Electron gun, vacuum device and method of activating getter

Abstract

To provide an electron gun, a vacuum device and a method of activating a getter capable of suppressing the constitution of the vacuum device from becoming complex even in the case where a non-evaporation type getter having a heater built in is provided.SOLUTION: An electron gun comprises: a cathode; a heater for heating the cathode; a getter which is electrically connected to the heater; and a switch circuit which are electrically connected to the heater and the getter, and switches between electric supply to the heater and electric supply to the getter.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] SUMMARY OF THE INVENTION Embodiments of the present invention relate to an electron gun, a vacuum apparatus, and a method for activating a getter. [Background technology]

[0002] Inside vacuum devices such as klystrons, getters are installed to adsorb gases remaining inside the vacuum device when it is manufactured, or gases released from elements installed inside the vacuum device. These getters include evaporative getters (flash getters), which are heated to scatter the getter material and then adsorb gas molecules with the scattered getter material. There are also non-evaporative getters, which are heated to activate the getter surface and then use a chemical reaction to adsorb gas molecules onto the activated getter surface.

[0003] Non-evaporable getters do not scatter getter material, so they can prevent the inside of the vacuum device from being contaminated by the getter material.Furthermore, they have the advantage that the timing for activating the getter surface can be set arbitrarily and they can be reactivated.

[0004] However, simply providing a non-evaporable getter with a built-in heater requires a terminal for supplying electricity to the electron gun and a terminal for supplying electricity to the non-evaporable getter, which creates a new problem of making the configuration of the vacuum device more complicated. Therefore, there has been a demand for the development of a technology that can prevent the configuration of the vacuum device from becoming complicated even when a non-evaporable getter with a built-in heater is provided. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-025454 [Patent Document 2] Japanese Patent Application Publication No. 2017-228505 Summary of the Invention [Problem to be solved by the invention]

[0006] The problem that the present invention aims to solve is to provide an electron gun, a vacuum device, and a getter activation method that can prevent the configuration of the vacuum device from becoming complicated, even when a non-evaporable getter with a built-in heater is provided. [Means for solving the problem]

[0007] The electron gun according to the embodiment includes a cathode, a heater for heating the cathode, a getter electrically connected to the heater, and a switching circuit electrically connected to the heater and the getter for switching between supplying electricity to the heater and supplying electricity to the getter. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a schematic cross-sectional view illustrating a vacuum apparatus including an electron gun according to an embodiment of the present invention; [Figure 2] FIG. 2 is a schematic cross-sectional view illustrating an electron gun. [Figure 3] 1(a) and 1(b) are schematic perspective views illustrating the form of a getter. [Figure 4] FIG. 10 is a circuit diagram illustrating a switching circuit. [Figure 5] 10 is a graph illustrating the voltage and frequency applied to the terminals when activating the getter. [Figure 6] 1 is a graph illustrating the voltage and frequency applied to the terminals when operating a vacuum device (electron gun). [Figure 7] FIG. 10 is a circuit diagram illustrating a switching circuit according to another embodiment. [Figure 8] FIG. 10 is a circuit diagram illustrating a switching circuit according to another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments will be illustrated with reference to the drawings. In the drawings, like components are designated by like reference numerals and detailed descriptions thereof will be omitted where appropriate. The electron gun according to the present embodiment may include a cathode that emits thermoelectrons. For example, vacuum devices that include the electron gun according to the present embodiment include klystrons, gyrotrons, transmitter tubes, X-ray tubes, and magnetrons. However, the electron gun according to the present embodiment is not limited to those provided in these devices, and may be any electron gun provided with a cathode that emits thermal electrons. In the following, as an example, a case will be described in which the vacuum device equipped with the electron gun according to this embodiment is a klystron.

[0010] FIG. 1 is a schematic cross-sectional view illustrating a vacuum apparatus 1 equipped with an electron gun 6 according to the present embodiment. As shown in FIG. 1, the vacuum device 1 includes a drift tube 2 , a collector 3 , a high frequency input section 4 , a high frequency output section 5 , and an electron gun 6 .

[0011] The drift tube 2 uses electrons 100a emitted from the electron gun 6 to amplify high frequency waves (e.g., microwaves) input from the high frequency input unit 4. The drift tube 2 is cylindrical and extends in one direction. The inner wall of the drift tube 2 is provided with a plurality of cavities 21a to 21c aligned in the axial direction of the drift tube 2. The cavity 21a is provided near the end of the drift tube 2 on the electron gun 6 side. The cavity 21c is provided near the end of the drift tube 2 on the collector 3 side. A plurality of cavities 21b can be provided between the cavities 21a and 21c.

