JP2001110600A - Dc electron beam acceleration apparatus and method for dc electcron beam acceleration - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a DC electron beam acceleration apparatus which can accelerator a high intensity DC electron beam. SOLUTION: The acceleration apparatus is provided with an electron beam generating part 12, a high frequency cavity 13, and the 1st and 2nd electron beam deflecting device 14, 15. The high frequency cavity 13 accelerate the DC electron beam by injecting high frequency electric field. The electron beam deflecting device deflects electron beam. The electron beam generated by the electron beam generating part 12, is guided to pass into the high frequency cavity 13 by advancing direction P (acceleration X). The advancing direction is changed by the 1st electron beam deflecting device 14. The electron beam is guided to pass into the high frequency cavity 13 by reverse direction (advancing direction Q) (acceleration Y). The electron beam is deflected by the 2nd electron beam deflection device 15, to pass outside of the high frequency cavity 13. The electron beam is deflected by the 1st electron beam deflection device 14, and guided to pass again the cavity 13 by advancing direction Q (acceleration Z). The DC electron beam is accelerated to have high energy by repeating the action of acceleration Z.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a direct-current electron beam accelerator and a direct-current electron beam accelerating method, and more particularly, to a high-intensity electron beam or X-ray used for sterilization of medical equipment, food irradiation, and the like.
The present invention relates to a DC electron beam accelerator and a DC electron beam acceleration method for generating a line and a high-intensity DC slow positron beam.

[0002]

2. Description of the Related Art FIG. 9 shows, for example, "Development of compact synchrotron radiation source" Aurora "" (by Takahashi and Yamada, Sumitomo Heavy Industries, Vol. 39, No. 116, 1991, pp. 2 to 10). 3) is a conventional electron beam accelerator. This type of electron beam accelerator is called a racetrack microtron. In the figure, 111 is an electron gun, 1
Reference numeral 12 denotes an incident electromagnet, 113 denotes a high-frequency cavity (linac), 114 denotes a bending electromagnet, and 115 denotes an electron beam orbit.

The operation will be described. The electron is an electron gun 11
Occurs at 1. The frequency of the generated electron beam is several Hz
A few hundreds Hz and a pulse width is about several tens ns to several tens μs. The generated electrons are incident on the racetrack microtron by the incident electromagnet 112. In the microtron, it is accelerated each time it passes through the high-frequency cavity 113 while passing through the electron beam orbit 115. Racetrack microtrons mainly use the s-band (2.8 GHz)
The acceleration is performed by the high frequency electric field of z). The energy obtained when passing through the high-frequency cavity once is often about 5 MeV. In addition, bending electromagnets 114 are provided on both sides of the high-frequency cavity 113 to form the electron beam trajectory 115.

FIG. 10 shows, for example, “Slow positro
n production using an 18MeV electron linac ”(H.Ta
naka and T. Nakanishi, Nuclear Instruments and Met
hodsin Physics Research, B62, 1991, pp.259-26
FIG. 3 is a diagram schematically illustrating a device arrangement when a slow positron is generated by the conventional electron beam accelerator described in 3). In FIG. 10, 121 is a linear accelerator for accelerating the electron beam, 122 is a target for colliding the electron beam, 123 is a moderator for lowering the speed of the positron beam generated by the collision, and 124 is a transporter for the low-speed positron beam. A transport line, 125 is a DC converter for converting a pulsed slow positron beam into DC, and 126 is a measuring device for measuring the slow positron beam.

The operation will be described. Linear accelerator 121
The electron beam accelerated by collides with the target 122,
After passing through the moderator 123, the slow positron beam (several e)
V to several hundred eV). The low-speed positron beam is transported by the transport line 124,
Lead to 5. The electron beam accelerated by the linear accelerator 121 has a frequency of several Hz to several hundreds Hz and a pulse width of several tens n.
It is a pulse beam of about s to several μs, and the generated slow positron beam is also a pulse beam having the same time characteristics. Therefore, when the light is guided to the measuring device 126 as it is, a slow positron in the form of a pulse enters the measuring device, and the measurement is difficult due to saturation of the detector. Therefore, the low-speed positrons are accumulated in the DC converter 125, and the low-speed positrons are guided to the measuring device 126 little by little.

[0006]

The above-mentioned conventional electron beam accelerator has the following problems.

First, in the conventional example shown in FIG.
Since a high-frequency cavity for a band (frequency of about 2.8 GHz) was used, the size of one cell in the cavity was small, and the characteristics of the cavity were largely changed by a change in temperature. And pulsed operation was indispensable. In pulse operation, the average current is low,
There is a problem that it cannot be used in an application field requiring a high-intensity electron beam.

In the conventional example shown in FIG.
First, the low-speed positrons generated in the moderator are pulse-like, and it was necessary to use a DC converter to use for measurement.However, the efficiency was low because some of the low-speed positrons disappeared during the DC conversion stage. There was a problem of becoming. Also,
There is a problem in that the arrangement of the direct current converter increases the scale of the apparatus.

