A 200kv direct current type high voltage photoelectron gun

Abstract

The application discloses a 200kV direct-current type high-voltage photoelectron gun, wherein a cathode electrode and an anode electrode adopt a multi-section curved surface structure design, and the front surface structures are symmetrically distributed, so that the risk of vacuum breakdown caused by local field enhancement of the direct-current high-voltage electron gun is reduced; a displacement adjusting structure is installed on the anode electrode, so that the distance between the anode electrode and the cathode electrode can be adjusted, and then the working voltage of the electron gun can be adjusted within 50-200kV; a photocathode transfer device is installed in the cathode electrode, and is used for replacing different types of photocathodes or damaged photocathodes; meanwhile, transmission and reflection type two photocathode working modes are arranged, and in the reflection type working mode, a detection laser can realize 15° and 45° two angle incidences, so that the direct-current type high-voltage electron gun has higher expansibility, and can be expanded to more application fields.

Description

TECHNICAL FIELD

[0001] The present application relates to a direct current high voltage photoelectron gun, in particular to a 200kV direct current high voltage photoelectron gun. BACKGROUND

[0002] The direct current high voltage photoelectron gun is an electron source generating device based on the photoelectric effect of the photocathode and the classical direct current acceleration principle, which is used to provide an electron source for various accelerator devices such as ultrafast electron diffraction devices, ultrafast electron microscopes, free electron lasers, etc. The electron beam generated by the internal field emission of the electron gun impinges and breaks down the insulator, which may cause the dielectric buffer gas to leak into the vacuum chamber, making it difficult to increase the working voltage. The current typical devices are as follows:

[0003] A low-temperature-cooled 200kV direct current photoemission electron gun of an ultra-low emission degree photocathode is proposed by Arizona State University, the cathode and anode electrodes adopt a Pierce gun structure, the spacing between the cathode and anode is 1.17cm, the acceleration field strength of the electron beam is greater than 10MV / m, the longitudinal electric field strength on the surface of the photocathode is 11.6MV / m, and the maximum surface electric field of the conical anode is as high as 40MV / m due to the large curvature of the structural design, which is much larger than the limit of field emission in vacuum. Although the local field enhancement effect at this place is not the main factor limiting the electron gun, it also limits its popularization and application. Secondly, the small spacing between the cathode and anode leads to a longitudinal electric field on the surface of the photocathode greater than the limit of vacuum breakdown, resulting in easy damage to the photocathode.

[0004] In addition, a 300kV direct current high voltage photoelectron gun is proposed by the University of O'Dowd, the cathode and anode electrodes adopt a Pierce gun structure design to ensure that the electron beam emitted by the electron gun has a relatively low emission degree; the spacing between the cathode and anode is 5cm, and the longitudinal electric field on the surface of the photocathode can reach 7.8MV / m, but the large acceleration distance makes the acceleration field strength on the axis less than 10MV / m, and the time spread effect of the electron beam during transmission in the electron gun is more obvious; at the same time, the junction between the planar region and the curved surface region of the cathode electrode appears local field enhancement, which seriously limits the increase of the working voltage of the electron gun.

[0005] In addition, a low-temperature-cooled high-voltage direct current photoelectron source is proposed by Cornell University, the entire cathode electrode adopts a two-section electrode structure to facilitate the installation of the internal photocathode transfer module, and the whole presents a spherical shape, the center of the front electrode is a planar region with a diameter of 1.4cm, and the center of the rear electrode exists an opening with a diameter of 2cm to facilitate the transfer of the photocathode; the anode electrode adopts a grounded mesh with a density of 22 lines / cm; the spacing between the cathode and anode is 2cm, and the highest working voltage is 230kV. However, the junction between the planar region of the front electrode and the spherical surface in the cathode electrode structure design has an obvious inflection point, which makes it a point of local field enhancement, and there is a risk of vacuum breakdown. SUMMARY

[0006] The purpose of the present application is to reduce the risk of vacuum breakdown caused by the local field enhancement effect due to the unreasonable design of the positive and negative electrode structure of the direct current high voltage electron gun, and to solve the problem that the single function cannot meet the application requirements in different fields, and a 200kV direct current type high voltage photoelectron gun is provided.

