Electron gun, electron beam application device, and electron beam emitting method

Abstract

The present invention provides an electron gun capable of extending the life of a photocathode, comprising a substrate having a photocathode film formed on a first surface, a light source for irradiating excitation light onto the photocathode film, an anode, a heating device for heating the photocathode film and / or the substrate, and an output adjustment device for adjusting the heating temperature of the heating device.

Description

Technical Field

[0001] The present invention relates to an electron gun, an electron beam application device and an electron beam emitting method. Background Art

[0002] Electron beam application devices such as electron guns equipped with photocathodes, electron microscopes incorporating such electron guns, free electron laser (FEL) accelerators, and inspection devices are known (hereinafter, devices in which the electron gun is removed from the electron beam application device may be referred to as "partner devices"). For example, Patent Document 1 discloses an electron microscope device that uses a photocathode that emits an electron beam by irradiating excitation light from a light source.

[0003] Electron beam applications such as electron microscopes require stable electron beam emission. However, continuous light exposure degrades the electron emission characteristics of photocathodes, and as the amount of emitted electrons decreases, electron beam intensity decreases over time in electron beam sources using photocathodes. Patent Document 1 discloses a technique for restoring electron beam intensity by increasing the excitation light intensity or performing Cs (cesium) vapor deposition.

[0004] Furthermore, an electron gun is also known that measures the intensity of an electron beam emitted from a photocathode using a measuring electron beam shielded by an electron beam shielding member and adjusts the intensity of the electron beam emitted from the photocathode based on the measurement result (see Patent Document 2).

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 2002-313273

[0008] Patent Document 2: Japanese Patent No. 6578529 Summary of the Invention

[0009] Problems to be solved by the invention

[0010] As described in Patent Documents 1 and 2, when the photocathode's function deteriorates due to continued use, it is known that the electron beam intensity can be restored by increasing the excitation light intensity or performing Cs re-evaporation. However, to improve the operating rate of electron beam application devices equipped with electron guns using photocathodes, it is preferable to reduce the frequency of Cs re-evaporation; in other words, the longer the life of the photocathode, the better. However, methods for extending the life of photocathodes in electron guns using photocathodes are still unknown.

[0011] The present inventors, through diligent research, have newly discovered an invention capable of extending the life of a photocathode by emitting an electron beam while the photocathode is heated.

[0012] The present invention discloses an electron gun capable of extending the life of a photocathode, an electron beam application device equipped with the electron gun, and an electron beam emission method. Any additional effects disclosed in the present invention will become more apparent in the embodiments of the invention.

[0013] Means of solving problems

[0014] (1) An electron gun comprising:

[0015] a substrate having a photocathode film formed on a first surface;

[0016] a light source, for irradiating excitation light onto the photocathode film;

[0017] anode;

[0018] a heating device for heating the photocathode film and / or the substrate; and

[0019] The output adjustment device is used to adjust the heating temperature of the heating device.

[0020] (2) The electron gun as described in (1) above, further comprising:

[0021] vacuum chamber;

[0022] The heating device is disposed in the vacuum chamber and heats the substrate directly or indirectly.

[0023] (3) The electron gun as described in (2) above, comprising:

[0024] A fixing seat for holding the substrate;

[0025] Wherein, the heating device is arranged on the fixing seat.

[0026] (4) An electron gun comprising:

[0027] a substrate having a photocathode film formed on a first surface;

[0028] a light source, for irradiating excitation light onto the photocathode film;

[0029] anode;

[0030] a heating device for heating the photocathode film and / or the substrate; and

[0031] vacuum chamber;

[0032] The heating device is arranged outside the vacuum chamber and heats the photocathode film and / or the substrate from the outside of the vacuum chamber.

[0033] (5) The electron gun as described in (4) above further includes an output adjustment device for adjusting the heating temperature of the heating device.

[0034] (6) The electron gun according to any one of (1) to (3) and (5) above, further comprising:

[0035] a measuring unit for measuring a change in intensity of an electron beam emitted from the photocathode film due to degradation of the photocathode film; and

[0036] The control unit controls the output adjustment device based on the measurement result of the measurement unit.

[0037] (7) The electron gun as described in (6) above, wherein the control unit adjusts the intensity of the electron beam emitted from the photocathode film based on the measurement result of the measurement unit.

[0038] (8) An electron beam application device comprising the electron gun according to any one of (1) to (7), wherein the electron beam application device is:

[0039] Free electron laser accelerator;

[0040] Electron microscopy;

[0041] Electron beam holography devices;

[0042] electron beam patterning device;

[0043] Electron ray diffraction device;

[0044] Electron ray inspection equipment;

[0045] Electron beam metal lamination molding device;

[0046] Electron beam lithography equipment;

[0047] Electron beam processing equipment;

[0048] Electron ray hardening device;

[0049] Electron beam sterilization device;

[0050] Electron ray sterilization device;

[0051] plasma generating device;

[0052] Atomic element production device;

[0053] Rotating polarized electron beam generating device;

[0054] a cathodoluminescent device; or

[0055] Inverse photon emission spectroscopy device.

