JPH022253B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a streak tube that can be suitably used for analyzing the light intensity distribution of a light source over time.

Streak tubes display changes in incident light over a period of about 1 nanosecond on a fluorescent surface over a length of several tens of millimeters.
The time resolution is so excellent that it can read changes down to picoseconds or less. For this reason, streak tubes are used for waveform analysis of laser pulse light.

First, the structure of a conventional streak tube and the problem to be solved by the present invention will be briefly explained with reference to FIG.

FIG. 1 is a longitudinal sectional view showing the configuration of a conventional streak tube, and a schematic diagram showing the relationship between a photocathode and an optical image.

One end surface of the vacuum-tight container 3 of the streak tube forms a window 1 through which an optical image to be analyzed is incident, and the other end surface forms a window 2 through which a processed optical image exits.
Along the tube axis of this vacuum-tight container 3, a photocathode 4, a mesh electrode 5,
A focusing electrode 6, an aperture electrode 7, a deflection electrode 8, and a fluorescent surface 9 are provided. A higher voltage is then applied to the photocathode 4 to the mesh electrode 5, the focusing electrode 6, and the aperture electrode 7 in this order, and the same potential as the aperture electrode 7 is applied to the fluorescent surface 9. A linear optical image 4 passing through the center of the photocathode 4 is formed on the photocathode 4 through the entrance window 1 using a device not shown.
Suppose that a is projected. The photocathode 4 emits an electron image corresponding to the optical image, and the emitted electrons are accelerated by the mesh electrode 5, focused by the focusing electrode 6, passed through the aperture electrode 7, and then transferred to the deflection electrode 8.
The light travels through the gap in the direction of the fluorescent surface 9. The period during which the linear electron image passes through the gap between the deflection electrodes 8,
A deflection voltage is applied to the deflection electrode 8. The direction of the electric field generated by this voltage is perpendicular to the tube axis and the linear electron image (perpendicular to the plane of the paper in the cross-sectional view of FIG. 1), and its strength is proportional to the deflection voltage. By scanning a linear electron beam on the fluorescent surface 9 perpendicular to the linear direction, a linear optical image projected onto the photocathode 4 is finally formed on the fluorescent surface 9. Optical images arranged sequentially in time perpendicular to the linear direction, so-called streak images, are formed. Therefore, a change in brightness in the arrangement direction of the streak image, that is, in the sweep direction, represents a temporal change in the intensity of the optical image incident on the photocathode 4.

Such streak tubes are usually manufactured by the following method.

First, a glass cylinder forming a side wall of the vacuum-tight container 3, a first glass disk forming one bottom surface of the vacuum-tight container 3, into which an optical image is incident, and serving as a substrate of a photocathode; The second part constitutes the other bottom surface and serves as the window for outputting the optical image and the substrate for the fluorescent surface.
A glass disk and electrode members constituting the mesh electrode 5, focusing electrode 6, aperture electrode 7, and deflection electrode 8 are prepared.

Next, an electrode member is assembled and attached within the glass cylinder. At this time, an antimony evaporation source is placed at an appropriate position facing the photocathode substrate, for example, by storing antimony pieces in a tungsten coil.

At the same time, a phosphor is applied to one side of the second glass disk. Next, the first glass disk and the second glass disk are hermetically sealed to appropriate sides of the bottom surface of the glass cylinder.

Next, a branch pipe is provided on the side wall of the airtight container, and the alkali metal source is contained in this branch pipe.

Next, the air is exhausted through this exhaust pipe provided on the side wall of the airtight container.

Next, the tungsten coil is energized to deposit antimony on the photocathode substrate, and then the alkali metal is gradually fed into the container from the branch pipe, and at the same time the sensitivity of the photocathode is monitored to reach the maximum sensitivity or slightly exceed it. Cancel when. Cut off this posterior branch.

After this, cut out the exhaust pipe to complete the streak pipe.

As can be understood from the above description of the manufacturing method, when the alkali metal is fed into the airtight container, it is inevitable that a small amount of the alkali metal will adhere to each electrode.

When the streak tube manufactured by the above process is operated, the alkali metal causes the inconvenience that the fluorescent surface emits light even in the absence of incident light.

It shines particularly brightly when a high frequency voltage is applied to the deflection electrode and the deflection electrode is repeatedly operated.

Such light emission becomes the background of the streak image, lowering the S/N ratio and narrowing the dynamic range.

The inventor of the present application believes that the above-mentioned light emission is caused by photoelectrons generated when gas molecules or atoms that collide with electrons are excited or ionized and incident on a photocathode, or that electrons or ions are generated on the inner wall of an airtight container. They speculated that this was caused by photoelectrons generated when the light collided with the photocathode, and discovered that the main cause was near the deflection electrode.

In other words, even if a high voltage is applied between the photocathode 4 and the aperture electrode 7, the light emission from the fluorescent surface 9 is extremely weak unless a voltage is applied between the opposing deflection electrodes, and a repeated sweep voltage is applied to the deflection electrodes. I learned that the luminescence of the fluorescent surface becomes significantly stronger.

