JP2817936B2 - Traveling wave type deflection electrode - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a traveling wave type deflection electrode for deflecting a charged particle beam by a traveling wave electric field in a vacuum, and more particularly, to a distribution in a beam traveling direction and a width direction orthogonal to the deflection direction. The present invention relates to a signal-wave-type deflection electrode capable of applying a deflection voltage that is not provided in accordance with the traveling speed of charged particles.

[Prior art]

In a vacuum device, for example, an electron tube such as a streak tube or an oscilloscope, there are various methods for deflecting charged particles by an electric field. In the simplest configuration, two simple flat conductive electrodes (deflecting plates) face each other. However, when a charged particle is deflected by a high-frequency (high-speed) electric signal, the frequency characteristic of the deflection system is limited by a band determined by a time during which electrons pass through the deflection plate (electron transit time). In order to reduce the electron transit time effect, the deflection plate may be shortened or the acceleration voltage may be increased to increase the electron transit speed. Not a target. In order to widen the frequency band without lowering the deflection sensitivity and effective deflection range, the traveling speed of the deflection voltage, which is higher than the speed of the electrons, is delayed by causing the deflection plate to have a certain delay structure, and passes through the deflection plate. It is necessary to obtain a traveling wave deflection electric field which is almost equal to the electron traveling speed. As shown in Television, Vol. 18, No. 6, pp. 46 to 51, a deflecting plate is divided into small portions in the beam traveling direction and one of the deflecting electrodes for obtaining the traveling wave deflecting electric field is used. There is a lumped-constant-type deflecting electrode with a split-type deflecting plate having a delay structure composed of a constant K-type constant-pass filter circuit balanced by L and C lumped constants by connecting the plates with a small inductance. A delay line having a zigzag shape in the width direction orthogonal to the beam traveling direction and the deflection direction delays the traveling speed (component) of the deflection voltage in the beam traveling direction. As has been done,
A so-called meander type traveling wave deflection system in which comb-shaped electrode wires are combined with their phases shifted, or a prismatic linear electrode is bent in a zigzag shape in the width direction orthogonal to the beam traveling direction and deflection direction. Also, a trough-type signal wave deflecting system that is an improvement of this is devised. Further, there has been proposed a meander type traveling wave deflection system or trough type signal wave deflection system in which a dielectric is mounted on one side (non-electron beam side) of a zigzag bent linear electrode. Japanese Patent Publication No. Sho 44-16697, Japanese Patent Publication No. Sho 53-26475, and Japanese Patent Publication No. Sho 56-27984 disclose the use of a spiral delay line to delay the traveling speed (component) of the deflection voltage in the beam traveling direction. . On the other hand, in a vacuum device such as a streak tube or an oscilloscope having a charged particle deflecting electrode and an output surface, the charged particles are discharged from the output surface by a focus system in the vacuum device.
It is made to focus on a point. Therefore, when a time-varying voltage is applied to the deflection electrode to deflect the charged particle beam, the charged particles simultaneously incident on the deflection electrode must be deflected to the same position on the output surface.

[Problems to be solved by the invention]

However, since the charged particle beam spreads due to the different initial velocities of the individual charged particles themselves, they always have a finite spread in the width direction even when passing through the deflection electrode. For a charged particle beam having such a spread in the width direction, as shown in a streak tube shown in FIG. 6, a conventional meandering deflection electrode 10 (two overlapping in a direction perpendicular to the paper surface of FIG. 6). ), Trough-type deflecting electrodes, spiral deflecting electrodes, etc., which are not uniform in the beam running direction and the width direction orthogonal to the deflecting direction, electrons travel in the Z direction, and output (sweep)
When arranged so as to be deflected in the Y direction (the direction perpendicular to the paper surface of FIG. 6) on the surface 20, the one-pitch line 10A is oriented in the X direction, so that the voltage V applied to the deflection electrode 10 is As time change is increased (frequency is increased),
As shown in the figure, a voltage distribution occurs in the X direction of the deflection electrode 10. In FIG. 6, 12 is a photocathode, 14 is a mesh acceleration electrode, 16 is a focus electrode, and 18 is an anode. That is, when two time-varying ramp voltages V ₁ and V ₂ are applied to the deflection electrode 10 as shown in FIG. 9, the electron beam is deflected in a direction perpendicular to the plane of FIG. Is done.
Here, if the temporal change of the voltage applied to the deflection electrode 10 is increased, a voltage distribution as shown in FIG. 7 is formed in the X direction of the deflection electrode 10, so that the deflection electrode 10
The electrons a, b, and c, which have spread in the X direction, are deflected by receiving different voltages, and have different amounts of deflection, so that they are output to different positions in the Y-axis direction and output to the output surface 20. The above will cause blurring. Actually, in the next line in FIG. 7, the phase of the voltage applied to each of the electrons a, b, and c is
Since the phase is opposite to that in the figure, the blur amount is considerably corrected. However, as can be seen from the manner in which the beam is focused (see FIG. 6), the distance between the electrons a, b, and c Since it becomes narrower as approaching, it is not completely corrected and a phase shift actually occurs. Therefore, on the output surface 20, a,
A difference in the amount of deflection occurs between each of the electrons b and c, which results in blurring of the beam. The blur in the Y-axis direction is caused by applying a high-speed voltage to the deflection electrode 10. However, for example, in a streak tube having a time resolution of femtosecond, it becomes a problem even in a practical range. In the case of a simple deflecting system including only two opposing deflecting plates or a split type deflecting plate, the band is originally low.
It was impossible to apply a high-speed deflection voltage. The present invention has been made to solve the above-mentioned conventional problems, and applies a deflection voltage having no distribution in the width direction orthogonal to the beam traveling direction and the deflection direction in the beam traveling direction according to the speed of the charged particles. It is an object of the present invention to provide a traveling wave type deflection electrode capable of performing the following.

