CN110489881B - Design method and device for cusp electron gun - Google Patents
Design method and device for cusp electron gun Download PDFInfo
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- CN110489881B CN110489881B CN201910778352.2A CN201910778352A CN110489881B CN 110489881 B CN110489881 B CN 110489881B CN 201910778352 A CN201910778352 A CN 201910778352A CN 110489881 B CN110489881 B CN 110489881B
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Abstract
The invention relates to a design method and a device of a cusp electron gun, and relates to the technical field of millimeter wave and terahertz wave power amplifiers. Wherein, the method comprises the following steps: obtaining a dispersion curve of the threaded waveguide; constructing a dispersion curve of an electron beam generated by the cusp electron gun according to the dispersion curve of the threaded waveguide; the dispersion curve of the electron beam generated by the cusp electron gun is matched with the dispersion curve of the threaded waveguide in a working frequency band; and determining technical parameters of the cusp electron gun based on the dispersion curve of the electron beam. Through the steps, the cusp electron gun matched with the thread waveguide can be designed, and the problem of low performance of the electron gun in the conventional electromagnetic wave amplifier is solved.
Description
Technical Field
The invention relates to the technical field of millimeter wave and terahertz wave power amplifiers, in particular to a cusp electron gun design method and a cusp electron gun design device.
Background
The threaded waveguide is a core device of a W-band electromagnetic wave amplifier, can perform mode coupling on electromagnetic waves, reduces the sensitivity of the electromagnetic waves to speed dispersion while expanding the bandwidth of the electromagnetic waves, and can increase the capability of inhibiting mode competition.
When developing a W-band electromagnetic wave amplifier, a high-performance electron gun is required to be designed. The electron beam generated by the electron gun can exchange energy with the electromagnetic wave under a certain condition so as to achieve the purpose of amplifying the power of the electromagnetic wave. The performance of the electron gun directly determines the performance of the amplifier.
The electron gun is mainly classified into a magnetron injection electron gun, a pierce gun, and a cusp (magnetic cusp) electron gun. Among these, the magnetron injection electron gun generates a ring-shaped electron beam, which is ideal for a gyrotron operating in a fundamental mode, but is liable to generate parasitic oscillation for a gyrotron operating in a harmonic mode. The disadvantage of the pierce gun is that it is difficult to operate in continuous wave mode and the tight electron beam after depletion can cause bright spots on the surface of the spot where it is collected and damage the system. The cusp electron gun can generate an electron beam which moves around a shaft in a circular mode and supports a continuous wave mode, and the transverse-longitudinal velocity ratio of the electron beam can be controlled by changing the magnetic field intensity at the cathode.
In the process of implementing the invention, the inventor of the invention finds that: for the W-band electromagnetic wave amplifier, a cusp electron gun may be selected. However, no solution is provided in the prior art how to design a high performance cusp electron gun. In view of the above, it is desirable to provide a design scheme for designing a high-performance cusp electron gun, so as to solve the problem of low performance of the electron gun in the conventional electromagnetic wave amplifier.
Disclosure of Invention
Technical problem to be solved
The invention aims to solve the technical problem of low performance of an electron gun in the existing electromagnetic wave amplifier.
(II) technical scheme
In order to solve the above technical problems, in one aspect, the present invention provides a design method of a cusp electron gun.
The design method of the cusp electron gun comprises the following steps: obtaining a dispersion curve of the thread waveguide; constructing a dispersion curve of an electron beam generated by the cusp electron gun according to the dispersion curve of the threaded waveguide; the dispersion curve of the electron beam generated by the cusp electron gun is matched with the dispersion curve of the threaded waveguide in a working frequency band; and determining technical parameters of the cusp electron gun based on the dispersion curve of the electron beam.
Optionally, the step of constructing a dispersion curve of an electron beam generated by a cusp electron gun according to the dispersion curve of the threaded waveguide includes: taking the slope of the dispersion curve of the threaded waveguide as the slope of the dispersion curve of the electron beam, taking the intercept of the dispersion curve of the threaded waveguide as the intercept of the dispersion curve of the electron beam, and constructing the dispersion curve of the electron beam generated by the cusp electron gun based on the slope of the dispersion curve of the electron beam and the intercept of the dispersion curve of the electron beam; wherein, the dispersion curve of the electron beam generated by the cusp electron gun satisfies the following conditions:
ω＝k z v z +sω ce ；
in the formula, ω is the radiation frequency, v z Is the slope of the dispersion curve of the electron beam, which represents the axial velocity, k, of the electron beam motion z Is the axial wave number, s ω ce Is the intercept of the dispersion curve of the electron beam, s is the radiation mode, ω ce The angular frequency of the electron beam in the axial magnetic field.