Further, in the conventional example shown in FIG. 10, since the electron beam used for generation is pulse-shaped, the average current is small, and in order to generate high-intensity slow positrons, the acceleration energy of the electrons is reduced to, for example, about 100 MeV. Must be higher. Therefore, there is a problem that the linear accelerator becomes very large. Also, when a high-energy electron beam collides with the target, neutrons with high intensity are generated, so large-scale shielding of the linac room and measures to activate the atmosphere are indispensable, and the overall system becomes large-scale. was there.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and it is possible to accelerate a high-intensity DC electron beam and to efficiently reduce the size of the apparatus while efficiently producing a large-intensity slow positron beam. It is an object of the present invention to provide a DC electron beam acceleration device and a DC electron beam acceleration method capable of generating dc.

[0011]

SUMMARY OF THE INVENTION The present invention provides an electron beam generating means for generating a DC electron beam, an electron beam accelerating means for applying a high-frequency electric field to accelerate the DC electron beam, and one end of the electron beam accelerating means. The trajectory of the accelerated DC electron beam, which is provided close to the trajectory, is deflected during the first pass so that the exit trajectory is the same as the incident trajectory and the traveling direction is the opposite direction. Thereafter, the emission trajectory is not the same as the incidence trajectory, and the first electron beam deflecting means that deflects the traveling direction to be in the opposite direction, and is provided near the other end of the electron beam accelerating means, And a second electron beam deflecting means for deflecting the trajectory of the DC electron beam so that the emission trajectory is not the same as the incident trajectory and the traveling direction is opposite to the trajectory. did The flowing electron beam is passed through the electron beam accelerating means in the first traveling direction (acceleration X), and the traveling direction of the DC electron beam is changed by the first electron beam deflecting means. The DC electron beam is passed in the second traveling direction opposite to the first traveling direction (acceleration Y), and the DC electron beam is deflected by the second electron beam deflecting means to pass outside the electron beam accelerating means. Is again deflected by the first electron beam deflecting means, and again passes through the electron beam accelerating means in the same orbit and in the second traveling direction (acceleration Z). This is a DC electron beam accelerator that accelerates the electron beam.

Further, the electron beam generating means generates a DC electron beam at the same frequency as the frequency of the high frequency electric field applied to the electron beam accelerating means and in synchronization with the electron beam accelerating means.

Further, the electron beam generating means may be an integer fraction of the frequency of the high frequency electric field applied to the electron beam accelerating means.
And a direct current electron beam synchronized with the electron beam acceleration means.

The acceleration phases when the DC electron beam passes through the electron beam acceleration means are acceleration X, acceleration Y and
The acceleration Z differs from each other.

Further, the apparatus further includes a beam scraper for blocking a part of the DC electron beam that has passed through the electron beam acceleration means.

Further, the apparatus further includes a target for generating high-speed positrons by collision of a DC electron beam accelerated by repeating the operation of acceleration Z, and a moderator for decelerating high-speed positrons.

The present invention also provides an electron beam generating step for generating a DC electron beam, and passing the DC electron beam generated in the electron beam generating step in a first traveling direction through a high-frequency cavity into which a high-frequency electric field is applied. An accelerated X step of accelerating and accelerating, and deflecting the traveling direction of the DC electron beam accelerated in the accelerated X step, again in the high-frequency cavity, in the same orbit and in a second direction opposite to the first traveling direction. An accelerating Y step of passing through and accelerating in the traveling direction;
The DC electron beam accelerated in the acceleration Y step is deflected, passed outside the high-frequency cavity in the first traveling direction, then deflected again, and passed through the high-frequency cavity in the same orbit and in the second traveling direction. And an accelerating Z step of accelerating the DC electron beam by repeating the operation of the accelerating Z step at least once or more.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram showing a configuration of a DC electron beam accelerator according to an embodiment of the present invention. In the figure, 1 is an electron beam orbit, 12 is an electron gun, etc., an electron beam generating unit for generating electrons, 13 is composed of two cells, a high-frequency cavity for accelerating the electron beam, and 14 and 15 are First and second electron beam deflecting means for deflecting the electron beam to change the traveling direction of the electron beam. The first electron beam deflecting means 14, as shown in the figure,
It is composed of two electromagnets. The polarities of the magnets are different from each other, and the magnetic field strength and the distance between the magnets are values adjusted so that the electron trajectory and the electron trajectory during the first passage are the same. On the other hand, the second electron beam deflecting means 15 is also composed of two electromagnets as shown in the figure, and the polarities of the magnets are different from each other. The trajectory and the exit trajectory are not the same, and are adjusted so that the exit trajectory passes outside the entrance trajectory.

