CN108878236B - Method for inhibiting thermal initial velocity effect in traveling wave tube electron gun - Google Patents
Method for inhibiting thermal initial velocity effect in traveling wave tube electron gun Download PDFInfo
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J23/00—Details of transit-time tubes of the types covered by group H01J25/00
- H01J23/02—Electrodes; Magnetic control means; Screens
- H01J23/06—Electron or ion guns
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J25/00—Transit-time tubes, e.g. klystrons, travelling-wave tubes, magnetrons
- H01J25/34—Travelling-wave tubes; Tubes in which a travelling wave is simulated at spaced gaps
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Abstract
The invention belongs to the field of traveling wave tube electron guns, and relates to a method for inhibiting a thermal initial velocity effect in a traveling wave tube electron gun. Firstly, increasing the anode voltage, and adjusting the cathode radius according to the anode voltage to enable the cathode emission current to meet the design requirement; the ratio of the radius of the cathode to the radius of curvature of the cathode is then increased to reduce the effect of thermal initial velocity effects. Changes in anode voltage and cathode shape cause changes in electron beam parameters that are desired by adjusting the distance between the anode and cathode and between the control electrode and cathode. Therefore, under the condition of ensuring that the calculation parameters of the electron gun meet the requirements, the designed electron gun is optimized into the electron gun with smaller thermal initial velocity effect, so that the goodness of fit between the design and the processing assembly of the electron gun is improved.
Description
Technical Field
The invention belongs to the field of traveling wave tube electron guns, and relates to a method for inhibiting a thermal initial velocity effect in a traveling wave tube electron gun.
Background
The traveling wave tube is a microwave electronic vacuum device which realizes a microwave amplification function by utilizing the interaction between an electron beam and a microwave signal, and is widely applied to the fields of radar, electronic countermeasure, millimeter wave communication and the like due to the characteristics of high output power, high efficiency and wide frequency band. The electron gun as an important component part for electron beam emission and formation of the traveling wave tube directly influences the performance of the whole traveling wave tube.
The cathode emission in the electron gun is a key factor influencing the quality of the electron beam, and the thermal initial velocity effect in the cathode emission system can cause the influences of electron beam divergence, laminar flow deterioration, range reduction and the like, which are particularly obvious in the electron gun with low conductivity coefficient, for example, the electron gun with low conductivity coefficient in a Ka-band traveling wave tube is difficult to achieve the accurate design of the traveling wave tube if the influence of the thermal initial velocity effect is not considered, so that the magnetic focusing system can not focus the electron beam in the actual test, thereby causing part of electrons to hit the anode wall or spiral line, and seriously influencing the service life of the traveling wave tube.
The thermal initial velocity effect generated by cathode emission is due to the fact that the velocity direction of electrons emitted at the cathode surface is not perpendicular to the emitting surface, and therefore deviation of electron trajectories is caused. At present, the electron gun hot cathode emission model generally adopts a macro electron emission model, and macro electrons are the integral effect of a large number of electrons and describe the state of electrons emitted from a small cathode surface. The calculation model of the macro-electron thermal initial velocity needs to consider parameters such as energy distribution, emission angle distribution and the like of macro-electrons.
A large gap still exists between the simulation result of the existing macro-electron thermal initial velocity emission model and the actual thermal emission physical process, and the reason for the large gap is that the existing thermal emission model is still not accurate enough. The existing designers design the electron gun when considering the influence of the electron thermal initial velocity, and the error between the design result and the actual physical process is large and inaccurate; the accuracy of the design result depends largely on the experience of the designer and can only be used as a rough reference. Therefore, the reliability of the conventional electron gun is poor when the conventional designer designs the electron gun in consideration of the influence of the electron thermal initial velocity.
The electron beam parameters of the electron gun capable of effectively inhibiting the thermal initial velocity effect are closer to the actual physical state, and the method has important reference value for the subsequent design of a high-frequency system. The thermal initial velocity effect suppression method can enable the design of the traveling wave tube to be more accurate, and enables the design and the processing assembly to have higher goodness of fit. Therefore, an electron gun design method considering the influence of electron thermal initial velocity more accurately is urgently needed.
