in close contact with the metal oxide 9.

(Fourth Embodiment) Next, based on FIG.
The gas discharge tube cathode C4 according to the fourth embodiment will be described.
FIG. 8 is a schematic sectional view showing a cathode for a gas discharge tube according to the present fourth embodiment.

As shown in FIG. 8, the gas discharge tube cathode C4 includes a heater 1 for heating, a double coil 7 as a coil member, a plate member 41 as an electric conductor, and an electron-emissive substance (cathode). And a metal oxide 9 as a substance.

The double coil 7 is formed with an aluminum layer covering at least a part of its surface. This aluminum layer is formed by vapor deposition (physical vapor deposition (PVD) method, chemical vapor deposition (CVD) method), plating or the like of aluminum (Al) on the surface of the double coil 7, and is electrically connected to the double coil 7. It is in the state of doing. The vacuum deposition method and the ion plating method in the PVD method are particularly effective for forming the aluminum layer. The aluminum layer does not have to be formed on the entire surface of the double coil 7, and may be formed on at least a part of the surface of the double coil 7.

The plate-like member 41 formed in a plate-like shape is a rigid body (metal conductor) having conductivity, and is IIIa to VII in the periodic table.
a, VIII, Ib group, specifically, tungsten, tantalum, molybdenum, rhenium, niobium, osmium,
It is made of a simple metal such as iridium, iron, nickel, cobalt, titanium, zirconium, manganese, chromium, vanadium, rhodium, or a rare earth metal (melting point 1000 ° C. or higher), or an alloy thereof. In this embodiment, a tungsten plate member having a width of 1.5 mm and a thickness of 25.4 μm is used.

The plate member 41 is provided inside the double coil 7 (between the heating heater 1 and the double coil 7) over the longitudinal direction of the double coil 7 substantially orthogonal to the discharge direction. . The plate member 41 is in a state of being electrically connected to the double coil 7. In addition, the plate member 41 includes the double coil 7
It contacts a plurality of coil portions inside the and forms a plurality of contacts with the double coil 7. Plate member 41
Is grounded (GND) by being connected to the grounding side terminal of the heating heater 1. When the plate member 41 is grounded, the double coil 7 is also grounded. Instead of using the plate member 41, a linear member (for example, a tungsten element wire having a diameter of about 0.1 mm) formed in a linear shape or a mesh member formed in a mesh shape may be used. Further, each contact point between the plate member 41 and the double coil 7 may be welded.

The metal oxide 9 is held by the double coil 7 and the heater 1 for heating, and is provided in contact with the plate member 41. The surface of the metal oxide 9 and the surface of the double coil 7 are exposed to the outside of the cathode C4 for a gas discharge tube, and the surface portion of the double coil 7 contacts the surface portion of the metal oxide 9. .

The metal oxide 9 is a metal carbonate (eg barium carbonate, strontium carbonate,
It is obtained by subjecting the applied metal carbonate to thermal decomposition under vacuum. When vacuum heating decomposition is performed by energizing the heating heater 1,
AC pyrolysis is preferable to DC pyrolysis. The metal oxide 9 thus obtained finally becomes an electron-emissive substance. As shown in FIG. 8, the metal carbonate as the cathode material is placed inside the double coil 7 by the heater 1 for heating.
And the plate-shaped member 41 is disposed inside the double coil 7 on the discharge surface side.
Is applied from the front side. It is not necessary to apply the metal carbonate so as to cover the entire circumference of the gas discharge tube cathode C4 (double coil 7), and only the portion on the discharge surface side where the plate-like member 41 is provided is provided. It may be applied.

As shown in FIG. 8, the heating heater 1 is in contact with the metal oxide 9 and the double coil 7 via the electric insulating layer 2. Therefore, the heat of the heating heater 1 can be reliably and efficiently transferred to the metal oxide 9 and the double coil 7 during preheating. In addition, Japanese Examined Japanese Patent Publication Sho 62-5662
As compared with the indirectly heated cathode for a gas discharge tube having a heat-conductive cylinder disclosed in Japanese Patent Publication No. 8, it is possible to suppress the loss of the amount of heat required for hot cathode operation. Therefore, it is possible to design the electrode so that the electrode operates only by the amount of heat generated by self-heating, without the need to supply the amount of heat to the electrode from the outside or forced overheating. Here, self-heating means that when electrons are emitted from the electrode in the gas discharge tube, ionized gas molecules in the discharge space collide and are electrically neutralized, but due to the impact of the gas molecules colliding with the electrode, It means that heat is generated.

