JPS61250946A - Streak tube and its using method - Google Patents

Abstract

PURPOSE:To increase the time resolution and the red sensibility by forming a projection at a portion of the inner face of incident window while providing a photoelectric face onto the surface at the projected end through an electrode thin film to be connected to the external circuit and arranging in close proximity to the acceleration electrode. CONSTITUTION:In a streak tube, an electronic image focuses onto the photoconductive face of incident window 101 is accelerated quickly through a mesh electrode 105 to obtain the time sequential variation of the strength of image onto a screen 109 through a focus, aperture and deflection electrodes 106-108. A glassfiber 131 is secured in the center of the incident window 101 to form a photoelectric face 134 onto the surface at the projected end through an electrode thin film 132 to be connected with the external circuit and arranged in close proximity of the mesh electrode 105. While the electric field of the photoelectric face 134 is increased through the electric field augment effect achieved by the projected structure. Consequently, high time resolution can be obtained by driving such that sharp variation of electric field is applied only for the necessary quite short time interval.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a streak tube that can measure temporal changes in brightness that change at high speed on the order of picoseconds, and a method of using the same.

(Prior Art) A streak device is a device that converts a temporal intensity distribution of light to be measured into a spatial intensity distribution on an output surface.

It is used for analysis of ultra-high continuous light development because it can provide time resolution on the order of picoseconds.

First, the configuration and operation of a conventional streak device will be briefly described.

FIG. 7 includes a tube axis showing the configuration of a conventional streak tube,
2 is a cross-sectional view taken along a plane parallel to a deflection electrode, and a schematic diagram showing the relationship between a photocathode and an optical image.

FIG. 8 is a cross-sectional view of the streak tube taken along a plane that includes the tube axis and is perpendicular to the deflection electrode.

One end surface of the vacuum-tight container 103 of the streak tube forms an entrance window 101 where an optical image to be analyzed is formed, and the other end surface forms an exit window 102 from which a processed optical image is output.

Along the tube axis of this vacuum-tight container 103, an entrance window 101
A photocathode 104 , a mesh electrode 105 , a focusing electrode 106 , an aperture electrode 107 , a deflection electrode 108 , and a fluorescent surface 109 are arranged in this order between and the exit window 102 .

Then, a higher voltage is applied to the focusing electrode 106, the mesh electrode 105, and the aperture electrode 107 in this order to the photocathode 104, and then the aperture electrode 1 is applied to the fluorescent surface 109.
Apply the same potential as 07.

A device (not shown) passes the photocathode 10 through the entrance window 101.
4, an optical image 104 is formed on a line passing through the center of the photocathode 104.
Suppose that a is projected.

The photocathode 104 emits an electronic image corresponding to the optical image,
The emitted electrons are accelerated by the mesh electrode 105,
Focused by focusing electrode 106 and aperture electrode 107
and is made incident on the gap between the deflection electrodes 108.

While this linear electron image passes through the gap between the deflection electrodes 108, a gradient deflection voltage is applied to the deflection electrodes 108.

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. 7, parallel to the plane of the paper in Fig. 8), and its strength is proportional to the deflection voltage. .

The light is then deflected by the deflection electric field of the deflection electrode 108 and made incident on the fluorescent surface 109.

The direction of deflection is indicated by arrow 120 in FIG.

A linear electron beam is scanned on the fluorescent surface 109 perpendicular to the linear direction, so that the fluorescent surface 109 is finally scanned.
An optical image, a so-called streak image, is formed on the photocathode 9 by arranging the linear optical images projected onto the photocathode 104 sequentially in time perpendicular to the direction of the line.

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 104.

(Problems to be Solved by the Invention) In the conventional streak tube described above, since the photoelectrons emitted from the photocathode have various energies, a group of photoelectrons emitted from the photocathode at the same time is fluorescent, which is a swept surface. The times at which the surface is reached are scattered and have a time modulus.

This temporal expansion is the most important factor that impairs the time resolution of streak tubes.

In order to reduce this temporal spread, the electrons emitted from the photocathode are uniformly and rapidly accelerated.

Generally, in a streak tube, as shown in FIGS. 7 and 8, a mesh electrode 105 is provided close to the photocathode 104, and the photoelectrons are rapidly accelerated so that the photoelectrons are generated while they are traveling at low speed. This keeps the travel time spread small.