[0056] (9) A method for emitting an electron beam, wherein:

[0057] The electron beam is emitted by an electron gun, which includes:

[0058] a substrate having a photocathode film formed on a first surface;

[0059] a light source, for irradiating excitation light onto the photocathode film;

[0060] an anode; and

[0061] a heating device for heating the photocathode film and / or the substrate;

[0062] Injection methods include:

[0063] An electron beam emitting step of irradiating the photocathode film with excitation light from a light source while heating the photocathode film and / or the substrate, and emitting an electron beam from the photocathode film in response to the reception of the excitation light.

[0064] (10) The emission method as described in (9) above includes a photocathode temperature adjustment step of adjusting the heating temperature of the photocathode film and / or the substrate.

[0065] (11) The injection method as described in (10) above, further comprising:

[0066] a measuring unit for measuring a change in intensity of an electron beam emitted from the photocathode film due to degradation of the photocathode film;

[0067] Here, the photocathode temperature adjustment step is performed based on the measurement result of the measurement unit.

[0068] Effects of the Invention

[0069] The life of the photocathode can be extended by emitting an electron beam while heating the photocathode. BRIEF DESCRIPTION OF THE DRAWINGS

[0070] Figure 1 Schematic diagram showing the electron gun 1A according to the first embodiment and a partner device E equipped with the electron gun 1A.

[0071] Figure 2 1A and 1B are diagrams showing another embodiment of the arrangement of the heating device 5 in the electron gun 1A according to the first embodiment.

[0072] Figure 3Schematic diagram showing an electron gun 1B according to a second embodiment and a partner device E equipped with the electron gun 1B.

[0073] Figure 4 Schematic diagram showing an electron gun 1C according to a third embodiment and a partner device E equipped with the electron gun 1C.

[0074] Figure 5 It is a schematic diagram showing an electron beam shielding member.

[0075] Figure 6 It is a diagram showing another example of the measuring unit in the electron gun 1C according to the third embodiment.

[0076] Figure 7 A is a drawing showing the measurement results of Example 1, Figure 7 B is a diagram showing the measurement results of Comparative Example 1.

[0077] Figure 8 A is a drawing showing the measurement results of Example 2, Figure 8 B is a diagram showing the measurement results of Comparative Example 2. DETAILED DESCRIPTION

[0078] The following describes in detail an electron gun, an electron beam application device, and an electron beam emission method, with reference to the accompanying drawings. In this specification, components with identical functions are designated by identical or similar reference numerals. Furthermore, for components designated by identical or similar reference numerals, duplicate descriptions may be omitted.

[0079] In addition, the positions, sizes, and ranges of various structures shown in the drawings may not represent actual positions, sizes, and ranges for ease of understanding. Therefore, the disclosure in this application is not necessarily limited to the positions, sizes, and ranges disclosed in the drawings.

[0080] (First embodiment of electron gun)

[0081] Reference Figure 1 and Figure 2 The electron gun 1A according to the first embodiment will be described. Figure 1 Schematic diagram showing the electron gun 1A according to the first embodiment and a partner device E equipped with the electron gun 1A. Figure 2 It is a diagram showing another embodiment of the arrangement of the heating device 5 .

[0082] The electron gun 1A of the first embodiment includes at least a photocathode 2 , a light source 3 , an anode 4 , a heating device 5 , and an output adjustment device 6 .

[0083] exist Figure 1In the example shown, the photocathode 2 is formed by adhering the photocathode film 22 to the first surface 21a of the substrate 21. Figure 1 In the example shown, an electron beam B is emitted from the photocathode film 22 in response to the excitation light L incident from the second surface 21b side opposite to the first surface 21a on which the photocathode film 22 is formed. For this reason, the substrate 21 is preferably a transparent substrate 21. The transparent substrate 21 is not particularly limited as long as it can allow the excitation light from the light source 3 to pass through. For example, quartz glass or sapphire glass can be mentioned. In addition, when the excitation light L from the light source 3 is irradiated from the first surface 21a side of the substrate 21, the substrate 21 does not necessarily have to be transparent, and can also be a material other than quartz glass or sapphire glass as long as it can adhere to the photocathode film 22.

[0084] The photocathode film 22 is not particularly limited as long as it can emit electron beams when irradiated with excitation light, and examples thereof include materials requiring EA surface treatment (electron affinity reduction treatment) and materials not requiring EA surface treatment. Figure 2 A is an example showing the use of materials requiring EA surface treatment. Examples of materials requiring EA surface treatment include III-V semiconductor materials and II-VI semiconductor materials. Specifically, AlN, Ce2Te, GaN, compounds of one or more alkali metals and Sb, AlAs, GaP, GaAs, GaSb, InAs, and mixed crystals thereof can be cited. Other examples include metals, specifically Mg, Cu, Nb, LaB6, SeB6, Ag, and the like. By subjecting the surface of the photocathode film substrate 22a requiring EA surface treatment to EA surface treatment, a photocathode film 22 having an EA surface 22b formed on the photocathode film substrate 22a can be prepared. The photocathode film 22 not only becomes capable of selectively exciting light in the near-ultraviolet-infrared wavelength region corresponding to the gap energy of the semiconductor, but also, through the selection of the semiconductor material or structure, enables the electron beam source performance (quantum yield, durability, monochromaticity, time responsiveness, spin polarization) corresponding to the purpose of the electron beam.