By the way, when the applied metal carbonate (for example, barium carbonate) is decomposed (heat activated) under vacuum, it is contained in the layered aluminum and the metal oxide 9. Barium oxide (BaO) is formed between the metal (for example, barium) to be formed, and aluminum (Al) is formed between the barium oxide and the refractory metal (tungsten (W)) forming the double coil 7.
Serves as a bridge between tungsten and barium, etc., and is an oxygen interstitial type, that is, an oxygen interstitial type intermetallic compound (WAlO
Ba) will be formed. In intermetallic compounds,
A covalent bond and an ionic bond are mixed, and free barium (Ba) is present as described above.

Aluminum (Al) has a lower ionization potential and melting point than tungsten, and has the same ionization potential as barium. The ionization potential of aluminum is 5.984 eV (577 kJ / m).
ol), and the melting point is 660 ° C. Therefore, barium in the Ba-oxygen (O) compound formed by thermally decomposing barium carbonate is easily replaced by aluminum,
A compound having a Ba—Al—O bond having heat resistance is formed. Further, since tungsten and aluminum are metallic bonds and aluminum and barium are in a bond state in which electrons are easily supplied, there is conductivity between tungsten, aluminum and barium.

From the above, according to the present fourth embodiment, aluminum becomes a bridge, and between the aluminum layer formed on the surface of the double coil 7 and the double coil 7 and the metal oxide 9, Oxygen interstitial intermetallic compounds having a WAlOBa composition can be easily produced. The intermetallic compound is a circuit in which discharge electrons supplied from a connected power source are continuously and in large quantities supplied from the double coil 7 to a metal (barium or the like) which becomes an electron-emissive substance through Al. Is formed, the cathode C4 for gas discharge tube is formed.
In the thermally activated state, thermionic emission can be started, and the initial startability is improved.

Further, in the fourth embodiment, aluminum is formed in layers so as to cover at least a part of the surface of the double coil 7. As a result, aluminum coats at least a part of the surface of the double coil 7 in a layered manner, so that the exposed surface area of Al becomes large, and the oxygen intercalation type intermetallic compound becomes a double coil 7 and an electron-emissive substance. It is possible to form a large amount between the metal and the metal. Further, the amount of aluminum contributing to the formation of the above-mentioned intermetallic compound can be controlled easily and appropriately.

Now, let us consider the discharges at three predetermined discharge parts on the surface of the double coil 7 (1A, 1B, 1C from the side closer to the ground (GND) as the electron supply source). Each discharge part 1A, 1B, 1C is a plate-shaped member 4
Winding resistance component of the double coil 7 from 1 R1A, R1B, R
It has 1C. The discharge current amount varies depending on the work function of the part, but assuming that I1A>I1B> I1C (7), when the main discharge occurs in the discharge portion 1A having the winding resistance R1A, The heat generation (W) due to the Joule heat represented by the equation (8) increases, and W = I1A ² × R1A (8) The work function decreases due to the temperature increase. This allows
Most of the discharge is collected in the discharge part 1A, and the degree of concentration of the discharge is increased, and the discharge distribution becomes a mountain range-like continuous distribution having gentle unevenness. The larger the winding resistance R1A, the larger the slope of the discharge distribution. Conversely, the smaller the winding resistance R1A, the smaller the discharge distribution becomes. It will converge to a continuous distribution.

From the above, in the gas discharge tube cathode C4 of the present embodiment, the plate member 41 is provided in contact with the metal oxide 9 and the double coil 7, so that the plate member 41 is provided. 41 effectively forms an equipotential surface with the inner portion of the double coil 7 on the back surface (the surface opposite to the discharge surface) of the double coil 7. That is, the plate member 41 and the inner portion of the double coil 7 are composed of a plurality of electric wirings (conductive paths) and are not regulated so that current flows in a single direction. Therefore,
The electrical resistance between the ends of the plate member 41 is extremely small, and the surface of the plate member 41 is in a substantially equipotential state, and the electric potentials of the discharge surfaces composed of a plurality of discharge points or discharge lines are substantially equal. . In other words, the plate member 41
Form a plurality of electric circuits in which discharge current can flow in the direction parallel to the discharge surface, that is, discharge electrons (emissions)
A plurality of paths (equipotential circuits) will be formed.

