Quadrupole electron gun and working method

Abstract

The invention discloses a quadrupole type electron gun, and the electron gun comprises an electron gun housing, and the interior of the electron gun housing comprises a bunching electrode, a cathode, a control electrode, and an anode which are sequentially arranged in the axial direction. Wherein the control electrode is at least used for segmenting the electric field between the cathode and the anode to obtain a first electric field region and a second electric field region, that is, the control electrode in the electron gun can segment the electric field between the cathode and the anode into two parts, including the first electric field region and the second electric field region; therefore, electron beams emitted by the cathode can be accelerated twice through the first electric field area and the second electric field area, the electron beams can be boosted step by step, the situation of high-voltage sparking is avoided, normal operation of the electron gun is guaranteed, and the electron beams are focused twice through the first electric field area and the second electric field area. Therefore, the beam divergence angle is reduced, and the focusing precision of the electron beam is improved while the electron beam is prevented from ablating the anode hole.

Description

Technical Field

[0001] The present application relates to the technical field of electron beam extraction, and in particular to a quadrupole electron gun and a working method thereof. Background Art

[0002] The current electron gun is mainly a three-pole Pierce electron gun, which consists of a bunching electrode, a cathode, and an anode. Its voltage level is 60kV and the power does not exceed 6kW. During use, the cathode is connected to a -60kV voltage to emit electrons; the anode is grounded, and an accelerating electric field is formed between the cathode and the anode to draw out and accelerate electrons. The current voltage difference between the cathode and the anode of the electron gun is usually 60kV.

[0003] However, if the voltage level is increased from 60kV to 150kV, the electric field strength will rise rapidly, which is very likely to cause high-voltage discharge. High-voltage discharge not only makes the high-voltage power supply unstable, but also causes strong electromagnetic interference to other equipment on the power grid (such as programmable logic controller (PLC) system, servo control system, etc.), thereby affecting the normal operation and life of the electron gun. Summary of the Invention

[0004] The embodiment of the present application provides a quadrupole electron gun, which can avoid high-voltage sparking when the electric field intensity rises rapidly, thereby ensuring the normal operation of the electron gun.

[0005] The technical solution of the embodiment of the present application is implemented as follows:

[0006] In a first aspect, an embodiment of the present application provides a quadrupole electron gun, comprising: an electron gun housing, wherein the interior of the electron gun housing comprises a focusing electrode, a cathode, a control electrode, and an anode arranged in axial order; wherein the control electrode is at least used to divide the electric field between the cathode and the anode to obtain a first electric field region and a second electric field region.

[0007] In a second aspect, an embodiment of the present application provides a method for operating an electron gun, the method being applied to the electron gun, the method comprising:

[0008] A first electron beam emitted by a cathode in the electron gun is accelerated and focused by a first electric field region to obtain a second electron beam; wherein the first electric field region includes an electric field region between the cathode and a control electrode in the electron gun, and the second electron beam includes an electron beam obtained by initially accelerating the first electron beam;

[0009] The second electron beam is accelerated and focused again through a second electric field region to obtain a third electron beam, so that the third electron beam reaches the target object; wherein the second electric field region includes the electric field region between the control electrode and the anode in the electron gun.

[0010] An embodiment of the present application provides a quadrupole electron gun, which includes an electron gun housing, wherein the interior of the electron gun housing includes a focusing electrode, a cathode, a control electrode, and an anode arranged in axial order; wherein the control electrode is at least used to divide the electric field between the cathode and the anode to obtain a first electric field region and a second electric field region, and a first electron beam emitted by the cathode is accelerated and focused through the first electric field region to obtain a second electron beam; wherein the first electric field region includes the electric field region between the cathode and the control electrode in the electron gun, and the second electron beam includes the electron beam after the first acceleration of the first electron beam; the second electron beam is accelerated and focused again through the second electric field region to obtain a third electron beam, so that the third electron beam reaches the target object; wherein the second electric field region includes the electric field region between the control electrode and the anode in the electron gun. It can be seen from this that the present application can propose a quadrupole electron gun, which includes a focusing electrode, a cathode, a control electrode and an anode arranged in axial order, that is, the electric field between the cathode and the anode can be divided into a first electric field region and a second electric field region through the control electrode, and then the first electron beam emitted by the cathode can be accelerated twice through the first electric field region and the second electric field region respectively, so that the first electron beam can be boosted step by step to avoid high-voltage sparking, thereby ensuring the normal operation of the electron gun, and the first electron beam is focused twice through the first electric field region and the second electric field region respectively, thereby reducing the beam divergence angle, while avoiding the electron beam ablation of the anode hole, improving the focusing accuracy of the first electron beam. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 Schematic diagram of the quadrupole electron gun structure proposed in this embodiment Figure 1 ;

[0012] Figure 2 Schematic diagram of the quadrupole electron gun structure proposed in this embodiment Figure 2 ;

[0013] Figure 3 A schematic diagram of the working method of the electron gun proposed in an embodiment of the present application;

[0014] Figure 4 A schematic diagram showing the relationship between the cumulative ion yield and the electron beam energy proposed in an embodiment of the present application;

[0015] Figure 5 A schematic diagram comparing the ionization cross section curve and the ionization curve proposed in the embodiment of the present application;

[0016] Figure 6 Schematic diagram of a double-layer ion trap proposed in an embodiment of the present application;

[0017] Figure 7 A schematic diagram showing the relationship between ion number and ion energy proposed in an embodiment of the present application;

[0018] Figure 8 A schematic diagram of the ion position and energy distribution mapped on the cathode emission surface proposed in an embodiment of the present application;

[0019] Figure 9 This is a schematic diagram of dual voltage joint adjustment for 90kV, 10kW electron gun emission power compensation proposed in an embodiment of the present application;

[0020] Figure 10 This is a schematic diagram of the 90kV, 10kW electron gun emission power compensation effect proposed in the embodiment of the present application;

[0021] Figure 11 This is a schematic diagram of a dual-voltage joint adjustment diagram for 150kV, 20kW electron gun emission power compensation proposed in an embodiment of the present application;

[0022] Figure 12 This is a schematic diagram of the 150kV, 20kW electron gun emission power compensation effect proposed in the embodiment of the present application. DETAILED DESCRIPTION

[0023] The following will be combined with the accompanying drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. It should be understood that the specific embodiments described herein are only used to explain the related applications and are not intended to limit the applications. It should also be noted that for ease of description, only the portions relevant to the related applications are shown in the drawings.

