JPH04137441A - High-frequency cavity type electron gun - Google Patents

Abstract

PURPOSE:To obtain electron beams with a large inclusion rate of a specific energy by forming a cavity resonator to be resonated by both a standard frequency and its third higher harmonic. CONSTITUTION:A high-frequency cavity type electron gun 1 furnishes a cavity resonator 2, a cathode 3 for electron emission, a cathode 4 with the needle-form tip, and tuning mechanisms (or resonance frequency movable mechanisms) 5 and 6. And the cavity resonator 2 is formed to be resonated by both a standard frequency and its third higher harmonic. By adding the third higher harmonic to the standard frequency in an adequate ratio, the energy of electron can be distributed as shown in the figure, and in this case, the electrons furnishing the energy within the error + or -1% reach 15% of the all value in the case of the largest value. As a result, electron beams with a large inclusion rate of a specific energy can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION a. Field of Industrial Application The present invention relates to a high frequency cavity type electron gun, and particularly to an electron gun using a high frequency cavity resonator.

b. Prior Art Generally, in devices that generate electron beams (hereinafter referred to as electron guns), electrostatic electron guns that use DC voltage are often used. That is, for example, a needle-shaped tungsten whose tip has a radius of curvature of about 10 on- is used as the cathode that emits electrons by an electric field, and a voltage of several kV is applied between it and the opposing anode to generate a strong electric field ( >10'V/C11
) to emit electrons.

A part of the emitted electrons is further accelerated to the required energy by a multi-stage anode.

However, in recent years, this has been replaced by a high-frequency cavity electron gun, which emits electrons using a high-frequency electric field, and has been increasingly used. This method has the advantage that high-energy electrons can be generated with a small body and that there is no need to punch the electrons when further accelerating them.

Problems to be solved by the C0 invention However, as shown in Figure 4, the energy of the electrons generated by this method has a sinusoidal distribution over time, so it is difficult to use a magnetic field etc. when entering the accelerator. hand,
There is a problem in that it is necessary to extract only the electrons with the necessary energy, and the other electrons distributed at this time result in power loss.

In addition, in recent years, the development of accelerators has progressed, and so-called flat-top high-frequency accelerators mix third-order harmonics with the high-frequency electric field for acceleration, making the electric field uniform over a large period of time to accelerate electrons. has been constructed, but conventional high-frequency cavity electron guns were not able to bring out the full potential of this device.

The present invention has been made in view of the above-mentioned problems, and its purpose is to provide a high-frequency cavity electron gun that can provide an electron beam with a high content of a certain specific energy.

69 Means for Solving the Problems The structure of the present invention for achieving the above-mentioned object is a high-frequency cavity electron gun in which a cathode that emits electrons by an electric field is disposed inside a high-frequency cavity resonator. It is characterized in that the body resonator is formed to resonate at both the fundamental frequency and its third harmonic.

81 Effect Since the present invention is constructed as described above, this high frequency cavity electron gun is excited by both the fundamental frequency and its third harmonic.

Test results of the present invention will be explained in comparison with conventional ones. First, the energy of electrons generated by a conventional high-frequency cavity electron gun has a sinusoidal distribution with respect to time, as shown in FIG. In other words, the proportion of electrons with energy within a certain range is extremely small; for example, the electrons with energies within ±1% of the total account for 6.4% of the total. do not.

However, by adding the third harmonic to the fundamental frequency at an appropriate rate, it is possible to distribute the electron energy as shown in Figure 3, in which case it is ±1%.
The largest number of electrons with energy within the error range is 15% of the total.

f. Examples Hereinafter, preferred embodiments of the present invention will be described in detail by way of example based on the drawings.

FIG. 1 is a block diagram of a high frequency cavity type electron gun showing one embodiment of the present invention, and FIG. 2 is a schematic sectional view of a high frequency cavity resonator. In the figure, 1 is a high-frequency cavity electron gun, 2 is a cavity resonator, 3 is a cathode part for electron emission, 4 is a cathode with a needle-like tip, and 5 and 6 are the resonance frequencies of the cavity resonator 2. A tuning mechanism (or resonant frequency variable mechanism) for adjusting the resonance frequency, numeral 5 is a fundamental frequency, and numeral 6 is a part that can vary the third harmonic thereof.

7.8 is a matching mechanism for the fundamental frequency and its third harmonic, which can be adjusted independently, 9.10 is a high frequency generator that outputs the fundamental frequency and its third harmonic, respectively, and 11 is a cathode. Part 3. This is a power supply device for operating the high frequency generators 9 and 10.

The cavity resonator 2 has T M or with respect to the fundamental frequency. The mode is a cylindrical resonant cavity, but the normal shape does not resonate with the third harmonic, so as shown in Figure 2, the impedance is changed depending on the shape of the edge 2a, and the two It is designed to resonate at one frequency. and,
The cavity resonator 2 has a resonant fundamental frequency (TM, mode).
and third harmonic (TMozo mode), and adjust each power 1 phase so that the electric field at the radial center of the resonator 2 has a characteristic 20 that is as flat as possible in time at its maximum. do. In this state, electrons are generated from the cathode 4 and an electron beam is extracted using a high frequency electric field.
2 shows the path of the generated electron flow.

FIG. 3 shows a distribution diagram of the energy E of the emitted electrons from the cavity resonator 2 with respect to time T in this state, and when compared with the distribution diagram of the conventional one shown in FIG. It is possible to obtain an electron flow with a high content of a certain energy.

Note that the tuning mechanisms 5 and 6 of the cavity resonator 2 are preferably provided in an embodiment that does not affect the frequencies of other modes as much as possible so that the resonance frequencies of the two modes can be finely adjusted respectively. .

Note that the technology of the present invention is not limited to the technology in the above-mentioned embodiments, but may also be implemented by means of other modes that achieve the same function (also, the technology of the present invention may be modified in various ways within the scope of the above-mentioned configuration). , can be added.

g0 Effects of the Invention As is clear from the above explanation, according to the high frequency cavity electron gun of the present invention, the cavity resonator is formed to resonate at both the fundamental frequency and its third harmonic. Therefore, it is possible to obtain an electron beam with a high content of a certain specific energy.

Further, the present invention is extremely useful for techniques that require uniformity of electron energy, such as improving processing efficiency in physical property processing using direct electron beam radiation.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a high-frequency cavity electron gun showing an embodiment of the present invention, FIG. 2 is a schematic cross-sectional view of a cavity resonator, and FIG. 3 is a diagram showing the energy of emitted electrons according to this embodiment versus time. Distribution diagram, FIG. 4 is a distribution diagram of the energy of emitted electrons by a conventional cavity resonator versus time. DESCRIPTION OF SYMBOLS 1... High frequency cavity electron gun, 2... Cavity resonator, 4... Cathode, 9... High frequency (fundamental frequency) generator, lO... High frequency (third harmonic) generator. Figure/1 Figure

Claims (1)

[Claims] In an electron gun in which a cathode that emits electrons by an electric field is disposed inside a high-frequency cavity resonator, the cavity resonator resonates at both the fundamental frequency and its third harmonic. A high frequency cavity type electron gun characterized by being formed.