[0007] In order to achieve the above purpose, the present application adopts the following technical scheme:

[0008] A 200kV direct current type high voltage photoelectron gun, comprising a vacuum cavity, characterized in that: the vacuum cavity is connected with a vacuum flange a and a vacuum flange b, a high voltage cable extending into the vacuum cavity is arranged in the vacuum flange a, one end of the high voltage cable in the vacuum cavity is electrically connected with a cathode electrode, the cathode electrode is connected with a photocathode transfer device, one end of the vacuum flange b in the vacuum cavity is connected with an anode electrode through a displacement adjusting structure, and the anode electrode is arranged opposite to the cathode electrode.

[0009] A vacuum flange c is connected with the photocathode transfer device on the vacuum cavity, a transmission optical window is connected with the vacuum flange c, a middle anode small hole is arranged in the middle part of the anode electrode, the middle axes of the transmission optical window, the photocathode transfer device, the cathode electrode, the middle anode small hole and the vacuum flange b are located on the same straight line.

[0010] A plurality of pairs of vacuum flanges d are symmetrically connected with the central axis of the vacuum flange b on the vacuum cavity, and a plurality of pairs of inclined anode small holes are arranged on the central axis of each vacuum flange d on the anode electrode, each pair of vacuum flange d, corresponding inclined anode small hole and cathode electrode form a reflection route of the light beam and generated electron beam.

[0011] Further, the vacuum flanges d are two pairs, and the setting of the inclined angles of each pair is:

[0012] Taking the intersection point of the central axis of the vacuum flange b and the cathode electrode as O, the central axis of each vacuum flange d passes through the intersection point O, the included angle between the central axis of one pair of vacuum flanges d and the central axis of the vacuum flange b is 15°, and the included angle between the central axis of the other pair of vacuum flanges d and the central axis of the vacuum flange b is 45°.

[0013] Further, the cathode electrode and the anode electrode are both designed as a multi-section electrode, and both include a Bruce curved surface electrode.

[0014] The Bruce curve electrode of the cathode electrode is arranged opposite to the Bruce curve electrode of the anode electrode, the Bruce curve electrode of the cathode electrode is connected with a conductor circular ring a extending to a vacuum flange c direction, the conductor circular ring a is connected with a conductor rear end cylindrical structure through a conductor spherical ring, the conductor rear end cylindrical structure is a chamfer structure away from one end of the conductor circular ring a, the conductor rear end cylindrical structure is connected with a high-voltage cable, and the conductor rear end cylindrical structure is connected with a cathode transfer device inside.

[0015] The Bruce curve electrode of the anode electrode is connected with a conductor circular ring b extending to a vacuum flange b direction, and the conductor circular ring b is connected with a vacuum cavity through a displacement adjusting structure.

[0016] Further, the light cathode transfer device comprises a mounting assembly with a circular hole in the middle, an adapter, a plurality of clamping springs, a focusing lens and a light cathode window.

[0017] The mounting assembly is connected with the rear end cylindrical structure through a screw, the adapter is connected in the circular hole of the mounting assembly through the clamping spring, the focusing lens and the light cathode window are fixedly connected on the adapter through the clamping spring respectively, the surface of the light cathode window is plated with a light cathode film, the light cathode window is arranged opposite to the cathode electrode, and the center axes of the focusing lens, the light cathode window, the transmission optical window, the cathode electrode, the middle anode small hole and the vacuum flange b are located on the same straight line.

[0018] Further, the light cathode window is a boss structure, and the material adopted is magnesium fluoride or sapphire substrate or single crystal copper.

[0019] The material adopted by the light cathode film is gold, silver or single crystal copper.

[0020] Further, the outer wall of the high-voltage cable is covered with an inverted insulator, a shielding electrode is connected on the inverted insulator, the shielding electrode is connected with the side wall of the conductor rear end cylindrical structure through a conductor bolt, and the shielding electrode is an ear-shaped structure.

[0021] Further, the inverted insulator and the vacuum flange a and the bottom of the conductor rear end cylindrical structure are connected through Kovar rings respectively.

