200kV direct-current high-voltage photoelectron gun

Abstract

The invention discloses a 200kV direct-current high-voltage photoelectron gun, which is characterized in that 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 photoelectron gun is reduced; a displacement adjusting structure is mounted on the anode electrode, so that the distance between the anode electrode and the cathode electrode can be adjusted, and the working voltage of the electron gun can be adjusted within 50-200kV; a photocathode transfer device is arranged in the cathode electrode and is used for replacing different types of or damaged photocathodes; meanwhile, a transmission type photocathode working mode and a reflection type photocathode working mode are arranged, and in the reflection type working mode, incidence of the detection laser at two angles of 15 degrees and 45 degrees can be achieved, 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 invention relates to a direct current high voltage photoelectron gun, in particular to a 200 kV direct current type high voltage photoelectron gun. Background Art

[0002] A DC high-voltage photoelectron gun is an electron source generator based on the photoelectric effect of a photocathode and the principle of classical DC acceleration. It is used to provide electron sources for various accelerator devices such as ultrafast electron diffraction devices, ultrafast electron microscopes, and free electron lasers. The electron beam generated by field emission inside the electron gun hits and breaks through the insulator, which may cause the dielectric buffer gas to leak into the vacuum chamber, making it difficult to increase its operating voltage. The current typical devices are as follows:

[0003] A low-temperature cooled 200kV DC light-emitting electron gun with an ultra-low emissivity photocathode proposed by Arizona State University has a Pierce gun-like structure for the anode and cathode. The spacing between the anode and cathode is 1.17cm, the acceleration field strength of the electron beam is greater than 10MV / m, and the longitudinal electric field strength on the surface of the photocathode is 11.6MV / m. Due to the large curvature of the conical anode's structural design, its maximum surface electric field is as high as 40MV / m, which is much greater than the limit of field emission in a vacuum. Although the local field enhancement effect at this location is not the main factor limiting the electron gun, it also limits its popularization and application. Secondly, the small spacing between the anode and cathode causes the longitudinal electric field on the surface of the photocathode to be greater than the vacuum breakdown limit, making the photocathode easily damaged.

[0004] In addition, Old Dominion University proposed a 300kV DC high-voltage photoelectron gun, in which the anode and cathode electrodes adopt the structural design of the Pierce gun, ensuring that the electron beam line emitted by the electron gun has a relatively low emissivity; the spacing between the anode and cathode is 5cm, which can achieve a longitudinal electric field of 7.8MV / m on the surface of the photocathode, but the larger acceleration distance makes the acceleration field strength on the axis less than 10MV / m, and the time broadening effect of the electron beam during transmission in the electron gun is more obvious; at the same time, local field enhancement occurs at the junction of the planar area and the curved area of ​​the cathode electrode, which seriously limits the increase in the operating voltage of the electron gun.

[0005] There is also a low-temperature cooled high-voltage direct current photoelectron source proposed by Cornell University. The entire cathode electrode adopts a two-stage electrode structure to facilitate the installation of the internal photocathode transfer module. The overall shape is spherical, with a plane area with a diameter of 1.4 cm in the center of the front electrode, and an opening with a diameter of 2 cm in the center of the rear electrode to facilitate the transfer of the photocathode; the anode electrode adopts a grounded mountain grid with a density of 22 lines / cm; the spacing between the positive and negative electrodes is 2 cm, and the maximum operating voltage is 230 kV. However, in the cathode electrode structure design, there is an obvious inflection point at the junction of the plane area of ​​the front electrode and the spherical surface, making it a point of local field enhancement, with the risk of vacuum breakdown. Summary of the invention

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

[0007] In order to achieve the above object, the present invention adopts the following technical solution:

[0008] A 200kV DC high-voltage photoelectron gun includes a vacuum cavity, and is special 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 located in the vacuum cavity is electrically connected to a cathode electrode, the cathode electrode is connected to a photocathode transfer device, one end of the vacuum flange b located in the vacuum cavity is connected to an anode electrode through a displacement adjustment structure, and the anode electrode is arranged opposite to the cathode electrode;

[0009] A vacuum flange c is connected to the vacuum chamber relative to the photocathode transfer device, a transmission optical window is connected to the vacuum flange c, a middle anode hole is provided in the middle of the anode electrode, and the central axes of the transmission optical window, the photocathode transfer device, the cathode electrode, the middle anode hole, and the vacuum flange b are located on the same straight line;

[0010] The vacuum chamber is obliquely connected with multiple pairs of vacuum flanges d that are symmetrical about the central axis of the vacuum flange b, and an inclined anode hole is provided on the anode electrode corresponding to the central axis of each vacuum flange d. Each pair of vacuum flanges d, the corresponding inclined anode hole, and the cathode electrode form a reflection route for passing the light beam and generating the electron beam.