[0024] The current electron gun is mainly a three-pole Pierce electron gun, which consists of a buncher, a cathode, and an anode. Its voltage level is 60kV and its power does not exceed 6kW. During use, the cathode is connected to a -60kV voltage to emit electrons; the anode is grounded, and an accelerating electric field is formed between the cathode and the anode to extract and accelerate electrons; the buncher voltage is suspended above the 60kV high voltage and is adjustable between -62 and -60kV. By adjusting the voltage, the number of electrons extracted is controlled, and the emission beam intensity is controlled. The current electron beam powder bed melting electron gun has a high voltage resistance level that cannot meet the processing requirements of refractory metal additive manufacturing. At present, the voltage difference between the cathode and the anode of the electron gun is usually 60kV, the structure is sophisticated, the axial length generally does not exceed 15cm, and the vacuum degree is 10 -3 Pa level,

[0025] However, if the voltage level is increased to 150kV, the electric field strength rises rapidly, which can easily cause high-voltage discharge. High-voltage discharge not only makes the high-voltage power supply unstable, but also generates voltage or peak current that causes strong electromagnetic interference to other equipment on the power grid (PLC system, servo control system, etc.), thereby affecting the normal operation and life of the electron gun.

[0026] Furthermore, electron gun filament life is a major challenge in additive manufacturing of large-scale refractory metals, which can take hundreds of hours to process. Positive ion back-bombardment is the primary cause of reduced cathode life. In the complex and extreme environment of high-temperature metal vapor, positive ions generated by ionization within the cathode-cathode gap are accelerated by the electric field and moved toward the cathode. Under the influence of the electron gun electric field and the spatial charge force of the bunch, ions downstream of the anode may drift into the cathode-cathode gap and be accelerated, gaining kinetic energy corresponding to the electron gun voltage. This creates a positive ion back-bombardment effect, significantly damaging the cathode crystal surface. Current triode electron guns are unable to effectively counteract this positive ion back-bombardment, resulting in reduced cathode life.

[0027] In order to solve the problem that current electron guns are extremely prone to the risk of high-voltage discharge, thereby affecting the normal operation of the electron gun, an embodiment of the present application provides a quadrupole electron gun, which includes an electron gun shell, and the interior of the electron gun shell includes a focusing electrode, a cathode, a control electrode and an anode arranged in axial order; wherein the control electrode is at least used to divide the electric field between the cathode and the anode to obtain a first electric field region and a second electric field region, and the first electron beam emitted by the cathode is accelerated and focused through the first electric field region to obtain a second electron beam; wherein the first electric field region includes the electric field region between the cathode and the control electrode in the electron gun, and the second electron beam includes the electron beam after the first acceleration of the first electron beam; the second electron beam is accelerated and focused again through the second electric field region to obtain a third electron beam, so that the third electron beam reaches the target object; wherein the second electric field region includes the electric field region between the control electrode and the anode in the electron gun. It can be seen from this that the present application can propose a quadrupole electron gun, which includes a focusing electrode, a cathode, a control electrode and an anode arranged in axial order, that is, the electric field between the cathode and the anode can be divided into a first electric field region and a second electric field region through the control electrode, and then the first electron beam emitted by the cathode can be accelerated twice through the first electric field region and the second electric field region respectively, so that the first electron beam can be boosted step by step to avoid high-voltage sparking, thereby ensuring the normal operation of the electron gun, and the first electron beam is focused twice through the first electric field region and the second electric field region respectively, thereby reducing the beam divergence angle, while avoiding the electron beam ablation of the anode hole, improving the focusing accuracy of the first electron beam.

[0028] The technical solutions in the embodiments of the present application will be described clearly and completely below in conjunction with the drawings in the embodiments of the present application.

[0029] The embodiment of the present application provides a quadrupole electron gun, Figure 1 Schematic diagram of the quadrupole electron gun structure proposed in this embodiment Figure 1 ,like Figure 1 As shown, the electron gun 10 includes an electron gun housing 11 , wherein the electron gun housing 11 includes a bunching electrode 12 , a cathode 13 , a control electrode 14 and an anode 15 arranged in axial order.

[0030] It should be noted that, in the embodiment of the present application, the control electrode 14 is at least used to divide the electric field between the cathode 13 and the anode 15 to obtain a first electric field region and a second electric field region.

[0031] It should be noted that in the embodiment of the present application, the control electrode 14 in the electron gun 10 can divide the electric field between the cathode 13 and the anode 15 into two parts, including a first electric field region and a second electric field region. As a result, after the cathode 13 in the electron gun 10 emits an electron beam, the free electrons can be accelerated for the first time in the first electric field region under the voltage difference between the cathode 13 and the control electrode 14. Due to the second-level voltage difference between the control electrode 14 and the anode 15, the free electrons are accelerated and focused again in the second electric field region. The light beam is accelerated and focused twice in the electron gun, reducing the beam divergence angle and preventing the electron beam from ablating the anode hole. Without adding a magnetic confinement device, the electron beam focusing accuracy is improved from the electron beam source. The electron beam is gradually boosted in the first and second electric field regions, thereby reducing the risk of high-voltage ignition and ensuring the normal operation of the electron gun.

[0032] Optionally, in an embodiment of the present application, the interior of the electron gun housing 11 may further include an insulating support member 16 and a fixing member 17; wherein the insulating support member 16 is at least used to insulate the cathode 13, the control electrode 14 and the anode 15. The present application does not specifically limit the type and quantity of components included in the interior of the electron gun housing.

[0033] Optionally, in an embodiment of the present application, the electron gun 10 may further include a vacuum chamber 18, an electrode socket 19 and a vacuum pump 20; wherein the electrode socket 19 includes a control electrode socket 21 and a focusing electrode socket 22, the anode 15 is connected to the vacuum chamber 18, and a vacuum pump 20 is provided outside the vacuum chamber 18.