Next, an outline of the operation of the DC electron beam accelerator of the present invention will be described. The electrons generated by the electron beam generator 12 are incident on an acceleration trajectory (ie, the trajectory 1 of the electron beam in FIG. 1). The incident electron beam passes through the high-frequency cavity 13 once in the traveling direction P (acceleration X).
Thereafter, the traveling direction of the electron beam is changed by the first electron beam deflecting means 14 so that the trajectories of the electrons are in the same trajectory and in the opposite direction (the traveling direction Q), and the electron beam travels in the high-frequency cavity 13 in the opposite direction (the traveling direction). Pass in the direction Q) (acceleration Y). The passed electron beam is deflected by the second electron beam deflector 15. This time, although deflected in the traveling direction P, the trajectory is not the same as the above-mentioned incident trajectory and passes outside the high-frequency cavity 13. Next, the electron beam
Again, it is deflected by the first electron beam deflector 14,
The high-frequency cavity 13 is again passed in the traveling direction Q (acceleration Z). Thereafter, by repeating the process of acceleration Z, the DC electron beam passes through the high-frequency cavity 13 in the traveling direction Q and is accelerated to high energy.

The configuration and operation of the present invention will be described in more detail. In this embodiment, a DC electron beam accelerator of CW (DC) for accelerating electrons to 5 MeV will be described as an example. It is assumed that the acceleration voltage in the high-frequency cavity 13 is about 1 MV. The electron beam generator 12 generates electrons,
As described above, the first electron beam deflecting means 14 and the second electron beam deflecting means 15 form the trajectory 1 of the electron beam. The acceleration of the DC electron beam is performed in the high-frequency cavity 13.
Apply a high frequency electric field of less than MHz. In order to accelerate a high-current DC electron beam, it is necessary to apply a high-intensity power (high-frequency electric field) to the high-frequency cavity 13. When a high-frequency electric field is applied, heat is generated by the electric resistance of the wall of the high-frequency cavity 13. If the dimensions of the high-frequency cavity 13 change due to heat, it becomes impossible to apply a predetermined high-frequency electric field, so it is necessary to remove the heat. The power that can be applied to the high-frequency cavity 13 has a correlation with the size at which heat can be removed. Generally, the larger the size of the high-frequency cavity 13, the more power can be applied. In order to increase the size of the high-frequency cavity 13, it is necessary to lower the frequency of the high-frequency electric field. In order to accelerate a large current of several tens of kW or more as in the present invention, it is desirable to use a high-frequency electric field having a frequency of 900 MHz or less. The lower the frequency of the high-frequency electric field, the larger the size of the high-frequency cavity 13 and the larger the size of the electron beam accelerator. Also,
The lower the frequency of the high-frequency electric field, the smaller the acceleration energy per unit length. On the other hand, the lower the frequency of the high-frequency electric field, the easier it is to remove power lost at the cavity wall. Therefore, the frequency to be selected is determined by the above correlation. When accelerating a high-power DC electron beam, it is necessary to select a lower-frequency high-frequency electric field.

On the other hand, when the voltage of the high-frequency electric field is high, the wall loss increases. Generally, the wall loss is proportional to the square of the acceleration voltage.
Since it is desired that a DC electron beam accelerator requires low power, it is desirable that the acceleration voltage is low in order to reduce wall loss. By the way, the incident energy of the device of the present invention is 100 keV or less, and the difference between the speed of light and the speed of light at low energy cannot be ignored. If there is a speed difference from the speed of light, if the cavity voltage is lengthened by lowering the acceleration voltage,
During acceleration, the electron beam deviates from the phase of the high-frequency electric field and cannot be accelerated. Therefore, the acceleration voltage cannot be reduced below a certain value. Therefore, if the frequency of the accelerating high-frequency electric field is determined, the required accelerating voltage is limited to a certain range.

As described above, the acceleration frequency of the high-frequency electric field is limited to about 900 MHz or less in consideration of the acceleration of the electron beam of about several tens of kW in the apparatus of the present invention. In addition, the acceleration voltage, the number of hollow cells, and the like are also limited to certain ranges.
For example, when 500 MHz is selected as the frequency, in order to accelerate to 5 MeV, it is desirable that the number of cells of the high-frequency cavity 13 is 2, the acceleration voltage is 1 MV, and the number of passing through the cavity is about 5 times. In that case, the wall loss in the high-frequency cavity 13 is 60 k
It is about W. In order to accelerate a 30 kW beam, a power supply power of about 90 kW to 100 kW is required as a high frequency power supply. As a high frequency power supply, in addition to a klystron power supply, IOT (Inductive Output Tube)
A power supply can be used.

