JP3361402B2 - Gas discharge tube - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gas discharge tube used as an ultraviolet light source for a spectrophotometer or liquid chromatography.

[0002]

2. Description of the Related Art A gas discharge tube is a discharge light source that utilizes positive column emission due to arc discharge of gas enclosed in the tube. As a typical example of the gas discharge tube, a deuterium discharge tube that emits ultraviolet light by discharging the enclosed deuterium is well known. In this deuterium discharge tube, its main application is a continuous spectrum light source for ultraviolet used in spectrophotometers,
In continuous lighting for a long time, a subtle output fluctuation of 0.01% and 0.001% poses a problem, and in many cases, strict characteristics are required.

The structure and operation of the conventional gas discharge tube will be briefly described below with reference to FIGS. 9 to 11. This gas discharge tube is a side-on type deuterium discharge tube that takes out light from the side of the tube.

As shown in FIG. 9, this gas discharge tube 170 is provided.
In the case, the light emitting unit assembly 180 that takes out light by the occurrence of arc discharge is housed in the inside of the container 171 made of glass, and deuterium gas (not shown) has a pressure of about Torr inside the container 171. It is enclosed. The light emitting unit assembly 180 is composed of a metal discharge shielding box, mounted by a stem 172, and via lead pins 173 to 176 (not shown).
It is connected to an external power supply.

As shown in FIGS. 10 and 11, in this light emitting section assembly 180, the discharge shield rear plate 18 is made of metal.
2. The discharge shield box is assembled from the discharge shield lower plate 181, the discharge shield upper plate 183, the discharge shield front plate 194, the focus electrode portion 184 formed by welding the focus electrode 189, the front cover 185, and the cathode cover 186. Inside the discharge shielding box, a hot cathode 188 that emits thermoelectrons, an anode 187 that receives thermoelectrons, and a converging electrode portion 184 that converges arc discharge generated between both electrodes are in contact with the lead pins 173 to 176. It is accommodated in a non-conforming form, that is, in a floating form.

Next, the operation of such a gas discharge tube 170 will be described.

First, the hot cathode 188 is preheated by supplying about 10 W of electric power to the hot cathode 188 for about 20 seconds before discharge. After the hot cathode 188 is sufficiently heated, 150 V is applied between the hot cathode 188 and the anode 187.
Apply a DC open voltage of the order of magnitude. When the preparation for the arc discharge is thus completed, the arc discharge is started by applying the trigger voltage of 350 to 500 V between the hot cathode 188 and the anode 187. At this time, the flow path of thermoelectrons traveling in the direction of arrow 190 is limited to only one discharge path 191 due to the converging effect of the converging electrode portion 184 and the shielding effect of the discharge shielding box. That is, the thermoelectrons emitted from the hot cathode 188 pass through the discharge path 191 converged by the focus electrode portion 184 and are received by the anode 187. Here, an arc ball 192 is generated on the side opposite to the anode 187 in the front space of the converging electrode portion 184 as a high-density discharge region due to arc discharge. Therefore, the ultraviolet light extracted from the positive column emission generated by the arc discharge is projected in front of the anode 187, that is, in the direction of arrow 193.

Apart from these conventional techniques, as an example of a gas discharge tube, there is also known one in which a discharge vessel which also serves as a vessel is made of ceramics. This gas discharge tube is of a type that extracts ultraviolet light from the anode side, and the hot cathode, the anode, and the focusing electrode section are accommodated in a discharge shield box made of ceramics in a floating form that does not contact with anything other than the lead wires. . As an example of such a deuterium discharge tube,
There is a publication "Japanese Patent Laid-Open No. 4-255662".

[0009]

However, in the above-mentioned conventional gas discharge tube, the anode and the converging electrode part are included in the discharge shielding box in a floating form, respectively, and the insulation state between the two electrodes is that of the anode and the converging electrode part. It is maintained by taking a space in between. Therefore, when light is emitted for a long time, the anode generates heat by receiving thermoelectrons, and the focusing electrode section also generates heat due to collision of cations, so that the anode and the focusing electrode section themselves become considerably high in temperature. At this time, the temperatures of the anode and the focusing electrode may exceed 1000 ° C., and the focusing electrode itself may be deformed by residual stress. If the anode and the focusing electrode part installed in the floating form are deformed at a high temperature, the distance between the hot cathode and the anode, which has been set to a desired interval in advance, changes. At, the flow path of thermoelectrons is changed. Therefore, the state of arc discharge becomes unstable, which causes the stability of light emission of the discharge tube to be impaired. Further, since the loss of the anode increases, it has been a cause of shortening the life of the discharge tube.