[0034] It should be noted that, in the embodiments of this application, Figure 2 Schematic diagram of the quadrupole electron gun structure proposed in this embodiment Figure 2 ,like Figure 2As shown, the electron gun 10 may include an electron gun housing 11, and the interior of the electron gun housing 11 includes a focusing electrode 12, a cathode 13, a control electrode 14 and an anode 15 arranged in axial order. The interior of the electron gun housing 11 also includes an insulating support 16 and a fixing member 17. The electron gun 10 may also include a vacuum chamber 18, a control electrode socket 21, a focusing electrode socket 22, a cathode heating wire 23 and a cathode heating pin 24.

[0035] For example, in an embodiment of the present application, the material used for the cathode may include lanthanum hexaboride, so that the cathode has a stronger emission capability and a longer life. Other materials that enable the cathode to have a stronger emission capability and a longer life may also be used. The present application does not specifically limit the type of material used for the cathode.

[0036] Optionally, in an embodiment of the present application, a negative high voltage may be applied to the cathode 13 in the electron gun 10, a secondary negative high voltage may be applied to the control electrode 14, and the voltage on the bunching electrode 12 may be slightly lower than that of the cathode 13. The bias voltage refers to the negative voltage applied to the bunching electrode 12 relative to the cathode 13, which is generally adjustable within 0 to 2 kV and is used to control the number of emitted electrons and focus the electron beam. The present application does not impose any specific limitation on the size of the applied negative high voltage.

[0037] For example, in an embodiment of the present application, the negative high voltage applied to the bunching electrode 12 may be -151 kV, the negative high voltage applied to the cathode 13 may be -150 kV, the negative high voltage applied to the control electrode 14 may be -100 kV, and the anode may be 0 V. That is, in an embodiment of the present application, a high voltage of -150 kV may be applied to the electron gun 10 without causing high voltage sparks, thereby ensuring the normal operation of the electron gun.

[0038] Exemplarily, in the embodiments of the present application, the bias voltage may refer to the negative voltage applied on the bunching electrode 12 relative to the cathode 13. For example, the bias voltage may be the difference between the voltage of the bunching electrode 12 and the voltage of the cathode 13. Assuming that the negative high voltage applied on the bunching electrode 12 can range from -152kV to -150kV, and the negative high voltage applied on the cathode 13 can be -150kV, the bias voltage can be adjusted in the range of 0 to 2kV. The present application does not specifically limit the size setting of the bias voltage.

[0039] An embodiment of the present application provides a quadrupole electron gun, which includes: an electron gun housing, wherein the interior of the electron gun housing includes a focusing electrode, a cathode, a control electrode and an anode arranged in axial order; wherein the control electrode is at least used to divide the electric field between the cathode and the anode to obtain a first electric field region and a second electric field region, that is, the present application can divide the electric field between the cathode and the anode into two parts through the control electrode in the electron gun, including the first electric field region and the second electric field region, so that the electron beam emitted by the cathode can be accelerated twice by the first electric field region and the second electric field region respectively, so that the electron beam can be boosted step by step to avoid high-voltage sparking, thereby ensuring the normal operation of the electron gun, and the electron beam is focused twice by the first electric field region and the second electric field region respectively, thereby reducing the beam divergence angle, while avoiding the electron beam ablation of the anode hole, and improving the focusing accuracy of the electron beam.

[0040] Based on the above embodiment, another embodiment of the present application provides a method for operating an electron gun. The method is applied to an electron gun. Figure 3 This is a schematic diagram of the working method of the electron gun proposed in the embodiment of the present application, as shown in FIG. Figure 3 As shown, the working method of the electron gun may include the following steps:

[0041] Step 101: A first electron beam emitted from a cathode in an electron gun is accelerated and focused through a first electric field region to obtain a second electron beam; wherein the first electric field region includes the electric field region between the cathode and a control electrode in the electron gun, and the second electron beam includes the first electron beam after initial acceleration.

[0042] Step 102 : Accelerate and focus the second electron beam again through the second electric field region to obtain a third electron beam, so that the third electron beam reaches the target object; wherein the second electric field region includes the electric field region between the control electrode and the anode in the electron gun.

[0043] In an embodiment of the present application, the first electron beam emitted by the cathode in the electron gun is accelerated and focused through the first electric field region to obtain the second electron beam, and then the second electron beam can be accelerated and focused again through the second electric field region to obtain the third electron beam, so that the third electron beam reaches the target object.

[0044] For example, in an embodiment of the present application, the target object may include metal powder, and the present application does not specifically limit the type of metal included in the target object.

[0045] It should be noted that, in the embodiment of the present application, the third electron beam may include an electron beam obtained by initially accelerating the second electron beam.

[0046] That is to say, in the embodiment of the present application, the first electron beam emitted by the cathode can be accelerated twice by the first electric field region and the second electric field region respectively, so that the first electron beam can be boosted step by step to avoid high-voltage ignition.

[0047] Optionally, in an embodiment of the present application, when the beam current size of the first electron beam drops from a maximum value to a preset threshold, the emission power of the first electron beam is compensated by a preset dual voltage strategy to maintain the beam current size within a preset range.

[0048] It should be noted that, in the embodiments of the present application, the preset threshold can be set according to actual needs, and the present application does not specifically limit the size of the preset threshold.

[0049] For example, in an embodiment of the present application, the preset range can be set according to actual needs. The preset range can include the maximum beam current emitted by the electron gun. Assuming that the maximum beam current emitted by the electron gun is 127mA, the preset range can be set to 120~130mA. The present application does not make any specific limitations on the setting of the preset range.

[0050] For example, in an embodiment of the present application, assuming that the maximum beam current of the first electron beam emitted by the electron gun is a beam current of 133 mA, if the maximum beam current of 133 mA drops to 120 mA (i.e., the preset threshold value), the emission power of the first electron beam can be compensated by a preset dual-voltage strategy to maintain the beam current within a preset range, for example, within the range of 133 to 140 mA, thereby ensuring that the beam current emitted by the electron gun is always maintained within the range of 133 to 140 mA, the power is greater than 20 kW, and the maximum value of the spatial electric field is below the safety threshold, and high-voltage sparks will not occur.