[Means for achieving the object]

The present invention is a traveling wave type deflection electrode for changing a charged particle beam by a traveling wave electric field in a vacuum, and has a uniform configuration in a width direction of a plate-like electrode orthogonal to a beam traveling direction and a deflection direction, And a pair of opposing plate-shaped electrodes formed in the traveling direction of the beam over substantially the entire width of the plate-shaped electrodes, and at least one of the plate-shaped electrodes includes a dielectric material and the dielectric material. It has a three-layer structure consisting of two electrode plates sandwiching the body, its outer electrode plate is grounded, and a connection lead for applying a deflection voltage to the end surface of the beam side electrode plate in the beam traveling direction is provided. The object has been achieved in that the deflection voltage propagates from the input end face in the beam running direction of the plate-shaped electrode to the output end face at a propagation speed substantially equal to the beam running speed. Further, both of the plate-like electrodes have the three-layer structure, and a deflection voltage having the same amplitude and opposite signs is applied to both of them. Further, the connecting portion between the plate-shaped electrode and the connection lead has a substantially isosceles triangular shape with the connection point of the connection lead as the apex and the end surface of the plate-shaped electrode as the base. Further, the plate-like electrode is bent in a zigzag shape in a deflection direction.

[Action and effect]

The present invention relates to a traveling wave type deflection electrode for deflecting a beam of charged particles 30 by a traveling wave electric field in a vacuum as in the first embodiment shown in FIG.
Direction) and a width direction (X direction perpendicular to the paper plane) orthogonal to the deflection direction (Y direction), and a pair of opposing plates formed continuously in the beam running direction. Electrode
32, 34 and connection leads 3 for applying a deflection voltage to at least one end surface (32) of the plate-like electrodes in the beam traveling direction.
6 and 38, for example, the deflection voltage generated by the deflection voltage generator 40 propagates from the beam traveling direction input side end face 32A of the plate-shaped electrode 32 to the output side end face 32B at a propagation velocity substantially equal to the beam traveling velocity. It is something to do. In this manner, the voltage distribution in the width direction orthogonal to the beam traveling direction and the deflection direction of the deflection electrode can be eliminated. Therefore, even when a high-speed deflection voltage is applied to charged particles having a wide beam, all the charged particles simultaneously incident on the deflection electrode can be deflected to the same position on the output surface. It can prevent blurring. Also, since the speed of the deflection voltage in the beam traveling direction and the speed of the charged particles substantially match, the band can be increased.