Therefore, an object of the present invention is to provide a gas discharge tube which can improve the operation stability in long-time continuous light emission and has a long life.

[0011]

The gas discharge tube of the present invention comprises:
A conductive cathode electrode support that supports a hot cathode that generates thermoelectrons, an anode portion that receives the thermoelectrons, and a focusing electrode portion that converges thermoelectrons on the front surface, that is placed between the hot cathode and the anode portion. A member, a conductive anode support member fixed to the back surface of the focusing electrode support member to accommodate the anode portion, and a back surface of the focusing electrode support member and a front surface of the anode portion, and a front surface of the anode support member. It is configured to be brought into contact with the back surface of the anode portion, sandwich the anode portion, and an electrically insulating spacer that holds the anode portion between the back surface of the focusing electrode support member and the front surface of the anode support member. .

The spacer is made of ceramics.

[0013]

In the gas discharge tube of the present invention, when arc discharge occurs between the hot cathode, the focusing electrode and the anode part, the anode part generates heat by receiving thermoelectrons, and the focusing electrode part also collides with cations. Generates heat. The anode part is sandwiched by electrically insulating spacers to be held at a predetermined position between the back surface of the conductive focusing electrode support member and the front surface of the conductive anode supporting member, and the focusing electrode part is Since it is supported by the front surface of the conductive focusing electrode supporting member, the anode part and the focusing electrode part can be electrically insulated by the electrically insulating spacer, and moreover, the anode part and the focusing electrode supporting member are The interval can be kept constant. Therefore, even if the focusing electrode section and the anode section are heated during use of the gas discharge tube, the distance between the anode section and the focusing electrode section can be kept constant.

[0014]

EXAMPLES First Example A first example of the gas discharge tube of the present invention will be described below. The gas discharge tube of this embodiment is a side-on type deuterium discharge tube that takes out light from the side of the tube. In this embodiment, the front and rear are specified based on the light emitting direction.

In the deuterium discharge tube 10 shown in FIG.
Inside the cylindrical container 11 made of glass, the light emitting unit assembly 2 is provided.
0 is stored and deuterium gas (not shown)
Is enclosed in about several Torr. A glass stem 12 is formed at the bottom of the container 11. Further, the container 11 is formed of ultraviolet-transparent glass, quartz glass, or the like having a good ultraviolet transmittance.

The stem 12 has four lead pins 13 ...
16 are fixed in parallel in a straight line, and each lead pin 13
Nos. 16 to 16 penetrate the stem 12, are covered with an insulating material 110, and are connected to an external power source (not shown). Further, the light emitting unit assembly 20 includes a front cover 23 made of metal (Ni or SUS) or ceramics arranged in the front part, a metal (Ni or SUS) anode support member 22 arranged in the rear part, and this anode. It has a metal (Ni or SUS) focusing electrode support member 21 arranged between the support member 22 and the front cover 23.

Next, the structure of the light emitting section assembly 20 will be described in detail.

As shown in FIGS. 2, 3 and 5, a metal anode portion 24 is fixed to the tip of the lead pin 14. The anode portion 24 is composed of a rectangular anode fixing plate 24a fixed to the tip of the lead pin 14 and a plate-shaped anode 24b fixed to the front surface 24aB of the anode fixing plate 24a.

An anode accommodating recess 25 is formed in the front portion of the anode support member 22 for accommodating the anode portion 24. Furthermore, in the center of the bottom wall 25A of the anode accommodating recess 25,
A bulging portion 26 for housing the lead pin 13 is formed, and the lead pin housing recess 2 is formed in the center of the bulging portion 26.
6a is provided. Further, in the lower wall 22a of the anode support member 22, a through hole 22b for penetrating the lead pin 13 is provided at the rear end, and a front end M1 of the insulating pipe M surrounding the lead pin 14 is inserted at the front end. Is provided with a notch 22c. Therefore, the anode portion 24 can be arranged in the anode support member 22 by mounting the tip M1 of the insulating pipe M in the cutout portion 22c with the anode portion 24 fixed to the lead pin 14.