[0051] Optionally, in an embodiment of the present application, when the electron gun compensates for the emission power of the first electron beam through a preset dual-voltage strategy, the emission power can be compensated by adjusting the voltage and bias voltage of the control electrode to maintain the size of the beam current within a preset range; wherein the bias voltage includes the difference voltage between the first voltage applied to the focusing electrode and the second voltage applied to the cathode, and the first voltage is an adjustable voltage, and the first voltage is lower than the second voltage.

[0052] For example, in the embodiment of the present application, assuming that the negative high voltage applied to the bunching electrode is -151 kV and the negative high voltage applied to the cathode is -150 kV, the bias voltage can be 1 kV. The present application does not specifically limit the setting of the bias voltage.

[0053] For example, in an embodiment of the present application, assuming that the bias voltage is initially set to 200V and the control voltage is initially set to -100kV, the maximum beam current that can be drawn out can reach 133mA. If the maximum beam current of 133mA drops to 120mA (i.e., the preset threshold), the emission power of the first electron beam can be compensated by the preset dual-voltage strategy, and the bias voltage can be gradually reduced to 50V, and the control electrode voltage can be increased to -90kV. The bias voltage, the control voltage and the diameter of the effective emission surface of the cathode are almost linearly related, thereby ensuring that the beam current drawn out by the electron gun is always maintained within the preset range.

[0054] Optionally, in an embodiment of the present application, when the electron gun compensates for the emission power of the first electron beam through a preset dual-voltage strategy, the emission power of the electron beam can be compensated by reducing the bias voltage and increasing the control electrode voltage, so that the electron gun output beam current is always maintained within a preset range, that is, by reducing the bias voltage and increasing the control electrode voltage, the emission beam current can be increased and the beam shape can be controlled, thereby improving the control ability of the beam current, realizing the decoupling of the beam intensity and the beam spot size, and improving the electron gun beam current quality.

[0055] Optionally, in an embodiment of the present application, when first ions are generated around the motion trajectory of the first electron beam and / or around the motion trajectory of the second electron beam, the motion direction of the first ions is adjusted through the first electric field region and / or the second electric field region so that the first ions are captured by the control electrode and / or the bunching electrode in the electron gun, and the first ions include positive ions released in a high-temperature environment.

[0056] It should be noted that, in the embodiments of the present application, the first ions may include positive ions released under high temperature conditions, for example, H2O + , this application does not specifically limit the type and quantity of the positive ions included in the first ions.

[0057] Optionally, in the embodiment of the present application, for the electron beam powder bed melting electron gun (ie, quadrupole electron gun), the vacuum degree can generally reach 10 -4 The stainless steel cavity and electrodes continuously release hydrogen at high temperatures, with H2 accounting for a high proportion. High-temperature oxidation reactions (such as oxidation of carbon impurities in stainless steel) lead to an increase in CO2 release. After baking, the adsorbed water is basically desorbed, and the remaining H2O mainly comes from tiny leaks or deep release of the material. Therefore, under high-temperature conditions, the residual gas in the electron gun low-vacuum system is mainly H2, supplemented by CO2, H2O, and hydrocarbons. The main mechanism for the ionization of gas molecules in the electron gun is the inelastic scattering between electrons and gas molecules, and the main ions produced are H2O +The ion yield is mainly related to the type and density distribution of the residual gas and the energy of the electron beam. Ions are generated around the electron beam trajectory. As electrons move from the cathode to the anode, their energy gradually increases, and the accumulated ion yield in the electron gun also gradually increases. Figure 4 This is a schematic diagram of the relationship between the cumulative ion yield and the electron beam energy proposed in the embodiment of the present application, as shown in FIG. Figure 4 As shown in the figure, it can be seen that the growth rate of the cumulative yield of the three ions shows a trend of first increasing rapidly and then gradually slowing down. The highest ion yield.

[0058] Optionally, in an embodiment of the present application, Figure 5 This is a schematic diagram comparing the ionization cross section curve and the ionization curve proposed in the embodiment of the present application, as shown in FIG. Figure 5 As shown, For example, ions By taking the derivative of the cumulative ion yield of the ions, we can get the ion production rate at different electron beam energies, such as Figure 5 As shown in the figure, the curve change trend of the ion production rate is consistent with the ionization cross-section curve, which shows that the change of the cumulative ion yield is determined by the electron beam energy and verifies the accuracy of the simulation.

[0059] For example, in the embodiment of the present application, a first electron beam and / or a second electron beam are generated around the motion trajectory. H2O + In the case of the first electric field region, and / or the second electric field region (i.e., the double-layer ion trap) H2O + The direction of motion is adjusted to deflect the axially moving counter-bombarding ions. H2O + The electron gun is captured by the control electrode and / or the bunching electrode in the electron gun, and the axially moving counter-bombarding ions can be deflected by the physical blocking method constructed by the double-layer ion trap to make the electron gun H2O + is captured by the control electrode and / or the buncher in the electron gun, Figure 6 A schematic diagram of a double-layer ion trap proposed in an embodiment of the present application is shown in FIG. Figure 6 As shown, the above method can deflect the axially moving counter-bombardment ions and eventually capture them by the control electrode and / or the bunching electrode in the electron gun, so that the double-layer ion trap of the quadrupole electron gun absorbs most of the high-energy ions, thereby effectively suppressing the ion counter-bombardment effect and extending the cathode life.