[0022] Further, the displacement adjusting structure is used for adjusting the distance between the cathode electrode and the anode electrode, and the distance between the cathode electrode and the anode electrode is 5mm-20mm.

[0023] Further, the aperture of the middle anode small hole and the inclined anode small hole is 1mm.

[0024] Further, the vacuum cavity is connected with vacuum flanges f and g, the vacuum flange f is used for installing a molecular pump or a composite ion pump, and the vacuum flange g is used for installing a vacuum gauge; the vacuum cavity is connected with a vacuum flange h near the light cathode transfer device, and the vacuum flange h is connected with a cathode electrode observation window; and the vacuum cavity is connected with a plurality of vacuum flanges e near the electrode surface of the opposite cathode electrode, and the vacuum flanges e are connected with light cathode observation windows.

[0025] Advantages of the present application:

[0026] 1. The 200kV direct-current high-voltage photoelectron gun can adjust the distance between the anode electrode and the cathode electrode by installing a displacement adjustment structure on the anode electrode, thereby realizing adjustable working voltage of the electron gun within a certain range and expanding the application field of the electron gun.

[0027] 2. The 200kV direct-current high-voltage photoelectron gun can replace a suitable light cathode window and a light cathode film according to the wavelength of the detected light by connecting a light cathode transfer device to the cathode electrode, and the transmission light path and the reflection light path are set as two working modes, and in the working mode of the reflection light path, the detected laser can realize the incidence of two angles of 15° and 45°, and has higher expansibility.

[0028] 3. In the 200kV direct-current high-voltage photoelectron gun, the cathode electrode adopts a multi-section electrode design, which can realize an average acceleration field strength of 10MV / m, and the local maximum field strength of the electrode surface is less than 10.5MV / m, thereby reducing the risk of vacuum breakdown of the vacuum cavity. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 It is a front view of an embodiment of the 200kV direct-current high-voltage photoelectron gun.

[0030] Figure 2 It is a rear view of an embodiment of the 200kV direct-current high-voltage photoelectron gun.

[0031] Figure 3 It is a sectional view of the 200kV direct-current high-voltage photoelectron gun through the transmission light path.

[0032] Figure 4 It is a sectional view of the 200kV direct-current high-voltage photoelectron gun through the reflection light path.

[0033] Figure 5 It is a structure schematic view of the light cathode transfer device in the 200kV direct-current high-voltage photoelectron gun.

[0034] Figure 6A structure sectional view of the shielding electrode, the cathode electrode and the anode electrode in an embodiment of the 200kV DC high-voltage photoelectron gun of the present application is shown in the figure;

[0035] Figure 7 A schematic diagram of the electric field intensity distribution on the front electrode surface of the cathode electrode under 100kV and 200kV working voltage in an embodiment of the 200kV DC high-voltage photoelectron gun of the present application is shown in the figure;

[0036] Figure 8 A schematic diagram of the axial acceleration field intensity distribution under 100kV and 200kV working voltage in an embodiment of the 200kV DC high-voltage photoelectron gun of the present application is shown in the figure;

[0037] Figure 9 A schematic diagram of the equal field intensity line distribution in an embodiment of the 200kV DC high-voltage photoelectron gun of the present application is shown in the figure.

[0038] In the figure, 1-vacuum flange a; 2-vacuum flange b; 3-high-voltage cable; 4-vacuum flange c; 5-vacuum flange d; 6-vacuum flange e; 7-vacuum flange f; 8-vacuum flange g; 9-vacuum flange h; 10-transmission optical window; 11-vacuum cavity; 12-kovar ring; 13-inverted insulator; 14-shielding electrode; 15-cathode electrode; 16-anode electrode; 17-focusing lens; 18-photocathode window; 19-mounting assembly; 20-adapter. DETAILED DESCRIPTION

[0039] The technical solutions of the present application will be described clearly and completely below in combination with the drawings and embodiments. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments of the present application, all the other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the present application.

[0040] The 200kV DC high-voltage photoelectron gun of the present embodiment comprises a vacuum cavity 11, as shown in Figure 1 and Figure 2 shown, the vacuum cavity 11 is connected with a vacuum flange a1, a vacuum flange b2, a vacuum flange c4, a plurality of vacuum flanges d5, a vacuum flange e6, a vacuum flange f7, a vacuum flange g8 and a vacuum flange h9.