[0011] Furthermore, there are two pairs of vacuum flanges d, and the inclination angle of each pair is set as follows:

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

[0013] Furthermore, the cathode electrode and the anode electrode both adopt a multi-segment structure electrode design, and both include Bruce curved surface electrodes;

[0014] The Bruce curved surface electrode of the cathode electrode is arranged opposite to the Bruce curved surface electrode of the anode electrode, the Bruce curved surface electrode of the cathode electrode is connected to a conductor ring a extending in the direction of the vacuum flange c, the conductor ring a is connected to 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 chamfered structure, the conductor rear end cylindrical structure is connected to a high voltage cable, and a cathode transfer device is connected inside the conductor rear end cylindrical structure;

[0015] The Bruce curved surface electrode of the anode electrode is connected to a conductor ring b extending in the direction of the vacuum flange b, and the conductor ring b is connected to the vacuum cavity through a displacement adjustment structure.

[0016] Furthermore, the photocathode transfer device includes a mounting assembly with a circular hole in the middle, an adapter, a plurality of clips, a focusing lens, and a photocathode window;

[0017] The mounting assembly is connected to the rear end cylindrical structure by screws, and the circular hole of the mounting assembly is connected to the adapter by a retaining spring, and the adapter is fixedly connected to the focusing lens and the photocathode window by retaining springs respectively, and the surface of the photocathode window is coated with a photocathode film, and the photocathode window and the cathode electrode are arranged opposite to each other, and the central axes of the focusing lens, the photocathode window and the transmission optical window, the cathode electrode, the middle anode hole, and the vacuum flange b are located on the same straight line.

[0018] Furthermore, the photocathode window is a boss structure, and the material used is magnesium fluoride or sapphire substrate or single crystal copper;

[0019] The material used for the photocathode film is gold, silver or single crystal copper.

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

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

[0022] Furthermore, the displacement adjustment structure is used to adjust 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] Furthermore, the apertures of the middle anode aperture and the inclined anode aperture are both 1 mm.

[0024] Furthermore, the vacuum chamber is connected to a vacuum flange f and a vacuum flange g, the vacuum flange f is used to install a molecular pump or a compound ion pump, and the vacuum flange g is used to install a vacuum gauge; a vacuum flange h is connected to the vacuum chamber near the photocathode transfer device, and the vacuum flange h is connected to a cathode electrode observation window; a plurality of vacuum flanges e are connected to the vacuum chamber near the electrode surface relative to the cathode electrode, and the vacuum flange e is connected to a photocathode observation window.

[0025] Beneficial effects of the present invention:

[0026] 1. A 200kV DC high-voltage photoelectron gun of the present invention has a displacement adjustment structure installed on the anode electrode, which can adjust the distance between the anode electrode and the cathode electrode, thereby achieving adjustable working voltage of the electron gun within a certain range, which can expand the application field of the electron gun.

[0027] 2. The present invention provides a 200kV DC high-voltage photoelectron gun, in which a photocathode transfer device is connected to the cathode electrode, and a suitable photocathode window and a photocathode film can be replaced according to the wavelength of the detection light. At the same time, two working modes of a transmission light path and a reflection light path are set. In the working mode of the reflection light path, the detection laser can be incident at two angles of 15° and 45°, and has higher scalability.

[0028] 3. In a 200kV DC high-voltage photoelectron gun of the present invention, the cathode electrode adopts a multi-segment structure electrode design method, which can achieve an average acceleration field strength of 10MV / m, and the local maximum field strength on the electrode surface is less than 10.5MV / m, reducing the risk of vacuum breakdown in the vacuum chamber. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a front view of an embodiment of a 200kV DC type high voltage photoelectron gun of the present invention;

[0030] Figure 2 It is a rear view of an embodiment of a 200kV DC type high voltage photoelectron gun of the present invention;

[0031] Figure 3 A cross-sectional view of a transmission light path in an embodiment of a 200 kV DC high voltage photoelectron gun of the present invention;

[0032] Figure 4 A cross-sectional view of a reflected light path in an embodiment of a 200kV DC type high voltage photoelectron gun of the present invention (partially omitted);