[0085] in addition, Figure 2Figure B illustrates an example using a material that does not require EA surface treatment. Examples of materials that do not require EA surface treatment include single metals such as Cu, Mg, Sm, Tb, and Y, as well as alloys, metal compounds, diamond, WBaO, and Cs2Te. The photocathode film 22c that does not require EA surface treatment can be prepared using known methods (e.g., see Japanese Patent No. 3537779).

[0086] The light source 3 is not particularly limited as long as it can emit an electron beam B by irradiating the photocathode 2 with the excitation light L. Examples of the light source 3 include high-output (watt class), high-frequency (hundreds of MHz), ultrashort pulse laser light sources, relatively inexpensive laser diodes, LEDs (Light Emitting Diodes), etc. The irradiated excitation light L can be either pulse light or continuous light, as long as it is appropriately adjusted according to the purpose. In addition, although Figure 1 In the described example, the light source 3 is disposed outside the vacuum chamber CB, and the excitation light L is irradiated from the second surface 21 b side of the photocathode 2 . However, the light source 3 may be disposed inside the vacuum chamber CB instead.

[0087] The anode 4 is not particularly limited as long as it can form an electric field with the cathode 3 , and an anode generally used in the field of electron guns can be used.

[0088] exist Figure 1 In the example shown, a photocathode 2 and an anode 4 are disposed within a vacuum chamber CB. Electrons in the photocathode 2 are excited by excitation light L, and the excited electrons are emitted from the photocathode 2. The emitted electrons form an electron beam B due to the electric field formed by the anode 4 and the cathode 2. In this specification, the terms "photocathode" and "cathode" may be referred to as "photocathode" when referring to the device that emits the electron beam B, and as "cathode" when referring to the device as the opposite pole to the "anode." However, the symbol 2 is used for both "photocathode" and "cathode."

[0089] As long as the electron beam B can be emitted from the cathode 2 toward the anode 4, the configuration of the power supply is not particularly limited. Figure 1 In the example shown, the electric field is formed by configuring the power supply in such a way that an electric potential difference is generated between the cathode 2 and the anode 4 .

[0090] The heating device 5 is used to heat the photocathode film 22 and / or the substrate 21. As will be described in the embodiments below, when the excitation light L is irradiated onto the photocathode film 22 and the electron beam B is emitted, if the excitation light L is irradiated while the photocathode 2 (photocathode film 22) is already heated, the life of the photocathode 2 is prolonged. In other words, the degradation rate of the photocathode film 22 is slowed down.

[0091] The heating device 5 is not particularly limited as long as it can heat the photocathode film 22 when emitting the electron beam B. Furthermore, the heating device 5 may directly heat the photocathode film 22 or indirectly heat the photocathode film 22 by directly heating the substrate 21. Furthermore, the heating device 5 may indirectly heat the photocathode film 22 by indirectly heating the substrate 21.

[0092] exist Figure 1 In the example shown, the heating device 5 is embedded in the fixing base 7 for holding the substrate 21. As the heating device 5, for example, a heater that can be heated by energizing a resistance heating heater or the like, or a high-frequency heating device can be cited. Figure 1 In the illustrated example, the heating device 5 is embedded in the mounting base 7. By heating the mounting base 7, the substrate 21 is heated, and the heated substrate 21 in turn heats the photocathode film 22. In other words, the heating device 5 indirectly heats the substrate 21 and the photocathode film 22. Therefore, the mounting base 7 is preferably formed of a material with good thermal conductivity. Examples of such materials include metals such as titanium, molybdenum, alloys thereof, Inconel, and stainless steel (SUS).

[0093] In addition, Figure 1 In the example shown, the heating device 5 is in non-contact with the end of the substrate 21. As an alternative, the heating device 5 can also be configured in a manner that directly contacts the substrate 21. Figure 1 Although not shown in the figure, when the fixing base 7 is included, a condenser lens can also be arranged on the fixing base 7. When the condenser lens is provided, the excitation light L from the light source 3 can be condensed while irradiating the photocathode film 22. Therefore, when the condenser lens is provided, a smaller and more intense electron beam B can be emitted from the photocathode film 22.

[0094] When the photocathode film 22 has deteriorated, the photocathode film 22 is regenerated by heating the photocathode 2. In this specification, regeneration of the photocathode film 22 refers to: (1) when using a photocathode film substrate 22a that requires EA surface treatment, cleaning is performed by heating the EA surface 22b, followed by retreatment (reformation of the EA surface) using a surface treatment material described later; and (2) when using a photocathode film 22c that does not require EA surface treatment, removing dirt attached to the surface of the photocathode film 22c by heating. In the electron gun 1A of the first embodiment, the heating device 5 can be used for both regeneration of the photocathode film 22 and extension of the life of the photocathode 2.

[0095] It is worth noting that the temperature during the regeneration of the photocathode film 22 varies depending on the composition (crystal structure) of the photocathode film 22, but can be very high. On the other hand, if the heating temperature of the photocathode 2 (photocathode film 22) is too high when the electron beam B is emitted, the photocathode film 22 may be damaged. Therefore, the temperature at which the photocathode film 22 and / or the substrate 21 are heated when the electron beam B is emitted is lower than the temperature during the regeneration of the photocathode film 22.

[0096] To this end, the electron gun 1A of the first embodiment includes an output adjustment device 6 for adjusting the heating temperature of the heating device 5, in order to enable heating the photocathode 2 to different temperatures. For example, if the heating device 5 is a resistive heater, the output adjustment device 6 can simply control the current output to the resistive heater. If the heating device 5 is a high-frequency heater, the output adjustment device 6 can simply control the AC current output to the coil.