When accelerating a high-power DC electron beam, it is necessary to match the emission timing of the electrons generated from the electron beam generator 12 with the phase of the high-frequency electric field applied to the high-frequency cavity 13. FIG. 2 shows the energy that can be obtained when passing through the high-frequency cavity 13 once. The horizontal axis indicates the position (coordinate) in the traveling direction of the electron beam, and the vertical axis indicates the energy of the electron at that position. This graph is a result of simulating 10 electrons by shifting the initial phase of the electrons and the phase of the high-frequency electric field by 10 degrees. It can be seen that the energy obtained when passing through the high-frequency cavity 13 changes greatly depending on the initial phase of the electrons. The energy width of the electron beam that can be accelerated by the DC electron beam accelerator of the present invention is at most about 30 degrees in the entire phase width. I will be. Therefore, in order to efficiently accelerate the electron beam emitted from the electron beam generator, it is necessary to control the phase difference from the high-frequency acceleration electric field.

FIG. 3 shows the relationship between the high-frequency electric field of the conventional electron beam accelerator shown in FIG. 9 and the acceleration phase of the electron beam. In the figure, 30 is an accelerating high-frequency electric field, 31 is an electron gun output, and 32 is an accelerating beam phase. From the electron gun 111, as described above, a frequency of several Hz to several hundred Hz,
A pulse beam having a pulse width of several tens ns to several tens μs is emitted. Therefore, the beam that can be accelerated was limited to a part of the beam within the pulse width as shown in FIG. Therefore, the average acceleration current was low.

FIG. 4 shows the relationship between the high-frequency electric field and the acceleration phase of the electron beam in the DC electron beam accelerator of the present invention.
In the figure, 40 is an accelerating high-frequency electric field, and 41 is an electron beam emitted from the electron beam generator 12. A pulse synchronized with the high-frequency electric field is emitted from the electron beam generator 12. Therefore, any wave of the high-frequency electric field can be accelerated by an electron, and a high-power electron beam can be accelerated. The efficiency of the electron beam emitted from the electron beam generator 12 is most efficient when the frequency is the same as the frequency of the high-frequency acceleration electric field, but may be one half or one third. When the frequency of the high-frequency accelerating electric field is high, it may be difficult to make the emission frequency of the electron beam the same, and in that case, it is necessary to perform the operation with the frequency reduced to an integral number as described above. .

FIG. 5 is a schematic configuration diagram showing an example of the electron beam generating section (electron gun) 12. In the figure, 211 is a cathode,
212 is a grid, 213 is an anode, 214 is a beam power source, 215 is a grid power source, and 216 is an electron beam. A high DC voltage of about 50 kV to 100 kV is applied to the beam power supply 214. Grid power supply 215
Is a power supply capable of generating a high-frequency pulse synchronized with the frequency of the high-frequency cavity 13 (FIG. 1). Electrons are generated by thermionic emission from the cathode 211. Thereafter, the pulse is modulated by the grid 212 and becomes a pulse synchronized with the high-frequency cavity 13, and is extracted from the anode 213. The amplifier is operated with class C amplification. In this embodiment, 500M
Although it is necessary to perform modulation of about Hz, it can be achieved by using an electron gun portion of a high-frequency amplifier used in a base station of a television station. In the present embodiment, a pulse synchronized with a high-frequency electric field is emitted from the electron beam generator 12, but a DC electron beam may be generated like an electron gun of a CRT. In the case of a thermionic emission type electron gun, an electron beam of about 3 A / cm ² can be generated. In the apparatus of the present embodiment, an electron beam having a radius of about 2 mm is assumed.
It is possible to extract a DC beam of about 0 mA.
Since the acceleration phase width of the present invention is assumed to be about 30 degrees,
It is possible to accelerate an average current of about 380 mA × 30/360 = 32 mA. For example, when accelerating to 5 MeV, it is possible to obtain a high intensity electron beam of about 160 kW. However, in the case of using a DC beam, only a part of the generated electron beam is accelerated, so that the efficiency is low and a high-output high-voltage power supply is required.

As described above, in this embodiment, the high-frequency cavity 13 for applying a high-frequency electric field and accelerating a direct current (CW) electron beam has the same frequency as that of the high-frequency electric field or a frequency that is a fraction of an integer. An electron beam generator 12 for generating a CW electron beam synchronized with the high-frequency cavity 13;
First and second electron beam deflecting means 14 for deflecting electrons
And 15, the electron beam generated by the electron beam generator 12 is passed through the high-frequency cavity 13 in the traveling direction P (acceleration X), and the traveling direction of the electron beam is changed by the first electron beam deflecting means 14. The high-frequency cavity 13 is again passed through the high-frequency cavity 13 in substantially the same orbit and in the opposite direction (the traveling direction Q) (acceleration Y). Then, the electron beam is deflected by the second electron beam deflecting means and passes outside the high-frequency cavity 13. Deflected by the first electron beam deflecting means 14 again, and
Are passed in substantially the same orbit and in the traveling direction Q (acceleration Z), and the operation of acceleration Z is repeated to accelerate the CW electron beam to high energy. It is possible to accelerate, and it is possible to obtain an effect that it can be used in application fields that require a high-intensity electron beam (for example, sterilization of medical devices and irradiation of foods).