Therefore, in the gas discharge tube cathode C4,
Since the equipotential surface is effectively formed on the back surface (the surface opposite to the discharge surface) of the double coil 7 by the plate member 41 and the double coil 7, the formed equipotential surface is wide. Thermionic emission occurs in the region, the discharge area increases, the amount of electron emission per unit area (electron emission density) increases, and the load at the discharge position is reduced. It is possible to suppress the spattering and the stabilization (mineralization) due to the oxidation with the reduced metal, that is, the decrease in the thermoelectron emission ability. As a result, the occurrence of local discharge can be suppressed and the life of the cathode can be extended. Further, since the movement of the discharge position is also suppressed, stable discharge can be obtained for a long time. Further, since the discharge area is increased, the operating voltage and the amount of heat generated of the gas discharge tube cathode C4 can be reduced.

Further, in the cathode C4 for gas discharge tube,
In connection with the increase in the discharge area, the current density is slightly increased to slightly increase the load, that is, even if the discharge current is increased,
Damage can be reduced compared to the conventional one. This makes it possible to provide an indirectly heated cathode for a gas discharge tube with a large discharge current, which has substantially the same shape as the conventional one, and can realize pulse operation and large current operation.

Further, since the plate-like member 41 is used as the electric conductor, the electric conductor having a structure capable of suppressing the decrease in thermionic emission capability and the movement of the discharge position can be realized at low cost and more easily. . Further, since the plate member 41 (electric conductor) is a rigid body, it is easy to process and can be provided in close contact with the metal oxide 9. Furthermore, it is possible to easily provide a large number of locations where the plate-shaped member 41 and the metal oxide 9 come into contact with each other.

Further, the cathode C4 for gas discharge tube of this embodiment
In the above, the heater 1 for heating is used as a core, and the double coil 7 holding the metal oxide 9 is arranged around the heater 1 as a core, and the double coil 7 is arranged so as to contact the metal oxide 9 inside the double coil 7. By disposing the member 41, the vibration suppressing effect of the double coil 7 works, and the metal oxide 9 can be prevented from falling. Further, a large amount of metal oxide 9 is held between the pitches of the double coil 7, which has an effect of replenishing the amount of metal oxide lost due to deterioration over time during discharge.

(Fifth Embodiment) Next, based on FIG.
The gas discharge tube cathode C5 according to the fifth embodiment will be described.
FIG. 9 is a schematic sectional view showing a cathode for a gas discharge tube according to the present fifth embodiment.

As shown in FIG. 8, the gas discharge tube cathode C5 includes a heater 1, a double coil 7, a linear member 35, a metal oxide 9 as an electron-emissive substance, and a base metal. 3 and 3. The base metal 3 has a function of separating the metal oxide 9 as the electron-emissive substance from the electric insulating layer 2 formed on the heater 1 for heating.

As the material of the base metal 3, a refractory metal having a melting point higher than the cathode temperature during operation can be used. Further, as the base metal 3, a cylindrical tubular member is generally used, but an arcuate (opened) tubular member having a cutout portion may be used.

The linear member 35 formed in a linear shape is formed by bending a single linear member a plurality of times outside the double coil 7 to make it meander, and extends in the discharge direction over the longitudinal direction of the double coil 7. They are arranged substantially orthogonally. As shown in FIG. 8, the linear member 35 is provided in electrical contact with a plurality of coil portions of the double coil 7 along the longitudinal direction of the double coil 7. In addition, the linear member 35,
It is grounded by being connected to the grounding side terminal of the heating heater 1. As a result, the double coil 7 is grounded, and the metal oxide 9 as an electron-emissive substance is
Is at ground potential. The base metal 3 is also grounded via the lead rod 4.

When the applied metal carbonate (for example, barium carbonate) is decomposed (heat activated) in a vacuum, the aluminum contained in layers on the surface of the linear member 35 and the metal contained in the metal oxide 9. Barium oxide (BaO) is formed between the barium oxide and the refractory metal (tungsten (W)) forming the linear member 35, and aluminum (Al) is tungsten and barium. Oxygen invasion type, acting as a bridge between
That is, an oxygen interstitial intermetallic compound (WAlOBa) is formed. In the intermetallic compound, covalent bonds and ionic bonds are mixed, and free barium (Ba) is present as described above.