Disclosure of Invention
Aiming at the problems or the defects, in order to solve the error caused by the thermal initial velocity effect in the simulation calculation of the electron gun, the electron gun with smaller relative influence of the thermal initial velocity effect is designed under the condition of ensuring that the electron beam parameters are not changed, so that higher goodness of fit between the design and the processing assembly is ensured; the invention provides a method for inhibiting a hot initial velocity effect in a traveling wave tube electron gun.
The technical scheme is as follows:
the larger the anode voltage is, the smaller the influence of the thermal initial speed on the electron gun is, and due to the limitation of a power supply in the electron gun, the anode voltage cannot be increased too much, and the variation is in the range of 0-20%.
since the larger the ratio of the radius of the cathode to the radius of curvature of the cathode, the smaller the influence of the thermal initial velocity effect on the electron gun, the larger the anode voltage in step 1, the larger the increase of the cathode emission current, and the smaller the emission current by reducing the cathode emission area, i.e. the smaller the radius of curvature of the cathode, the smaller the influence of the thermal initial velocity effect. The ratio of the radius of the cathode to the radius of curvature of the cathode is increased in a small range, so that the suppression of the thermal initial velocity effect is not obvious, and the increase in the range can lead to the convergence of electron beams before an anode channel to cause the deterioration of laminar flow property.
The specific method for increasing the ratio of the radius of the cathode to the radius of curvature of the cathode comprises the following steps:
1. scanning the radius of the cathode, and determining the optimized radius r of the cathode according to the emission current of the cathodek' size;
2. increasing the ratio of the radius of the cathode to the radius of curvature of the cathode, i.e. rk′/Rk′>rk/RkWherein r iskTo optimize the cathode radius, Rk' optimized radius of curvature of cathode, RkTo optimize the radius of curvature of the cathode before optimization.
Step 3, adjusting the distance between the anode and the cathode and the distance between the control electrode and the cathode:
the front is the suppression of the thermal initial velocity effect in the electron gun, the beam waist radius can be changed along with the change of the anode voltage and the cathode shape, and the distances between the anode and the cathode and between the control electrode and the cathode need to be adjusted under the condition of ensuring that the electron beam parameters meet the requirements.
The specific method comprises the following steps: and scanning the distance between the anode and the cathode and the distance between the control electrode and the cathode to obtain the distance between the anode and the cathode and the distance between the control electrode and the cathode which best meet the calculation result of the electron gun. And finally, applying the optimized electron gun parameters in all the steps to the corresponding electron gun to be optimized.
On the basis of considering a thermal emission model under the constraint of a spherical cathode, the invention designs a method for designing the electron gun, which can effectively inhibit the influence of the thermal initial velocity effect, and verifies the effectiveness of the design method. The design method is suitable for the design of any axisymmetric spherical hot cathode electron gun, and can effectively inhibit the influence of the thermal initial velocity effect of emitted electrons.
In summary, the invention optimizes the designed electron gun into the electron gun with smaller thermal initial velocity effect under the condition of ensuring that the calculation parameters of the electron gun meet the requirements, thereby solving the problem of inconsistency between design and processing assembly caused by the influence of the thermal initial velocity effect.
Drawings
FIG. 1 is an initial block diagram of an electron gun;
FIG. 2 is a schematic view of a cathode structure of the electron gun;
FIG. 3 effect of cathode radius on cathode emission current;
FIG. 4 is a diagram of an optimized electron gun;
FIG. 5 is a view of electron trajectories of an electron gun in an initial configuration at a thermal initial velocity;
fig. 6 considers the electron trajectory of the optimized electron gun at thermal initial velocity.
Detailed Description
The invention is further explained in detail with reference to the drawings and examples.