An object of the present invention is to provide a method for manufacturing a streak tube that can prevent the above-mentioned unwanted light emission.

In order to achieve the above object, a method for manufacturing a streak tube according to the present invention includes a method for manufacturing a streak tube in which photoelectrons emitted from a photocathode are deflected and observed. a first space containing at least a surface on which a photocathode is formed and a focusing electrode; and a second space containing at least a deflection electrode and a fluorescent surface; an assembling step in which the first and second spaces are separated at or near the opening, and a lid that is closed during the manufacturing process is provided in the opening; a step in which the first and second spaces are evacuated; A step of forming a photocathode by introducing a metal forming the photocathode from a branch pipe communicating with the space, and a step of cutting the branch pipe and exhausting the interior while heating it, thereby removing a photocathode that does not contribute to the formation of the photocathode. The method consists of a step of discharging the material for forming the surface, and a step of removing the lid from the opening after evacuation is completed. That is, in the manufacturing process, the first space is filled with alkali metal vapor for forming the photocathode, but care is taken to prevent the alkali metal vapor from reaching the deflection electrode in the second space, and during operation, the aperture is kept to a minimum. Since the first space having the photocathode and the second space having the deflection electrode are connected, movement of the alkali metal is less likely to occur during operation. Therefore, even during use, the deflection electrodes are not contaminated by residual alkali metals. As a result, even if a high frequency voltage is applied to the deflection electrode, light emission occurs in this part,
This light reaches the photocathode and the phenomenon of background rise on the fluorescent surface is eliminated.

Hereinafter, the present invention will be explained in more detail with reference to the drawings and the like.

FIG. 2 is a sectional view showing the manufacturing process of the streak tube manufacturing method of the present invention. Portions common to the streak tube shown in FIG. 1 are designated by the same reference numerals.

First, the configuration of this streak tube will be explained.

The streak tube according to the present invention includes a space inside a vacuum-tight container 3 including a photocathode 4, a mesh electrode 5, a focusing electrode 6, and an aperture electrode 7, a deflecting electrode 8,
The space inside the vacuum-tight container 3 containing the fluorescent surface 9 is divided by partition walls 30. This partition wall 30 is provided with an opening 13, and a lid 14 is made to correspond to this opening 13. FIG. 3A shows a state in which the lid 14 closes the opening 13, and FIG. 3B shows a state in which the lid 14 opens the opening 13.

The lid 14 is rotatably fixed to the partition wall 30 with a pin 15, and during the manufacturing process, it is shown in FIG.
It is maintained in the closed shape shown in FIG. 3A, and after completion, it is clamped and fixed by leaf springs 16 provided on the partition wall 30. The center of this aperture 13 is aligned with the tube axis, and its position in the tube axis direction is located at or near the crossover point 11 where the photoelectron beam is focused.

Next, the method for manufacturing the streak tube was repeated in a second manner.
This will be explained with reference to the figures.

An exhaust pipe 19 connected to a vacuum pump (not shown) is provided in a space (hereinafter referred to as a first space) in which the photocathode 4, mesh electrode 5, focusing electrode 6, and aperture electrode 7 are to be included.

In addition, an exhaust pipe 20 is similarly provided in the space within the vacuum-tight container 3 (hereinafter referred to as the second space) where the deflection electrode 8 and the fluorescent surface 9 are contained.

These spaces are filled with the lid 14 during the manufacturing process.
are separated by closing the opening 13 in the partition.

A branch pipe 17 containing an alkali metal and a branch pipe 18 containing an antimony evaporation source are connected to the first space.

First, each space in the container is evacuated to a predetermined vacuum.

Next, a magnetic force is applied to the antimony evaporation source from the outside through the branch pipe 18 accommodating the antimony evaporation source, the antimony is taken out into the streak tube, and antimony is evaporated onto the photocathode substrate 1 by heating with electricity.

Next, the alkali metal is evaporated from the branch pipe 17 and combined with antimony on the photocathode substrate 1.

At the same time, the photoelectric sensitivity of the photocathode is monitored, and when the maximum sensitivity is slightly exceeded, the branch pipe 18 containing the alkali metal is
Cut out.

The branch pipe 17 containing the antimony evaporation source is also cut out.

The container is further heated to stabilize the photocathode.
At this time, excess alkali metal is discharged to the outside of the container 3. After this, the exhaust pipes 19 and 20 are cut out,
The streak tube is completed.

After completion, when the streak tube is turned upside down as shown in Fig. 2 (in its normal usage position), the lid 14 will be placed under the opening 13 due to the gravity acting on itself, and the leaf spring 16 will be placed under the opening 13.
The tip of the lid 14 is captured and fixed. Note that FIG. 3B is shown with the top and bottom upside down compared to the usage state.

FIG. 4 is an explanatory diagram showing a second configuration of the partition wall and lid of the streak tube.