[0033] Figure 5 It is a structural schematic diagram of a photocathode transfer device in an embodiment of a 200kV DC type high voltage photoelectron gun of the present invention;

[0034] Figure 6It is a structural cross-sectional view of a shielding electrode, a cathode electrode and an anode electrode in an embodiment of a 200kV DC type high voltage photoelectron gun of the present invention;

[0035] Figure 7 Schematic diagram of the electric field intensity distribution on the front electrode surface of the cathode electrode at working voltages of 100 kV and 200 kV in an embodiment of a 200 kV DC high-voltage photoelectron gun of the present invention;

[0036] Figure 8 It is a schematic diagram of the distribution of the axis acceleration field strength under the working voltages of 100kV and 200kV in an embodiment of a 200kV DC high-voltage photoelectron gun of the present invention;

[0037] Fig. 9 The figure is a schematic diagram of the distribution of equal field intensity lines of a 200kV DC high voltage photoelectron gun embodiment of the present invention.

[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 solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0040] The present embodiment is a 200 kV DC high voltage photoelectron gun, comprising a vacuum chamber 11, such as Figure 1 and Figure 2 As shown, the vacuum chamber 11 is connected to 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, a high-voltage cable 3 extending into the vacuum chamber 11 is arranged in the vacuum flange a1, and one end of the high-voltage cable 3 located in the vacuum chamber 11 is electrically connected to the cathode electrode 15, and the cathode electrode 15 is connected to the photocathode transfer device; the high-voltage cable 3 is used to supply power to the cathode electrode 15, so as to form an electric field between the cathode electrode 15 and the anode electrode 16.

[0042] One end of the vacuum flange b2 located in the vacuum chamber 11 is connected to the anode electrode 16 through a displacement adjustment structure. A central anode hole is opened in the middle of the anode electrode 16. An inclined anode hole is opened on the central axis of each vacuum flange d5 on the anode electrode 16. The cathode electrode 15 is arranged on the side of the anode electrode 16 away from the photocathode transfer device. The vacuum flange b2 serves as an outlet for the electron beam obtained by transmission. The displacement adjustment structure can adopt a guide rail-slider combination structure or a telescopic rod structure to achieve the adjustment of the position of the anode electrode 16.

[0043] In this embodiment, the diameters of the middle anode holes and the inclined anode holes are both 1 mm.

[0044] The vacuum flange c4 is connected to the vacuum chamber 11 at a position relative to the photocathode transfer device, and the vacuum flange c4 is connected to the transmission optical window 10 for inputting laser light. Figure 3 As shown, after being transmitted by the photocathode transfer device, it is incident on the cathode electrode 15, and excites the other side of the cathode electrode 15 to generate a transmitted electron beam, which is discharged through the middle anode hole and the vacuum flange b2.

[0045] The four vacuum flanges d5 are connected in pairs to the vacuum chamber 11 at an angle and are located on both sides of the vacuum flange b2, and are symmetrically arranged about the central axis of the vacuum flange b2; an inclined anode hole is provided on the anode electrode 16 at the central axis of each vacuum flange d5, and each pair of vacuum flanges d5, corresponding inclined anode holes and cathode electrode 15 form a reflection route for generating an electron beam from a light beam.

[0046] like Figure 4 As shown, the laser is incident into the vacuum chamber 11 through one of the vacuum flanges d5, passes through the corresponding inclined anode aperture and is incident on the cathode electrode 15, exciting the same surface of the cathode electrode 15 to produce a reflected electron beam, and the reflected electron beam passes through another paired inclined anode aperture and another paired vacuum flange d5.

[0047] In this embodiment, there are two pairs of vacuum flanges d5, and the inclination angle of each pair is set as follows:

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

[0049] The vacuum flange e6 is connected to the electrode surface of the vacuum chamber 11 close to the cathode electrode 15. The vacuum flange e6 is connected to a photocathode observation window, through which changes of the photocathode transfer device are observed.

[0050] The vacuum flange f7 is connected to the vacuum chamber 11 and is used to install a molecular pump or a compound ion pump to make the vacuum degree of the vacuum chamber 11 reach 10 -8 Pa.

[0051] The vacuum flange g8 is connected to the vacuum chamber 11 and is used for installing a vacuum gauge to measure the vacuum degree in the vacuum chamber 11 .

[0052] The vacuum flange h9 is connected to the vacuum chamber 11 near the photocathode transfer device and is used to connect to the cathode electrode observation window, through which the changes of the cathode electrode 15 are observed.

