CN1997260A - A kind of electron linear accelerator and using method thereof - Google Patents

Abstract

The present invention relates to the field of modern physics. The invention provides an electron linear accelerator with multi-gear energy adjustment, which comprises an electron gun (11), an accelerating structure, a microwave power source (14), isolators (12, 17) and an excitation power source (101), wherein the accelerating structure is divided into two parts, the two parts are respectively connected to a power divider (13) through the isolators, and the microwave power is obtained from the microwave power source (14); the two sections of accelerating structures are connected by a magnet (18) and keep a certain microwave phase; the track length of the electron beam can be changed by changing the magnetic induction intensity of the magnet (18), so that the time and the phase of the electron beam entering the second half accelerating structure are different, and the electron beam with different energy is finally output. By adopting the invention, the control and adjustment of the electron beam energy can be easily realized by changing the current intensity, thereby obtaining the electron accelerator with high speed and wide adjustable range.

Description

A kind of electron linear accelerator and using method thereof

technical field

The invention relates to the field of modern physics, in particular to an electron linear accelerator with multi-level energy regulation.

Background technique

Charged particles will be accelerated and their energy will be increased by force in the electric field. This is the principle adopted by electron accelerators so far. Neutral particles cannot be accelerated under such a principle. Thus, an electron accelerator is defined as a device that accelerates charged particles using electromagnetic fields. Electron accelerators can accelerate charged particles such as electrons, protons, ions, etc., so that the speed of the particles can reach thousands of kilometers per second, tens of thousands of kilometers per second, or even close to the speed of light. In the fields of radiation therapy, medical imaging, and non-destructive testing, electron accelerators are mainly used in radiation therapy devices, material-resolving non-destructive testing imaging systems, and other applications that require X-rays or electron beams. In these applications, the tunability of the electron beam energy is of great significance. Especially in the field of security inspection, it can realize the interval adjustment of electron beam energy between different pulses, and can partially realize the material identification of the inspected items.

The existing electronic energy adjustment methods of medical electron linear accelerators mainly change the coupling coefficient between the accelerating cavities through the mechanical movement of the energy switch, thereby changing the axial electric field distribution in the accelerating cavity chain, and realizing the adjustment of the electronic energy. The existing electron linear accelerators for non-destructive testing usually directly adjust the voltage of the pulse modulator to change the output pulse power of the microwave power source; and adjust the cathode high voltage of the electron gun of the accelerating tube to change the beam current load to realize the change of the electron beam energy. . The disadvantage of these methods is that it is difficult to change the energy of the electron beam in a large range, and it is difficult to realize the rapid adjustment of the electron energy between pulses.

Contents of the invention

(1) Technical problems to be solved

The purpose of the present invention is to overcome the defects of the current prior art, and propose an electron linear accelerator capable of changing electron beam energy in a large range and realizing rapid adjustment of electron energy.

(2) Technical solution

The invention proposes an electron linear accelerator, including an electron gun, an accelerating structure, a microwave power source, an isolator and an excitation power supply, wherein the electron gun obtains microwave power from the microwave power source through the isolator, generates an electromagnetic field, and emits electron beams, which pass through the accelerating structure The output after acceleration is characterized in that the acceleration structure is divided into two parts, namely the transverse acceleration structure and the longitudinal acceleration mechanism, which are respectively connected to the power divider through two isolators, the transverse isolator and the longitudinal isolator, and the microwave is obtained from the microwave power source. Power; The transverse acceleration structure and the longitudinal acceleration structure are connected by magnets and maintain a certain microwave phase.

A preferred solution of the above electron linear accelerator further includes a synchronous trigger control system for controlling the synchronization of the microwave power source and the excitation power source.

In the above electron linear accelerator, the angle between the transverse acceleration structure and the longitudinal acceleration structure is 80°-100°, and they are connected by magnets. One of the preferred schemes is that the angle between the transverse accelerating structure and the longitudinal accelerating structure is 90°.

In the above-mentioned electron linear accelerator, a preferred solution is that the trajectory of the electron beam in the magnet is in the shape of α.

In the above-mentioned electron linear accelerator, a preferred solution is that the variation range ΔL of the electron track length is from 0 to 5 cm.

The use method of the electron linear accelerator proposed by the present invention is to change the track length of the electron beam by changing the magnetic induction intensity of the magnet, so that the time and phase of the electron beam entering the longitudinal acceleration structure are different, and finally output electron beams with different energies.