According to the rule of the influence of the diversion coefficient, the anode voltage, the ratio of the cathode radius to the cathode curvature radius on the thermal initial velocity effect in the electron gun, when the electron gun is designed, the influence of the thermal initial velocity effect can be reduced by increasing the voltage and increasing the values of the cathode radius and the cathode curvature radius, but the change of the parameters can influence the cathode emission current and the beam waist radius, so that the change of the parameters needs to ensure that the electron beam parameters change within a certain range. Under the condition that the electron gun meets the design requirement, the electron gun with smaller influence of the thermal initial velocity effect is designed, and the error between design and processing assembly can be directly reduced.
The anode channel and cathode operating temperature in the electron gun cannot be changed due to the limitations of the cathode material and the subsequent high frequency structure.
Taking a spherical cathode axisymmetric electron gun with 70mA of current and 0.40mm of beam waist radius as an example, the parameters are optimized to reduce the influence of the thermal initial velocity effect.
Main initial parameter values of the electron gun: voltage of 2000V, conductivity of 0.77 μ P, and cathode radius rkIs 2mm, the radius of curvature R of the cathodekIs 4mm, i.e. the ratio r of the radius of the cathode to the radius of curvaturek/RkIs 0.5. The initial structure of the electron gun is shown in FIG. 1, and the calculation results of the initial structure electron gun are shown in Table 1.
TABLE 1 initial electron gun calculated results
The influence of the hot initial quick result on the waist injection radius of the electron gun is 43.21 percent, the influence on the waist injection position is-13.31 percent, namely the influence of the hot initial velocity effect is very large, and according to the limitation of the self condition of the electron gun and the requirement on the electron injection, the optimization steps of the electron gun on the inhibition of the hot initial velocity effect are provided:
step 1: the anode voltage is increased. The larger the anode voltage is, the smaller the influence of the thermal initial speed on the electron gun is, and due to the limitation of power supply equipment in the electron gun, the anode voltage cannot be increased too much, and the variation is in the range of 0-20%.
Here, the anode voltage is increased to 2400V, and since the increase in voltage leads to an increase in cathode emission current, it is necessary to reduce the cathode emission area to reduce the cathode emission current.
Step 2: the ratio of the radius of the cathode to the radius of curvature of the cathode is increased. The influence of the thermal initial velocity effect on the electron gun is smaller according to the larger the ratio of the cathode radius to the cathode curvature radius, so that the influence of the thermal initial velocity effect can be reduced by reducing the cathode curvature radius.
1. Scanning the radius of the cathode, and determining the optimized radius r of the cathode according to the emission current of the cathodekThe size of the prime symbol.
Since the increase of the anode voltage in step 1 will result in the increase of the cathode emission current, the cathode emission area needs to be reduced to reduce the cathode emission current, so as to make the cathode emission current meet the design requirement, fig. 2 is a schematic diagram of the cathode structure of the electron gun, rkIs the radius of the cathode, RkIs the radius of curvature of the cathode.
Effect of cathode radius on cathode emission current over cathode radius scan as shown in fig. 3, it can be seen that the cathode emission current is close to that in the initial electron gun at a cathode radius of 1.7mm, thus determining the cathode radius at 1.7 mm.
Meanwhile, in order to inhibit the influence of the thermal initial velocity effect in the electron gun, the curvature radius of the cathode is reduced to increase the ratio of the cathode radius to the cathode curvature radius.
2. Increasing the ratio of the radius of the cathode to the radius of curvature of the cathode, i.e. rk′/Rk′>rk/RkWherein r isk' optimized cathode radius, rkTo optimize the cathode radius, Rk' optimized radius of curvature of cathode, RkTo optimize the radius of curvature of the cathode before optimization. The ratio of the cathode radius to the cathode radius of curvature increases in a range between 40% and 60% of the initial value.