The lid 14 is fixed to a support rod 41 provided on the outer periphery of the partition wall 30 via a bimetal 42 . When the streak tube is at room temperature, the lid 14 does not cover the opening 13, as shown in FIG. 4C.
When feeding alkali metal, the inside of the streak tube is heated to about 200℃, so bimetal 42
It is curved and kept covering the opening 13 as shown in Figure B.

Such a configuration can also prevent the alkali metal from entering the second space.

FIG. 5 is an explanatory diagram showing a third structure of the partition wall and lid of the streak tube.

The lid 13 is fixed to one end of a rotating shaft 51 rotatably directed to a shaft 50 provided on the partition wall 30.

A head 52 made of a ferromagnetic material is fixed to the other end of the rotating shaft 51, and is kept in the position shown in FIGS. 5A and 5B during the manufacturing process to close the opening 13.

By applying magnetic force to the head from the outside or changing the posture of the streak tube after manufacturing is completed,
As shown in FIG. 5C, the leaf spring 53 holds the opening 13 in a position that does not prevent it from opening.

FIG. 6 is an explanatory diagram showing a fourth configuration of the partition wall and lid of the streak tube.

FIGS. 6A and 6B show the manufacturing state, and FIGS. 6C and D show the usage state.

In the manufactured state, the lid 14 is held against the partition wall 3 by the spring 61.
It is pressed against the opening 13 of 0.

60 is a frame that receives the lid 14, and receives the lid 14 after manufacturing is completed. Note that the spring 61 has a bent end 61a, which comes into contact with the shoulder portion of the lid 14 and serves to prevent the lid 14 from moving.

Since the streak tube according to the present invention is constructed and manufactured as described above, alkali metal is not introduced into the vicinity of the deflection electrode when forming the photocathode, and even when a high frequency voltage is applied to the deflection electrode, Unnecessary light emission in this portion can be eliminated. Next, the results of a comparative test of images on a fluorescent surface of streak tubes manufactured by the manufacturing method of the present invention and streak tubes manufactured by a conventional manufacturing method and having similar shapes will be described.

The photocathode of the streak tube is irradiated with a pulsed light source (mode locked dye laser light with a repetition rate of 130 MHz), and a sine wave voltage synchronized with the pulsed light is applied to the deflection electrode to perform continuous and repeated deflection.

FIG. 7A shows a comparison between the output of the streak tube according to the present invention and the output of a conventional streak tube.

In the case of the conventional product shown in Figure 7A, the brightness of the valley, which is background noise, is 90% compared to the peak brightness.
% has been reached.

On the other hand, it can be said that the background noise of the output of the streak tube according to the present invention shown in FIG. 7B is reduced to less than 1% of the peak and can be almost ignored.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view showing the configuration of a conventional streak tube, and a schematic diagram showing the relationship between a photocathode and an optical image. FIG. 2 is a sectional view showing the manufacturing process of the streak tube manufacturing method of the present invention. FIG. 3 is an explanatory diagram showing the relationship between the partition wall and the lid of the streak tube shown in FIG. 2. FIG. 4 is an explanatory diagram showing a second configuration of the partition wall and lid of the streak tube. Fifth
The figure is an explanatory view showing a third configuration of the partition wall and lid of the streak tube. FIG. 6 is an explanatory diagram showing a fourth configuration of the partition wall and lid of the streak tube. FIG. 7 is a graph comparing the operating characteristics of a streak tube manufactured by the method of the present invention and a conventional equivalent. 1...Window into which the optical image enters, 2...Output window, 3
... Vacuum-tight container, 4 ... Photocathode, 5 ... Mesh electrode, 6 ... Focusing electrode, 7 ... Aperture electrode, 8 ... Deflection electrode, 9 ... Fluorescent surface, 11 ... Crossover point, 13...Opening provided in the partition wall,
14... Lid, 16... Spring, 17... Branch pipe accommodating alkali metal, 18... Branch pipe accommodating antimony evaporation source, 19... Photocathode side (first space)
exhaust pipe, 20...exhaust pipe on the fluorescent surface side (second space), 30...partition wall, 42...bimetal, 52
...Ferromagnetic piece, 60...Frame, 61...Spring.

Claims (1)

[Claims] 1. In a method for manufacturing a streak tube that deflects and observes photoelectrons emitted from a photocathode, a first tube is formed in a container that is evacuated to form a vacuum, and includes at least a surface on which a photocathode is formed and a focusing electrode. a second space including at least a deflection electrode and a fluorescent surface;
an assembly step in which the space is separated by a partition wall having an opening in the tube axis at a position where the opening is located at or near a photoelectron crossover point, and a lid that is closed during the manufacturing process is provided at the opening; a step of evacuating the first and second spaces; a step of introducing metal forming a photocathode from a branch pipe communicating with the first space to form a photocathode; and cutting the branch pipe. The method is characterized by comprising a step of evacuation while heating the inside, and discharging material for forming the photocathode that does not contribute to the formation of the photocathode, and a step of removing the lid from the opening after the evacuation is finished. A method for manufacturing streak tubes.