In the above method of use, the relationship between the spatial distribution of the magnetic induction intensity of the magnet and the direction along the north pole of the magnet satisfies B _z (s)=k·s, where z represents the direction perpendicular to the paper surface, and s represents the displacement in the direction of the north pole.

In the above method of use, a preferred solution is that the output electron beam energy is realized by adjusting the magnetic induction intensity of the magnet, and other parameters of the electron accelerator remain unchanged.

In the above method of use, a preferred solution is to adjust the magnetic induction of the magnet so that there are two types of magnetic induction. When the electron beam enters the longitudinal acceleration structure, it corresponds to two different phases, corresponding to the final output of the electron beam. There are two states of energy, high energy and low energy.

In the above method of use, a preferred solution is to adjust the magnetic induction of the magnet so that the magnetic induction has three sizes. When the electron beam enters the longitudinal acceleration structure, it corresponds to three different phases, corresponding to the final output of the electron beam. Energy has three energy states.

In the above method of use, a preferred solution is to adjust the magnetic induction of the magnet so that the change of the magnetic induction over time is periodic and continuous, and the acceleration phase of the electron beam when it enters the longitudinal acceleration structure also changes continuously, corresponding to the final output The energy of the electron beam is continuously adjustable from We ₁ -We ₂ to We ₁ + We ₂ , and the energy of the electron beam is determined by the timing of the electron beam pulse and the change of magnetic induction intensity; where We ₁ is the acceleration of the electron beam through the first section The energy obtained after the structure, We ₂ is the energy obtained after the electron beam passes through the second accelerated structure.

(3) Beneficial effects

By adopting the invention, the control and adjustment of electron beam energy can be easily realized by changing the current intensity, thereby obtaining a fast electron accelerator with a large adjustable range, which has great effects on the fields of radiation medicine and non-destructive detection.

Description of drawings

Fig. 1 is a block diagram of the present invention;

Fig. 2 is the relationship diagram of the electron energy of the first kind of output and magnetic field intensity, phase shift;

Fig. 3 is the relation diagram of the electron energy of the second kind of output and magnetic field intensity, phase shift;

Fig. 4 is the relationship figure of the electron energy of the third kind of output and magnetic field intensity, phase shift;

Fig. 5 is the relationship diagram between the electric field intensity and the acceleration phase of the electron beam in the first acceleration structure;

Fig. 6 is a diagram showing the relationship between the electric field intensity of the electron beam and the acceleration phase in the second acceleration structure.

Among them, 11. Electron gun; 12. Transverse isolator; 13. Power divider; 14. Pulse microwave power source; 15. Transverse acceleration structure; 16. Vertical acceleration structure; 17. Longitudinal isolator; 18. Magnet; 19. Electronic beam movement track; 100, synchronous trigger control system; 101, excitation power supply.

Detailed ways

The present invention proposes an electron linear accelerator with multi-level energy adjustment, which is described below in conjunction with the drawings and embodiments. The following embodiments are only used to illustrate the present invention, but not to limit the present invention. Those of ordinary skill in the relevant technical field can also make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, all Equivalent technical solutions also belong to the category of the present invention, and the patent protection scope of the present invention should be defined by each claim.

The device of this invention, except including pulsed microwave power source 14, electron gun 11, isolator 12, acceleration structure, synchronous trigger control system 100 etc. all of general electron linear accelerator, wherein, acceleration structure is divided into independent two sections, namely transverse The acceleration structure 15 and the longitudinal acceleration structure 16 are close to each other and form an included angle of 90 degrees. The microwave power of the transverse acceleration structure 15 and the vertical direction 16 is respectively connected to the pulsed microwave power source 14 through the transverse isolator 12 and the longitudinal isolator 17, and the power divider 13, and obtains the microwave power from the microwave power source, which is used to establish the acceleration electron microwave electromagnetic field. The two acceleration structures are connected together by magnets 18. After the electron beam is accelerated in the transverse acceleration structure 15, it enters the longitudinal acceleration structure 16 through the magnet 18. According to the different track lengths of the electron beams in the magnet 18, in the acceleration structure 16 Different energies are obtained, wherein the trajectory 19 of the electron beam in the magnet 18 is similar to the shape of α, and the trajectory length is determined by the magnetic induction of the magnet 18, which is controlled by the excitation power supply 101.

According to the present invention, the relationship between the spatial distribution of magnetic induction and the direction along the north pole of the magnet satisfies B _z (s)=k·s, where z represents the direction perpendicular to the paper surface, and s represents the displacement in the direction of the north pole.