Optionally, the step of determining a technical parameter of the cusp electron gun based on the dispersion curve of the electron beam comprises: determining the axial speed of the electron beam and the forward magnetic field intensity according to the dispersion curve of the electron beam; determining the speed of the electron beam according to the axial speed of the electron beam and the speed ratio of the speed of the electron beam in the vertical direction to the axial direction; determining the acceleration voltage of the cathode of the electron gun according to the speed of the electron beam; determining electron beam current according to the power of the electron beam and the accelerating voltage of the cathode of the electron gun; the average radius of the cathode is determined from the ratio of the velocity in the vertical direction of the electron beam to the velocity in the axial direction.
Optionally, the method further comprises: optimizing the technical parameters of the cusp electron gun based on a plurality of simulation evaluation indexes to obtain the optimized technical parameters of the cusp electron gun; wherein the plurality of simulation evaluation indexes include: the distribution of the electron beam, the velocity ratio of the electron beam in the vertical direction to the velocity in the axial direction.
In order to solve the above technical problem, in another aspect, the present invention further provides a cusp electron gun design apparatus.
The cusp electron gun design device of the invention comprises: the acquisition module is used for acquiring a dispersion curve of the threaded waveguide; the construction module is used for constructing a dispersion curve of an electron beam generated by the cusp electron gun according to the dispersion curve of the threaded waveguide; the dispersion curve of the electron beam generated by the cusp electron gun is matched with the dispersion curve of the threaded waveguide in a working frequency band; and the determining module is used for determining technical parameters of the cusp electron gun based on the dispersion curve of the electron beam.
Optionally, the constructing module constructs a dispersion curve of an electron beam generated by a cusp electron gun according to the dispersion curve of the threaded waveguide includes: the construction module takes the slope of the dispersion curve of the threaded waveguide as the slope of the dispersion curve of the electron beam, takes the intercept of the dispersion curve of the threaded waveguide as the intercept of the dispersion curve of the electron beam, and constructs the dispersion curve of the electron beam generated by the cusp electron gun based on the slope of the dispersion curve of the electron beam and the intercept of the dispersion curve of the electron beam; wherein, the dispersion curve of the electron beam generated by the cusp electron gun satisfies the following conditions:
ω＝k z v z +sω ce ；
where ω is the radiation frequency, v z Is the slope of the dispersion curve of the electron beam, which represents the axial velocity, k, of the electron beam motion z Is the axial wave number, s ω ce Is the intercept of the dispersion curve of the electron beam, s is the radiation mode, ω ce The angular frequency of the electron beam in the axial magnetic field.
Optionally, the determining module determining the technical parameter of the cusp electron gun based on the dispersion curve of the electron beam comprises: the determining module determines the axial speed and the forward magnetic field strength of the electron beam according to the dispersion curve of the electron beam; the determining module determines the speed of the electron beam according to the axial speed of the electron beam and the speed ratio of the speed of the electron beam in the vertical direction to the speed of the electron beam in the axial direction; the determining module determines the accelerating voltage of the cathode of the electron gun according to the speed of the electron beam; the determining module determines the current of the electron beam according to the power of the electron beam and the accelerating voltage of the cathode of the electron gun; the determining module determines the average radius of the cathode according to the speed ratio of the vertical direction of the electron beam to the axial direction of the electron beam.
Optionally, the apparatus further comprises: the optimization module is used for optimizing the technical parameters of the cusp electron gun based on a plurality of simulation evaluation indexes to obtain the optimized technical parameters of the cusp electron gun; wherein the plurality of simulation evaluation indexes include: the distribution of the electron beam, the velocity ratio of the electron beam in the vertical direction to the velocity in the axial direction.