[0097] The lower limit of the heating temperature of the photocathode film 22 during the emission of the electron beam B can be higher than room temperature, for example, 50°C or higher, 75°C or higher, 100°C or higher, 120°C or higher, 140°C or higher, 160°C or higher, or 180°C or higher, and can be appropriately adjusted depending on the material forming the photocathode film 22. Furthermore, the upper limit of the heating temperature of the photocathode film 22 during the emission of the electron beam B can be any temperature that does not damage the photocathode film 22 due to heating, in other words, a temperature lower than the temperature at which the photocathode film 22 is regenerated. Although it varies depending on the composition and crystal structure of the photocathode film 22, examples thereof include 600°C or lower, 550°C or lower, 500°C or lower, 450°C or lower, 300°C or lower, 250°C or lower, or 200°C or lower.

[0098] The output adjustment device 6 only needs to adjust the output of the heating device 5 for directly or indirectly heating the photocathode film 22 so that the photocathode film 22 (photocathode 2) is kept within the above-mentioned temperature range. As described above, the heating device 5 can switch between at least two temperatures: a temperature suitable for regenerating the photocathode film 22 and a temperature suitable for emitting the electron beam B. Therefore, the output adjustment device 6 can be a device that can provide at least two different output intensities to the heating device 5. Although Figure 1 Although the icons are omitted, the output adjustment device 6 and the heating device 5 only need to be connected by electric wires or the like.

[0099] in addition, Figure 1 The electron gun 1A of the first embodiment shown is an example in which a driving device 8 for moving the fixing seat 7 up and down relative to the traveling direction of the electron beam B, a storage container 9 for storing the photocathode 2, and a surface treatment material 91 for performing EA surface treatment on the photocathode 2 in the storage container 9 are arbitrarily additionally configured. In the case where the driving device 8 includes a driving unit 81 in a vacuum chamber, the output adjustment device 6 and the heating device 5 can also be connected via the driving unit 81 in the vacuum chamber. As long as the driving device 8 is capable of moving the photocathode 2 (in the vacuum chamber), the output adjustment device 6 and the heating device 5 can be connected. Figure 1 In the illustrated example, the drive mechanism is not particularly limited to the embodiment described herein (moved via a fixed base 7). For example, the drive mechanism described in International Publication No. 2015 / 008561 or International Publication No. 2018 / 186294 may be used. The technical contents described in International Publication No. 2015 / 008561 and International Publication No. 2018 / 186294 are incorporated into this specification.

[0100] There is no particular limitation on the material of the storage container 9, and the storage container 9 may be made of heat-resistant materials such as glass, molybdenum, ceramics, sapphire, titanium, tungsten, and tantalum that can withstand temperatures above 300°C, preferably 400°C.

[0101] The surface treatment material 91 disposed within the storage container 9 is not particularly limited as long as it is a material capable of EA surface treatment. Examples of elements that constitute the surface treatment material 91 include Li, Na, K, Rb, Cs, Te, and Sb. It is worth noting that, among these elements, Li, Na, K, Rb, and Cs spontaneously combust when present alone and therefore cannot be stored or utilized. Therefore, Li, Na, K, Rb, and Cs must be used in the form of composite elements or compounds containing these elements. Furthermore, when using these elements in the form of compounds, care must be taken to prevent the generation of impurity gases during the deposition of these elements. Therefore, when using an element selected from Li, Na, K, Rb, and Cs as the surface treatment material 91, it is preferable to combine a compound such as Cs2CrO4, Rb2CrO4, Na2CrO4, or K2CrO4 with a reducing agent to suppress the generation of impurity gases. The surface treatment material 91 is vaporized within the storage container 9 by heating and then deposited onto the photocathode 2.

[0102] exist Figure 1 In the example shown, the heating device 5 is arranged on the fixing base 7. Figure 2 In the illustrated example, the fixing base 7 for holding the substrate 21 is not used, and the heating device 5 is directly disposed on the substrate 21 to perform heating.

[0103] exist Figure 2 The example shown in A shows an example in which the heating device 5 is directly arranged on the substrate 21. When the heating device 5 is directly arranged on the substrate 21, the heating device 5 can be adhered to the substrate 21 using an adhesive having heat resistance higher than the upper limit of the heating temperature of the heating device 5, such as an inorganic adhesive. Figure 2 In the example shown in A, the heating device 5 is arranged above the substrate 21 , but the heating device 5 may be arranged on the side or below the substrate 21 .

[0104] exist Figure 2 In the example shown in Figure B, a clamping member 51 is provided with the heating device 5 to more securely hold the heating device 5 on the substrate 21. The clamping member 51 is not particularly limited as long as it can clamp the substrate 21 and the heating device 5 and is heat-resistant. For example, the clamping member 51 can be formed from the same material as the fixing base 7 and has a substantially concave shape.

[0105] In addition, Figure 2 A and Figure 2 In the example shown in B, a rod 23 for moving the photocathode 2 up and down is formed on the substrate 21. Figure 2 A and Figure 2 In the example shown in B, by Figure 1 The driving unit 81 in the vacuum chamber of the driving device 8 shown is connected to the rod 23 to drive the photocathode 2 in the vertical direction. In addition, when the light source 3 is irradiated from the second surface 21b side of the substrate 21, the rod 23 can be formed of a transparent material or a hollow member through which the excitation light L can pass.