The entire device is controlled by the timing of the synchronous trigger control system 100. The trigger pulse sent by the synchronous trigger control system 100 controls the microwave power source 14 to generate microwave pulses, and at the same time controls the electron gun 11 to emit electron beam pulses. The electron beams are accelerated in the acceleration structure 15 to obtain energy. We ₁ . These belong to the prior art, and those skilled in the art know the specific conditions of the device, so details are not repeated here. The synchronous trigger control system 100 also controls the excitation power supply 101 to change the magnetic induction intensity in the magnet 18 .

Refer to Figure 1, Figure 5, and Figure 6. After the electron beam is accelerated by the transverse acceleration structure 15, the relationship between the output electric field intensity and the acceleration phase is shown in FIG. 5 . After the electron beam is input into the magnet 18, the length of the electron trajectory 19 is determined by the energy of the electron beam and the magnetic induction of the magnet 18, which can be expressed as L=f(We, B). Under different B of magnetic induction intensity, the track length of the electron changes, and the change in length is ΔL=f(We, B ₁ )-f(We, B ₂ ), and the change of the track length of the electron causes the electron to accelerate in the second section The change of the acceleration phase in the structure is specifically Δ=ω ₀ ·(ΔL/c). where _ω0 is the angular frequency of the accelerating electric field, and c is the speed of light. In order to adjust the variation range of the energy of accelerated electrons, from the maximum value We ₁ + We ₂ to the minimum value We ₁ -We ₂ , the phase variation range Δφ in the second acceleration structure should be from 0 to π, as shown in Figure 6 . Taking a microwave electric field operating at a frequency of 2998MHz as an example, the variation range of the electron trajectory length ΔL is from 0 to 5cm, and such a variation range can cover the phase variation range, that is, Δφ is from 0 to π.

For the magnetic induction intensity B of the magnet 18, the electron beam trajectory ₁₉ satisfies the electron acceleration in the first stage of the acceleration structure to obtain the energy of We ₁ , and the electron beam is also in the best acceleration phase in the second stage to obtain the highest output energy, namely Corresponding to the position 50 in FIG. 6 , the electron beam obtains the energy of We ₂ in the second section. The greater the magnetic induction of the magnet 18, the shorter the track length of the electrons, the earlier the electrons reach the second stage, and the greater the phase difference. For a magnetic induction greater than B ₀ , the phase of the electron beam in the second segment is in a position similar to 51; for a magnetic induction lower than B ₀ , the phase of the electron beam in the second segment is in a position similar to 52-55. The electron beam is in a different phase position in the second segment, which will make it get a different energy in the second segment, or even reduce the energy it gets in the first segment, such as similar to 54, or even reach the lowest output energy , such as the position of 55.

For the adjustment scheme of the electronic energy output, referring to FIG. 2 , a two-stage adjustable scheme is adopted. Among them, the change of the magnetic field strength with time is a step, there are 2 kinds of strength; correspondingly with the change of the magnetic field strength, the change of the phase shift with time is also a step, there are 2 kinds of sizes; the output electron energy changes with time The change is impulsive, and there are two kinds of sizes. The phase shift corresponding to low magnetic field strength is greater than 0, corresponding to low electron energy; the phase shift corresponding to high magnetic field strength is 0, corresponding to high electron energy.

For the situation in Figure 3, a three-level adjustable scheme is adopted. Among them, the change of the magnetic field strength with time is a step, and there are 3 kinds of strength; correspondingly with the change of the magnetic field strength, the change of the phase shift with time is also a step, with 3 kinds of sizes; therefore, the output pulse electron energy has Three cases, in which the phase shift corresponding to low magnetic field strength is close to 180 degrees, corresponding to low electron energy; the phase shift corresponding to medium magnetic field strength is between 0 degrees and 180 degrees, corresponding to medium electron energy; the phase corresponding to high magnetic field strength A shift of 0 degrees corresponds to high electron energy.

For the situation in Figure 4, a continuously adjustable scheme is adopted. Among them, the change of the magnetic field strength with time is continuous, correspondingly with the change of the magnetic field strength, the change of the phase shift with time is also continuous; therefore, the size of the output electron energy is also steplessly adjustable; where the magnetic field strength The change is inversely proportional to the change in phase shift, and the change in magnetic field strength is in direct proportion to the change in electron energy.