[0012] A counter coil and a focusing coil can also be provided on the outside of the drift tube 2. The counter coil and the focusing coil form a magnetic field parallel to the axial direction of the drift tube 2. If a magnetic field parallel to the axial direction of the drift tube 2 is formed, it is possible to prevent the electrons 100a emitted from the electron gun 6 from being incident on the inner wall of the drift tube 2. This makes it possible to suppress the loss of the electrons 100a.

[0013] The collector 3 captures and cools the electrons 100a that have passed through the drift tube 2. The collector 3 is provided at the end of the drift tube 2 on the side where the cavity 21c is provided. The radio frequency input unit 4 is connected to the cavity 21a. The radio frequency input unit 4 introduces a radio frequency of a predetermined frequency into the cavity 21a. The radio frequency input unit 4 is, for example, a coaxial cable or a waveguide connected to a radio frequency power source. The radio frequency output unit 5 is connected to the cavity 21c. An output window 51 may be provided near the end of the radio frequency output unit 5 opposite to the cavity 21c side. The radio frequency output unit 5 is, for example, a waveguide.

[0014] The electron gun 6 is provided at the end of the drift tube 2 on the side where the cavity 21a is provided. The electron gun 6 emits electrons 100a into the drift tube 2. As shown in FIG. 1, electrons 100a emitted from the electron gun 6 into the drift tube 2 are accelerated or decelerated depending on the phase of the high-frequency wave introduced into the cavity 21a. The accelerated electrons 100a and the decelerated electrons 100a are gradually bunched together as they pass through a region where multiple cavities 21b are provided. The bunched electrons 100b are gradually intensified by a self-induced high-frequency electric field in the region where multiple cavities 21b are provided. Then, as the bunched electrons 100b pass through the cavity 21c, a strong AC electric field is induced, and high-power high-frequency waves are output through the output window 51.

[0015] Furthermore, a Wehnelt electrode or the like for focusing and shaping the electrons 100a emitted from the electron gun 6 may be further provided.

[0016] Next, the configuration of the electron gun 6 will be further explained. FIG. 2 is a schematic cross-sectional view illustrating the electron gun 6. As shown in FIG. 2 is a schematic enlarged view of a portion A of the vacuum device 1 in FIG. As shown in FIG. 2, the electron gun 6 includes, for example, a housing 61, a storage portion 62, a cathode 63, a heater 64, an anode 65, a connection pin 66, a terminal 67, a terminal 68, and an adsorption portion 69.

[0017] The housing 61 is cylindrical and houses therein a storage section 62, a cathode 63, a heater 64, a connection pin 66, and an adsorption section 69. The housing 61 is made of, for example, an insulating material. The internal space of the housing 61 is connected to the internal spaces of the drift tube 2 and the collector 3. These internal spaces are in a vacuum state.

[0018] The storage section 62 is cylindrical and can be made of, for example, metal. A cathode 63 can be provided at the end of the storage section 62 on the drift tube 2 side. A terminal 67 can be provided at the end of the storage section 62 opposite to the drift tube 2 side.

[0019] The cathode 63 emits electrons 100a when heated by the heater 64. The cathode 63 may be, for example, a so-called impregnated cathode containing an electron emitting material. The heater 64 can be provided inside the storage section 62. The heater 64 generates Joule heat when energized. The generated heat is transferred to the cathode 63. That is, the heater 64 heats the cathode 63.

[0020] The anode 65 is provided at the end of the drift tube 2 on the electron gun 6 side. The anode 65 faces the cathode 63. The anode 65 extracts electrons 100a from the cathode 63 and introduces them into the drift tube 2.

[0021] The connection pin 66 is electrically conductive and extends inside the storage portion 62 in the axial direction of the drift tube 2. The connection pin 66 is electrically connected to the heater 64 and a terminal 68.

[0022] The terminal 67 is electrically conductive and is provided at the end of the housing 61 opposite to the drift tube 2 . The terminal 68 is electrically conductive and is connected to the terminal 67 via an insulating portion 68a. The terminals 67 and 68 are electrically connected to a power source or the like provided outside the vacuum device 1.