(III) advantageous effects
The technical scheme of the invention has the following advantages: the method comprises the steps of obtaining a dispersion curve of the threaded waveguide, constructing a dispersion curve of an electron beam generated by a cusp electron gun matched with the dispersion curve of the threaded waveguide according to the dispersion curve of the threaded waveguide, and determining technical parameters of the cusp electron gun based on the dispersion curve of the electron beam, so that the cusp electron gun matched with the threaded waveguide can be designed, and the problem of low performance of the electron gun in the conventional electromagnetic wave amplifier is solved.
Drawings
Fig. 1 is a schematic flow chart of a cusp electron gun design method according to a first embodiment of the present invention;
FIG. 2 is a schematic flow chart illustrating a design method of a cusp electron gun according to a second embodiment of the present invention;
FIG. 3 is an exemplary schematic of an electron gun dispersion curve and a helical waveguide dispersion curve;
FIG. 4 is a schematic cathode view of a cusp electron gun;
FIG. 5 is a schematic cross-sectional view of a cusp electron gun simulation model;
fig. 6 is a schematic view of the distribution of electron beams in an axial cross section obtained by CST simulation;
fig. 7 is a schematic composition diagram of a cusp electron gun design apparatus according to a third embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.
Example one
Fig. 1 is a schematic flow chart of a cusp electron gun design method according to a first embodiment of the present invention. As shown in fig. 1, a method for designing a cusp electron gun according to an embodiment of the present invention includes:
and S101, obtaining a dispersion curve of the threaded waveguide.
In this step, the dispersion curve of the threaded waveguide can be determined by simulation or experimental measurement. In specific implementation, related technical parameters of the threaded waveguide, such as geometric parameters of the threaded waveguide and a dispersion curve of the threaded waveguide, can be obtained through the design of the threaded waveguide in the early stage.
And S102, constructing a dispersion curve of the electron beam generated by the cusp electron gun according to the dispersion curve of the threaded waveguide.
The cusp electron gun comprises two solenoids, one solenoid is positioned at the waveguide cavity, the other solenoid is positioned behind the cathode, and the directions of the two solenoids are opposite. The magnetic field generated by the two solenoids generates a cusped magnetic field in the region of the front end of the cathode, and the electron beam generated by the cathode makes a helical motion in the magnetic field. Along with the increase of the magnetic field, the gyration radius of the electron beam is gradually reduced, finally, in the region with stable magnetic field intensity, the radius of the electron beam tends to be stable, and the electron beam with proper transverse-longitudinal velocity ratio enters the wave injection interaction region to exchange energy with electromagnetic waves.
In the embodiment of the present invention, in order to obtain a high-performance cusp electron gun, the dispersion curve of the electron beam generated by the cusp electron gun needs to be matched with the dispersion curve of the threaded waveguide in an operating frequency band (such as a W band). In view of this, a dispersion curve of the electron beam generated by the cusp electron gun may be constructed starting from the dispersion curve of the threaded waveguide.
And step S103, determining technical parameters of the cusp electron gun based on the dispersion curve of the electron beam.
After determining the dispersion curve of the electron beam, at least one of the following technical parameters of the cusp electron gun may be determined based on the dispersion curve of the electron beam: acceleration voltage of electron gun cathode, electron beam current, velocity ratio, axial velocity diffusion, cathode region magnetic field, downstream region magnetic field, cathode average radius, cathode ring radius difference, etc.
In the embodiment of the invention, the cusp electron gun matched with the thread waveguide can be designed through the steps, so that the problem of low performance of the electron gun in the conventional electromagnetic wave amplifier is solved.
Example two
Fig. 2 is a schematic flow chart of a cusp electron gun design method according to a second embodiment of the present invention. As shown in fig. 2, the method for designing a cusp electron gun according to the embodiment of the present invention includes:
and step S201, obtaining a dispersion curve of the threaded waveguide.
In this step, the dispersion curve of the threaded waveguide may be determined by simulation or experimental measurements. In specific implementation, related technical parameters of the threaded waveguide, such as geometric parameters of the threaded waveguide and a dispersion curve of the threaded waveguide, can be obtained through the design of the threaded waveguide in the early stage.
And S202, constructing a dispersion curve of the electron beam generated by the cusp electron gun according to the dispersion curve of the threaded waveguide.