[0106] (Second embodiment of electron gun)

[0107] Reference Figure 3 Next, an electron gun 1B according to the second embodiment will be described. Figure 3 Schematic diagram showing an electron gun 1B according to a second embodiment and a partner device E equipped with the electron gun 1B.

[0108] The electron gun 1B of the second embodiment includes a heating device 52 disposed outside the vacuum chamber CB and heating the photocathode film 22 and / or substrate 21 from outside the vacuum chamber CB. The electron gun 1A of the first embodiment differs from the electron gun 1A in that the heating device 5 and output adjustment device 6 are optional additions. Otherwise, the second embodiment is the same as the first embodiment. Therefore, the second embodiment will focus on the differences from the first embodiment, and any overlapping descriptions of matters already described in the first embodiment will be omitted. Therefore, even if not explicitly described in the second embodiment, matters already described in the first embodiment may be incorporated into the second embodiment.

[0109] The electron gun 1B of the second embodiment includes a heating device 52 that heats the photocathode film 22 and / or the substrate 21 from outside the vacuum chamber CB. Therefore, the heating device 52 is not particularly limited as long as it can be a lamp heater, a laser heater, a high-frequency heater, a resistance heater, or other heating device that can heat a remote heating object.

[0110] In the electron gun 1B of the second embodiment, the heating device 52 is not used to regenerate the photocathode 2, but rather to extend the life of the photocathode 2. Therefore, since the heating device 52 can be driven with a single, pre-set output type, the electron gun 1B of the second embodiment does not necessarily require an output adjustment device 6. However, this does not preclude heating the photocathode film 22 and / or substrate 21 at two or more different temperatures for the purpose of extending the life of the photocathode 2. Therefore, the electron gun 1B of the second embodiment may optionally include an output adjustment device 6 for adjusting the output of the heating device 52. If the heating device 52 is a lamp heater, laser heater, or the like, the output adjustment device 6 simply adjusts the current used to adjust the intensity of the lamp heater, laser heater, or the like. If the heating device 52 is a resistive heater, the output adjustment device 6 simply controls the current output to the resistive heater. If the heating device 52 is a high-frequency heater, the output adjustment device 6 simply controls the AC current output to the coil. In addition, in the case of the electron gun 1B of the second embodiment, the photocathode film 22 can be directly heated from the outside of the vacuum chamber CB using a lamp heater, a laser heater, a resistance heating heater, a high-frequency heating device, etc., or the photocathode film 22 can be heated through the substrate 21 by heating the substrate 21.

[0111] In the electron gun 1B of the second embodiment, the heating device 5 for regenerating the photocathode 2 is not essential as a means for solving the problem of the present application. However, the electron gun 1B of the second embodiment may also be optionally provided with the heating device 5 .

[0112] In the electron gun 1A of the first embodiment, the heating device 5 for regenerating the photocathode 2 and the heating device 5 for extending the life of the photocathode 2 can be commonalized. Meanwhile, in the electron gun 1B of the second embodiment, the heating device 52, which is used more frequently than the heating device 5 for regenerating the photocathode 2, can be located outside the vacuum chamber CB. Therefore, in the electron gun 1B of the second embodiment, even if the heating device 52 malfunctions, the heating device 52 can be replaced without opening the vacuum chamber CB.

[0113] (Third Embodiment of Electron Gun)

[0114] Reference Figure 4 and Figure 5 An electron gun 1C according to the third embodiment will be described. Figure 4 Schematic diagram showing an electron gun 1C according to a third embodiment and a partner device E equipped with the electron gun 1C. Figure 51 is a schematic diagram showing the electron beam shielding member 11 a.

[0115] The electron gun 1C of the third embodiment differs from the electron gun 1A of the first embodiment and the electron gun 1B of the second embodiment in that it includes a measuring unit 11 for measuring changes in the intensity of the electron beam B emitted from the photocathode 2 as the photocathode 2 degrades, and a control unit 12 for controlling the output adjustment device 6 based on the measurement results of the measuring unit 11. All other aspects are the same. Therefore, the description of the third embodiment will focus on the differences from the first and second embodiments, and any overlapping descriptions of matters already described in the first and second embodiments will be omitted. Therefore, even if not explicitly described in the third embodiment, matters already described in the first and second embodiments can naturally be incorporated into the third embodiment.

[0116] exist Figure 4 In the example shown, the electron beam shielding member 11a and the measuring device 11b disposed in the electron gun 1C form a measuring unit 11. Next, a control unit 12 for controlling the output adjustment device 6 based on the measurement results of the measuring unit 11 is provided.