[0023] The adsorption section 69 can be provided inside the storage section 62. The adsorption section 69 has, for example, a getter 69a and a switching circuit 69b. The getter 69a may be a non-evaporable getter. Therefore, when current is applied to the getter 69a, the getter 69a is heated, and a highly reactive surface is generated on the getter 69a. That is, when current is applied to the getter 69a, the getter 69a is activated. When the getter 69a is activated, gas molecules are adsorbed onto the surface of the activated getter 69a through a chemical reaction.

[0024] If the getter 69a is a non-evaporable getter, the material of the getter 69a will not scatter when the getter 69a is activated, so that the internal space of the drift tube 2 and the collector 3 can be prevented from being contaminated by the material of the getter 69a. Another advantage is that by appropriately changing the timing of energization, the timing for activating the surface of the getter 69a can be set arbitrarily, and reactivation is possible.

[0025] Furthermore, the main gas sources in the vacuum-state internal spaces of the housing 61, drift tube 2, and collector 3 are the cathode 63 and heater 64. Therefore, it is preferable to provide the getter 69a near the cathode 63 and heater 64. For example, as shown in FIG. 2, the getter 69a can be provided inside the storage section 62.

[0026] 3(a) and 3(b) are schematic perspective views illustrating the form of the getter 69a. As shown in Fig. 3(a), the getter 69a has, for example, a columnar shape. Although Fig. 3(a) shows a cylindrical getter 69a as an example, the getter 69a may have a shape of a prism such as a triangular prism, or may have a columnar shape having any cross-sectional shape. Furthermore, terminals 69a1 can be provided at the opposing ends of the getter 69a. When activating the getter 69a, electricity is passed through the getter 69a via the pair of terminals 69a1. The positions of the pair of terminals 69a1 can be changed as appropriate. For example, the pair of terminals 69a1 may be provided on the sides of the getter 69a.

[0027] As shown in FIG. 3(b), the getter 69a may also have holes 69a2. The holes 69a2, for example, penetrate between opposing ends of the getter 69a. Note that recesses may be provided in place of or in addition to the holes 69a2. The positions of the holes 69a2 and the recesses may be changed as appropriate. For example, the holes 69a2 and the recesses may be provided on the side of the getter 69a. If at least one of the holes 69a2 and the recesses is provided, the surface area (adsorption area) of the getter 69a is increased, thereby increasing the amount of gas that can be adsorbed. The getter 69a may be in the form of a thin, wound strip, etc. In this way, the surface area (adsorption area) of the getter 69a can be increased.

[0028] The material of the getter 69a may include, for example, at least one of titanium (Ti), zirconium (Zr), vanadium (V), a ZrVFe alloy, and a TiZrV alloy.

[0029] As described above, when activating the getter 69a, electricity is passed through the getter 69a. Therefore, the vacuum device 1 can be provided with a pair of terminals for passing electricity through the getter 69a. In this case, a pair of terminals electrically connected to the getter 69a can be provided in addition to the terminals 67 and 68 described above. However, if a pair of terminals for passing electricity through the getter 69a is provided in addition to the terminals 67 and 68, the configuration of the vacuum device 1 becomes complicated.

[0030] Therefore, the adsorption unit 69 is provided with a getter 69a electrically connected to the heater 64 and a switching circuit 69b. The switching circuit 69b is electrically connected to the heater 64 and the getter 69a. The switching circuit 69b switches between energizing the heater 64 and energizing the getter 69a. If the switching circuit 69b is provided, the getter 69a and the switching circuit 69b can be electrically connected to the terminals 67 and 68 to which the heater 64 is electrically connected. In other words, the terminals 67 and 68 can be used as a single terminal. If the terminals 67 and 68 can be used as a single terminal, the configuration of the vacuum device 1 can be prevented from becoming complicated.

[0031] FIG. 4 is a circuit diagram illustrating the switching circuit 69b. 4, the switching circuit 69b may include a capacitor 69b1. The capacitor 69b1 may be connected in series with the getter 69a. The series-connected capacitor 69b1 and getter 69a may be connected in parallel with the heater 64. The series-connected capacitor 69b1 and getter 69a, and the heater 64 may be electrically connected to terminals 67 and 68.

[0032] In this case, since getter 69a has an electric resistance, a high-pass filter can be configured by the electric resistance R of getter 69a and the capacitance C of capacitor 69b1. In this case, the cutoff frequency fc is "fc=1 / 2πRC".

[0033] Therefore, if a voltage having a frequency higher than the cutoff frequency fc is applied to the terminals 67 and 68, a current flows through the getter 69a, thereby activating the getter 69a. In this case, a current also flows through the heater 64, but if the voltage applied to the terminals 67 and 68 is lower than the rated voltage of the heater 64, the heater 64 will not be overheated.