The travel time spread Δt that generally occurs around this area is expressed by the following equation.

△t=2.34X10-6 X (Δε)'/2/
E (S) Here, E is the electric field (V
/ m ) and Δε is the half-width (e V) of the energy distribution of photoelectrons emitted from the photocathode.

For example, if 100 OV is applied between the photocathode and the mesh and the distance therebetween is 1 mm, E becomes lXIO3 (V/m).

On the other hand, Δε is generally determined by the wavelength of the light to be measured and the type of photocathode used. For example, if the wavelength is 0.53 μm and the photocathode is a multi-alkali photocathode, Δε is approximately 0.5 e
It is V.

By substituting these values into the above equation, it can be seen that the travel time spread of photoelectrons near the photocathode at this time is about 1.7 ps.

In order to further reduce the travel time spread, the electric field between the photocathode and the mesh may be increased.

Furthermore, the inventors of the present invention have also focused on the fact that increasing the electric field can increase the sensitivity of the photocathode in the long wavelength region, although this is conventionally known.

FIG. 9 is a graph showing the relationship between the electric field between the photocathode and the mesh electrode and the wavelength sensitivity of the photocathode.

This graph uses S-20 (standard of the American Electronics Industries Association) as a photocathode, and uses wavelengths of 0.6 μm, 0.8 μm, and 0.5 μm.
The electric field dependence of 85 μm incident light is measured.

This graph shows that as the electric field increases, the sensitivity increases,
In particular, it shows that the sensitivity on the long wavelength side increases.

As is well known, in order to increase the electric field on the surface of the photocathode, it is sufficient to narrow the distance between the photocathode and the mesh and increase the voltage applied therebetween.

However, in conventional streak tubes, there is a problem in that dark current increases when the electric field between the photocathode and the mesh electrode is increased.

FIG. 10 is a graph showing the relationship between accelerating electric field and dark current in a conventional Q-streak tube.

As shown in FIG. 10, as the accelerating electric field is increased, the dark current emitted from the photocathode gradually increases.

The generation of such dark current reduces the S/N of the streak image.

If there are minute scratches on the surface of the photocathode, electrons are emitted by field emission. The inventors of the present invention refer to the noise image that appears on the output surface due to these electrons as white flaws (or white spots).

In addition, in order to improve the S/N of the streak image obtained with a streak tube, photoelectrons are emitted from the photocathode for a short period of time when the output surface is swept, and at other times, the voltage of the mesh electrode is lowered. One possible method is to prevent photoelectrons from being generated from the surface.

In order to increase the electric field between the photocathode and the mesh electrode, it is sufficient to increase the amplitude of the applied pulse voltage during operation in the forward direction (acceleration direction), but generation of short duration voltage pulses with large amplitudes is difficult. It's not easy.

As described above, by narrowing the distance between the photocathode and the mesh electrode, which is the accelerating electrode, a large accelerating voltage can be obtained with a low voltage.

However, reducing the interval to, for example, 1 mm or less poses a problem in that it is difficult to achieve mechanical precision.

Furthermore, when a photocathode manufacturing method is adopted in which photocathode material is supplied to an entrance window through a mesh electrode, there is a problem in that the photocathode is not formed in a portion that is in the shadow of the mesh electrode.

For this reason, in the streak tube, the distance between the photocathode and the mesh electrode cannot be made extremely narrow.

The main object of the present invention is to provide a streak tube and method of using the same that can solve the above-mentioned problems.

(Means for Solving the Problem) In order to achieve the above object, the streak tube according to the present invention is an electron tube having a photocathode formed on the inner surface of an entrance window and an electrode for accelerating photoelectrons generated by the photocathode. A protrusion is formed on a part of the inner surface of the entrance window, a photocathode is formed on the surface of the protruding end of the protrusion through an electrode thin film connected to an external circuit, and the photocathode is formed on the inner surface of the entrance window. It is arranged closest to the accelerating electrodes arranged facing each other, and is configured to accelerate photoelectrons with the accelerating electrodes and deflect them with the deflecting electrodes.