[0117] The electron beam shielding member 11a includes a hole 11a1 through which a portion of the electron beam B emitted from the photocathode 2 passes. The width of the hole 11a1 is set to be smaller than the width of the electron beam B. Figure 5 As shown in the example, when the width of the electron beam B when it reaches the electron beam shielding component 11a is set to D1 and the width of the hole 11a1 is set to D2, the portion of the electron beam B that overlaps with the hole 11a1 will pass through the electron beam shielding component 11a. On the other hand, the difference in the electron beam B that does not pass through the hole 11a1 is shielded by the electron beam shielding component 11a. Next, the electron beam B shielded by the electron beam shielding component 11a is used as a "measurement electron beam" and its intensity is measured by the measuring device 11b. In addition, D2 is not particularly limited as long as it is a size that allows the required amount of electron beam B to pass through. In addition, the size of D1 relative to D2 is not particularly limited as long as a measurable measurement electron beam B can be obtained using the measuring device 11b. While increasing the size of D1 relative to D2 increases the amount of measuring electron beam B and improves the measurement accuracy of measuring device 11b, the amount of electron beam B emitted from photocathode 2 that enters partner device E decreases, reducing the operating efficiency of the electron beam application device. Conversely, if D1 is too small relative to D2, the amount of measuring electron beam B decreases, and the measurement accuracy of measuring device 11b also decreases. Therefore, the sizes of D1 and D2 should be appropriately adjusted while considering both measurement accuracy and operational efficiency.

[0118] The material of the electron beam shielding member 11a is not particularly limited as long as it is a conductor or a semiconductor. In the case of a conductor, metals such as stainless steel (SUS) and copper can be used, for example.

[0119] The measuring device 11b measures the intensity of the electron beam B using a measuring electron beam that is a portion of the electron beam B shielded by the electron beam shielding member 11a. The measuring device 11b is not particularly limited as long as it can measure the intensity of the electron beam B. For example, when the electron beam shielding member 11a is a conductor, a current is generated between the electron beam shielding member 11a and the measuring device 11b by the measuring electron beam. For this reason, the intensity of the electron beam B can be measured as a current value in the measuring device 11b. In addition, the current value can be measured using a known ammeter. Then, since the measured current value becomes dependent on the intensity of the electron beam B, the change in the intensity of the electron beam B can be monitored by monitoring the change in the current value. In addition, a semiconductor can be used as the electron beam shielding member 11a, and the current value generated by the measuring electron beam hitting the semiconductor can be measured.

[0120] Alternatively, measuring device 11b can measure the intensity of electron beam B using fluorescence intensity instead of current. More specifically, a conductor pre-coated with a fluorescent material can be used as electron beam shielding member 11a, and measuring device 11b can measure the intensity of the fluorescence generated by the measuring electron beam striking the fluorescent material. Fluorescence intensity can be measured using a known fluorophotometer.

[0121] As described in Patent Document 2, it is known to use an electron beam shielding member 11a to measure changes in the intensity of the electron beam B emitted from the photocathode 2 as the photocathode 2 deteriorates, and to adjust the intensity of the light source 3, etc., based on the measurement results of the measuring unit 11, thereby adjusting the intensity of the electron beam B emitted from the photocathode 2. On the other hand, in the electron gun 1C of the third embodiment, the control unit 12 controls the output adjustment device 6 based on the measurement results of the measuring unit 11, thereby adjusting the temperature of the photocathode 2. Therefore, this control differs from the control described in Patent Document 2.

[0122] In addition, although Figure 4 and Figure 5 The example in which the measuring unit 11 is formed by only the structure of the electron gun 1C is shown, but the measuring unit 11 is not limited to the structure in which the degradation of the photocathode 2 can be measured. Figure 4 and Figure 5 The example shown. For example, Figure 6 1 is another example of the measuring unit 11. Figure 6In the example shown, the electron beam shielding member 11a may be replaced with a Faraday cup 11c provided in the partner device E, and the measuring unit 11 may be configured with the electron beam B captured by the Faraday cup 11c and the ammeter (measuring device) 11b.

[0123] Although not shown in the figure, the measuring unit 11 can also be formed by combining a component for shielding the electron beam B, such as an aperture provided in the electron gun 1 or the partner device E, with an ammeter (measuring device) 11b. Alternatively, since there is a correlation between the amount of light from the light source 3 and the intensity of the electron beam B, the measuring unit 11 can also be formed by a measuring device for measuring the leakage current from the electron gun 1C (or the partner device E) and a computing unit for calculating the intensity change of the electron beam B based on the ratio of the leakage current to the amount of light. Furthermore, the measuring unit 11 can also be formed by an ammeter for measuring the current supplied to the photocathode from the acceleration power supply that accelerates the electron beam B.

[0124] The electron gun 1C according to the third embodiment includes the control unit 12 , and thus can perform the following control, for example.

[0125] (1) The photocathode 2 may be heated by the heating device 5 instead of being heated when the electron beam B starts to be emitted. Instead, the photocathode 2 may be heated based on the measurement result of the measurement unit 11. In this case, the burden on the heating device 5 and the running cost can be reduced.

[0126] (2) The heating temperature of the photocathode 2 is changed according to the measurement result of the measurement unit 11 .

[0127] Furthermore, the control unit 12 of the electron gun 1C of the third embodiment may also adjust the intensity of the electron beam B emitted from the photocathode 2 as needed, in addition to the control of the output adjustment device 6. In this case, for example, the following control can be performed.

[0128] (1) When the intensity of the electron beam B decreases, the intensity of the electron beam B may be adjusted by adjusting the light source 3, etc., and when the adjustment of the light source 3, etc. becomes difficult, the photocathode 2 may be heated by the heating device 5. In this case, the burden on the heating device 5 and the running cost can be reduced.