[0041] Among them, the high-voltage cable 3 extending into the vacuum cavity 11 is arranged in the vacuum flange a1, one end of the high-voltage cable 3 located in the vacuum cavity 11 is electrically connected with the cathode electrode 15, and the photocathode transfer device is connected to the cathode electrode 15; the high-voltage cable 3 is used for supplying power to the cathode electrode 15, and an electric field is formed between the cathode electrode 15 and the anode electrode 16.

[0042] Vacuum flange b2 is connected to anode electrode 16 through displacement adjustment structure at one end of vacuum cavity 11, middle part of anode electrode 16 is provided with middle part anode aperture, anode electrode 16 is provided with inclined anode aperture on the central axis of each vacuum flange d5, cathode electrode 15 is arranged on the side of anode electrode 16 away from the light cathode transfer device, vacuum flange b2 is used as the exit of the obtained transmission electron beam, displacement adjustment structure can adopt the combination structure of guide rail and sliding block or telescopic rod structure form, and the position of anode electrode 16 is adjusted.

[0043] In the embodiment, the aperture of the middle part anode aperture and the inclined anode aperture is 1mm.

[0044] Vacuum flange c4 is connected to the position of vacuum cavity 11 opposite to the light cathode transfer device, and vacuum flange c4 is connected to transmission optical window 10 for inputting laser, as shown in Figure 3 The laser is transmitted through the light cathode transfer device and then enters cathode electrode 15, and the other side of cathode electrode 15 generates transmission electron beam, which is discharged through the middle part anode aperture and vacuum flange b2.

[0045] Four vacuum flanges d5 are connected to the two sides of vacuum flange b2 on vacuum cavity 11 and are symmetrically arranged about the central axis of vacuum flange b2, and the anode electrode 16 is provided with inclined anode aperture on the central axis of each vacuum flange d5, and each pair of vacuum flange d5, corresponding inclined anode aperture and cathode electrode 15 form the reflection route of the generated electron beam.

[0046] As shown in Figure 4 The laser enters vacuum cavity 11 through one of the vacuum flanges d5, enters cathode electrode 15 through the corresponding inclined anode aperture, and excites cathode electrode 15 to generate reflection electron beam on the same side, and the reflection electron beam passes through the other inclined anode aperture of the pair and the other vacuum flange d5 of the pair.

[0047] In the embodiment, the vacuum flanges d5 are two pairs, and the setting of the inclined angle of each pair is:

[0048] The intersection of the central axis of vacuum flange b2 and cathode electrode 15 is taken as O, and the central axis of each vacuum flange d5 passes through intersection O, as shown in Figure 4 The angle between the central axis of one pair of vacuum flanges d5 and the central axis of vacuum flange b2 is 15°, and the angle between the central axis of the other pair of vacuum flanges d5 and the central axis of vacuum flange b2 is 45°.

[0049] Vacuum flange e6 is connected to vacuum cavity 11 near the electrode surface opposite to cathode electrode 15, and light cathode observation window is connected to vacuum flange e6, and the change of the light cathode transfer device is observed through the light cathode observation window.

[0050] A vacuum flange f7 is connected to the vacuum cavity 11 for mounting a molecular pump or a compound ion pump to make the vacuum degree of the vacuum cavity 11 reach 10 -8 Pa.

[0051] A vacuum flange g8 is connected to the vacuum cavity 11 for mounting a vacuum gauge to measure the vacuum degree in the vacuum cavity 11.

[0052] A vacuum flange h9 is connected to the vacuum cavity 11 near the photocathode transfer device for connecting a cathode electrode observation window to observe the change of the cathode electrode 15 through the cathode electrode observation window.

[0053] In the embodiment, the cathode electrode 15 and the anode electrode 16 are both made of stainless steel with a thickness of 2 mm and are both designed as multi-section electrodes and include Bruce curved electrodes; the acceleration field strength can reach 10 MV / m, and the local maximum field strength on the electrode surface is less than 10.5 MV / m, thereby reducing the risk of vacuum breakdown of the vacuum cavity.