【Example】

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. As shown in FIG. 1, a first embodiment of the present invention is a traveling wave type deflection electrode for deflecting a charged particle 30 traveling in a Z direction in a vacuum in a Y direction by a traveling wave electric field. On the other hand, a plate electrode 32 having a three-layer structure composed of a dielectric 50 and two plate electrode plates 52 and 54 sandwiching the dielectric 50 is provided, and a beam side electrode plate 52 of the plate electrode 32 is provided. From the deflection voltage generator 40 to the transmission line 56 from the direction in which the charged particles 30 are incident.
A deflection voltage is applied via the connection lead 36, and the outer electrode plate 54 is connected to the ground lines of the transmission lines 56 and 58, so that the three-layer plate electrode 32 has a transmission line structure. Things. As the dielectric 50, for example, LiTaO ₃ can be used. The electrode plates 52 and 54 preferably have high conductivity, and for example, a copper plate can be used. Alternatively, a highly conductive material, for example, Al may be directly vacuum-deposited on the dielectric 50, or Au may be vacuum-deposited with Cr as a base to form a three-layer structure. The other plate electrode 34 is a normal flat plate and is grounded. In the figure, 56 is a transmission line composed of a coaxial cable, a strip line, etc., for applying the deflection voltage generated by the deflection voltage generator 40 to the plate-shaped electrode 32 without distorting the voltage waveform. Is a transmission line for grounding the output-side end face of the electrode plate 52 against the terminating resistor 60, and the grounds of the transmission lines 56 and 58 are connected to the outer electrode plate 54. Hereinafter, the operation of the first embodiment will be described. The charged particle 30 traveling in the Z direction is an electrode plate of the plate electrode 32.
It is deflected in the Y direction by the voltage applied to 52. In this case, the electrode plate 52 through which the deflection voltage passes is a grounded electrode plate 54.
In addition, it passes between the opposing plate-like electrodes 34 to form a strip line transmission line as a whole. Here, since the electrode plate 52 is plate-shaped, the deflection voltage does not distribute in the X direction, but moves only in the Z direction with time. The moving speed of the electric field can be adjusted to the moving speed of the charged particles 30 by the dielectric constant of the dielectric 50, the interval between the electrode plates 52 and 54, and the interval between the plate electrodes 34 facing the electrode plate 52. Accordingly, the deflection voltage travels at substantially the same speed as the charged particles 30, and simultaneously the charged particles 30 that have entered the deflection electrode and spread in the X direction are deflected by the same deflection voltage, so that the deflection voltage on the output surface is reduced. There is no spread in the Y direction. In addition, since the traveling wave type deflection electrode is matched with the speed of the charged particles 30 and the moving speed of the electric field, the bandwidth of the deflection electrode is wide,
A high-speed deflection voltage (high-frequency voltage) can be applied to the deflection electrode. The output end of the electrode plate 52 is connected to the transmission line 58 similarly to the input end, and is terminated by a terminating resistor 60 so that the reflection of the voltage wave does not finally occur. It is also possible to omit the terminating resistor 60 and open the terminating end. Next, a second embodiment of the present invention will be described in detail. In this second embodiment, as shown in FIG. 2, two deflection voltage generators 40A and 40B for generating deflection voltages by facing plate electrodes 32 having the same three-layer structure as in the first embodiment are provided. Installed near the electrode plate 52 so that there is no need to connect with a transmission line,
Voltages of equal amplitude and opposite signs are generated. Also, the terminal ends immediately after the output end of the electrode plate 52. The other points are the same as those in the first embodiment, and the description is omitted. Hereinafter, the operation of the second embodiment will be described. When deflection voltages having the same amplitude and opposite signs are applied to the electrode plates 52 of the two opposing plate electrodes 32, an intermediate point between the two deflection electrodes can be regarded as a virtual ground potential. At this time, the distance between the deflection electrodes is D, the thickness of the dielectric 50 is d, and the relative permittivity is εr.
Then, the electrode plate sandwiched between the virtual ground plane and the upper electrode plate 54
The equivalent relative permittivity εr ′ of 52 is obtained by the following equation, ignoring the end effect. εr ′ = (d + D · εr / 2) / (d + D / 2) (1) where the equivalent relative permittivity εr ′ given by equation (1)
Are the (signal) electrode plate 52 and the virtual ground plane, and the (ground) electrode plate 54
It can be regarded as the relative dielectric constant of the transmission line having the strip line structure constituted by the above. Generally, the traveling speed V of the electric field on the transmission line is given by the following equation. Therefore, in the transmission line on the deflection electrode, μ = μ ₀ , ε =
Since it can be considered as ε ₀ · εr ′, the following equation holds. Here, C is the speed of light. As practical values, D = 5 mm, d = 1 mm, and dielectric 50
If LiTaO ₃ with εr = 43 is used, εr ′ = 31 and V = 5.38 × 10 ⁷ (m / sec). This makes the electron 8.2
It corresponds to the speed when accelerating at kV. Therefore, it can be seen that such a deflection electrode works effectively with a practical acceleration voltage of an electron tube such as an oscilloscope or a streak tube. As in the second embodiment, when the plate-like electrodes 32 having a three-layer structure are opposed to each other and voltages having the same amplitude and opposite signs are applied to each other, the voltage required to apply the same electric field to the load particles 30 is reduced. This has the advantage that the amplitude is only half that of the first embodiment. Next, another embodiment of the plate electrode 32 having a three-layer structure will be described. The plate-like electrode 32 of the following embodiment may be used in combination with a normal plate-like electrode 34 as in the first embodiment, or may be used in the second embodiment.
As in the embodiment, two plate electrodes 32 having the three-layer structure can be used to face each other. As shown in FIG. 3, the plate electrode 32 according to the third embodiment of the present invention has a wide electrode plate 52 at the input / output end of the electrode plate 52, for example, having a width of 5 to 20 mm. The width of the signal line of the transmission line 56 connecting the electrode 40 and the electrode plate 52 is, for example, 0.5 to 1
When the transmission line is as thin as
An approximately isosceles triangular connection plate 62 having a taper of 0.5 to 1 mm on the 56 side and a taper of 5 to 20 mm on the electrode plate 52 side is used. In the third embodiment, the electrode plate 54 has a structure extended near the connection plate 62, and the end of the rectangular extension plate 64 can be connected to the ground of the transmission lines 56 and 58. Thereby, reflection of the deflection voltage due to a difference in size between the transmission lines 56 and 58 and the electrode plate 52 can be eliminated. Next, a fourth embodiment of the present invention will be described in detail. In the fourth embodiment, as shown in FIG. 4, in a traveling wave type deflection electrode for deflecting charged particles traveling in the Z direction in the Y direction, the two electrode plates 52 and 54 are bent in a zigzag manner in the deflection direction. , While keeping the interval constant, for example,
It has a slow wave structure of the voltage wave in the Z direction, such as + Z → + Y → + Z → −Y → + Z → + Y. In the fourth embodiment, the speed of the electric field determined by the dielectric constant and the structure of the dielectric 50 can be further reduced. Next, a fifth embodiment of the present invention will be described in detail. In the fifth embodiment, as shown in FIG. 5, a plate electrode having a bent structure similar to that of the fourth embodiment, wherein the gap of the concave portion of the outer electrode plate 54 is set to zero, and the outer surface thereof is made flat. It is. In the present embodiment, since one of the electrode plates 54 has a planar shape, the shape accuracy is easily obtained. In the above description, the present invention has been described using a streak tube as an example, but the scope of the present invention is not limited to this, and other electronic tubes such as an oscilloscope and general electronic tubes other than the electronic tube are used. It is apparent that the present invention can be similarly applied to the case where the charged particle beam is to be deflected by an electric field.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a configuration of a first embodiment of a traveling wave type deflection electrode according to the present invention, FIG. 2 is a cross-sectional view showing a configuration of a second embodiment of the present invention, FIG. FIG. 4 is a perspective view showing a configuration of a third embodiment of the present invention. FIG. 4 is a perspective view showing a configuration of a fourth embodiment of the present invention. FIG. 5 is a perspective view showing a configuration of a fifth embodiment of the present invention. Fig. 6, Fig. 6 is a longitudinal sectional view of a streak tube for explaining the problems of the prior art, Fig. 7 is a transverse sectional view taken along the line VII-VII of Fig. 6, and Fig. FIG. 3 is a diagram illustrating an example of a voltage applied to an electrode. 30: charged particles, 32, 34: plate electrode, 32A: input end face, 32B: output end face, 36, 38: connection lead, 40, 40A, 40B ... deflection voltage generator, Z ... Beam running direction, Y ... Deflection direction, X ... Width direction, 50, 50A, 50B, 50C ... Dielectric, 52, 54 ... Electrode plate, 56, 58 ... Transmission line, 62 ... Connection Board.