[0060] Optionally, in an embodiment of the present application, the relationship between the ionization cross section of the residual gas in the electron gun and the electron beam energy distribution can be further deduced, thereby obtaining the spatial distribution of ions in the electron gun; based on the multi-physics field simulation, the ion motion trajectory simulation calculation is performed, and the ions bombarding the cathode emission surface can be numbered. Figure 7 This is a schematic diagram of the relationship between ion number and ion energy proposed in the embodiment of the present application, such as Figure 7 As shown in the figure, there are many low-energy ions but they cause less damage to the cathode. Although the number of high-energy particles is far lower than that of low-energy ions, they are indeed the main factor causing damage to the cathode emission surface. Among them, the left figure (a) is the energy distribution result of the back-bombarding ions in the triode electron gun, and the right figure (b) is the energy distribution result of the back-bombarding ions in the quadrupole electron gun. Figure 8 This is a schematic diagram of the ion position and energy distribution mapped on the cathode emission surface proposed in the embodiment of the present application, such as Figure 8 As shown, the left figure (c) is the ion position and energy distribution diagram of the tripole electron gun mapped on the cathode emission surface, and the right figure (d) is the ion position and energy distribution diagram of the quadrupole electron gun mapped on the cathode emission surface. It can be seen that the double-layer ion trap of the quadrupole electron gun absorbs most of the high-energy ions. Compared with the tripole electron gun, the number of ions with energy higher than 60 keV on the cathode emission surface of the quadrupole electron gun is greatly reduced, and the existence of the control electrode reduces the ion energy in the low-energy region, effectively suppressing the ion bombardment effect, thereby extending the cathode life.

[0061] For example, in an embodiment of the present application, a quadrupole electron gun can reduce the energy of low-energy ions bombarding the cathode emission surface by adding a control electrode to construct a double-layer ion trap, thereby reducing the number of high-energy ions. In a tripole electron gun, the number of ions bombarding the cathode emission surface accounts for 6.6% of the cumulative ion yield, the number of ions with energy greater than 60 keV accounts for 20.4% of the number of ions bombarding the cathode emission surface, and the low-energy ion energy is 16.9 keV. In a quadrupole electron gun, the number of ions bombarding the cathode emission surface accounts for 5.3% of the cumulative ion yield, the number of ions with energy greater than 60 keV accounts for 3.2% of the number of ions bombarding the cathode emission surface, and the low-energy ion energy is 11.5 keV, which is 32% reduced compared to a tripole electron gun.

[0062] In summary, the first electron beam emitted by the cathode in the quadrupole electron gun can be accelerated twice by the first electric field region and the second electric field region, respectively, so that the first electron beam can be gradually boosted to avoid high-voltage sparking. When the beam current of the first electron beam drops from a maximum value to a preset threshold, the emission power of the first electron beam can be compensated by a preset dual-voltage strategy. For example, the emission power of the electron beam can be compensated by reducing the bias voltage and increasing the gate voltage, so that the electron gun extracted beam current is always maintained within a preset range. That is, by reducing the bias voltage and increasing the gate voltage, the emission beam current can be increased and the beam shape can be controlled, thereby improving the controllability of the beam current, achieving decoupling of the beam current intensity and the beam spot size, and improving the electron gun beam quality. When first ions are generated around the motion trajectory of the first electron beam and / or around the motion trajectory of the second electron beam, the motion direction of the first ions can be adjusted by the first electric field region and / or the second electric field region so that the first ions are captured by the gate and / or the buncher in the electron gun, thereby effectively suppressing the ion bombardment effect and extending the cathode life.

[0063] An embodiment of the present application provides a method for operating an electron gun, which is applied to an electron gun, and includes: accelerating and focusing a first electron beam emitted by a cathode in the electron gun through a first electric field region to obtain a second electron beam; wherein the first electric field region includes an electric field region between the cathode and a control electrode in the electron gun, and the second electron beam includes an electron beam after the first electron beam is initially accelerated; accelerating and focusing the second electron beam again through a second electric field region to obtain a third electron beam, so that the third electron beam reaches a target object; wherein the second electric field region includes an electric field region between the control electrode and an anode in the electron gun. It can be seen that the first electron beam emitted by the cathode in the electron gun proposed in the present application can be accelerated twice respectively through the first electric field region and the second electric field region, so that the first electron beam can be boosted step by step to avoid high-voltage sparking, thereby ensuring the normal operation of the electron gun.

[0064] Based on the above embodiments, another embodiment of the present application provides a quadrupole electron gun, which can increase the high voltage resistance level of the electron gun for additive manufacturing from 60kV to 150kV, and the power from 6kW to 20kW, thereby realizing the extraction of ultra-high voltage and high-power electron beams and reducing the risk of ignition; in addition, under high-power and large-beam current conditions, the space charge effect of the non-relativistic electron beam is strong, and the electron beam divergence angle is large, which can easily damage the anode hole of the traditional electron gun, resulting in the destruction of the vacuum environment in the electron gun, and the irregular anode hole can cause tip discharge, affecting the extraction of the electron beam. The present application adds a control electrode to the quadrupole electron gun, constructs two major focusing electric fields (i.e., the first electric field region) inside the electron gun, and the second electric field region is formed. and the second electric field region), so that the electron beam is focused twice, the beam divergence angle is reduced, the electron beam is prevented from ablating the anode hole, and the electron beam focusing accuracy is improved from the electron beam source without adding a magnetic confinement device; at the same time, the number of ions bombarding the cathode emission surface can be reduced, and the positive ion back bombardment effect can be suppressed to extend the service life of the cathode; and in response to the situation where the cathode emission capability decreases during use, the present application can increase the emission beam and control the beam shape by reducing the bias voltage and increasing the control electrode voltage, that is, adopting a dual-voltage joint modulation strategy to achieve emission power compensation, thereby improving the control capability of the beam, realizing the decoupling of the beam intensity and the beam spot size, and improving the beam quality of the electron gun.

[0065] It should be noted that in the embodiment of the present application, a quadrupole tunable electron gun is introduced with a control electrode. The quadrupole electron gun 10 can be composed of a cathode 13, a focusing electrode 12, a control electrode 14, an anode 15, a vacuum chamber 18, two high-voltage electrode sockets (i.e., a control electrode socket 21 and a focusing electrode socket 22), a vacuum pump 20, an insulating support 16, and other fixing parts 17.