[0129] (2) The control of the light source 3 and the like may be combined with the heating control by the heating device 5 to implement the control.

[0130] In addition, the adjustment of the intensity of the electron beam is described in Patent Document 2. The matters described in Patent Document 2 (Japanese Patent No. 6578529) are included in this specification.

[0131] (Embodiment of Electron Beam Application Device)

[0132] Examples of the electron beam application device E equipped with the electron gun 1 include known devices equipped with the electron gun 1. Examples include free electron laser accelerators, electron microscopes, electron-beam holography devices, electron-beam lithography (EB lithography) devices, electron-beam diffraction devices, electron-beam inspection devices, electron-beam metal lamination devices, electron-beam lithography devices, electron-beam processing devices, electron-beam curing devices, electron-beam sterilization devices, electron-beam disinfection devices, plasma generating devices, atomic element generating devices, spin-polarized electron beam generating devices, cathodoluminescence (CL) devices, and inverse photoemission spectroscopy (IPES) devices.

[0133] (Embodiment of Electron Beam Emission Method)

[0134] The electron beam emission method includes using the electron gun 1 or electron beam application device of the first to third embodiments to heat the photocathode film 22 and / or the substrate 21 while irradiating the excitation light L from the light source 3 to the photocathode 2, and emitting an electron beam B from the photocathode 2 based on the light received by the excitation light L.

[0135] The electron beam emission method can implement a photocathode temperature adjustment step as needed to adjust the heating temperature of the photocathode film 22 and / or substrate 21. The photocathode temperature adjustment step can be performed by switching the output of the heating device 5 using the output adjustment device 6. The output of the heating device 5 can be switched by the output adjustment device 6 at any time by the operator. Alternatively, the output of the heating device 5 can be switched by the output adjustment device 6 based on the measurement results of the measurement unit 11 used to measure the intensity change of the electron beam B emitted from the photocathode 2 due to the degradation of the photocathode 2.

[0136] Although the following examples are provided to specifically illustrate the embodiments disclosed in this application, these examples are only used to illustrate the embodiments and are not intended to limit or restrict the scope of the invention disclosed in this application.

[0137] (Example)

[0138] (Example 1)

[0139] A laser light source (iBeamSmart manufactured by Toptica) was used as the light source 3. The photocathode 2 was made of an InGaN photocathode using the known method described in DaikiSATO et al. 2016 Jpn. J. Appl. Phys. 55 05FH05. The EA treatment of the photocathode surface was performed using a known method. The electron beam shielding member 11a was made of stainless steel. In addition, a tantalum (Ta) resistive heating heater was used in the heating device 5, and the heating device was arranged so as to contact the substrate 21. In addition, the temperature of the photocathode 2 when a predetermined amount of current was flowing through the heating device 5 was measured in advance, and the correlation between the current values required to set the photocathode 2 to the desired temperature was obtained.

[0140] The electron beam B is emitted from the photocathode 2 by irradiating the photocathode 2 with excitation light L from the light source 3 and applying an acceleration voltage of 30 kV between the photocathode 2 and the anode 4. Next, the current value of the measuring electron beam obtained by the electron beam shielding component 11a is obtained by measuring and converting the voltage across a 100 kΩ shunt resistance using a data logger (MW100 manufactured by Yokogawa Electric). The measurement is performed once per second. The current value measured by the measuring unit 11 is set to approximately 2×10-5A, and the result of the current value measured by the measuring unit 11 is fed back to the light source 3 once every 5 seconds. In addition, while irradiating the excitation light L, current is caused to flow through the heating device 5 to heat the photocathode 2 so that the temperature is approximately 100°C. The measurement results are as follows. Figure 7 As shown in A.

[0141] (Comparative Example 1)

[0142] The experiment was conducted in the same manner as in Example 1 except that the heating device 5 was not used for heating and the excitation light L was irradiated to the photocathode 2 at room temperature (about 27°C). Figure 7 As shown in B.

[0143] like Figure 7As shown in A, when the electron beam B is emitted while the photocathode 2 is heated to about 100°C, a stable electron beam B can be emitted for about 28 hours. Figure 7 As shown in Figure B, when the electron beam B is emitted without heating the photocathode 2, a stable electron beam B can be emitted for approximately 14 hours. It is generally believed that if the photocathode 2 is heated while emitting the electron beam B, the energy dispersion of the electron beam B will increase. Therefore, even those skilled in the art would not have thought of emitting the electron beam B while heating the photocathode 2. The disclosure of this application confirms that by emitting the electron beam B while heating the photocathode 2, an effect that would not have been thought of even by those skilled in the art can be achieved, such as extending the life of the photocathode 2 (extending the time during which a stable electron beam B can be generated).

[0144] (Example 2)

[0145] The experiment was conducted in the same manner as in Example 1, except that the InGaN photocathode was replaced with GaAs. GaAs was prepared by molecular beam epitaxy (MBE). Figure 8 As shown in A.

[0146] (Comparative Example 2)

[0147] The experiment was conducted in the same manner as in Comparative Example 1 except that the InGaN photocathode was replaced with GaAs. Figure 8 As shown in B.

[0148] like Figure 8 As shown in A, when the electron beam B is emitted while the photocathode 2 is heated to about 100°C, a stable electron beam B can be emitted for about 3.5 hours. Figure 8 As shown in B, when the electron beam B is emitted without heating the photocathode 2, the time for which the stable electron beam B can be emitted is approximately 1.9 hours.