As shown in FIGS. 2, 4 and 5, a rectangular opening 27 is provided in the plate-shaped focusing electrode support member 21 arranged in front of the anode 24, and the opening 27 is formed. ,
It is provided at a position facing the anode 24b. A metal focusing electrode fixing plate 28 is abutted and fixed to the front surface 21a of the focusing electrode supporting member 21, and a metal focusing electrode portion 29 is fixed to the front surface 28a of the focusing electrode fixing plate 28. ing. Then, the converging opening 29a of the converging electrode portion 29
Are arranged so as to face the opening 27 of the focusing electrode support member 21 and face each other with the anode 24b.

As shown in FIGS. 2 and 5, the front cover 23 made of metal or ceramics is formed in a substantially U-shaped cross section, and is fixed to both ends of the front surface 21a of the focusing electrode support member 21. . In the center of this front cover 23,
An opening window 30 for projecting light is formed so as to face the converging opening 29a and the anode 24b. Also, the front cover 23
In the space S formed by and the focusing electrode support member 21,
A spiral hot cathode 31 for generating thermoelectrons is arranged. The hot cathode 31 is arranged at a position deviated from the optical path, that is, laterally inside the front cover 23, and has electrode rods 31a and 31b at both ends thereof.

Further, between the hot cathode 31 and the focusing electrode portion 29, a discharge rectifying plate 32 made of metal (Ni or SUS) or ceramics is arranged at a position deviated from the optical path.
One end of the discharge rectifying plate 32 is fixed to the front surface 21a of the focusing electrode support member 21, and the other end is brought into contact with the inner wall surface 23a of the front cover 23. In addition, the discharge rectifying plate 32 is formed with a slit 32a for connecting the hot cathode 31 and the converging electrode portion 29 to each other, and the slit 32a rectifies thermoelectrons generated from the hot cathode 31.

Now, the assembling of the light emitting section assembly 20 will be described.

As shown in FIG. 2, a metal front cover 2
A pair of left and right flange portions 23a are integrally formed at both ends of the flange 3. Then, after each flange portion 23a is brought into contact with the front surface 21a of the focusing electrode support member 21, the flange portion 23a is fixed to the focusing electrode support member 21 by welding. Further, a protruding piece 32b is integrally formed at one end of the metal discharge rectifying plate 32. Then, after the protrusion 32b is brought into contact with the front surface 21a of the focusing electrode support member 21 at the inner position of the flange portion 23a, the protrusion 32b is fixed to the focusing electrode support member 21 by welding.

The front cover 23 and the discharge rectifying plate 32
When the ceramic is formed of ceramics, the front cover 23 and the discharge rectifying plate 32 are fixed to the focusing electrode support member 21 by using rivets or the like. Although not shown, the converging electrode support member 21 is provided with bendable claw pieces, and the front cover 23 and the discharge rectifying plate 32 are provided with claw through holes for inserting the claw pieces. The front cover 23 and the discharge rectifying plate 32 can be fixed to the focusing electrode support member 21 by inserting the claw pieces into the claw through holes of the front cover 23 and the discharge rectifying plate 32 and bending them.

Further, as shown in FIGS. 2 and 5, at the inner position of the front cover 23, the focusing electrode fixing plate 28 is fixed to the front surface 21a of the focusing electrode supporting member 21 by welding. Further, the flange portion 22d of the anode support member 22 is fixed to the back surface 21b of the focusing electrode support member 21 by welding.

A plate-shaped lid portion 28a extending rearward is integrally formed at the upper end of the focusing electrode fixing plate 28,
The shape of the lid portion 28 a is substantially the same as the shape of the upper opening portion of the anode support member 22. Therefore, when the focusing electrode fixing plate 28 is fixed to the focusing electrode support member 21, the lid portion 28 is
With a, the upper opening of the anode support member 22 can be closed (see FIG. 1).

A cylindrical member 43 made of ceramics for inserting the L-shaped electrode rod 48 is disposed on the side of the anode supporting member 22. The tubular member 43 is fixed to the outer side surface of the anode support member 22 by a semicircular stop member 46 welded to the anode support member 22.

The tip of the lead pin 13 inserted into the through hole 22b is welded to the tongue piece 47 integrally formed on the top of the focusing electrode fixing plate 28 (see FIG. 1). Further, when fixing the hot cathode 31 in the space S, after inserting the electrode rod 48 into the tubular member 48, the lower end of the electrode rod 48 is welded to the tip of the lead pin 15, and the hot cathode 31 is attached to the tip of the electrode rod 48. The electrode rod 31b of 1 is welded, and the electrode rod 31a of the hot cathode 31 is welded to the tip of the lead pin 16.