[0066] It should be noted that, in the embodiment of the present application, in the quadrupole electron gun, the bunching electrode 12, cathode 13, control electrode 14 and anode 15 are arranged in axial order, the cathode 13 is applied with negative high voltage, the control electrode 14 is applied with secondary negative high voltage, the anode 15 is connected to the electron gun vacuum chamber, the voltage on the bunching electrode 12 is slightly lower than that on the cathode 13, and the bias voltage refers to the negative voltage applied to the bunching electrode 12 relative to the cathode 13, which is generally adjustable within 0 to 2 kV and is used to control the number of emitted electrons and focus the electron beam.

[0067] For example, in an embodiment of the present application, the negative high voltage applied to the bunching electrode 12 may be -151 kV, the negative high voltage applied to the cathode 13 may be -150 kV, the negative high voltage applied to the control electrode 14 may be -100 kV, and the anode may be 0 V. That is, in an embodiment of the present application, a high voltage of -150 kV may be applied to the electron gun 10 without causing high voltage sparks, thereby ensuring the normal operation of the electron gun.

[0068] Exemplarily, in the embodiments of the present application, the bias voltage may refer to the negative voltage applied on the bunching electrode 12 relative to the cathode 13. For example, the bias voltage may be the difference between the voltage of the bunching electrode 12 and the voltage of the cathode 13. Assuming that the negative high voltage applied on the bunching electrode 12 can range from -152kV to -150kV, and the negative high voltage applied on the cathode 13 can be -150kV, the bias voltage can be adjusted in the range of 0 to 2kV. The present application does not specifically limit the size setting of the bias voltage.

[0069] It should be noted that in the embodiment of the present application, the control electrode 14 is located between the cathode 13 and the anode 15, dividing the high-voltage electric field between the cathode and the cathode into two parts (i.e., the first electric field region and the second electric field region), and extracting the electron beam through the medium-voltage electric field between the cathode 13 and the control electrode 14. Under the voltage difference between the cathode 13 and the control electrode 14, the free electrons are excited and accelerated for the first time. The size of this voltage difference affects the number of extracted electrons, and thus affects the beam intensity and the shape of the electron beam. Due to the second-level voltage difference between the control electrode 14 and the anode 15, the free electrons are accelerated and focused again in the electrostatic field. The light beam is accelerated and focused twice in the electron gun, reducing the beam divergence angle, avoiding the electron beam ablation of the anode hole, and improving the electron beam focusing accuracy from the electron beam extraction source without adding a magnetic confinement device. By optimizing the electrode structure and the spacing between the electrodes, a high-quality laminar light beam can be obtained. By adjusting the focusing electrode voltage and the control electrode voltage, the beam intensity and beam spot diameter can be adjusted.

[0070] It should be noted that in the embodiments of this application, the quadrupole electron gun uses a control electrode to extract the electron beam, thereby increasing the electric field strength at the cathode emitter, giving the electron beam high current characteristics. By dividing the electric field between the cathode and anode, the electron beam voltage is gradually increased, reducing the risk of high-voltage ignition.

[0071] For example, in the embodiments of the present application, the high voltage resistance level of the electron gun for additive manufacturing can be increased from 60kV to 150kV, and the power can be increased from 6kW to 20kW, thereby achieving the extraction of ultra-high voltage and high-power electron beams and reducing the risk of ignition.

[0072] Optionally, in an embodiment of the present application, when first ions are generated around the motion trajectory of an electron beam (i.e., the first electron beam and / or the second electron beam), the motion direction of the first ions is adjusted through the first electric field region and / or the second electric field region so that the first ions are captured by the control electrode and / or the bunching electrode in the electron gun, and the first ions include positive ions released in a high-temperature environment.

[0073] It should be noted that, in the embodiments of the present application, the first ions may include positive ions released under high temperature conditions, for example, H2O +, this application does not specifically limit the type and quantity of the positive ions included in the first ions.

[0074] Optionally, in the embodiment of the present application, the quadrupole electron gun can construct a double-layer ion trap between the cathode and the control electrode, and between the control electrode and the anode, to reduce the number of ions bombarding the cathode emission surface and extend the cathode life. For the electron beam powder bed melting electron gun (i.e., quadrupole electron gun), the vacuum degree can generally reach 10 -4 The stainless steel cavity and electrodes continuously release hydrogen at high temperatures, with H2 accounting for a high proportion. High-temperature oxidation reactions (such as oxidation of carbon impurities in stainless steel) lead to an increase in CO2 release. After baking, the adsorbed water is basically desorbed, and the remaining H2O mainly comes from tiny leaks or deep release of the material. Therefore, under high-temperature conditions, the residual gas in the electron gun low-vacuum system is mainly H2, supplemented by CO2, H2O, and hydrocarbons. The main mechanism for the ionization of gas molecules in the electron gun is the inelastic scattering between electrons and gas molecules, and the main ions produced are H2O + The ion yield is mainly related to the type and density distribution of the residual gas and the energy of the electron beam. Ions are generated around the electron beam trajectory. As electrons move from the cathode to the anode, their energy gradually increases, and the accumulated ion yield in the electron gun also gradually increases. Figure 4 As shown in the figure, it can be seen that the growth rate of the cumulative yield of the three ions shows a trend of first increasing rapidly and then gradually slowing down. The highest ion yield.

[0075] Optionally, in the embodiments of the present application, Figure 5 As shown, For example, ions By taking the derivative of the cumulative ion yield of the ions, we can get the ion production rate at different electron beam energies, such as Figure 3 As shown in the figure, the curve change trend of the ion production rate is consistent with the ionization cross-section curve, which shows that the change of the cumulative ion yield is determined by the electron beam energy and verifies the accuracy of the simulation.

[0076] For example, in the embodiment of the present application, a first electron beam and / or a second electron beam are generated around the motion trajectory. H2O + In the case of the first electric field region, and / or the second electric field region (i.e., the double-layer ion trap) H2O + The direction of motion is adjusted to deflect the axially moving counter-bombarding ions. H2O +The electron gun is captured by the control electrode and / or the bunching electrode in the electron gun, and the axially moving counter-bombarding ions can be deflected by the physical blocking method constructed by the double-layer ion trap to make the electron gun H2O + Captured by the control electrode and / or the buncher in the electron gun, such as Figure 6 As shown, the above method can deflect the axially moving counter-bombardment ions and eventually capture them by the control electrode and / or the bunching electrode in the electron gun, so that the double-layer ion trap of the quadrupole electron gun absorbs most of the high-energy ions, thereby effectively suppressing the ion counter-bombardment effect and extending the cathode life.