Further, the method of using the streak tube according to the present invention includes an airtight container having an entrance window, a protrusion formed on a part of the inner surface of the entrance window, and a surface of the protruding end of the protrusion connected to an external circuit. A photocathode formed through an electrode thin film, an accelerating electrode for rapidly accelerating the photoelectron beam emitted from the photocathode in the direction of an output screen, and a photoelectron image emitted from the photocathode onto the output screen. an anode electrode having a focusing electrode and an aperture for re-imaging the photoelectron beam, a deflection electrode for sweeping this photoelectron beam onto an output screen, a fluorescent surface for forming an output image, and an inner surface of the fluorescent surface. It is configured to apply a pulse-like accelerating voltage to the accelerating electrode of the streak tube consisting of the provided output window in the acceleration direction so that the photoelectrons reach the screen only when the photoelectron beam is swept.

(Example) The present invention will be described in more detail below with reference to the drawings and the like.

1 and 2 are diagrams showing a first embodiment of the streak tube according to the present invention, in which FIG. 1 is a sectional view taken along a plane parallel to the deflection electrode, and FIG. 2 is a cross-sectional view taken along a plane parallel to the deflection electrode. FIG. 3 is a cross-sectional view taken along a plane that includes the tube axis of the streak tube and is perpendicular to the deflection electrode.

FIG. 3 is an enlarged sectional view showing the relationship between the central part of the entrance window and the accelerating electrode in the first embodiment.

This embodiment does not differ from the structure of the streak tube described above with reference to FIGS. 7 and 8, except for the relative positional relationship between the entrance window and the accelerating electrode.

A glass fiber 1 with a diameter of 40 μm is placed at the center of the entrance window 101.
31 is fixed so as to extend to the entrance window surface.

This glass fiber 131 can be fixed by making a small hole in the entrance window, inserting the glass fiber 131, and heating it.
As described later, the entrance window is divided and corresponding grooves are provided.
The glass fiber 131 may be sandwiched and heated to be fixed.

The glass fiber 131 extends 200 μm from the inner surface of the entrance window toward the mesh electrode, which is an accelerating electrode, and the radius of curvature of the surface is 20 μm.

An electrode thin film 132 connected to an external circuit is formed on the side surface of the protruding end of the glass fiber 131 and on the inner surface of the entrance window.

A photocathode 134 is formed on the surface of the glass finder 131 via the electrode thin film 132 attached to the side surface of the glass fiber 131.

The distance between the photocathode 134 and the mesh electrode 105 is approximately 2 m.
It is m.

Although it is sufficient that the photocathode 134 is formed on the protruding end, there is no problem in operation even if the photocathode 134 is attached to the inner surface of the entrance window.

The field enhancement effect resulting from structures protruding from the substrate has been well known for some time.

FIG. 4 is a schematic diagram for explaining the electric field enhancement effect.

Generally, when a voltage of V [■] is applied between parallel plates separated by a distance d (m), the average electric field E formed between them is E
= V/d (V/m).

At this time, as shown in FIG. 4, it is assumed that there is a protrusion on one of the plates whose height h can be considered to be sufficiently small compared to the distance d.

If the top of the protrusion is a hemisphere with radius r, and the column below is cylindrical, for example, the electric field on the surface near the top with radius r will be enhanced by a factor of βE and β.

β is expressed by the following formula.

β−h/r+2・・・・・・・・・・・・・・・
-(l)' For example, if r is 10 μm and height h is 100 μm, β is 10, which means that the electric field will be enhanced about 10 times.

In general, when the protrusion does not satisfy h<<d or the shape is not cylindrical, Equation (1) does not apply, but electric field enhancement occurs, and the greater the height of the protrusion, the more pointed it becomes. It will be strengthened as much as possible.

The present invention takes advantage of this phenomenon, and in order to perform time resolution in a streak tube, incident light is incident on the photocathode in a dotted or linear manner, and only this portion is used as a photocathode. The shape of the part into which the light to be measured is incident is made to protrude in the form of a point or line, a photocathode is formed in this part, and a voltage is applied between it and the accelerating electrode.

This makes it possible to create a stronger electric field near the surface of this area compared to other areas, which is advantageous in terms of time resolution and red sensitivity of the photocathode.

On the other hand, since this strong electric field is limited to only the area where point-like or linear light is incident, the probability of bank ground rising due to an increase in dark current and the occurrence of white spots is lower than that of conventional methods. It decreases by that area ratio.

On the other hand, due to the electric field enhancement effect, the voltage applied between the photocathode substrate and the mesh electrode is l/ β is sufficient, and the gate operation becomes easy.