Aluminum (Al) has a lower ionization potential and melting point than tungsten, and has the same ionization potential as barium. Aluminum has an ionization potential of 5.984 eV and a melting point of 6
It is 60 ° C. Therefore, barium in the Ba-oxygen (O) compound formed by thermally decomposing barium carbonate is easily replaced by aluminum, and Ba-A having heat resistance is used.
A compound having a l-O bond is formed. Further, since tungsten and aluminum are metallic bonds and aluminum and barium are in a bond state in which electrons are easily supplied, there is conductivity between tungsten, aluminum and barium.

From the above, according to the present embodiment, aluminum becomes a bridge, and the WAlOBa composition is formed between the aluminum layer formed on the surface of the linear member 35, the linear member 35 and the metal oxide 9. The oxygen interstitial intermetallic compound can be easily produced. This intermetallic compound is a circuit in which discharge electrons supplied from a connected power source are continuously and in large quantities supplied from the linear member 35 to a metal (barium or the like) which becomes an electron-emissive substance through Al. Therefore, the cathode C5 for a gas discharge tube is in a thermally activated state and is ready to start thermionic emission, which improves the initial startability.

Further, the cathode C for gas discharge tube of the fifth embodiment
In FIG. 5, the linear member 35 is provided in contact with the metal oxide 9, and the linear member 35 makes electrical contact over a plurality of positions of the double coil 7 so that the linear member 35 contacts the metal oxide 9. Since the equipotential surface is effectively formed by the member 35, thermoelectron emission occurs in a wide region of the formed equipotential surface, so that the discharge area increases and the amount of electron emission per unit area (electron emission density). Is increased, the load at the discharge position is reduced, and the stabilization (mineralization) by the sputtering of the metal oxide 9 and the oxidation with the reducing metal, that is, the deterioration factor, that is, the decrease in thermionic emission capability is suppressed. be able to. As a result, the occurrence of local discharge can be suppressed and the life of the cathode can be extended. Further, since the movement of the discharge position is also suppressed, stable discharge can be obtained for a long time.

Further, in the gas discharge tube cathode C5,
In connection with the increase in the discharge area, the current density is slightly increased to slightly increase the load, that is, even if the discharge current is increased,
Damage can be reduced compared to the conventional one. As a result, it is possible to provide a cathode for a gas discharge tube having a large discharge current and a substantially same shape as a conventional one, and it is possible to realize pulse operation and large current operation.

Further, since it has the base metal 3, when the metal carbonate as the thermoelectron supply source is changed (thermal decomposition) to the metal oxide 9, the thermal decomposition can be promoted as a heat conductor. . Moreover, the metal oxide 9 and the heater 1 for heating can be reliably separated. Further, the reducing ability of the base metal 3 can be utilized to reduce the metal oxide 9 during operation to generate a free metal element, thereby improving the electron emissivity. Furthermore, the heat of the heater 1 for heating can be surely transmitted to the metal oxide 9 when activated.

The present invention is not limited to the above embodiment. For example, the size of the aluminum foil 11 in the first embodiment, the number of the aluminum wires 23 in the second embodiment, etc. can be appropriately set.

In the first and second embodiments, after the discharge of the gas discharge tube cathodes C1 and C2 is started,
Since the above-mentioned intermetallic compound is formed according to the amount of heat of discharge and the like, it is not necessary to form an aluminum layer on the entire inner portion of the double coil 7. For the same reason, also in the third to fifth embodiments, it is not necessary to coat the entire surface of the linear member 35 or the entire surface of the double coil 7 with aluminum.

[0132]

As described in detail above, according to the present invention, it is possible to provide an indirectly heated cathode having discharge characteristics suitable for large current operation and improved initial starting property.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing a cathode for a gas discharge tube according to a first embodiment of the present invention.

FIG. 2 is a schematic front view showing the cathode for a gas discharge tube according to the first embodiment of the present invention.

FIG. 3 is a schematic sectional view showing a cathode for a gas discharge tube according to a second embodiment of the present invention.

FIG. 4 is a diagram for explaining an example of a manufacturing process for the cathode for a gas discharge tube according to the second embodiment of the present invention.

FIG. 5 is a diagram for explaining an example of a manufacturing process for the cathode for a gas discharge tube according to the second embodiment of the present invention.

FIG. 6 is a diagram for explaining an example of a manufacturing process in the cathode for gas discharge tube according to the second embodiment of the present invention.

FIG. 7 is a schematic sectional view showing a cathode for a gas discharge tube according to a third embodiment of the present invention.

FIG. 8 is a schematic sectional view showing a cathode for a gas discharge tube according to a fourth embodiment of the present invention.