The ratio of the cathode radius to the cathode curvature radius needs to be increased according to the fact that the larger the ratio of the cathode radius to the cathode curvature radius, the smaller the influence of the thermal initial velocity effect on the electron gun, and the larger the ratio of the cathode radius to the cathode curvature radius in the initial electron gun structure is to suppress the influence of the thermal initial velocity effect in the electron gunValue 0.5, optimized cathode radius rk' determined to be 1.7mm, the ratio r of the radius of the cathode to the radius of curvature of the cathode is smaller since the larger the ratio of the radius of the cathode to the radius of curvature of the cathode is, the smaller the influence of the thermal initial velocity effect on the electron gun isk′/Rk' is greater than 0.5, i.e. the radius of curvature R of the cathode after optimizationk' less than 3.4mm is required to increase the ratio of the radius of the cathode to the radius of curvature of the cathode, but the radius of curvature of the cathode should not be too small, which would lead to convergence of electron streams before the anode channel and thus poor laminar flow.
And step 3: adjusting the distance between the anode and the cathode and between the control electrode and the cathode
The first two steps are to reduce the influence of thermal initial velocity effect in the electron gun, and we need to adjust the calculation parameters of the electron gun to the design requirements.
The distance between the anode and the cathode and the distance between the control electrode and the cathode are scanned, and the rule is obtained that the smaller the distance between the anode and the cathode is, the larger the cathode emission current and the beam waist radius are, the smaller the distance between the control electrode and the cathode is, and the larger the cathode emission current and the beam waist radius are. And adjusting the distances between the anode and the cathode and between the control electrode and the cathode to obtain the cathode emission current and the beam waist radius meeting the design requirements, and finally applying the optimized electron gun parameters in all the steps to the corresponding electron gun to be optimized.
The comparison of the optimized gun parameters with the initial gun parameters is shown in table 2.
Table 2: optimized gun to initial parameter comparison
The structure of the optimized electron gun is shown in fig. 6.
Table 3: optimized electron gun calculation result
As can be seen from tables 1 and 3, the anode voltage increases as the optimized electron gun parameters are the same as the emission current before optimization, so the current conductivity decreases to 0.59 μ P; the influence of the hot initial velocity in the initial electron gun on the waist injection radius is 43.21%, the influence of the hot initial velocity in the optimized electron gun on the waist injection radius is 9.56%, the influence of the hot initial velocity effect on the waist injection radius is obviously reduced, and meanwhile, the cathode emission current and the waist injection position meet the design requirements, which shows that the inhibition effect of the hot initial velocity effect in the electron gun has an obvious effect. Fig. 5 and 6 are an electron trajectory of the electron gun in the initial configuration and an optimized electron trajectory diagram, respectively, in consideration of the thermal initial velocity.
In conclusion, the thermal initial velocity effect in the electron gun of the traveling wave tube is effectively inhibited under the condition that the calculation parameters of the electron gun are not changed.
Claims (1)
1. A method for inhibiting a hot initial velocity effect in a traveling wave tube electron gun comprises the following specific steps:
step 1, increasing the anode voltage of a spherical cathode axisymmetric electron gun, wherein the variation is within the range of 0-20%;
step 2, increasing the ratio of the radius of the cathode to the radius of curvature of the cathode, wherein the increased range is 40-60% of the initial value;
2-1, scanning the radius of the cathode, and determining the optimized radius r of the cathode according to the emission current of the cathodek' size;
2-2. increasing the ratio of the radius of the cathode to the radius of curvature of the cathode, i.e. rk′/Rk′>rk/RkWherein r iskTo optimize the cathode radius, Rk' optimized radius of curvature of cathode, RkThe radius of curvature of the cathode before optimization;
step 3, adjusting the distance between the anode and the cathode and the distance between the control electrode and the cathode:
the first two steps are the inhibition of the heat initial velocity effect in the electron gun, the beam waist radius can be changed along with the change of the anode voltage and the cathode shape, the distance between the anode and the cathode and the distance between the control electrode and the cathode are adjusted under the condition of ensuring that the electron beam parameters meet the requirements, and finally the optimized electron gun parameters in all the steps are applied to the corresponding electron gun to be optimized;
the electron gun parameters are as follows: anode voltage, cathode radius of curvature, distance between anode head and cathode, and distance between control head and central axis.
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| CN106128908A (en) * | 2016-07-26 | 2016-11-16 | 西北核技术研究所 | A kind of method for designing of Pierce electron gun |
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