The cusp electron gun comprises two solenoids, one solenoid is positioned at the waveguide cavity, the other solenoid is positioned behind the cathode, and the directions of the two solenoids are opposite. The magnetic field generated by the two solenoids can generate a tangential magnetic field in the region of the front end of the cathode, and the electron beam generated by the cathode makes a helical motion in the magnetic field. Along with the increase of the magnetic field, the gyration radius of the electron beam is gradually reduced, finally, in the region with stable magnetic field intensity, the radius of the electron beam tends to be stable, and the electron beam with proper transverse-longitudinal velocity ratio enters the wave injection interaction region to exchange energy with electromagnetic waves.
Generally, since the electron beam dispersion curve and the waveguide dispersion curve have only one intersection, the electron beam generally interacts with only one frequency of the electromagnetic wave, thereby transferring energy to the electromagnetic wave. In order to solve the problem, when the threaded waveguide is designed in the prior period, the reasonable design of the threaded waveguide and the external magnetic field can be used for obtaining the ideal dispersion curve of the threaded waveguide. That is, the portion of the dispersion curve of the threaded waveguide that is within the operating frequency range is approximated to a straight line.
In the embodiment of the present invention, in order to obtain a high-performance cusp electron gun, a dispersion curve of an electron beam generated by the cusp electron gun needs to be matched with a dispersion curve of the threaded waveguide within an operating frequency band (for example, a W band), or a dispersion curve of an electron beam generated by the cusp electron gun needs to be overlapped with a dispersion curve of the threaded waveguide as much as possible within the operating frequency band (for example, the W band), as shown in fig. 3. In view of this, a dispersion curve of an electron beam generated by a cusp electron gun may be constructed starting from the dispersion curve of the threaded waveguide.
Specifically, step S202 includes: and constructing the dispersion curve of the electron beam generated by the cusp electron gun based on the slope of the dispersion curve of the electron beam and the intercept of the dispersion curve of the electron beam.
And S203, determining technical parameters of the cusp electron gun based on the dispersion curve of the electron beam.
After determining the dispersion curve of the electron beam, the following technical parameters of the cusp electron gun may be determined based on the dispersion curve of the electron beam: acceleration voltage of electron gun cathode, electron beam current, velocity ratio, axial velocity spread, cathode region magnetic field, downstream region magnetic field, cathode average radius, cathode ring radius difference, etc.
In one example, step S203 specifically includes: step a1 to step a5.
Step a1, determining the axial speed of the electron beam and the forward magnetic field intensity according to the dispersion curve of the electron beam.
Wherein, the dispersion curve of the electron beam generated by the cusp electron gun can be expressed as:
ω＝k z v z +sω ce ；
in the formula, ω is the radiation frequency, v z Is the slope of the dispersion curve of the electron beam, which represents the axial velocity, k, of the electron beam motion z Is the axial wave number, s ω ce Is the intercept of the dispersion curve of the electron beam, s is the radiation mode, ω ce Is the angular frequency of the electron beam in the axial magnetic field.
In this step, the axial velocity v of the electron beam can be determined from the slope of the dispersion curve of the electron beam z S ω can be determined from the intercept of the dispersion curve of the electron beam ce The value of (c). Furthermore, the electromagnetic wave after passing through the spiral waveguide is mainly TE 21 The mode is dominant, and the interaction condition of electromagnetic wave and electron beam requires s = m, so s =2 can be obtained, and ω can be determined ce The value of (c). And because of
Is electron charge-to-mass ratio (-1.75881963 x 10) 11 C/kg), gamma is a relativistic factor of the electron beam, so that the strength B of the forward magnetic field can be determined 0 (i.e., "downstream magnetic field strength").
And a2, determining the speed of the electron beam according to the axial speed of the electron beam and the speed ratio of the speed of the electron beam in the vertical direction to the speed of the electron beam in the axial direction.
Wherein, the velocity ratio of the electron beam in the vertical direction to the velocity in the axial direction can be represented by α, and it satisfies:
in the formula, v ⊥ Is the vertical velocity, v, of the electron beam z Is the axial velocity, V, of the electron beam 0 Is the electron velocity (or called "velocity of the electron beam"), r c Is the average radius of the cathode, omega c Is the cathode electron angular frequency, omega 0 Alpha is usually 1 to 3 for the electron angular frequency in the downstream region.
In this step, the value of α is combined with the axial velocity v of the electron beam determined in step a1 z Can determine the velocity V of the electron beam 0 。
And a3, determining the accelerating voltage of the cathode of the electron gun according to the speed of the electron beam.