[0053] In this embodiment, the cathode electrode 15 and the anode electrode 16 are both made of stainless steel with a thickness of 2 mm, and both adopt a multi-segment electrode design, and both include Bruce curved electrodes; an acceleration field strength of 10 MV / m can be achieved, and the local maximum field strength on the electrode surface is less than 10.5 MV / m, reducing the risk of vacuum breakdown in the vacuum chamber.

[0054] 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 to the conductor ring a extending toward the vacuum flange c4. The conductor ring a is connected to the conductor rear end cylindrical structure through the conductor spherical ring. The end of the conductor rear end cylindrical structure away from the conductor ring a is a chamfered structure, which can make the local electric field strength on its surface less than 10MV / m. The conductor rear end cylindrical structure is connected to a high-voltage cable 3; power is supplied to the conductor rear end cylindrical structure, the conductor spherical ring, the conductor ring a, and the Bruce curved surface electrode through the high-voltage cable 3.

[0055] The Bruce curved surface electrode of the anode electrode 16 is connected to the conductor ring b extending toward the vacuum flange b2 , and the conductor ring b is connected to the vacuum flange b2 via a displacement adjustment structure. The middle anode aperture and the inclined anode aperture are both provided on the Bruce curved surface electrode of the anode electrode 16 .

[0056] In this embodiment, Figure 5 As shown, the photocathode transfer device includes a mounting assembly 19 with a circular hole in the middle, an adapter 20, a plurality of clips, a focusing lens 17, and a photocathode window 18;

[0057] The mounting assembly 19 is connected to the inside of the rear cylindrical structure by screws, and the circular hole of the mounting assembly 19 is connected to the adapter 20 by a spring clip. The adapter 20 is fixedly connected to the focusing lens 17 and the photocathode window 18 by spring clips, respectively, and plays a role of fixing and supporting the focusing lens 17 and the photocathode window 18, respectively, and does not affect the transmission light path. The surface of the photocathode window 18 is plated with a photocathode film, and the photocathode window 18 is arranged opposite to 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 middle anode small hole, and the vacuum flange b2 are located on the same straight line.

[0058] After the laser is emitted, it passes through the focusing lens 17, the photocathode window 18 and the photocathode film in the photocathode transfer device and is incident on the cathode electrode 15, which can stimulate the other side of the cathode electrode 15 to generate an electron beam. In this embodiment, replacing the photocathode film on the photocathode transfer device can realize the function of photocathode transfer.

[0059] The photocathode window 18 is a boss structure, and the material used is magnesium fluoride or sapphire substrate or single crystal copper;

[0060] The material used for the photocathode film is 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 rear end cylindrical structure of the conductor through a conductor bolt. The shielding electrode 14 is an ear-shaped structure, which is used to shield the internal high-voltage cable, the shielding electrode and the insulator connection. The ear-shaped structure is designed 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, and the rear end cylindrical structure of the conductor and the bottom of the inverted insulator 13 are connected respectively through a kovar ring 12. The inverted insulator 13 is made of insulating ceramic material and is coated with an insulating coating on the outer surface. It can withstand a maximum high voltage of 225kV. The interior is a hollow structure, serving as a socket for a high-voltage cable.

[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 achieve an adjustable working voltage of the electron gun within the range of 50kV-200kV, expanding the application prospects of the electron gun.

[0064] In this embodiment, a 200 kV DC high voltage photoelectron gun has two working modes, a reflection mode and a transmission mode.

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

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

[0067] In this embodiment, a 200 kV DC high voltage photoelectron gun has an electric field intensity distribution on the front cathode electrode surface of the cathode electrode at a working voltage of 100 kV and 200 kV as shown in FIG. Figure 7 As shown, according to Figure 7 It can be seen that under different working voltages (different anode displacement distances), the local maximum field intensity on the electrode surface is less than 10.3 MV / m, which reduces the probability of high-voltage field emission on the electrode surface.

[0068] The distribution of the axial acceleration field strength of the electron gun of this embodiment at the working voltage of 100 kV and 200 kV is as follows: Figure 8 As shown, according to Figure 8 It can be seen that under different operating voltages (different anode displacement distances), the longitudinal acceleration field strength on the photocathode surface is in the range of 9.95MV / m-10.06MV / m, which greatly limits the spatiotemporal broadening effect of electrons when they are emitted from the photocathode.