Because by adjusting the size of the magnetic induction intensity of the magnet 18, the energy obtained by the electron beam in the device can be adjusted conveniently, and other parameters of the electron accelerator, such as the power size of the microwave power source, the field strength in the accelerating structure, the electron gun Parameters such as emission flux intensity remain basically unchanged, which is the same as the general situation in the prior art. Therefore, the present invention can realize a wide range of adjustable electron beam output energy. As mentioned above, two-level adjustable, three-level adjustable, or similar multi-level adjustable or stepless adjustable adjustment schemes can be used .

The magnetic induction of the magnet 18 is excited by the current of the wire pack. Therefore, the magnetic induction can be easily adjusted by adjusting the current intensity of the wire pack in the excitation power supply 101, thereby adjusting the energy of the electron beam output by the device, while other parameters remain basically unchanged.

It can be seen that with the present invention, since the output energy of the electron beam depends on the current intensity of the excitation power supply, the control and adjustment of the energy of the electron beam can be easily realized by changing the current intensity, thereby obtaining a fast electron accelerator with a large adjustable range .

Claims (12)

1, a kind of electron linear accelerator, comprise electron gun (11), accelerating structure, microwave power source (14), isolator, field power supply (101), its electron gun obtains microwave power by isolator from microwave power source, generate an electromagnetic field, send electron beam, electron beam quickens back output by accelerating structure, it is characterized in that accelerating structure is divided into two parts, be respectively horizontal accelerating structure (15) and vertical acceleration mechanism (16), by 2 isolators is that lateral isolation device (12) and vertical isolator (17) are connected respectively to power divider (13), obtains microwave power from microwave power source (14); Laterally be connected and keep certain microwave phase by magnet (18) between accelerating structure (15) and the vertical accelerating structure (16).

2, electron linear accelerator as claimed in claim 1 is characterized in that also comprising synchronous triggering control system (100), is used for the synchronous of controlled microwave power source (14) and field power supply (101).

3, electron linear accelerator as claimed in claim 1, it is characterized in that horizontal accelerating structure (15) and vertically the angle between the accelerating structure (16) be 80 °-100 °, between link to each other by magnet (18).

4, electron linear accelerator as claimed in claim 1 is characterized in that the angle between horizontal accelerating structure (15) and the vertical accelerating structure (16) is 90 °.

5, electron linear accelerator as claimed in claim 1 is characterized in that the movement locus (19) of electron beam in magnet (18) is the α shape.

6, electron linear accelerator as claimed in claim 1 is characterized in that from 0 to 5 centimetre of the variation range delta L of electron trajectory (19) length.

7, a kind of using method of electron linear accelerator as claimed in claim 1, it is characterized in that by changing the magnetic flux density of magnet (18), can change the path length of electron beam, thereby it is different with phase place to make electron beam enter time of vertical accelerating structure (16), finally exports the different electron beam of energy.

8, using method as claimed in claim 7 is characterized in that the spatial distribution of the magnetic flux density of magnet (18), satisfies B with relation along magnet (18) direction to the north pole _z(s)=and ks, wherein z represents vertical paper direction, s represents the displacement of direction to the north pole.

9, using method as claimed in claim 7 is characterized in that the electron beam energy of exporting realizes that by the magnetic flux density of regulating magnet (18) other parameter of electron accelerator remains unchanged.

10, as the described using method of one of claim 7-9, it is characterized in that magnetic flux density by regulating magnet (18), make magnetic flux density have size and have two kinds, electron beam corresponds to two kinds of different phase places respectively when entering vertical accelerating structure (16), the electron beam energy that corresponds to final output has high energy and low energy two states.

11, as the described using method of one of claim 7-9, it is characterized in that magnetic flux density by regulating magnet (18), making magnetic flux density have size is three kinds, electron beam corresponds to three kinds of different phase places respectively when entering vertical accelerating structure (16), the electron beam energy that corresponds to final output has three kinds of energy state.

12, as the described using method of one of claim 7-9, it is characterized in that magnetic flux density by regulating magnet (18), making magnetic flux density is that the cycle is continuous over time, residing accelerating phase also changed continuously when electron beam entered vertical accelerating structure (16), and the electron beam energy that corresponds to final output is We ₁-We ₂To We ₁+ We ₂Continuously adjustable electron energy, the sequential decision that the energy of electron beam is changed by beam pulse and magnetic flux density; We wherein ₁Be the energy that electron beam obtains after by first section accelerating structure, We ₂The energy that obtains after by second section accelerating structure for electron beam.

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