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-59-148247 (JP, A) JP-A-58-220341 (JP, A) JP-B-45-9569 (JP, B1) (58) Field (Int.Cl. ⁶ , DB name) H01J 31/50 H01J 29/74 H01J 23/26-23/34

Claims (4)

(57) [Claims] 1. A traveling-wave type deflection electrode for deflecting a charged particle beam in a vacuum by a traveling-wave electric field, wherein the traveling-wave-type deflection electrode has a uniform configuration in a width direction of a plate-like electrode orthogonal to a beam traveling direction and a deflection direction. And a pair of opposed plate-shaped electrodes formed in the traveling direction of the beam over substantially the entire width of the plate-shaped electrodes, and at least one of the plate-shaped electrodes includes a dielectric and It has a three-layer structure consisting of two electrode plates sandwiching a dielectric, its outer electrode plate is grounded, and a connection lead for applying a deflection voltage to the end surface of the beam side electrode plate in the beam running direction is provided. A traveling wave type deflection electrode wherein a deflection voltage propagates from an input end face to an output end face in a beam traveling direction of the plate-like electrode at a propagation velocity substantially equal to a beam traveling velocity. 2. The traveling-wave deflection electrode according to claim 1, wherein both of said plate-like electrodes have said three-layer structure, and a deflection voltage of the same amplitude and opposite sign is applied to both. A traveling wave type deflection electrode characterized by the above-mentioned. 3. The traveling-wave deflection electrode according to claim 1, wherein the connecting portion between the plate-like electrode and the connection lead has a connection point of the connection lead as an apex and an end surface of the plate-like electrode as a bottom.
A traveling wave type deflection electrode having an equilateral triangular shape. 4. The traveling wave type deflection electrode according to claim 1, wherein said plate-like electrode is bent in a zigzag shape in a deflection direction.