As shown in FIGS. 3 to 5, the anode support member 2
In the second anode accommodating recess 25, four cylindrical spacers 50 made of electrically insulating ceramics are arranged. Each of the spacers 50 has a rear surface 21 of the focusing electrode supporting member 21 at positions on both sides in the anode accommodating recess 25.
b and the front surface 24aB of the anode fixing plate 24a, and the bottom surface 25a of the anode housing recess 25 (the anode support member 2).
2 (which constitutes a part of the front surface K of 2) and the back surface 24aA of the anode fixing plate 24a so as to sandwich the anode portion 24. When the focusing electrode support member 21 and the anode support member 22 are assembled by welding, the anode portion 24 is fixed to the back surface 2 of the focusing electrode support member 21 by the holding force of the spacer 50.
1b and the bottom surface 25a of the anode accommodating recess 25 (anode support member 2
2 which forms part of the front face K) of the front side of the housing 2. Therefore, by using the spacer 50, the distance between the converging electrode portion 29 and the anode portion 24 can be always kept constant. The shape of the spacer 50 may be spherical, prismatic, block-shaped or the like.

Next, the operation of the side-on type deuterium discharge tube 10 described above will be described.

First, the electric power of about 10 W is supplied to the hot cathode 31 from an external power source (not shown) for about 20 seconds before discharge to preheat the hot cathode 31. Then, a DC open voltage of about 150 V is applied between the hot cathode 31 and the anode 24b to prepare for arc discharge.

After the preparation is completed, the hot cathode 31 and the anode 2
A trigger voltage of 350 to 500 V is applied between the sensor and 4b. At this time, the thermoelectrons emitted from the hot cathode 31 pass through the elongated slit 32a of the discharge rectifying plate 32, reach the anode 24b while converging at the focusing aperture 29a of the focusing electrode part 29. Then, an arc discharge is generated in front of the converging opening 29a, and the ultraviolet rays taken out from the arc ball due to the arc discharge pass through the opening window 30 and then pass through the peripheral surface of the glass container 11 to be emitted to the outside. It

Further, the anode part 24 and the focusing electrode part 29 are
Since the temperature becomes higher than several hundreds of degrees Celsius, this heat is timely released to the outside by the aforementioned member made of ceramics or metal. Since the anode part 24 is firmly held in the anode support member 22 by the spacer 50, the anode part 24 is not easily deformed even under high temperature due to continuous light emission for a long time, and the positions of the anode part 24 and the focusing electrode part 29 are small. The accuracy can be kept good.

Second Embodiment A second embodiment of the gas discharge tube of the present invention will be described below. The gas discharge tube of this embodiment is a head-on type deuterium discharge tube that takes out light from the top of the tube. In this embodiment, the front and rear are specified based on the light emitting direction.

In the deuterium discharge tube 60 shown in FIG.
Inside the cylindrical container 61 made of glass, the light emitting unit assembly 7 is provided.
0 is stored and deuterium gas (not shown)
Is enclosed in about several Torr. A disk-shaped light emitting surface 62 is formed on the top of the container 61, and a disk-shaped stem 63 is provided on the bottom of the container 61. The stem 63 has a tip tube for exhausting gas and enclosing gas. 64 is provided. Therefore, the inside of the container 61 can be hermetically sealed by closing the chip pipe 64 after evacuating and filling the inside of the container 61 through the chip pipe 64. The container 11 is made of ultraviolet-transparent glass, quartz glass, or the like having a good ultraviolet transmittance.

The stem 63 has six lead pins 65a.
~ 65f are fixed, and the lead pins 65a to 65f are
While penetrating the stem 63, each is covered with an insulating material 120 and connected to an external power source (not shown). In addition, the light emitting unit assembly 70 includes a front cover 66 made of metal (Ni or SUS) or ceramics arranged at the front.
And a metal (Ni or SUS) anode support member 67 arranged at the rear part, and a metal (Ni or SUS) focusing electrode support member 68 fixed between the anode support member 67 and the front cover 66. have.

Next, the structure of the light emitting section assembly 70 will be described in detail.