In this step, according to the formula
The value of the potential difference U between the cathode and the anode of the electron gun can be determined. Further, the electron gun anode potential is made 0, and the acceleration voltage of the electron gun cathode can be determined.
And a4, determining the current of the electron beam according to the power of the electron beam and the accelerating voltage of the cathode of the electron gun.
Specifically, the power of the electron beam can be determined based on the output power of the amplifier in the operating band and the power conversion efficiency between the electron beam generated by the electron gun and the electromagnetic wave. For example, assuming that the output power of the amplifier in the W band is 5kW, it is determined that the power of the electron beam should be 20kW in the operating band of 90GHz to 100GHz, and the power conversion efficiency between the electron beam generated by the electron gun and the electromagnetic wave is about 25% according to the experimental measurement.
In the case where the power of the electron beam and the acceleration voltage of the electron gun cathode have been determined, a cathode emission-side electron beam current (simply referred to as "electron beam current") may be determined from the power of the electron beam and the acceleration voltage of the electron gun cathode.
And a5, determining the average radius of the cathode according to the speed ratio of the vertical direction of the electron beam to the axial direction.
Specifically, in this step, the cathode average radius may be determined according to the following formula:
in the formula, r c Is the average radius of the cathode, omega c Is the cathode electron angular frequency, omega 0 The electron angular frequency in the downstream region, α is the velocity ratio of the electron beam in the vertical direction to the axial direction, V 0 Is the electron velocity.
In addition, in addition to the above technical parameters of the electron gun determined by steps a1 to a5, the cathode ring radius difference Δ R, the cathode ring first radius R may also be determined by software simulation e1 The second radius R of the cathode ring e2 (as shown in fig. 4) and the like. In addition, in the present inventionIn an embodiment, the simulation can be optimized from the following aspects: 1. by taking the size of the cathode of the electron gun and the intensity of the applied magnetic field into consideration
2. Controlling the current density at 5-10A/cm 2 (ii) a 3. The acceleration voltage adopts a smooth rising function, and the rising time is set to be 1ns so as to avoid high-frequency load; 4. because the electron gun has larger thermal load at 1000 ℃, the heating coil can adopt double-strand winding in order to reduce parasitic magnetic field; 5. in order to reduce the heat load and prevent the migration of barium in the cathode, two grooves with a certain width (such as 0.1 mm) can be designed on the cathode to separate the cathode rings.
In a specific example, the technical parameters of the electron gun determined through steps S201 to S203 are shown in the following table:
TABLE 1
And S204, optimizing the technical parameters of the cusp electron gun based on a plurality of simulation evaluation indexes to obtain the optimized technical parameters of the cusp electron gun.
Wherein the plurality of simulation evaluation indexes include: the distribution of the electron beam, the velocity ratio of the electron beam in the vertical direction to the velocity in the axial direction. In specific implementation, the particle module of the CST software is used to perform electron gun modeling (an electron gun simulation model is shown in fig. 5), and parameters such as electron beam distribution (shown in fig. 6) and velocity ratio generated by the electron gun are obtained through simulation. Furthermore, by comparing parameters such as electron beam distribution obtained by multiple simulations, the technical parameters of the cusp electron gun can be optimized.
In the embodiment of the invention, the cusp electron gun matched with the thread waveguide can be designed through the steps, so that the high-efficiency amplification of the width electromagnetic wave can be realized, and the problem of low performance of the electron gun in the conventional electromagnetic wave amplifier is solved.
EXAMPLE III
Fig. 7 is a schematic composition diagram of a cusp electron gun design apparatus according to a third embodiment of the present invention. As shown in fig. 7, a cusp electron gun design apparatus 700 according to an embodiment of the present invention includes: an obtaining module 701, a constructing module 702, and a determining module 703.
An obtaining module 701 is configured to obtain a dispersion curve of the threaded waveguide. In particular, the acquisition module 701 may determine the dispersion curve of the threaded waveguide through simulation or experimental measurements. In specific implementation, related technical parameters of the threaded waveguide, such as the geometric parameters of the threaded waveguide and the dispersion curve of the threaded waveguide, can be obtained through the early design of the threaded waveguide.