Embodiment 2 Hereinafter, another embodiment of the present invention will be described with reference to the drawings. FIG. 6 shows the relationship between the high-frequency electric field phase and the phase of the acceleration beam when the electron beam passes through the high-frequency cavity. In FIG. 6, 51 is the acceleration X
, 52 indicates the phase of the electron beam of acceleration Y, 53 indicates the phase of the electron beam of acceleration Z, and 54 indicates the acceleration high-frequency electric field (RF acceleration electric field). Note that the basic structure of the DC electron beam accelerator according to the present embodiment is the same as that of FIG. 1 described above, and therefore, FIG. 1 will be referred to.

In the conventional electron beam accelerator described above, the electron beam accelerates at a phase close to the top of the high-frequency electric field. In the DC electron beam accelerator of the present invention, the energy of the electron beam is low, the speed of the electron beam changes greatly with the acceleration, and the energy gain decreases when the acceleration is performed near the top phase of the high-frequency electric field. When acceleration is performed near the top phase, acceleration is performed in the same spatial position as when the first electron beam passes through the high-frequency cavity and when a plurality of electron beams pass through the high-frequency cavity. The electron density increases and the effect of space charge increases. In a device for accelerating a large amount of current, the maximum current value is often determined by the influence of space charge. Therefore, it is necessary to reduce the electron density as much as possible.

Therefore, in the present invention, as shown in FIG. 6, the first electron beam (acceleration X) and the second electron beam (acceleration Y) are accelerated in opposite phases, so that the above-described problem occurs. do not do. The third and subsequent electron beams (acceleration Z) are accelerated with a phase closer to the second electron beam, but the acceleration Z is accelerated with a phase closer to the top. Therefore, the electron density does not increase, the influence of space charge is small, and more current can be accelerated. When the third and subsequent electron beams pass through the high-frequency cavity 13, they are accelerated in substantially the same phase, but since the energy has increased after passing through the high-frequency cavity 13, the effect of space charge is very small. Therefore, there is no problem if the current value is about the expected value.

As described above, in this embodiment, as shown in FIG. 6, the acceleration phases when the electron beam passes through the high-frequency cavity 13 are different from each other in the acceleration X, the acceleration Y, and the acceleration Z. Therefore, the effect of reducing the influence of space charge and accelerating the electron beam with a large direct current intensity can be obtained.

Embodiment 3 FIG. Hereinafter, another embodiment of the present invention will be described with reference to the drawings. FIG. 7 is a schematic configuration diagram showing a configuration of a DC electron beam accelerator according to Embodiment 3 of the present invention. In the figure, 1 is the trajectory of the electron beam,
Reference numeral 12 denotes an electron beam generator, 13 denotes a high-frequency cavity, 14 denotes first DC electron beam deflecting means, 15 denotes second DC electron beam deflecting means, and 61 denotes a beam scraper. That is, the present embodiment is obtained by adding the beam scraper 61 to the configuration of the first embodiment. The beam scraper 61 is for interrupting a part of the electron beam and removing the electron beam shifted from a predetermined acceleration phase of the high-frequency electric field during acceleration.

The operation will be described. The beam emitted from the electron beam generator 12 passes through the high-frequency cavity 13 and performs a first acceleration. Since the first acceleration is performed at a phase deviated from the top phase of the high-frequency electric field, the difference in energy gain due to the difference in the initial phase of the electron beam emitted from the electron beam generator 12 is large. Therefore, the high-frequency cavity 13
The energy dispersion (variation in energy) of the electron beam after passing through is considerably large.

The energy dispersion of the electron beam which can be accelerated by the DC electron beam accelerator of the present invention is at most about 3%, and a beam whose energy is deviated by 3% or more from the center beam cannot be accelerated to the final energy during the orbit. It is lost by colliding with walls. Since the device of the present invention accelerates large currents,
The radiation and heat generated when the electron beam collides with the wall are so large that the electron beam which cannot be accelerated to the final energy needs to be removed at a low energy as much as possible and at a controlled position.

Therefore, in this embodiment, the beam scraper 61 is provided in the first electron beam deflecting means 14 or on the exit side of the first electron beam deflecting means 14.
The electron beam passes through the bending electromagnet, where high-energy electrons pass outside and low-energy electrons pass inside.
By arranging the metal plates 61a and 61b on the outside and the inside, it becomes possible to pass only electrons having a predetermined range of energy, and it is possible to remove electrons whose energy dispersion is larger than a predetermined value. The amount of extra radiation generated can be suppressed.

In this embodiment, the beam scraper 61 has an example in which the metal plates 61a and 61b are provided on the outside and the inside. However, a configuration in which only the electron beam having a certain energy or more is accelerated is considered. In this case, the metal plate may be installed only inside.