When formula (1) is applied, the electric field on the tip surface (the surface of the photocathode 134) of the embodiment shown in FIG. 3 becomes 12 times the electric field on the electrode thin film surface on the inner surface of the entrance window.

When a voltage of 500 μ is applied between the electrode thin film 132 and the mesh electrode 105, the electric field at the photocathode 134 is 3 K.
V/mm.

Next, the operation of the streak tube will be explained.

A device (not shown) makes the light to be measured enter the entrance window 101 at a location corresponding to the protrusion where the photocathode is formed.

A portion of the surface of the entrance window 101 other than the portion corresponding to the photocathode may be shielded.

The light to be measured is guided to the photocathode 134 by the glass fiber 131, and photoelectrons are emitted.

As mentioned above, the electric field near the photocathode 134 is extremely large, so the emitted electrons are rapidly accelerated by the mesh electrode 105, focused by the focusing electrode 106, pass through the aperture electrode 107, and enter the gap between the deflection electrodes 108. I am made to do so.

While this linear electron image passes through the gap between the deflection electrodes 108, a gradient deflection voltage is applied to the deflection electrodes 108.

The direction of the electric field generated by this voltage is perpendicular to the tube axis and the linear electron image (as shown in the cross-sectional view of Figure 1), and perpendicular to the plane of the paper.
(in FIG. 2, it is parallel to the plane of the paper), and its strength is proportional to the deflection voltage.

The light is then deflected by the deflection electric field of the deflection electrode 108 and made incident on the fluorescent surface 109.

The direction of deflection is indicated by arrow 120 in FIG.

A streak image is formed on the fluorescent surface 109 by the dotted electron beam.

FIG. 5 is a perspective view showing still another embodiment of the entrance window.

This embodiment is also applied to the streak tube described above in the same manner as described above.

Ten glass fibers 151 having the same shape as the glass fibers 131 shown in FIG. 3 are arranged at intervals of Q, 5 mm in a direction perpendicular to the sweeping direction of the streak tube.

The glass fiber 151 is formed by dividing the entrance window 104 and attaching the glass fiber 151. A corresponding groove is formed and the parts are sandwiched and welded.

An electrode thin film and a photocathode are formed in the same manner as in the case of FIG.

Similarly, the distance between the photocathode and the mesh electrode is about 2 mm.

As in the first embodiment described above, the electric field on the surface of the photocathode can be easily increased.

Ten streak images are obtained on the fluorescent surface 109 by the ten electron beams.

FIG. 6 is a perspective view showing still another embodiment of the entrance window. This embodiment is also applied to the streak tube described above in the same manner as described above.

The front surface of the entrance window 101 is formed from a fiber plate with a pitch of 5 μm, and the center of the inner surface of the entrance window 101 is
The 0 μm portion protrudes toward the mesh electrode by a height of 200 μm, and the surface of the tip is 10 mm x 200 μm.
That is.

An electrode thin film and a photocathode are formed in the same manner as in the case of FIG.

Similarly, the distance between the photocathode and the mesh electrode is about 2 mm.

The longitudinal direction of the photocathode is perpendicular to the sweeping direction of the streak tube. As in the first and second embodiments described above, the electric field on the surface of the photocathode can be easily increased.

A linear electron beam is swept from top to bottom on the fluorescent surface 109 to form a streak image.

As shown in each of the above embodiments, when the photocathode portion is made to protrude, the electric field on the surface of the photocathode can be increased, so that the temporal resolution and red sensitivity of the streak tube can be improved.

Although the area of the photocathode is smaller than that of conventional phototubes, the dark current may become large.

This problem can be solved by using:

between the photocathode and the mesh, a period of time swept on the fluorescent surface;
For example, 500V is applied with positive polarity on the mesh side only for 5 ns, and Ov is applied at other times.

In this way, the dark current contributes to the background only during the sweep, so the influence of the dark current can be extremely reduced.

In a conventional streak tube (one without a protruding photocathode), in order to generate a high electric field of 3 KV/mm as described above, it is necessary to apply a voltage of 6 KV between the photocathode and the mesh. , it is difficult to apply such a large amplitude voltage for a short period of time (for example, 5 ns).

(Effects of the Invention) As described above in detail, the streak tube according to the present invention has a protrusion formed on a part of the inner surface of the entrance window, and an electrode thin film connected to an external circuit on the surface of the protruding end of the protrusion. , and the photocathode is arranged closest to the accelerating electrode, which is disposed facing the inner surface of the entrance window. The electric field can be easily increased.