As shown in FIGS. 7 and 8, a metal anode portion 71 is fixed to the tip of a lead pin 65c penetrating the anode support member 67. The anode portion 71 is a rectangular anode fixing plate 71 fixed to the tip of the lead pin 65c.
a and a plate-shaped anode 71b fixed to the front surface 71aB of the anode fixing plate 71a. Further, the anode part 7 is provided at the front part of the anode supporting member 67 having a cylindrical shape having a substantially concave cross section.
An anode accommodating recess 72 for accommodating 1 is formed.

In order to arrange the anode supporting member 67 in the container 61, the anode supporting member 67 is attached to the lead pin 65f.
It is fixed to the tip of. Further, when assembling the light emitting unit assembly 70, the flange portion 67 of the anode support member 67 is used.
After a is brought into contact with the peripheral edge of the back surface 68b of the focusing electrode support member 68, the flange portion 67a is fixed to the focusing electrode support member 68 by welding.

A rectangular opening 73 is provided in the plate-shaped focusing electrode supporting member 68 arranged in front of the anode 71, and the opening 73 is provided at a position facing the anode 71b. Further, a metal focusing electrode portion 74 is fixed to the front surface 68 a of the focusing electrode support member 68. The converging opening 74a of the converging electrode portion 74 is arranged to face the opening 73 of the converging electrode supporting member 68, and
It is in a relationship of facing the anode 71b. Further, the tip of a lead pin 65 a penetrating the anode supporting member 67 and the focusing electrode supporting member 68 is welded to the focusing electrode portion 74. In order to arrange the focusing electrode support member 68 in the container 61, the focusing electrode support member 68 is attached to the lead pin 65e.
It is fixed to the tip of.

A front cover 66 having a cup-shaped cross section
An opening window 75 for projecting light, which is opposed to the converging opening 74a and the anode 71b, is formed in the. A hot cathode 76 for generating thermoelectrons is arranged in a space P defined by the front cover 66 and the focusing electrode support member 68. The hot cathode 76 is arranged at a position deviated from the optical path, that is, laterally inside the front cover 66, and has electrode rods 76a and 76b at both ends thereof. The tip ends of lead pins 65b and 65d penetrating the anode support member 67 and the focusing electrode support member 68 are welded to the electrode rods 76a and 76b, respectively.

When assembling the light emitting portion assembly 70, the metal front cover 66 is fixed to the front surface 68a of the metal focusing electrode support member 68 by welding, but the front cover 66 is made of ceramics. In this case, the front cover 66 is fixed with rivets or claw pieces (not shown).

Further, between the hot cathode 76 and the focusing electrode portion 74, a discharge rectifying plate 77 made of metal (Ni or SUS) or ceramics is arranged at a position deviated from the optical path.
The discharge rectifying plate 77 is provided on the front surface 6 of the focusing electrode supporting member 68.
8a, and is in contact with the focusing electrode portion 74.

Here, eight spherical spacers 80 made of electrically insulating ceramics are arranged in the anode accommodating recess 72 of the anode supporting member 67. Four of these spacers 80 are brought into contact with the back surface 68b of the focusing electrode support member 68 and the front surface 71aB of the anode fixing plate 71a at the four corners of the front surface 71aB of the anode fixing plate 71a. Further, the other four spacers 80 are provided at the four corners of the back surface 71aA of the anode fixing plate 71a. It is brought into contact with the back surface 71aA. Therefore, the anode part 71 can be sandwiched by the four front and rear spacers 80 that are in a confronting relationship with the anode fixing plate 71a sandwiched therebetween.

Then, the focusing electrode supporting member 6 is welded.
8 and the anode support member 67 are assembled, a spacer 80
Due to the clamping force of the
Between the back surface 68b and the bottom surface 72a of the anode housing recess 72 (which constitutes a part of the front surface G of the anode support member 67). Therefore, by using the spacer 80, the distance between the converging electrode part 74 and the anode part 71 can be always kept constant. The shape of the spacer 80 may be cylindrical, prismatic, block-shaped or the like.

Next, the operation of the above-described head-on type deuterium discharge tube 60 will be described.

First, the electric power of about 10 W is supplied to the hot cathode 76 from an external power source (not shown) for about 20 seconds before the discharge to preheat the hot cathode 76. Then, a DC open voltage of about 150 V is applied between the hot cathode 76 and the anode 71b to prepare for arc discharge.