[0034] For example, to activate the getter 69a, a voltage higher than the cutoff frequency fc and lower than the rated voltage of the heater 64 may be applied to the terminals 67 and 68.

[0035] On the other hand, if a voltage having a frequency lower than the cutoff frequency fc is applied to the terminals 67 and 68, no current flows through the getter 69a. In this case, a current flows through the heater 64, which heats the heater 64 and thereby causes the cathode 63 to emit electrons 100a.

[0036] For example, when operating the vacuum device 1 (electron gun 6), the rated voltage of the heater 64 may be applied to the terminals 67 and 68 at a frequency lower than the cutoff frequency fc.

[0037] FIG. 5 is a graph illustrating the voltage and frequency applied to the terminal 67 and the terminal 68 when activating the getter 69a. 5, B1 is the current flowing through the heater 64, and C1 is the current flowing through the getter 69a. The cutoff frequency fc is 30 kHz, the rated voltage of the getter 69a is 5 V, the rated current of the getter 69a is 10 A, the rated voltage of the heater 64 is 10 V, and the rated current of the heater 64 is 30 A.

[0038] If the rated voltage (5 V) of the getter 69a is applied to the terminals 67 and 68 at a frequency of 50 kHz, which is higher than the cutoff frequency (30 kHz), then the rated current (10 A) can be passed through the getter 69a, as shown by C1 in Fig. 5. This allows activation of the getter 69a.

[0039] In this case, if the voltage applied to terminals 67 and 68 is 5 V, the current flowing through heater 64, which has a rated voltage of 10 V, is 15 A, which is smaller than the rated current (30 A) of heater 64, as shown by B1 in Fig. 5. Therefore, even if a current flows through heater 64 when getter 69a is activated, it is possible to prevent heater 64 from being excessively heated.

[0040] FIG. 6 is a graph illustrating the voltage and frequency applied to terminal 67 and terminal 68 when vacuum device 1 (electron gun 6) is operated. 6, B2 is the current flowing through the heater 64, and C2 is the current flowing through the getter 69a. The cutoff frequency fc is 30 kHz, the rated voltage of the getter 69a is 5 V, the rated current of the getter 69a is 10 A, the rated voltage of the heater 64 is 10 V, and the rated current of the heater 64 is 30 A.

[0041] If the rated voltage (10 V) of the heater 64 is applied to the terminals 67 and 68 and the frequency at that time is set to 50 Hz, which is lower than the cutoff frequency (30 kHz), it is possible to prevent current from flowing through the getter 69a, as shown by C2 in Fig. 5. This makes it possible to prevent activation of the getter 69a.

[0042] In this case, if the voltage applied to terminals 67 and 68 is the rated voltage (10 V) of heater 64, the current flowing through heater 64 will be the rated current (30 A) of heater 64, as shown by B2 in Fig. 6. Therefore, even if vacuum device 1 (electron gun 6) is operated, getter 69a will not be activated.

[0043] In the above, a high-pass filter is configured by the electrical resistance R of getter 69a and the capacitance C of capacitor 69b1, but a low-pass filter may also be configured by the electrical resistance R of getter 69a and the capacitance C of capacitor 69b1. For example, it is possible to provide getter 69a (electrical resistance R) connected in series with heater 64, and capacitor 69b1 connected in parallel with the heater 64 and getter 69a (electrical resistance R) connected in series.

[0044] When a low-pass filter is formed by getter 69a (electrical resistance R) and capacitor 69b1, getter 69a can be activated by applying a voltage to terminals 67 and 68 at a frequency lower than the cutoff frequency fc and lower than the rated voltage of heater 64.

[0045] Furthermore, when operating the vacuum device 1 (electron gun 6), it is sufficient to apply to the terminals 67 and 68 a frequency higher than the cutoff frequency fc and the rated voltage of the heater 64.

[0046] Here, the heater 64 is energized when the vacuum device 1 (electron gun 6) is operated, whereas the getter 69a is energized when it is activated. In general, the activation of the getter 69a can be performed before shipping the vacuum device 1. Therefore, the frequency with which the heater 64 is energized is much higher than the frequency with which the getter 69a is energized.