Furthermore, since a large electric field can be generated by applying a relatively low voltage, it can be driven and used so as to give a sharp change in the electric field for only a necessary extremely short period of time.

As a result, it is possible to obtain a streak tube that has high temporal resolution and high red sensitivity, and does not increase background or generate white spots.

As described above, since the amplitude of the pulse voltage when performing the gate operation can be reduced, the gate voltage generation circuit can be simplified.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a first embodiment of a streak tube according to the present invention, taken along a plane that includes the tube axis and is parallel to the deflection electrode. FIG. 2 is a cross-sectional view of the streak tube taken along a plane perpendicular to the deflection electrode. FIG. 3 is an enlarged sectional view showing the relationship between the central part of the entrance window and the accelerating electrode in the first embodiment. FIG. 4 is a schematic diagram for explaining the electric field enhancement effect. FIG. 5 is a perspective view showing still another embodiment of the entrance window. FIG. 6 is a perspective view showing still another embodiment of the entrance window. FIG. 7 includes a tube axis showing the configuration of a conventional streak tube,
FIG. 3 is a cross-sectional view taken along a plane parallel to the deflection electrodes. FIG. 8 is a cross-sectional view of the conventional streak tube taken along a plane that includes the tube axis and is perpendicular to the deflection electrode. FIG. 9 is a graph showing the relationship between the electric field between the photocathode and the mesh electrode and the wavelength sensitivity of the photocathode. FIG. 10 is a graph showing the relationship between accelerating electric field and dark current in a conventional streak tube. 101... Entrance window 102... Output window 1
03... Vacuum-tight container 104... Photocathode 10
5...Mesh electrode 106...Focusing electrode 10
7...Aperture electrode 108...Deflection electrode 10
9... Fluorescent surface 131... Glass fiber 132... Electrode thin film 134... Photocathode 1
51...Glass fiber protrusion row 161...Linear protrusion of glass fiber Patent applicant
Hamamatsu Photonics Co., Ltd. Agent Patent Attorney Inoro Hisaki 1 Kan 20 Horse] Father Ka 4 Figure 1) f7q (2) 尤wo wo Otsumen A9z + fpitsubo tO contract

Claims (5)

[Claims] (1) In a streak tube having a photocathode formed on the inner surface of the entrance window and an electrode that accelerates and deflects photoelectrons generated by the photocathode, a protrusion is formed on a part of the inner surface of the entrance window,
A photocathode is formed on the surface of the protruding end of the protrusion through an electrode thin film connected to an external circuit, and the photocathode is disposed closest to the acceleration electrode disposed facing the inner surface of the entrance window. A streak tube that accelerates photoelectrons with an acceleration electrode and deflects them with a deflection electrode. (2) A streak in which photoelectrons according to claim 1 are accelerated by an accelerating electrode and deflected by a deflection electrode, wherein the protrusion is a glass fiber provided at the center of the entrance window and extending to the surface of the entrance window. tube. (3) Accelerating photoelectrons according to claim 1, wherein the protrusions are glass fibers arranged on the entrance window at intervals in a direction perpendicular to the sweep direction and each extending to the surface of the entrance window. A streak tube that is accelerated by an electrode and deflected by a deflection electrode. (4) The protrusions are glass fibers arranged on the entrance window in a band shape perpendicular to the sweep direction, and each extending to the surface of the entrance window. A streak tube that is accelerated and deflected by a deflection electrode. (5) An airtight container having an entrance window, a protrusion formed on a part of the inner surface of the entrance window, and an electrode thin film connected to an external circuit formed on the surface of the protruding end of the protrusion. a photocathode; an acceleration electrode for rapidly accelerating a photoelectron beam emitted from the photocathode in the direction of an output screen; and a focusing electrode for refocusing a photoelectron image emitted from the photocathode onto the output screen. A streak tube consisting of an anode electrode having an electrode and an aperture, a deflection electrode for sweeping the photoelectron beam on an output screen, a fluorescent surface for forming an output image, and an output window with the fluorescent surface provided on the inner surface. A streak tube configured to apply a pulsed accelerating voltage in an accelerating direction to the accelerating electrode so that the photoelectrons reach the screen only when the photoelectron beam is swept; the photoelectrons are accelerated by the accelerating electrode and deflected by the deflection electrode. How to use.