[0054] The Bruce curved electrode of the cathode electrode 15 is oppositely arranged with the Bruce curved electrode of the anode electrode 16, the Bruce curved electrode of the cathode electrode 15 is connected with a conductor ring a extending to the direction of the vacuum flange c4, the conductor ring a is connected with a conductor rear-end cylindrical structure through a conductor spherical ring, the end of the conductor rear-end cylindrical structure away from the conductor ring a is a chamfer structure, which can make the local electric field strength on the surface thereof less than 10 MV / m, and the conductor rear-end cylindrical structure is connected with the high-voltage cable 3; the conductor rear-end cylindrical structure, the conductor spherical ring, the conductor ring a and the Bruce curved electrode are powered through the high-voltage cable 3.

[0055] The Bruce curved electrode of the anode electrode 16 is connected with a conductor ring b extending to the direction of the vacuum flange b2, the conductor ring b is connected with the vacuum flange b2 through a displacement adjusting structure, and the middle anode small hole and the inclined anode small hole are both arranged on the Bruce curved electrode of the anode electrode 16.

[0056] In the embodiment, as shown in Figure 5 The photocathode transfer device includes a mounting assembly 19 with a circular hole arranged in the middle, an adapter 20, a plurality of clamping springs, a focusing lens 17 and a photocathode window 18.

[0057] The mounting assembly 19 is connected to the interior of the rear cylindrical structure via screws. An adapter 20 is connected to the circular hole of the mounting assembly 19 via a snap ring. The adapter 20 is fixedly connected to the focusing lens 17 and the photocathode window 18 via snap rings, providing fixed support for the focusing lens 17 and the photocathode window 18 without affecting the transmission light path. The surface of the photocathode window 18 is coated with a photocathode film. The photocathode window 18 is positioned opposite the cathode electrode 15. The central axis of the focusing lens 17, the center of the photocathode window 18, the transmission optical window 10, the cathode electrode 15, the central anode aperture, and the vacuum flange b2 are all on the same straight line.

[0058] After laser emission, the light passes through the focusing lens 17, photocathode window 18, and photocathode film in the photocathode transfer device before incident on the cathode electrode 15, which can excite the other side of the cathode electrode 15 to generate an electron beam. In this embodiment, replacing the photocathode film in the photocathode transfer device can achieve the function of photocathode transferability.

[0059] The photocathode window 18 has a boss structure and is made of magnesium fluoride, sapphire substrate, or single crystal copper.

[0060] The photocathode thin film is made of gold, silver, or single-crystal copper.

[0061] like Figure 6 As shown, the outer wall of the high-voltage cable 3 is covered with an inverted insulator 13, and a shielding electrode 14 is connected to the inverted insulator 13. The shielding electrode 14 is connected to the cylindrical structure at the rear end of the conductor by conductor bolts. The shielding electrode 14 has an ear-shaped structure, which is used to shield the connection between the internal high-voltage cable, the shielding electrode, and the insulator from potential field-induced emission problems. The ear-shaped structure design is to reduce the field enhancement effect on the outer surface of the shielding electrode.

[0062] In this embodiment, the inverted insulator 13 and the vacuum flange a1 are connected by Kovar rings 12, and the conductor rear cylindrical structure and the bottom of the inverted insulator 13 are connected by Kovar rings 12. The inverted insulator 13 is made of insulating ceramic material and has an insulating coating on its outer surface. It can withstand a maximum voltage of 225kV. Its interior is a hollow structure and serves as a socket for high-voltage cables.

[0063] The displacement adjustment structure is used to adjust the distance between the cathode electrode 15 and the anode electrode 16. The distance between the cathode electrode 15 and the anode electrode 16 is 5mm-20mm, which can realize the adjustable working voltage of the electron gun in the range of 50kV-200kV, thus expanding the application prospects of the electron gun.

[0064] This embodiment describes a 200kV DC high-voltage photoelectron gun with two operating modes: reflection mode and transmission mode.

[0065] In the transmission mode, the laser is emitted along the central axis of the vacuum flange c4, and the transmission electron beam is generated by the photoelectric effect of the laser through the transmission optical window 10, the focusing lens 17 in the light cathode transfer device, the light cathode window 18 and the cathode electrode 15, and is accelerated by the high-voltage electric field between the cathode electrode 15 and the anode electrode 16, and is emitted from the middle anode aperture and the vacuum flange b2.