[0047] In this case, if a commercial power source can be used to power the heater 64, which is frequently energized, it becomes easy to simplify the power supply configuration. Therefore, it is preferable to configure a high-pass filter using the electrical resistance R of the getter 69a and the capacitance C of the capacitor 69b1. If a high-pass filter is configured, the frequency of the current supplied to the heater 64 can be set to 50 Hz, for example, as shown in Fig. 6, making it easier to use a commercial power source as the power source for the heater 64, which is frequently energized.

[0048] The switching circuit 69b according to this embodiment can be suitably used in an electron gun 6 to which an AC is applied. If the electron gun 6 to which an AC is applied is provided with the switching circuit 69b having the capacitor 69b1, it is possible to switch between energizing the heater 64 and energizing the getter 69a by changing the AC voltage and frequency applied to the terminals 67 and 68. This allows the terminals 67 and 68 to be used for both purposes, thereby preventing the configuration of the vacuum apparatus 1 from becoming complicated.

[0049] As described above, the activation method for the getter 69a according to this embodiment is a method for activating the getter 69a electrically connected to the heater 64 that heats the cathode 63. In the activation method for the getter 69a according to this embodiment, the frequency of the AC voltage applied to the heater 64 and the getter 69a is changed to switch between energizing the heater 64 and energizing the getter 69a. Note that the content of the activation method for the getter 69a can be the same as that described above, and therefore a detailed description thereof will be omitted.

[0050] FIG. 7 is a circuit diagram illustrating a switching circuit 69ba according to another embodiment. 7, the switching circuit 69ba may include a diode 69b2 (corresponding to an example of a first diode). The diode 69b2 may be connected in series with the getter 69a. The diode 69b2 and the getter 69a, which are connected in series, may be connected in parallel with the heater 64. The diode 69b2 and the getter 69a, which are connected in series, and the heater 64 may be electrically connected to the terminal 67 and the terminal 68.

[0051] As illustrated in FIG. 7, the cathode of the diode 69b2 is electrically connected to the terminal 67, and the anode of the diode 69b2 is electrically connected to the terminal 68. In such a case, when activating the getter 69a, the rated voltage (5V) of the getter 69a, which is lower than the rated voltage of the heater 64, is applied to the terminals 67 and 68. At this time, a positive voltage is applied to the terminal 68.

[0052] In this way, as shown by D1 in Fig. 7, a current can be passed through the getter 69a via the diode 69b2. This allows activation of the getter 69a. In this case, a current also flows through the heater 64, but since the current flowing through the heater 64 is smaller than the rated current of the heater 64, excessive heating of the heater 64 can be prevented.

[0053] On the other hand, when operating the vacuum device 1 (electron gun 6), the rated voltage (10 V) of the heater 64 is applied to terminals 67 and 68. At this time, a positive voltage is applied to terminal 67. In this way, as shown by D2 in FIG. 7, a current flows through the heater 64, which heats the heater 64 and thereby causes electrons 100a to be emitted from the cathode 63. In addition, the diode 69b2 prevents a current from flowing through the getter 69a. This prevents the getter 69a from being activated.

[0054] It is also possible to electrically connect the cathode of diode 69b2 to terminal 68 and the anode of diode 69b2 to terminal 67. In this case, when activating getter 69a, a positive voltage should be applied to terminal 67. When operating vacuum device 1 (electron gun 6), a positive voltage should be applied to terminal 68.

[0055] FIG. 8 is a circuit diagram illustrating a switching circuit 69bb according to another embodiment. The switching circuit 69bb is the same as the switching circuit 69ba described above, except that a diode 69b3 (which corresponds to an example of a second diode) is further provided. 8, the diode 69b3 can be connected in series with the heater 64. The series-connected diode 69b2 and getter 69a can be connected in parallel with the series-connected diode 69b3 and heater 64. In addition, the anode of the diode 69b2 can be electrically connected to the cathode of the diode 69b3.

[0056] When activating the getter 69a, the rated voltage (5V) of the getter 69a, which is lower than the rated voltage of the heater 64, is applied to the terminals 67 and 68. At this time, a positive voltage is applied to the terminal 68.

[0057] In this way, as shown by D1 in Fig. 8, a current can be passed through the getter 69a via the diode 69b2. This allows activation of the getter 69a. Furthermore, the diode 69b3 can prevent a current from flowing through the heater 64. This allows energy saving when activating the getter 69a.

[0058] On the other hand, when operating the vacuum device 1 (electron gun 6), the rated voltage (10 V) of the heater 64 is applied to terminals 67 and 68. At this time, a positive voltage is applied to terminal 67. In this way, as shown by D2 in FIG. 8, a current flows through diode 69b3, allowing a current to flow through the heater 64. This allows heating of the heater 64, and ultimately emission of electrons 100a from the cathode 63. Furthermore, diode 69b2 prevents a current from flowing through the getter 69a. This prevents activation of the getter 69a.