In FIG. 7, the beam scraper 61 is installed in the vicinity of the first electron beam deflecting means 14, but the same effect can be obtained by arranging it at any position on the downstream side of the electron beam deflecting means 14. be able to. However, after passing through the high-frequency cavity 13 many times, the energy of the electron beam becomes high, so that it becomes necessary to remove the high-intensity electron beam by the beam scraper 61, and it is difficult to remove the generated radiation dose and heat. For this reason, it is preferable to install the device near the first electron beam deflecting means 14.

The beam scraper 61 needs to be provided with a cooling structure according to the power of the electron beam to be removed. In order to adjust the energy, a driving mechanism that can move the metal plate of the beam scraper 61 may be provided.

In this embodiment, in addition to the structure of the first embodiment, a beam scraper 61 for blocking a part of the electron beam is provided so that the electron beam deviated from the acceleration phase of the high-frequency electric field is accelerated during the acceleration. I decided to remove it,
The effect of the first embodiment described above is obtained, and further, the amount of generation of extra radiation other than the intended purpose can be suppressed.

Embodiment 4 FIG. Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 8 is a diagram showing an arrangement of devices when a slow positron is generated by the DC electron beam accelerator of the present invention. In the figure, reference numeral 71 denotes the first embodiment.
A DC electron beam accelerating unit having the same configuration as any of the DC electron beam accelerators indicated by Nos. 1 to 3, 72 is a metal target, 73 is a moderator, and 74 is a metal target 72 and a moderator 73 disposed near the entrance. A transport line 75 for transmitting the generated positrons is a measuring unit provided near the exit of the transport line 74. It should be noted that the DC electron beam accelerator of the present embodiment
1, a metal target 72, and a moderator 73.

Next, the operation will be described. The CW electron beam accelerated by the DC electron beam acceleration unit 71 collides with the metal target 72. As a result, bremsstrahlung, and
Fast positrons are generated by pair generation. The high-speed positron is guided to the moderator 73 and decelerated. The beam emitted from the moderator 73 is a slow positron of about several eV. The positron is guided through a transport line 74 to a measuring device 75.

The number of low-speed positrons that can be generated by the apparatus of the present invention is 2.3 × 10 ⁸ / s when the electron beam acceleration energy is 15 MeV and the electron beam power is 90 kW.
ec to 1.4 × 10 ⁹ pieces / sec. The number of occurrences varies depending on the configuration and arrangement of the metal target and the moderator, and thus varies depending on the apparatus. As described in “Positron Laboratory in the World” (written by Sohei Okada, Radioisotopes, Vol. 42, No. 7, 1993), the conventional number of occurrences in the world is 1.1 × 10 ⁸ of the ORNL apparatus. / Sec. The device of the present invention is more compact than the conventional device and is capable of generating high-intensity slow positrons.

The conventional device generates (1) a positron emitted from an isotope by decelerating it, and (2) a pulse-like electron beam generated from an electron linear accelerator of about 100 MeV as in the above-described conventional example of FIG. (3) A few MeV proton beam generated by a proton accelerator or the like is caused to collide with the target and decelerate to obtain low-speed positrons. Was. Compared with them, the device of the present invention has the following advantages.

In comparison with the above-mentioned conventional method (1),
The device of the present invention can first obtain a high-intensity slow positron. In the conventional method (1), 10 ⁶ pieces / sec
However, in the present invention, it is possible to generate 10 ⁸ to 10 ⁹ cells / sec. In addition, isotopes always generate positrons and are therefore very complicated to handle. However, in the apparatus of the present invention, if the apparatus is stopped, no radiation is emitted, so that an easy-to-handle apparatus can be provided.

As compared with the above-mentioned conventional method (2), the apparatus of the present invention can provide a small-sized apparatus, and can easily block a building. In the conventional method (2), an electron linear accelerator of about 100 MeV is required to increase the number of positrons.
Further, the generated positron beam is pulse-shaped, and a low-speed positron DC converter was required for use in measurement. On the other hand, in the present invention, acceleration of about 15 MeV is sufficient, and a DC converter is not required. Further, in the conventional method (2), large-scale neutrons are generated, so that the building is shielded on a large scale. However, in the present invention, simple shielding may be used.

As compared with the above-mentioned conventional method (3), the apparatus of the present invention can obtain a high-intensity slow positron. In the conventional method (3), the number of occurrences is about 10 ⁷ pieces / sec, but in the present invention, the number of occurrences is 10 ⁸ to 10 ⁹ pieces / sec. Furthermore, in the conventional method (3), protons are accelerated, so that neutrons of high intensity are generated and the building is shielded on a large scale. However, in the present invention, simple shielding may be used. Furthermore,
In the conventional method (3), the residual radiation is large, but is hardly found in the apparatus of the present invention.

In the present invention, the target is 90 kW.
It is desirable to provide the target with a mechanism for removing the above power because the electron beam is collided with the electron beam. A configuration of a rotary target system in which the target itself is rotated by the pressure of the cooling water may be used.