[0066] In the reflection mode, the emitted laser beam includes two angles, 15° and 45°, the 15° laser beam is sequentially emitted to the vacuum flange d5 with a corresponding inclined angle, the inclined anode aperture and the cathode electrode 15 to generate the reflection electron beam by the photoelectric effect, and the reflection electron beam is accelerated by the high-voltage electric field between the cathode electrode 15 and the anode electrode 16, and is emitted from the inclined anode aperture with another corresponding inclined angle and the vacuum flange d5, and the emission and emission process of the electron beam of the 45° laser are the same.

[0067] The embodiment is a 200kV direct current type high-voltage photoelectron gun, and the electric field intensity distribution of the front cathode electrode surface of the cathode electrode under 100kV and 200kV working voltages is as shown in Figure 7 According to Figure 7 It can be known that under different working voltages (different anode displacement distances), the local maximum field intensity of the electrode surface is less than 10.3MV / m, and the probability of high-voltage field emission of the electrode surface is reduced.

[0068] The embodiment is a 200kV direct current type high-voltage photoelectron gun, and the electric field intensity distribution of the front cathode electrode surface of the cathode electrode under 100kV and 200kV working voltages is as shown in Figure 8 According to Figure 8 It can be known that under different working voltages (different anode displacement distances), the longitudinal acceleration field intensity of the light cathode surface is in the range of 9.95MV / m-10.06MV / m, and the time and space expansion effect of the electron emitted from the light cathode is greatly limited.

[0069] The embodiment is a 200kV direct current type high-voltage photoelectron gun, and the electric field intensity distribution of the front cathode electrode surface of the cathode electrode under 100kV and 200kV working voltages is as shown in Figure 9 According to Figure 9 It can be known that the local field intensity maximum is mainly in the rear end and the front end of the cathode electrode and the surface of the shielding electrode, but is less than 10.5MV / m.

[0070] Through the above analysis, it can be known that the 200kV direct current type high-voltage photoelectron gun has the functions of adjustable voltage or transferable light cathode, and widens the demand application field.

[0071] The above merely illustrates the specific embodiments of the present application, and the effects of the specific embodiments and the related comparative examples are compared, but the protection scope of the present application is not limited thereto, any change or replacement within the technical scope disclosed by the present application should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A 200 kV DC type high-voltage photoelectron gun comprising a vacuum chamber (11), characterized in that: The outer wall of the vacuum cavity (11) penetrates vacuum flange a (1), vacuum flange b (2), the high-voltage cable (3) extending into the vacuum cavity (11) is arranged in the vacuum flange a (1), one end of the high-voltage cable (3) located in the vacuum cavity (11) is electrically connected with the cathode electrode (15), the cathode electrode (15) is connected with the photocathode transfer device, one end of the vacuum flange b (2) located in the vacuum cavity (11) is connected with the anode electrode (16) through the displacement adjusting structure, and the anode electrode (16) is arranged opposite to the cathode electrode (15); The vacuum flange c (4) is connected with the transmission optical window (10) on the vacuum flange c (4) opposite to the photocathode transfer device, the middle part of the anode electrode (16) is provided with a middle anode small hole, and the middle axes of the transmission optical window (10), the photocathode transfer device, the cathode electrode (15), the middle anode small hole and the vacuum flange b (2) are located on the same straight line; The vacuum cavity (11) is connected with a plurality of pairs of vacuum flange d (5) which are symmetrical about the central axis of the vacuum flange b (2) through an inclined connection, and the anode electrode (16) is provided with an inclined anode small hole on the central axis of each vacuum flange d (5), each pair of vacuum flange d (5), the corresponding inclined anode small hole and the cathode electrode (15) form a reflection path of the light beam and the generated electron beam.