A building module 702, configured to build a dispersion curve of an electron beam generated by the cusp electron gun according to the dispersion curve of the threaded waveguide.
The cusp electron gun comprises two solenoids, one solenoid is positioned at the waveguide cavity, the other solenoid is positioned behind the cathode, and the directions of the two solenoids are opposite. The magnetic field generated by the two solenoids generates a cusped magnetic field in the region of the front end of the cathode, and the electron beam generated by the cathode makes a helical motion in the magnetic field. Along with the increase of the magnetic field, the gyration radius of the electron beam is gradually reduced, finally, in the region with stable magnetic field intensity, the radius of the electron beam tends to be stable, and the electron beam with proper transverse-longitudinal velocity ratio enters the wave injection interaction region to exchange energy with electromagnetic waves.
Generally, since the dispersion curve of the electron beam and the dispersion curve of the waveguide have only one intersection, the electron beam generally interacts with only one frequency of the electromagnetic wave, thereby transferring energy to the electromagnetic wave. In order to solve the problem, when the threaded waveguide is designed in the prior period, the reasonable design of the threaded waveguide and the external magnetic field can be used for obtaining the ideal dispersion curve of the threaded waveguide. That is, the portion of the dispersion curve of the threaded waveguide in the operating frequency range is approximated to a straight line.
In the embodiment of the present invention, in order to obtain a high-performance cusp electron gun, a dispersion curve of an electron beam generated by the cusp electron gun needs to match a dispersion curve of the threaded waveguide in an operating frequency band (for example, a W band), or a dispersion curve of an electron beam generated by the cusp electron gun needs to coincide as much as possible with a dispersion curve of the threaded waveguide in the operating frequency band (for example, the W band). In view of this, a dispersion curve of an electron beam generated by a cusp electron gun may be constructed starting from the dispersion curve of the threaded waveguide.
Specifically, the constructing module 702 constructing the dispersion curve of the electron beam generated by the cusp electron gun according to the dispersion curve of the threaded waveguide includes: the construction module 702 takes the slope of the dispersion curve of the threaded waveguide as the slope of the dispersion curve of the electron beam, the construction module 702 takes the intercept of the dispersion curve of the threaded waveguide as the intercept of the dispersion curve of the electron beam, and the construction module 702 constructs the dispersion curve of the electron beam generated by the cusp electron gun based on the slope of the dispersion curve of the electron beam and the intercept of the dispersion curve of the electron beam.
A determining module 703 for determining technical parameters of the cusp electron gun based on the dispersion curve of the electron beam.
After constructing the dispersion curve of the electron beam, the determining module 703 may determine the following technical parameters of the cusp electron gun based on the dispersion curve of the electron beam: acceleration voltage of electron gun cathode, electron beam current, velocity ratio, axial velocity diffusion, cathode region magnetic field, downstream region magnetic field, cathode average radius, cathode ring radius difference, etc.
In one example, the determining module 703 determining a technical parameter of the cusp electron gun based on the dispersion curve of the electron beam includes:
a1, a determining module 703 determines the axial speed of the electron beam and the forward magnetic field strength according to the dispersion curve of the electron beam.
Wherein, the dispersion curve of the electron beam generated by the cusp electron gun can be expressed as:
ω＝k z v z +sω ce ；
in the formula, ω is the radiation frequency, v z Is the slope of the dispersion curve of the electron beam, which represents the axial velocity, k, of the electron beam motion z Is the axial wave number, s ω ce Is the intercept of the dispersion curve of the electron beam, s isRadiation pattern, ω ce The angular frequency of the electron beam in the axial magnetic field.
In particular, the determination module 703 determines the axial velocity v of the electron beam from the slope of the dispersion curve of the electron beam z The determining module 703 may determine s ω according to the intercept of the dispersion curve of the electron beam ce The value of (c). Furthermore, the electromagnetic wave after passing through the spiral waveguide is mainly TE 21 The mode is dominant, and the interaction condition of electromagnetic wave and electron beam requires s = m, so s =2 can be obtained, and ω can be determined ce The value of (c). And because of
Is electron charge-to-mass ratio (-1.75881963 x 10) 11 C/kg), gamma is a relativistic factor of the electron beam, so that the strength B of the forward magnetic field can be determined 0 (i.e., "downstream magnetic field strength").