[0059] The cathode of the diode 69b2 may be electrically connected to the terminal 68, and the anode of the diode 69b2 may be electrically connected to the terminal 67. In this case, the cathode of the diode 69b2 may be electrically connected to the anode of the diode 69b3. In such a case, when activating the getter 69a, a positive voltage should be applied to the terminal 67. When operating the vacuum device 1 (electron gun 6), a positive voltage should be applied to the terminal 68.

[0060] As described above, the switching circuit 69ba or the switching circuit 69bb according to this embodiment can be suitably used in an electron gun 6 to which direct current is applied. If the electron gun 6 to which direct current is applied is provided with the switching circuit 69ba or the switching circuit 69bb having the diode 69b2, it is possible to switch between energizing the heater 64 and energizing the getter 69a by changing the polarity of the DC voltage applied to the terminals 67 and 68. This allows the terminals 67 and 68 to be used for both purposes, thereby preventing the configuration of the vacuum apparatus 1 from becoming complicated.

[0061] Furthermore, if the switching circuit 69bb further includes the diode 69b3, the heater 64 can be prevented from being energized when the getter 69a is activated, thereby achieving energy savings.

[0062] Furthermore, the heat resistance temperature of diodes 69b2 and 69b3 is higher than that of capacitor 69b1. Therefore, if a switching circuit is provided with diodes, it becomes easy to provide the switching circuit near cathode 63 and heater 64, which are high in temperature and serve as the main gas sources. This makes it easy to adsorb and remove gas generated from at least one of cathode 63 and heater 64.

[0063] As described above, the getter activation method according to this embodiment is a method for activating the getter 69a electrically connected to the heater 64 that heats the cathode 63. In the getter activation method according to this embodiment, the polarity of the DC voltage applied to the heater 64 and the getter 69a is changed to switch between energizing the heater 64 and energizing the getter 69a. Note that the details of the activation method for the getter 69a can be the same as those described above, and therefore a detailed description thereof will be omitted.

[0064] Although several embodiments of the present invention have been illustrated above, these embodiments are presented as examples and are not intended to limit the scope of the invention.

[0065] With respect to the above-described embodiments, those skilled in the art may add, delete, or modify components as appropriate, or add, omit, or change conditions of steps, as long as they retain the characteristics of the present invention, and these changes are also included within the scope of the present invention.

[0066] For example, the shape, dimensions, material, arrangement, etc. of each element included in the vacuum device 1 are not limited to those exemplified, and can be changed as appropriate. Furthermore, the elements of each of the above-described embodiments can be combined to the greatest extent possible, and such combinations are also included within the scope of the present invention as long as they include the features of the present invention. [Explanation of symbols]

[0067] 1 vacuum device, 2 drift tube, 3 collector, 4 high frequency input section, 5 high frequency output section, 6 electron gun, 63 cathode, 64 heater, 65 anode, 67 terminal, 68 terminal, 69 adsorption section, 69a getter, 69b switching circuit, 69ba switching circuit, 69bb switching circuit, 69b1 capacitor, 69b2 diode, 69b3 diode

Claims

1. a cathode; a heater for heating the cathode; a getter electrically connected to the heater; a switching circuit electrically connected to the heater and the getter, for switching between energization of the heater and energization of the getter; An electron gun equipped with

2. the switching circuit includes a capacitor; 2. The electron gun according to claim 1, wherein the getter and the capacitor form a high-pass filter or a low-pass filter.

3. the switching circuit includes a first diode; the first diode is connected in series with the getter; 2. The electron gun according to claim 1, wherein the first diode and the getter connected in series are connected in parallel with the heater.

4. the switching circuit further includes a second diode; the second diode is connected in series with the heater; 4. The electron gun according to claim 3, wherein the first diode and the getter connected in series are connected in parallel with the second diode and the heater connected in series.

5. A vacuum device comprising the electron gun according to any one of claims 1 to 4.

6. 1. A method for activating a getter electrically connected to a heater that heats a cathode, comprising: by changing the frequency of an AC voltage applied to the heater and the getter, switching between energization of the heater and energization of the getter; or A getter activation method in which the polarity of a DC voltage applied to the heater and the getter is changed to switch between energizing the heater and energizing the getter.

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