2. The 200 kV DC high voltage photoelectron gun of claim 1, wherein, The vacuum flange d (5) is two pairs, and the setting angles of each pair are as follows: Taking the intersection point of the central axis of the vacuum flange b (2) and the cathode electrode (15) as O, the central axes of each of the vacuum flange d (5) pass through the intersection point O, the included angle between the central axes of one pair of the vacuum flange d (5) and the central axis of the vacuum flange b (2) is 15°, and the included angle between the central axes of the other pair of the vacuum flange d (5) and the central axis of the vacuum flange b (2) is 45°.

3. The 200 kV DC high voltage photoelectron gun of claim 1, wherein: The cathode electrode (15) and the anode electrode (16) are all designed in a multi-section electrode structure, and both include Bruce curved surface electrodes; The Bruce curved surface electrode of the cathode electrode (15) is arranged opposite to the Bruce curved surface electrode of the anode electrode (16), the Bruce curved surface electrode of the cathode electrode (15) is connected with a conductor ring a extending to the direction of the vacuum flange c (4), the conductor ring a is connected with a conductor rear-end cylindrical structure through a conductor spherical ring, one end of the conductor rear-end cylindrical structure away from the conductor ring a is a chamfer structure, the conductor rear-end cylindrical structure is connected with the high-voltage cable (3), and the conductor rear-end cylindrical structure is connected with the cathode transfer device; The Bruce curved surface electrode of the anode electrode (16) is connected with a conductor ring b extending to the direction of the vacuum flange b (2), and the conductor ring b is connected with the vacuum cavity (11) through the displacement adjusting structure.

4. The 200kV DC high voltage photoelectron gun of claim 3, wherein: The photocathode transfer device includes a mounting assembly (19) provided with a circular hole in the middle, an adapter (20), a plurality of clamping springs, a focusing lens (17) and a photocathode window (18). The mounting assembly (19) is connected with the rear end cylinder structure by screw, the adapter (20) is connected in the round hole of the mounting assembly (19) by the snap spring, the focusing lens (17) and the photocathode window (18) are respectively fixed on the adapter (20) by the snap spring, the surface of the photocathode window (18) is plated with a photocathode film, the photocathode window (18) is arranged opposite to the cathode electrode (15), the center axis of the focusing lens (17), the photocathode window (18), the transmission optical window (10), the cathode electrode (15), the middle anode small hole and the vacuum flange b (2) are located on the same straight line.

5. The 200kV DC high voltage photoelectron gun of claim 4, wherein: The photocathode window (18) is a boss structure, and the material is magnesium fluoride or sapphire substrate or single crystal copper; The material of the photocathode film is gold or silver or single crystal copper.

6. The 200kV DC high voltage photoelectron gun of claim 3, wherein: The outer wall of the high-voltage cable (3) is covered with an inverted insulator (13), the shielding electrode (14) is connected to the inverted insulator (13), the shielding electrode (14) is connected to the side wall of the conductor rear end cylinder structure through the conductor bolt, and the shielding electrode (14) is an ear-shaped structure.

7. The 200kV DC high voltage photoelectron gun of claim 6, wherein: The inverted insulator (13) and the vacuum flange a (1), the conductor rear end cylinder structure and the bottom of the inverted insulator (13) are connected by the Kovar ring (12) respectively.

8. The 200kV DC high voltage photoelectron gun of claim 1, wherein: The displacement adjusting structure is used for adjusting the distance between the cathode electrode (15) and the anode electrode (16), and the distance between the cathode electrode (15) and the anode electrode (16) is 5mm-20mm.

9. The 200kV DC high voltage photoelectron gun of claim 1, wherein: The aperture of the middle anode small hole and the inclined anode small hole is 1mm.

10. The 200kV DC high voltage photoelectron gun of claim 1, wherein: The vacuum flange f (7) and the vacuum flange g (8) are connected to the vacuum cavity (11), the vacuum flange f (7) is used for installing a molecular pump or a composite ion pump, and the vacuum flange g (8) is used for installing a vacuum gauge; the vacuum flange h (9) is connected to the vacuum cavity (11) near the photocathode transfer device, the vacuum flange h (9) is connected with the cathode electrode observation window; a plurality of vacuum flanges e (6) are connected to the vacuum cavity (11) near the electrode surface opposite to the cathode electrode (15), and the vacuum flanges e (6) are connected with the photocathode observation window.

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