As described above, in this embodiment, a DC electron beam accelerating unit having the same configuration as the DC electron beam accelerators of the above-described first to third embodiments is provided. The same effects as in the first to third embodiments can be obtained, and further, in the present invention, since the electron beam emitted from the moderator 73 is not pulsed, a DC conversion device or the like is not required, and the disappearance of positrons due to DC conversion is eliminated. Because of this, large-intensity low-speed positrons can be generated efficiently and miniaturization can be achieved.Since no neutrons are generated, the building can be shielded easily and radiation can be generated if the device is stopped. Since there is almost no residual radiation, the effect of easy handling is obtained.

[0049]

According to the present invention, there is provided an electron beam generating means for generating a DC electron beam, an electron beam accelerating means for applying a high-frequency electric field to accelerate the DC electron beam, and an electron beam accelerating means provided near one end of the electron beam accelerating means. At the first pass, the trajectory of the accelerated DC electron beam is deflected so that the exit trajectory is the same as the incident trajectory and the traveling direction is opposite to the incident trajectory. A first electron beam deflecting means for deflecting the emission trajectory so that the traveling trajectories are not the same and the traveling directions are opposite to each other, and provided near the other end of the electron beam accelerating means; The orbit is not the same as the outgoing orbit with respect to the incoming orbit, and
A second electron beam deflecting means for deflecting the electron beam so that the traveling direction is opposite to that of the electron beam. The DC electron beam generated by the electron beam generating means is passed through the electron beam accelerating means in the first traveling direction (acceleration X ), The traveling direction of the DC electron beam is changed by the first electron beam deflecting means, and the electron beam accelerating means is passed again in the same orbit and in the second traveling direction opposite to the first traveling direction. (Acceleration Y), the DC electron beam is deflected by the second electron beam deflector,
It passes outside the electron beam accelerating means, is again deflected by the first electron beam deflecting means, and again passes the electron beam accelerating means in the same orbit and in the second traveling direction (acceleration Z). Since it is a DC electron beam accelerator that accelerates the DC electron beam by repeating the operation of Z,
There is an effect that a high intensity DC electron beam can be accelerated.

Further, the electron beam generating means generates a DC electron beam at the same frequency as the frequency of the high-frequency electric field applied to the electron beam accelerating means and in synchronization with the electron beam accelerating means. This has the effect of efficiently accelerating a high intensity DC electron beam.

Further, the electron beam generating means is provided with an integral frequency of the high frequency electric field applied to the electron beam accelerating means.
Since the DC electron beam is generated at the same frequency and synchronized with the electron beam accelerating means, when the frequency of the high frequency electric field is high, it may be difficult to make the emission frequency of the DC electron beam the same. In such a case, it is possible to perform a stable operation by setting the integral number to 1 /.

When the DC electron beam passes through the electron beam accelerating means, the acceleration phases are X, Y,
Since the acceleration Z is made different from each other, there is an effect that the influence of space charge is reduced and a large direct current beam can be accelerated.

Further, since a beam scraper for blocking a part of the DC electron beam passing through the electron beam accelerating means is further provided, there is an effect that a generation amount of extra radiation other than the purpose of use is small.

Further, a target for generating high-speed positrons and a moderator for decelerating high-speed positrons are further provided, because a DC electron beam accelerated by repeating the operation of the acceleration Z collides with each other. This is effective in that a large-scale DC low-speed positron can be obtained by a small-scale system.

The present invention also provides an electron beam generating step for generating a DC electron beam, and passing the DC electron beam generated by the electron beam generating step in a first traveling direction through a high-frequency cavity into which a high-frequency electric field is applied. An accelerated X step of accelerating and accelerating, and deflecting the traveling direction of the DC electron beam accelerated in the accelerated X step, again in the high-frequency cavity, in the same orbit and in a second direction opposite to the first traveling direction. An accelerating Y step of passing through and accelerating in the traveling direction;
The DC electron beam accelerated in the acceleration Y step is deflected, passed outside the high-frequency cavity in the first traveling direction, then deflected again, and passed through the high-frequency cavity in the same orbit and in the second traveling direction. A DC electron beam acceleration method for accelerating a DC electron beam by repeating the operation of the acceleration Z step at least once or more. It has the effect that it can be done.

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing a configuration of a DC electron beam accelerator according to Embodiment 1 of the present invention.

FIG. 2 is a graph showing an energy gain of an electron when the electron passes through a high-frequency cavity once.

FIG. 3 is a graph showing a phase relationship between a high-frequency electric field and an accelerated electron beam of a conventional electron beam accelerator.

FIG. 4 is a graph showing a relationship between a high-frequency electric field and a phase of an electron beam of the DC electron beam accelerator according to the present invention.

FIG. 5 is a configuration diagram showing a configuration of an electron beam generator (electron gun) provided in the DC electron beam accelerator of the present invention.