[0069] The distribution of equal field intensity lines in the 200 kV ultra-compact DC high-voltage photoelectron gun of the electron gun of this embodiment is as follows: Fig. 9 As shown, according to Fig. 9 It can be seen that the local field intensity maxima are mainly at the rear end and front end of the cathode electrode and the surface of the shielding electrode, but are all less than 10.5 MV / m.

[0070] Through the above analysis, it can be known that the 200kV DC high-voltage photoelectron gun of the present invention has the functions of adjustable voltage or transferable photocathode and broadens the application field.

[0071] The above description is only a specific embodiment of the present invention, and a comparison of the effects of the specific embodiments and the related comparative examples, but the protection scope of the present invention is not limited thereto. Any changes or substitutions within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

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

2. A 200 kV DC high voltage photoelectron gun according to claim 1, characterized in that: The vacuum flanges d (5) are provided in two pairs, and the inclination angle of each pair is set as follows: The intersection point of the central axis of the vacuum flange b (2) and the cathode electrode (15) is taken as O, and the central axis of each vacuum flange d (5) passes through the intersection point O, wherein the angle between the central axis of a pair of vacuum flanges d (5) and the central axis of the vacuum flange b (2) is 15°, and the angle between the central axis of another pair of vacuum flanges d (5) and the central axis of the vacuum flange b (2) is 45°.

3. A 200 kV DC high voltage photoelectron gun according to claim 1, characterized in that: The cathode electrode (15) and the anode electrode (16) both adopt a multi-segment structure electrode design 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 to a conductor ring a extending in the direction of the vacuum flange c (4); the conductor ring a is connected to a conductor rear end cylindrical structure via a conductor spherical ring; the end of the conductor rear end cylindrical structure away from the conductor ring a is a chamfered structure; the conductor rear end cylindrical structure is connected to a high voltage cable (3); and a cathode transfer device is connected inside the conductor rear end cylindrical structure; The Bruce curved surface electrode of the anode electrode (16) is connected to a conductor ring b extending in the direction of the vacuum flange b (2), and the conductor ring b is connected to the vacuum cavity (11) via a displacement adjustment structure.

4. A 200 kV DC high voltage photoelectron gun according to claim 3, characterized in that: The photocathode transfer device comprises a mounting assembly (19) with a circular hole in the middle, an adapter (20), a plurality of retaining springs, a focusing lens (17), and a photocathode window (18); The mounting assembly (19) is connected to the rear end cylindrical structure by means of screws, and the circular hole of the mounting assembly (19) is connected to the adapter (20) by means of a retaining spring, and the adapter (20) is fixedly connected to the focusing lens (17) and the photocathode window (18) by means of retaining springs, respectively. The surface of the photocathode window (18) is plated with a photocathode film, and the photocathode window (18) is arranged opposite to the cathode electrode (15), and the central axes of the focusing lens (17), the photocathode window (18), the transmission optical window (10), the cathode electrode (15), the middle anode aperture, and the vacuum flange b (2) are located on the same straight line.

5. A 200 kV DC high voltage photoelectron gun according to claim 4, characterized in that: The photocathode window (18) is a boss structure, and the material used is magnesium fluoride or a sapphire substrate or single crystal copper; The material used for the photocathode film is gold, silver or single crystal copper.

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

7. A 200 kV DC high voltage photoelectron gun according to claim 6, characterized in that: The inverted insulator (13) and the vacuum flange a (1), as well as the rear end cylindrical structure of the conductor and the bottom of the inverted insulator (13) are connected respectively via Kovar rings (12).

8. The 200 kV DC high voltage photoelectron gun according to claim 1, characterized in that: The displacement adjustment structure is used to adjust 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 5 mm-20 mm.

9. The 200 kV DC high voltage photoelectron gun according to claim 1, characterized in that: The apertures of the middle anode aperture and the inclined anode aperture are both 1 mm.

10. The 200 kV DC high voltage photoelectron gun according to claim 1, characterized in that: The vacuum chamber (11) is connected to a vacuum flange f (7) and a vacuum flange g (8), wherein the vacuum flange f (7) is used to install a molecular pump or a compound ion pump, and the vacuum flange g (8) is used to install a vacuum gauge; the vacuum chamber (11) is connected to a vacuum flange h (9) near a photocathode transfer device, and the vacuum flange h (9) is connected to a cathode electrode observation window; the vacuum chamber (11) is connected to a plurality of vacuum flanges e (6) near an electrode surface relative to a cathode electrode (15), and the vacuum flanges e (6) are connected to a photocathode observation window.

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