FIG. 9 is a schematic sectional view showing a cathode for a gas discharge tube according to a sixth embodiment of the present invention.

FIG. 10 is a diagram showing a relationship between a heater applied voltage and a cathode drop voltage (box potential) in a gas discharge tube.

FIG. 11 is a diagram showing a relationship between a heater applied voltage and a discharge current in a gas discharge tube.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Heating heater, 2 ... Electric insulating layer, 3 ... Base metal, 5
... Electron emission part, 7 ... Double coil, 9 ... Metal oxide, 11
Aluminum foil, 21 ... Linear member, 23 ... Aluminum wire, 33 ... Double coil, 34 ... Mandrel, 35 ... Linear member, 41 ... Plate member, C1-C5 ... Cathode for gas discharge tube.

Claims (15)

[Claims] 1. A heating heater having an electrically insulating layer formed on a surface thereof, and an electron emitting portion which emits electrons in response to heat from the heating heater. A metal oxide as a radiating material, a holding member that holds the metal oxide, an electric conductor that is provided on the outermost surface side portion of the electron emitting portion and has a predetermined length and is made of a refractory metal, Aluminum that is electrically conductive with a conductor, and the refractory metal and the metal oxide are bridged by the aluminum to form an oxygen intercalation-type intermetallic compound. Indirectly heated cathode. 2. The holding member is formed by winding a refractory metal in a coil shape, and the electric conductor contacts the metal oxide,
The indirectly heated cathode according to claim 1, wherein the indirectly heated cathode is provided in contact with a plurality of coil portions of the holding member along a longitudinal direction of the holding member. 3. The indirectly heated cathode according to claim 1, wherein the electric conductor is formed in a mesh shape, a linear shape, or a plate shape. 4. The indirectly heated cathode according to claim 1, wherein the aluminum is formed into a layer so as to cover at least a part of the surface of the electric conductor. 5. A high melting point metal wound in a coil shape, a heating heater disposed inside the high melting point metal and having an electric insulating layer formed on the surface thereof, and held by the high melting point metal. A metal oxide as an electron-emissive substance, an electric conductor provided inside the refractory metal in contact with the refractory metal, and having a predetermined length, and aluminum electrically conducting with the refractory metal. The indirectly heated cathode, wherein the refractory metal and the metal oxide are bridged by the aluminum to form an oxygen intercalation intermetallic compound. 6. The indirectly heated type according to claim 5, wherein the electric conductor is provided in contact with the metal oxide and in contact with a plurality of coil portions of the refractory metal. cathode. 7. The indirectly heated cathode according to claim 5, wherein the metal oxide is in contact with the heater for heating through the electrically insulating layer. 8. The indirectly heated cathode according to claim 5, wherein the refractory metal is in contact with the heater for heating via the electrical insulating layer. 9. The indirectly heated cathode according to claim 5, wherein the electric conductor is a refractory metal formed in a mesh shape, a linear shape, or a plate shape. 10. The indirectly heated cathode according to claim 5, wherein the aluminum is formed into a layer by covering at least a part of the surface of the refractory metal. 11. The aluminum according to claim 4, wherein the aluminum is formed into a layer by vapor deposition.
The indirectly heated cathode according to 1. 12. The refractory metal is tungsten, tantalum, molybdenum, rhenium, niobium, osmium,
The indirectly heated cathode according to claim 1 or 5, which is composed of a single metal of iridium, iron, nickel, cobalt, titanium, zirconium, manganese, chromium, vanadium, rhodium, or an alloy thereof. 13. The cathode for a gas discharge tube according to claim 12, wherein the refractory metal is made of a single metal of tungsten, tantalum, molybdenum, or an alloy thereof. 14. The metal oxide contains an oxide of any one of barium, strontium, and calcium, a mixture of these oxides, or an oxide of a rare earth metal. The indirectly heated cathode according to claim 1 or claim 5. 15. A heating heater having an electrically insulating layer formed on a surface thereof, and an electron emitting portion that emits electrons by receiving heat from the heating heater, wherein the electron emitting portion is an easy electron. A metal oxide as a radiating material, a refractory metal, and aluminum that is formed in a layer by covering at least a part of the surface of the refractory metal and is electrically conductive with the refractory metal. The indirectly heated cathode, wherein the refractory metal and the metal oxide are bridged by the aluminum to form an oxygen intercalation intermetallic compound.