JPS5840819B2 - Electron gun for X-ray generation - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electron gun for generating X-rays that deflects an electron beam to irradiate a target, and is capable of continuously varying the beam spot diameter on the target surface.

In order to generate X-rays, when a target made of a predetermined material is irradiated with an electron beam, it is possible to obtain X-rays with a wavelength and intensity determined by the accelerating voltage of the irradiated electron beam and the material of the target.

In the past, when analyzing materials using X-ray diffraction or fluorescent X-ray analysis, or in non-destructive testing or medical treatment, transmission methods were mostly used with short wavelengths. Hard X-rays were used, and most of the electron guns used for this purpose were of the straight-beam type, with a structure that narrowed down the beam spot diameter.

Recently, X-ray exposure using so-called soft X-rays with a wavelength of several 1 OA has started to be performed, but since long-wavelength soft X-rays are easily absorbed by materials, it is possible to improve X-ray generation efficiency. Various types of electron guns for X-ray exposure are used for this purpose.

When using soft X-rays, if a linear electron gun is used, the filament material of the electron gun, such as W or Ta, will adhere to the target and absorb the soft X-rays, causing the electron beam to become distorted. A deflection type electron gun is used, which has a structure that prevents filament material from adhering to the target.

Figures 1 and 2 are configuration diagrams of a conventionally used deflection type electron gun, where 1 is a filament, 2 is an electron beam,
3a and 3b are electrostatic deflection plates, 4 is a target, 5 is a soft X-ray, 6 is cooling water for cooling the target 4, 7 is a Wehnelt electrode, and 8 is an anode.

In the configuration shown in FIG. 1, an electron beam 2 emitted from a filament 1 is deflected by an electrostatic deflection plate 3 and irradiated onto a target 4, so that soft X-rays 5 are emitted.

In the configuration shown in FIG. 2, the electron beam 2 emitted from the filament 1 passes through the Wehnelt electrode 7 and the anode 8
The cross-sectional shape is shaped by electrostatic deflection plates 3a and 3b.
, and irradiates the target 4, from which soft X-rays 5 are emitted.

In Figures 1 and 2, the voltage applied to the electrostatic deflection plates 3.3a and 3b is generally the same as the voltage used for electron beam acceleration, or it is divided by a resistor or the like. use.

In the conventionally used deflection type electron gun having the configuration shown in FIGS. 1 and 2, once the electrode arrangement of the electron gun is determined, the trajectory of the electron beam 2 becomes constant and the beam spot diameter is adjusted on the target 4. I can't do that.

However, the electron gun used for X-ray exposure requires two conditions: high output and high brightness, and the beam spot diameter is changed depending on the size of the exposure area to meet both high output and high brightness conditions. It is necessary to operate the electron beam while satisfying the following conditions, and the deflection type electron gun conventionally used for this purpose has the disadvantage that the beam spot diameter cannot be adjusted as described above.

The X-ray generating electron gun according to the present invention solves the problems with the conventionally used deflection type electron gun, and has an electron beam spread angle adjustment coil (first An electron renderer 9 is disposed, followed by a deflection and convergence lens 10 having a three-dimensional convergence effect, and a spread angle adjustment coil 9 changes the angle of incidence of the electron beam to the deflection and convergence lens 10. The beam spot diameter on 4 can be adjusted.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An X-ray generating electron gun according to the present invention will be described in detail below based on embodiments thereof.

FIG. 3 shows the structure of an embodiment of an X-ray generating electron gun according to the present invention.

In the figure, an electron beam 2 emitted from a filament 1 is shaped by a Wehnelt electrode 7 and an anode 8.
It passes through the spread angle adjustment coil 9.

When the current of the spread angle adjustment coil 9 is changed.

The spread angle of the electron beam exiting the spread angle adjustment coil 9 changes.

Thereby, the spread angle of the electron beam incident on the deflection/convergence lens 10 can be adjusted.

The deflection/convergence lens 10 passes the magnetic field generated by the coil 12 through the pole piece 11 to form a uniform parallel magnetic field between two fan-shaped electrode plates arranged in parallel to each other, although not completely shown.

The electron beam 2 incident on the deflection/convergence lens 10 is deflected by 90 degrees and focused onto the target 4.

Soft X-rays 5 are emitted from the target 4 by the electron beam 2 irradiated onto the target 4.

In this case, since the divergence angle of the electron beam 2 incident on the deflection/convergence lens 10 can be changed by the divergence angle adjustment coil 9, the convergence point of the electron beam 2 can be adjusted to the target point t"4.
It is possible to align it on the plane or to shift it inside the target plane.

Therefore, when observed on the target 4 surface, the electron beam diameter changes.

With reference to FIG. 4, the action of the deflection and convergence lens in an embodiment of the X-ray generating electron gun according to the present invention will be explained in detail.

In the figure, 2a, 2b, 2c are electron beams, 4 is a target,
9 is a spread angle adjustment coil; 10 is a deflection/convergence lens; 11
is a pole piece, and 12 is a coil.

Further, FIG. 5 shows the shape of a beam spot obtained in an embodiment of the X-ray generating electron gun according to the present invention in the xy plane perpendicular to the direction of travel of the electron beam.