[0077] Optionally, in an embodiment of the present application, the relationship between the ion generation rate and the axial position can be further derived based on the ionization cross section of the residual gas in the electron gun and the electron beam energy distribution, thereby obtaining the spatial distribution of ions in the electron gun; based on the multi-physics field simulation, the ion motion trajectory simulation calculation is performed, and the ions bombarding the cathode emission surface can be numbered, such as Figure 7 As shown in the figure, the relationship between the number and the ion energy is shown. The number of low-energy ions is large but the damage to the cathode is small. Although the number of high-energy particles is far lower than that of low-energy ions, they are indeed the main factor causing damage to the cathode emission surface. Among them, the left figure (a) is the energy distribution result of the back-bombarding ions in the triode electron gun, and the right figure (b) is the energy distribution result of the back-bombarding ions in the quadrupole electron gun. Figure 8 As shown, the left figure (c) is the ion position and energy distribution diagram of the tripole electron gun mapped on the cathode emission surface, and the right figure (d) is the ion position and energy distribution diagram of the quadrupole electron gun mapped on the cathode emission surface. It can be seen that the double-layer ion trap of the quadrupole electron gun absorbs most of the high-energy ions. Compared with the tripole electron gun, the number of ions with energy higher than 60 keV on the cathode emission surface of the quadrupole electron gun is greatly reduced, and the existence of the control electrode reduces the ion energy in the low-energy region, effectively suppressing the ion bombardment effect, thereby extending the cathode life.

[0078] For example, in an embodiment of the present application, a quadrupole electron gun can reduce the energy of low-energy ions bombarding the cathode emission surface by adding a control electrode to construct a double-layer ion trap, thereby reducing the number of high-energy ions. In a tripole electron gun, the number of ions bombarding the cathode emission surface accounts for 6.6% of the cumulative ion yield, the number of ions with energy greater than 60 keV accounts for 20.4% of the number of ions bombarding the cathode emission surface, and the low-energy ion energy is 16.9 keV. In a quadrupole electron gun, the number of ions bombarding the cathode emission surface accounts for 5.3% of the cumulative ion yield, the number of ions with energy greater than 60 keV accounts for 3.2% of the number of ions bombarding the cathode emission surface, and the low-energy ion energy is 11.5 keV, which is 32% reduced compared to a tripole electron gun.

[0079] It should be noted that in the embodiments of the present application, due to the oxidation and burnout of the emitting crystal surface and the gradual reduction in the size of the emitting surface, the beam emission capability of the cathode will decrease with the increase in the length of use, and the criterion for the service life of the cathode can be that the maximum emission beam current of the cathode drops to half of the starting value. At the end of the cathode life, the diameter of the emitting surface will be reduced by 30%. In order to address the problem of decreased cathode emission capability during use, the present application can increase the emission beam and control the beam morphology by reducing the bias voltage and increasing the control electrode voltage, that is, adopting a dual-voltage joint modulation strategy to achieve emission power compensation. Improve the control capability of the beam, realize the decoupling of the beam intensity and the beam spot size, and improve the beam quality of the electron gun.

[0080] For example, in an embodiment of the present application, a quadrupole electron gun structure can produce a 90kV, 10kW electron beam. With a conventional cathode emitter diameter of 1.5mm, a bias voltage of 100V, and a control voltage of -53kV, the maximum beam current can reach 127mA. Without emission power compensation, the maximum beam current decreases from 127mA to 68mA over time, equivalent to a decrease in the cathode effective emission diameter from 1.5mm to 1mm. Figure 9 This is a schematic diagram of dual voltage joint adjustment for 90kV, 10kW electron gun emission power compensation proposed in the embodiment of this application, as shown in FIG. Figure 9 As shown, the present application compensates for the emission power by adopting a dual-voltage joint adjustment strategy. The bias voltage is gradually reduced to 50V, and the control voltage is increased to -47kV. The bias voltage, the control voltage and the diameter of the effective emission surface of the cathode are almost linearly related, which can ensure that the electron gun extracted beam current is always maintained in the range of 120-130mA, the power is greater than 10kW, and the maximum value of the spatial electric field is 4.8E6 V / m, which is below the safety threshold and high-voltage sparking will not occur.

[0081] For example, in the embodiments of the present application, Figure 10 This is a schematic diagram of the 90kV, 10kW electron gun emission power compensation effect proposed in the embodiment of this application, as shown in FIG. Figure 10 As shown in the figure, the emission power compensation effect of the 90kV, 10kW electron gun is shown. When the emission power compensation is not performed, the emission beam current of the electron gun gradually decreases. After the emission power of the electron beam is compensated by the bias voltage and the voltage of the control electrode, the emission beam current of the electron gun can be maintained within the preset range.

[0082] For example, in an embodiment of the present application, the preset range can be set according to actual needs. The preset range can include the maximum beam current emitted by the electron gun. Assuming that the maximum beam current emitted by the electron gun is 127mA, the preset range can be set to 120~130mA. The present application does not make any specific limitations on the setting of the preset range.

[0083] For example, in an embodiment of the present application, a quadrupole electron gun structure can produce a 150kV, 20kW electron beam. With a conventional cathode emitter diameter of 1.5mm, a bias voltage of 200V, and a control voltage of -100kV, the maximum beam current can reach 133mA. Without emission power compensation, the maximum beam current decreases from 133mA to 70mA over time, equivalent to a decrease in the cathode's effective emission diameter from 1.5mm to 1mm. Figure 11 This is a schematic diagram of a dual voltage joint adjustment diagram for 150kV, 20kW electron gun emission power compensation proposed in the embodiment of the present application, as shown in FIG. Figure 11 As shown, the present application can adopt a dual-voltage joint adjustment strategy to compensate for the emission power. The bias voltage is gradually reduced to 50V, and the control voltage is increased to -90kV. The bias voltage, the control voltage and the diameter of the effective emission surface of the cathode are almost linearly related, which can ensure that the electron gun output beam current is always maintained in the range of 133 to 140mA, the power is greater than 20kW, and the maximum value of the spatial electric field is 6.74E6V / m, which is below the safety threshold and high-voltage sparking will not occur.