FIG. 6 is a graph showing a relationship between a high-frequency electric field phase and an acceleration beam phase when an electron beam passes through a high-frequency cavity in the DC electron beam accelerator according to the second embodiment of the present invention.

FIG. 7 is a configuration diagram showing a configuration of a DC electron beam accelerator according to Embodiment 3 of the present invention.

FIG. 8 is a configuration diagram showing a configuration of a DC electron beam accelerator according to a fourth embodiment of the present invention.

FIG. 9 is a schematic plan view of a conventional electron beam accelerator.

FIG. 10 is a diagram showing an arrangement of devices when a slow positron is generated by a conventional electron beam accelerator.

[Explanation of symbols]

1 electron beam orbit, 12 electron beam generator, 13
High frequency cavity, 14 first electron beam deflecting means, 15
Second electron beam deflecting means, 30 high-frequency accelerating electric field, 3
1 electron gun output, 32 acceleration beam phase, 40 high-frequency acceleration electric field, 41 electron beam emitted from the electron beam generator, 51 acceleration X electron beam phase, 52 acceleration Y electron beam phase, 53 acceleration Z electron Beam phase, 61 Beam scraper, 71 DC electron beam accelerator, 72 Metal target, 73 Moderator, 74
Transport line, 75 measuring unit, 111 electron gun, 112
Incident electromagnet, 113 high-frequency cavity, 114 deflection electromagnet, 115 electron beam orbit, 121 linear accelerator, 1
22 targets, 123 moderators, 124 transport lines, 125 DC converters, 126 measuring devices, 211
Cathode, 212 grid, 213 anode, 214 beam power, 215 grid power, 216 electron beam.

Claims (7)

[Claims] 1. An electron beam generating means for generating a DC electron beam, an electron beam accelerating means to which a high-frequency electric field is applied to accelerate the DC electron beam, and an electron beam accelerating means provided near one end of the electron beam accelerating means. During the first pass, the trajectory of the accelerated DC electron beam is deflected so that the exit trajectory is the same as the incident trajectory and the traveling direction is opposite to the incident trajectory. A first electron beam deflecting means for deflecting the emission trajectories so that the traveling trajectories are not the same and the traveling directions are opposite to each other; and Second electron beam deflecting means for deflecting the trajectory so that the outgoing trajectory is not the same as the incident trajectory and the traveling direction is opposite to the trajectory. The DC electron beam is passed through the electron beam accelerating means in the first traveling direction (acceleration X), and the traveling direction of the DC electron beam is changed by the first electron beam deflecting means. In the acceleration means,
The electron beam is passed through the same orbit and in a second traveling direction opposite to the first traveling direction (acceleration Y), and the second electron beam deflecting means deflects the DC electron beam, thereby accelerating the electron beam. The first electron beam deflecting means passes through the outside of the means and is again deflected by the first electron beam deflecting means, and again passes through the electron beam accelerating means in the same orbit and in the second traveling direction (acceleration Z). A DC electron beam accelerator, wherein the DC electron beam is accelerated by repeating the operation of the acceleration Z at least once or more. 2. The method according to claim 1, wherein the electron beam generating means generates a DC electron beam at the same frequency as the frequency of the high-frequency electric field applied to the electron beam accelerating means and synchronized with the electron beam accelerating means. The direct-current electron beam accelerator according to claim 1, wherein: 3. The electron beam generating means generates a DC electron beam at a frequency which is a fraction of the frequency of the high frequency electric field applied to the electron beam accelerating means and synchronized with the electron beam accelerating means. 2. The direct-current electron beam accelerator according to claim 1, wherein: 4. An acceleration phase when said DC electron beam passes through said electron beam acceleration means is different from each other for said acceleration X, said acceleration Y, and said acceleration Z. 4. The direct-current electron beam accelerator according to any one of 3. 5. The DC electron beam accelerator according to claim 1, further comprising a beam scraper that blocks a part of the DC electron beam that has passed through the electron beam accelerator. 6. A target for generating a high-speed positron by collision of the DC electron beam accelerated by repeating the operation of the acceleration Z, and a moderator for decelerating the high-speed positron. The direct-current electron beam accelerator according to any one of claims 1 to 5, wherein 7. An electron beam generating step of generating a DC electron beam, and passing the DC electron beam generated by the electron beam generating step in a first traveling direction through a high-frequency cavity into which a high-frequency electric field is applied. An accelerating X step of accelerating, and deflecting the traveling direction of the DC electron beam accelerated in the accelerating X step, and again traverse the high-frequency cavity in the same orbit and in a direction opposite to the first traveling direction. After passing in the two traveling directions, an acceleration Y step to accelerate, and deflecting the DC electron beam accelerated in the acceleration Y step, after passing the outside of the high-frequency cavity in the first traveling direction, Deflected again, inside the high-frequency cavity,
And accelerating the DC electron beam by repeating the operation of the accelerating Z step at least once or more. DC electron beam acceleration method.