[0149] The above results show that even when the type of semiconductor used to form the photocathode film 22 is changed, the life of the photocathode 2 can be extended by emitting the electron beam B while heating the photocathode 2. The heat-resistant temperature of the photocathode film 22 varies depending on the type of semiconductor. Therefore, the upper limit of the heating of the photocathode 2 can be determined based on the results of Examples 1 and 2, and an appropriate temperature can be set according to the type of semiconductor.

[0150] Industrial Applicability

[0151] By using the electron gun, electron beam application device, and electron beam emission method disclosed in this application, the life of the photocathode can be extended, which is beneficial to electron gun practitioners.

[0152] Explanation of symbols:

[0153] 1.1A: Electron gun

[0154] 2: Photocathode

[0155] 21: Substrate

[0156] 21a: First surface of substrate

[0157] 21b: Second surface of substrate

[0158] 22: Photocathode film

[0159] 22a: Photocathode film substrate requiring EA surface treatment

[0160] 22b: EA surface

[0161] 22c: Photocathode film that does not require EA surface treatment

[0162] 23: Rod

[0163] 3: Light source

[0164] 4: Anode

[0165] 5: Heating device

[0166] 51: Clamping parts

[0167] 52: Heating device

[0168] 6: Output adjustment device

[0169] 7: Fixed seat

[0170] 8: Drive device

[0171] 81: Drive unit inside the vacuum chamber

[0172] 9: Storage container

[0173] 91: Surface treatment materials

[0174] 11: Measurement Department

[0175] 11a: Electron beam shielding components

[0176] 11a1: Hole

[0177] 11b: Measuring device

[0178] 11c: Faraday Cup

[0179] 12: Control Department

[0180] B: Electron beam

[0181] CB: Vacuum Chamber

[0182] D1: Width of the electron beam

[0183] D2: Width of the hole

[0184] E: Partner Device

[0185] L: Excitation light

Claims

1. An electron gun comprising: A substrate having a semiconductor photocathode film formed on a first surface thereof, wherein the semiconductor photocathode film emits an electron beam in response to the excitation light; A light source, for irradiating excitation light onto the semiconductor photocathode film; anode; A heating device for heating the semiconductor photocathode film and / or the substrate to a temperature between 50°C and 250°C; an output adjustment device for adjusting the heating temperature of the heating device; a measuring unit configured to measure a change in intensity of an electron beam emitted from the semiconductor photocathode film as the semiconductor photocathode film deteriorates; and The control unit controls the output adjustment device based on the measurement result of the measurement unit.

2. The electron gun according to claim 1, further comprising a vacuum chamber, in, The heating device is disposed in the vacuum chamber and heats the substrate directly or indirectly.

3. The electron gun according to claim 2, comprising: A fixing seat for holding the substrate; Wherein, the heating device is configured on the fixing seat.

4. An electron gun comprising: A substrate having a semiconductor photocathode film formed on a first surface thereof, wherein the semiconductor photocathode film emits an electron beam in response to the excitation light; A light source, for irradiating excitation light onto the semiconductor photocathode film; anode; A heating device for heating the semiconductor photocathode film and / or the substrate to a temperature between 50°C and 250°C; an output adjustment device for adjusting the heating temperature of the heating device; a measuring unit for measuring a change in intensity of an electron beam emitted from the semiconductor photocathode film due to degradation of the semiconductor photocathode film; a control unit configured to control the output adjustment device based on a measurement result of the measurement unit; as well as vacuum chamber; The heating device is arranged outside the vacuum chamber and heats the photocathode film and / or the substrate from outside the vacuum chamber.

5. The electron gun according to claim 1 or 4, wherein The control unit adjusts the intensity of the electron beam emitted from the semiconductor photocathode film based on the measurement result of the measurement unit.

6. An electron beam application device comprising the electron gun according to any one of claims 1 to 5, wherein: The electron ray application device is: Free electron laser accelerator; Electron microscopy; Electron beam holography devices; electron beam patterning device; Electron ray diffraction device; Electron ray inspection equipment; Electron beam metal lamination molding device; Electron beam lithography equipment; Electron beam processing equipment; Electron ray hardening device; Electron beam sterilization device; Electron ray sterilization device; plasma generating device; Atomic element production device; Rotating polarized electron beam generating device; a cathodoluminescent device; or Inverse photon emission spectroscopy device.

7. A method for emitting an electron beam, wherein: The electron beam is emitted by an electron gun, and the electron gun includes: a substrate having a semiconductor photocathode film formed on a first surface; A light source, for irradiating excitation light onto the semiconductor photocathode film; anode; A heating device for heating the semiconductor photocathode film and / or the substrate to a temperature between 50°C and 250°C; a measuring unit configured to measure a change in intensity of the electron beam emitted from the semiconductor photocathode film due to degradation of the semiconductor photocathode film; The injection method includes: an electron beam emitting step of irradiating the semiconductor photocathode film with the excitation light from the light source while heating the semiconductor photocathode film and / or the substrate, and emitting the electron beam from the semiconductor photocathode film in response to the excitation light; A photocathode temperature adjustment step is performed to adjust the heating temperature of the semiconductor photocathode film and / or the substrate based on the measurement result of the measurement unit.

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