After the preparation, the hot cathode 76 and the anode 7 are
A trigger voltage of 350 to 500 V is applied between 1b and 1b. At this time, the thermoelectrons emitted from the hot cathode 76 reach the anode 71b while being converged by the converging opening 74a of the converging electrode portion 74 while being rectified by the discharge rectifying plate 77. Then, an arc discharge is generated in front of the converging opening 74a, and the ultraviolet rays extracted from the arc ball due to this arc discharge pass through the opening window 75 and then pass through the light emitting surface 62 of the glass container 61 to the outside. Is released.

Further, the anode part 71 and the focusing electrode part 74 are
Since the temperature becomes higher than several hundreds of degrees Celsius, this heat is timely released to the outside by the aforementioned member made of ceramics or metal. Since the anode part 71 is firmly held in the anode support member 67 by the spacer 80, the anode part 71 is not easily deformed even under high temperature due to continuous light emission for a long time, and the positions of the anode part 71 and the focusing electrode part 74 are small. The accuracy can be kept good.

[0051]

Since the gas discharge tube according to the present invention is constructed as described above, the following effects can be obtained.

That is, an electrically insulative spacer is brought into contact with the back surface of the focusing electrode support member and the front surface of the anode portion, and is brought into contact with the front surface of the anode support member and the back surface of the anode portion. By sandwiching and holding the anode part between the back surface of the focusing electrode support member and the front surface of the anode support member, the anode part is firmly held by the spacer, so that the anode part is kept under high temperature due to continuous light emission for a long time. However, the deformation is unlikely to occur, the positional accuracy between the anode part and the focusing electrode part can be kept good, the stability of the operation of the gas discharge tube can be improved, and the life can be extended. Further, by forming the spacer and the ceramics, the heat dissipation effect and the electric insulation effect can be further enhanced.

Further, since the position of the spacer can be appropriately changed within the space formed by the focusing electrode supporting member and the anode supporting member, the spacer can be easily positioned at a position where the sputtered electrode material is unlikely to adhere. You can choose
A short circuit between the anode part and the focusing electrode part can be easily prevented only by changing the position of the spacer.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of a side-on type gas discharge tube of the present invention.

FIG. 2 is an exploded perspective view of the light emitting unit assembly shown in FIG.

FIG. 3 is a perspective view showing a relationship between an anode supporting member and an anode portion.

FIG. 4 is a perspective view showing a relationship among a focusing electrode support member, an anode portion, and a spacer.

5 is a cross-sectional view of the light emitting unit assembly shown in FIG.

FIG. 6 is a perspective view showing an embodiment of a head-on type gas discharge tube of the present invention.

7 is a vertical cross-sectional view of the gas discharge tube shown in FIG.

8 is a sectional view taken along the line VIII-VIII in FIG.

FIG. 9 is a perspective view showing a conventional side-on type gas discharge tube.

FIG. 10 is an exploded perspective view of the light emitting unit assembly shown in FIG.

11 is a cross-sectional view of the light emitting unit assembly shown in FIG.

[Explanation of symbols]

K, G ... Anode support member front surface, 21, 68 ... Focusing electrode support member, 21a, 68a ... Focusing electrode support member front surface, 2
1b, 68b ... Rear surface of the focusing electrode support member, 22, 67 ...
Anode support member, 24, 71 ... Anode part, 24aA, 71a
A ... Rear surface of anode part, 24aB, 71aB ... Front surface of anode part, 29, 74 ... Focusing electrode part, 31, 76 ... Hot cathode, 5
0,80 ... Spacer.

─────────────────────────────────────────────────── ─── Continuation of front page (56) Reference JP-A-4-255662 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01J 61/68 H01J 61/073

Claims (2)

(57) [Claims] 1. A hot cathode that generates thermoelectrons, an anode portion that receives the thermoelectrons, and a focusing electrode portion that is disposed between the hot cathode and the anode portion and that converges the thermoelectrons on the front surface. A conductive focusing electrode support member for supporting, a conductive anode support member fixedly mounted on the back surface of the focusing electrode support member to accommodate the anode portion, a back surface of the focusing electrode support member and a front surface of the anode portion. And abutting on the front surface of the anode supporting member and the back surface of the anode portion to sandwich the anode portion, and between the back surface of the focusing electrode supporting member and the front surface of the anode supporting member. A gas discharge tube comprising an electrically insulating spacer for holding the anode part. 2. The gas discharge tube according to claim 1, wherein the spacer is made of ceramics.