A2, the determining module 703 determines the velocity of the electron beam according to the axial velocity of the electron beam and the velocity ratio of the velocity in the vertical direction of the electron beam to the velocity in the axial direction.
Wherein the velocity ratio of the electron beam in the vertical direction to the velocity in the axial direction can be represented by α, and it satisfies:
in the formula, v ⊥ Is the vertical velocity, v, of the electron beam z Is the axial velocity, V, of the electron beam 0 Is the electron velocity (or called "velocity of the electron beam"), r c Is the average radius of the cathode, omega c Is the cathode electron angular frequency, omega 0 Alpha is usually 1 to 3 for the electron angular frequency in the downstream region.
Furthermore, the determination module 703 combines the value of α and the axial velocity v of the electron beam z Can determine the velocity V of the electron beam 0 。
A3, determining the acceleration voltage of the cathode of the electron gun according to the speed of the electron beam by the determining module 703.
In particular, a modulus is determinedBlock 703 is based on the formula
The value of the potential difference U between the cathode and the anode of the electron gun can be determined. Further, the electron gun anode potential is made 0, and the acceleration voltage of the electron gun cathode can be determined.
A4, determining module 703 determines the electron beam current according to the power of the electron beam and the accelerating voltage of the electron gun cathode.
Specifically, the determining module 703 may determine the power of the electron beam according to the output power of the amplifier in the operating frequency band and the power conversion efficiency between the electron beam generated by the electron gun and the electromagnetic wave. For example, assuming that the output power of the amplifier in the W band is 5kW, it is determined that the power of the electron beam should be 20kW in the operating band of 90GHz to 100GHz, and the power conversion efficiency between the electron beam generated by the electron gun and the electromagnetic wave is about 25% according to the experimental measurement.
In the case where the power of the electron beam and the acceleration voltage of the electron gun cathode have been determined, the determining module 703 may determine a cathode-emission-side electron beam current (simply referred to as "electron beam current") from the power of the electron beam and the acceleration voltage of the electron gun cathode.
A5, a determining module 703 determines the average radius of the cathode according to the speed ratio of the vertical direction speed of the electron beam to the axial direction speed.
Specifically, the determination module 703 may determine the cathode average radius according to the following equation:
in the formula, r c Is the average radius of the cathode, omega c Is the cathode electron angular frequency, omega 0 The electron angular frequency in the downstream region, α is the velocity ratio of the electron beam in the vertical direction to the axial direction, V 0 Is the electron velocity.
In addition, the determining module 703 may also determine the cathode ring radius difference Δ r and the cathode ring first by software simulationRadius R e1 Cathode ring second radius R e2 And the like.
Further, the apparatus of the embodiment of the present invention may further include: and the optimization module is used for optimizing the technical parameters of the cusp electron gun based on a plurality of simulation evaluation indexes to obtain the optimized technical parameters of the cusp electron gun. Wherein the plurality of simulation evaluation indexes include: the distribution of the electron beam, the velocity ratio of the electron beam in the vertical direction to the velocity in the axial direction.
In the embodiment of the invention, the cusp electron gun matched with the thread waveguide can be designed through the device, so that the high-efficiency amplification of the width electromagnetic wave can be realized, and the problem of low performance of the electron gun in the conventional electromagnetic wave amplifier is solved.
Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
Claims (6)
1. A cusp electron gun design method is characterized by comprising the following steps:
obtaining a dispersion curve of the thread waveguide;
constructing a dispersion curve of an electron beam generated by a cusp electron gun according to the dispersion curve of the threaded waveguide; the dispersion curve of the electron beam generated by the cusp electron gun is matched with the dispersion curve of the threaded waveguide in a working frequency band;
determining technical parameters of a cusp electron gun based on the dispersion curve of the electron beam;
the step of constructing a dispersion curve of an electron beam generated by a cusp electron gun according to the dispersion curve of the threaded waveguide comprises the following steps: taking the slope of the dispersion curve of the threaded waveguide as the slope of the dispersion curve of the electron beam, taking the intercept of the dispersion curve of the threaded waveguide as the intercept of the dispersion curve of the electron beam, and constructing the dispersion curve of the electron beam generated by the cusp electron gun based on the slope of the dispersion curve of the electron beam and the intercept of the dispersion curve of the electron beam; wherein, the dispersion curve of the electron beam generated by the cusp electron gun satisfies the following conditions:
in the formula (I), the compound is shown in the specification,
in order to be the frequency of the radiation,
the slope of the dispersion curve of the electron beam, which represents the axial velocity of the electron beam motion,
is the number of wave numbers in the axial direction,
is the intercept of the dispersion curve of the electron beam,
in order to be in the radiation mode,
the angular frequency of the electron beam in the axial magnetic field.