[0084] For example, in the embodiments of the present application, Figure 12 This is a schematic diagram of the 150kV, 20kW electron gun emission power compensation effect proposed in the embodiment of this application, as shown in FIG. Figure 12 As shown in the figure, the emission power compensation effect of the 150kV, 20kW electron gun is shown. When the electron gun does not perform emission power compensation, the emission beam current of the electron gun gradually decreases. After the emission power of the electron beam is compensated by the bias voltage and the voltage of the control electrode, the emission beam current of the electron gun can be maintained within the preset range.

[0085] In summary, the electron beam emitted from the cathode in the quadrupole electron gun can be accelerated twice by the first electric field region and the second electric field region, respectively, so that the electron beam can be gradually boosted to avoid high-voltage sparking. When the beam current of the electron beam drops from the maximum value to the preset threshold, the emission power of the electron beam can be compensated by a preset dual-voltage strategy. For example, the emission power of the electron beam can be compensated by reducing the bias voltage and increasing the gate voltage, so that the electron gun extracted beam current is always maintained within a preset range. That is, by reducing the bias voltage and increasing the gate voltage, the emission beam current can be increased and the beam shape can be controlled, thereby improving the controllability of the beam current, achieving decoupling of the beam current intensity and the beam spot size, and improving the electron gun beam quality. When first ions are generated around the motion trajectory of the first electron beam and / or around the motion trajectory of the second electron beam, the motion direction of the first ions can be adjusted by the first electric field region and / or the second electric field region so that the first ions are captured by the gate and / or the buncher in the electron gun, thereby effectively suppressing the ion bombardment effect and extending the cathode life.

[0086] An embodiment of the present application provides a quadrupole electron gun, which includes an electron gun housing, wherein the interior of the electron gun housing includes a focusing electrode, a cathode, a control electrode, and an anode arranged in axial order; wherein the control electrode is at least used to divide the electric field between the cathode and the anode to obtain a first electric field region and a second electric field region, and a first electron beam emitted by the cathode is accelerated and focused through the first electric field region to obtain a second electron beam; wherein the first electric field region includes the electric field region between the cathode and the control electrode in the electron gun, and the second electron beam includes the electron beam after the first acceleration of the first electron beam; the second electron beam is accelerated and focused again through the second electric field region to obtain a third electron beam, so that the third electron beam reaches the target object; wherein the second electric field region includes the electric field region between the control electrode and the anode in the electron gun. It can be seen from this that the present application can propose a quadrupole electron gun, which includes a focusing electrode, a cathode, a control electrode and an anode arranged in axial order, that is, the electric field between the cathode and the anode can be divided into a first electric field region and a second electric field region through the control electrode, and then the first electron beam emitted by the cathode can be accelerated twice through the first electric field region and the second electric field region respectively, so that the first electron beam can be boosted step by step to avoid high-voltage sparking, thereby ensuring the normal operation of the electron gun, and the first electron beam is focused twice through the first electric field region and the second electric field region respectively, thereby reducing the beam divergence angle, while avoiding the electron beam ablation of the anode hole, improving the focusing accuracy of the first electron beam.

[0087] The above description is merely a preferred embodiment of the present application and is not intended to limit the scope of protection of the present application.

Claims

1. A quadrupole electron gun, characterized in that: The electron gun includes: an electron gun housing, wherein the interior of the electron gun housing includes a bunching electrode, a cathode, a control electrode and an anode arranged in axial order; wherein the control electrode is at least used to divide the electric field between the cathode and the anode to obtain a first electric field region and a second electric field region.

2. The electron gun according to claim 1, wherein The electron gun housing further includes an insulating support member and a fixing member. The insulating support member is at least used to provide insulation between the cathode, the control electrode and the anode.

3. The electron gun according to any one of claims 1 to 2, characterized in that: The electron gun further comprises a vacuum chamber, an electrode socket and a vacuum pump; wherein the electrode socket comprises a control electrode socket and a focusing electrode socket, the anode is connected to the vacuum chamber, and the vacuum pump is arranged outside the vacuum chamber.

4. The electron gun according to any one of claims 1 to 2, characterized in that The material used for the cathode includes at least lanthanum hexaboride.

5. A method for operating an electron gun, characterized in that: The working method is applied to the electron gun, and the method comprises: A first electron beam emitted by a cathode in the electron gun is accelerated and focused by a first electric field region to obtain a second electron beam; wherein the first electric field region includes an electric field region between the cathode and a control electrode in the electron gun, and the second electron beam includes an electron beam obtained by initially accelerating the first electron beam; The second electron beam is accelerated and focused again through a second electric field region to obtain a third electron beam, so that the third electron beam reaches the target object; wherein the second electric field region includes the electric field region between the control electrode and the anode in the electron gun.

6. The method according to claim 5, characterized in that The method further comprises: When first ions are generated around the motion trajectory of the first electron beam and / or around the motion trajectory of the second electron beam, the motion direction of the first ions is adjusted by the first electric field region and / or the second electric field region so that the first ions are captured by the control electrode and / or the bunching electrode in the electron gun, and the first ions include positive ions released in a high-temperature environment.

7. The method according to claim 5, characterized in that The method further comprises: When the beam current of the first electron beam drops from a maximum value to a preset threshold, the emission power of the first electron beam is compensated by a preset dual-voltage strategy to maintain the beam current within a preset range.

8. The method according to claim 7, characterized in that The compensating the emission power of the first electron beam by using a preset dual voltage strategy so as to maintain the beam current within a preset range includes: The emission power is compensated by adjusting the voltage and bias voltage of the control electrode so that the size of the beam is maintained within a preset range; wherein the bias voltage includes the difference voltage between a first voltage applied to the bunching electrode and a second voltage applied to the cathode, and the first voltage is an adjustable voltage, and the first voltage is lower than the second voltage.

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