Generally, charged particles are focused at one point on the same xy plane in FIG.

Various types of electromagnetic field lenses have been considered for performing so-called three-dimensional convergence, but here, a magnetic field lens will be explained as an example.

In FIG. 4, consider the case where an electron beam is emitted from point A0 and draws a trajectory as shown in 2a.

The deflection and convergence lens 10 is arranged so that the end face of the deflection and convergence lens 10 is at an angle of 26.5 degrees with respect to the normal to the central axis of the electron beam 2a.

Using the coil 12, the strength of the magnetic field of the deflection/convergence lens 10 is changed to deflect the electron beam 2a by 90 degrees, and the normal to the central axis of the deflected electron beam 2a and the deflection/convergence lens 10 are
If the other end face of the deflection/convergence lens 10 is set at an angle of 26.5°, the electron beam 2a emitted from point A1, which is at a distance al from the end face of the deflection/convergence lens 10, will be at a distance b1 from the other end face of the deflection/convergence lens 10. Three-dimensional convergence in place.

Similarly, the electron beam 2b emitted from point A2, which is a distance a2 from the end surface of the deflection/convergence lens 10, is three-dimensionally converged at a distance b2 from the other end surface of the deflection/convergence lens 10.

Electron beam emission point A1. A2 to deflection converging lens 1
0 to the end face a1. The relationship between a2 and the distance from the other end face of the deflection/convergence lens 10 after deflection until the electron beam is three-dimensionally converged can be calculated from the theory of magnetic lens systems.

For example, let R be the deflection radius of the electron beams 2a and 2b, and a
If 1=3R, then b1=1.4H.

Moreover, when a 2 =2R, it becomes b2-2R.

Therefore, for example, from the other end surface of the deflection/convergence lens 10, bl
When the target 4 is placed at the point A0, the electron beam 2a emitted from the point A0 is three-dimensionally focused on the surface of the target 4.

At this time, the electron beam 2b emitted from point A2 will be three-dimensionally converged inside the target 4, so the electron beam 2b will form a spread image on the target 4, so it will become a point focal point on the target 4. Therefore, the beam spot diameter becomes larger.

Let us assume that the trajectory when the electron beam is incident on the spread angle adjustment coil 9 which is not being adjusted is 20.

By adjusting the magnetic field of the spread angle adjustment coil 9, the trajectory of the electron beam can be easily adjusted to 2a or 2b.

In this way, it is possible to adjust the beam spot diameter on the target 4 surface by changing the angle of incidence of the electron beam on the deflection/convergence lens 10 using the spread angle adjustment coil (first electron lens) 9. .

FIG. 5 shows a beam spot shape obtained in an embodiment of the X-ray generating electron gun according to the present invention.

The beam spot shape when three-dimensionally converged on the four surfaces of the target is as shown in 13a, and when three-dimensionally converged in front of the four targets, it is as shown in 13b.

When three-dimensional convergence is performed within the four surfaces of the target, a shape like 13c is obtained.

The reason why the shape of the beam spot becomes elliptical when three-dimensionally converged outside the target plane is that the converging actions of the deflection and convergence lens 10 in the X and Y directions do not completely match.

As explained in detail above, in the X-ray generating electron gun according to the present invention, the beam spot diameter on the target surface is continuously changed by adjusting the divergence angle of the incident electron beam to the deflection and convergence lens. I can do it.

Therefore, when applied to a soft X-ray exposure device, for example.

It is possible to use X-rays with optimal intensity that satisfies the requirements for exposure area and transfer accuracy.

In addition, by adjusting the beam spot diameter within the allowable range, the incident energy density of X-rays on the target surface can be changed, reducing damage to the target and improving the life and stability of the X-ray source. It is possible.

[Brief explanation of drawings]

1 and 2 are diagrams showing the configuration of a conventionally used deflection type electron gun, FIG. 3 is a diagram showing the configuration of an embodiment of the X-ray generation electron gun according to the present invention, and FIG. A diagram illustrating in detail the action of the deflection and convergence lens in the embodiment of the electron gun for X-ray generation according to the present invention, and FIG. 5 shows the beam spot shape obtained in the embodiment of the electron gun for X-ray generation according to the present invention. FIG. Explanation of symbols, 1... filament, 2...
... Electron beam, 3, 3a, 3b ... Electrostatic deflection plate, 4 ... Target, 5 ... Soft X-ray, 6 ... Cooling water . 7... Wehnelt electrode, 8... Anode, 9... Spread angle adjustment coil (first electron lens), 10... Deflection/convergence lens, 11 ...
...Pole piece, 12...Coil.

Claims (1)

[Claims] 1. A first electron lens disposed in the electron beam path and capable of adjusting the divergence angle of the electron beam; and a first electron lens disposed after the first electron lens to adjust the divergence angle set by the first electron lens. and a deflection and convergence lens having a three-dimensional convergence effect that adjusts the convergence point of the incident electron beam and makes it possible to adjust the effective spot diameter of the electron beam on a target disposed after the X-ray. Generation electron gun.