2. The method of claim 1, wherein the step of determining a specification of a cusp electron gun based on the dispersion curve of the electron beam comprises:
determining the axial speed of the electron beam and the forward magnetic field intensity according to the dispersion curve of the electron beam; determining the speed of the electron beam according to the axial speed of the electron beam and the speed ratio of the speed of the electron beam in the vertical direction to the axial direction; determining the acceleration voltage of the cathode of the electron gun according to the speed of the electron beam; determining electron beam current according to the power of the electron beam and the accelerating voltage of the cathode of the electron gun; the average radius of the cathode is determined according to the ratio of the velocity of the electron beam in the vertical direction to the velocity in the axial direction.
3. The method of claim 1, further comprising:
optimizing the technical parameters of the cusp electron gun based on a plurality of simulation evaluation indexes to obtain the optimized technical parameters of the cusp electron gun; wherein the plurality of simulation evaluation indexes include: the distribution of the electron beam, the velocity ratio of the electron beam in the vertical direction to the velocity in the axial direction.
4. A cusp electron gun design apparatus, said apparatus comprising:
the acquisition module is used for acquiring a dispersion curve of the threaded waveguide;
the construction module is used for constructing a dispersion curve of an electron beam generated by the cusp electron gun according to the dispersion curve of the threaded waveguide; the dispersion curve of the electron beam generated by the cusp electron gun is matched with the dispersion curve of the threaded waveguide in a working frequency band;
the determining module is used for determining technical parameters of the cusp electron gun based on the dispersion curve of the electron beam;
the building module builds a dispersion curve of an electron beam generated by the cusp electron gun according to the dispersion curve of the threaded waveguide, and comprises the following steps: the construction module takes the slope of the dispersion curve of the threaded waveguide as the slope of the dispersion curve of the electron beam, takes the intercept of the dispersion curve of the threaded waveguide as the intercept of the dispersion curve of the electron beam, and constructs the dispersion curve of the electron beam generated by the cusp electron gun based on the slope of the dispersion curve of the electron beam and the intercept of the dispersion curve of the electron beam; wherein, the dispersion curve of the electron beam generated by the cusp electron gun satisfies the following conditions:
in the formula (I), the compound is shown in the specification,
in order to be the frequency of the radiation,
is the slope of the dispersion curve of the electron beam, which represents the axial velocity of the electron beam motion,
in the case of the axial wave number,
is the intercept of the dispersion curve of the electron beam,
in order to be in the radiation mode,
the angular frequency of the electron beam in the axial magnetic field.
5. The apparatus of claim 4, wherein the determination module determines a technical parameter of the cusp electron gun based on the dispersion curve of the electron beam comprises:
the determining module determines the axial speed and the forward magnetic field strength of the electron beam according to the dispersion curve of the electron beam; the determining module determines the speed of the electron beam according to the axial speed of the electron beam and the speed ratio of the speed of the electron beam in the vertical direction to the speed of the electron beam in the axial direction; the determining module determines the accelerating voltage of the cathode of the electron gun according to the speed of the electron beam; the determining module determines the current of the electron beam according to the power of the electron beam and the accelerating voltage of the cathode of the electron gun; the determining module determines the average radius of the cathode according to the speed ratio of the vertical direction of the electron beam to the axial direction of the electron beam.
6. The apparatus of claim 4, further comprising:
the optimization module is used for optimizing the technical parameters of the cusp electron gun based on a plurality of simulation evaluation indexes to obtain the optimized technical parameters of the cusp electron gun; wherein the plurality of simulation evaluation indicators include: the distribution of the electron beam, the velocity ratio of the electron beam in the vertical direction to the velocity in the axial direction.
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| WO2016126780A1 (en) * | 2015-02-03 | 2016-08-11 | Massachusetts Institute Of Technology | Apparatus and methods for generating electromagnetic radiation |
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