Electron gun and electron beam apparatus field of invention

Abstract

For three types of the electron gun the brightness larger than Langmuir limit or the very high Emittance is obtained through a simulation. The first electron gun consists of a concave cathode and a convex anode, and for the gun with the cathode radius of Rc (mm) the emission current Ie (A) which give the brightness larger than Langmuir limit is in the range as,

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic electron gun model in this invention.

FIG. 2 is a comparison of simulated results for this invention and for the conventional electron gun.

FIG. 3 is an electron optics for the multiple beams with two optical axis offset.

FIG. 4 is a detailed figure of only the primary optics of FIG. 3, wherein the optical axis offset and two deflections are neglected.

FIG. 5 is a detailed figure of only the secondary optics of FIG. 3, wherein the optical axis offset and three deflections are neglected.

FIG. 6 is simulated results for the electron gun with a spherical beam drawing electrode, where cathode radius is parameter.

FIG. 7 is simulated results for 30 μm cathode radius electron gun, where a wehnelt angle is varied.

FIG. 8 is simulated results of the case where the cathode is not flat but concave with a 5 mm radius of curvature.

FIG. 9 is simulated electron beam trajectories, where the radial scale is magnified. (A) is a typical case where the conventional electron gun with a convex cathode.

• • (B) is the beam trajectory for the electron gun with a convex beam drawing electrode and 100 μm radius concave and 5 mm radius of curvature cathode.

FIG. 10 is a real model for FIGS. 2, 6, 7 and 8, where the beam drawing electrode is convex spherical.

FIG. 11 is a second preferred embodiment for the electron gun with a spherical beam drawing electrode and a concave cathode.

FIG. 12 is simulated comparison between Pierce type and non Pierce type electron guns.

FIG. 13 is the brightness vs. Emittance curves and the brightness vs. cathode current density curves for the simulated results of FIG. 12, wherein the brightness is 10⁴ A/cm²sr and the Emittance is μmrad, and the cathode current density is A/cm².

FIG. 14 is a simulated result for the model in FIG. 11, wherein a cathode radius: Rc is varied.

FIG. 15 is the brightness vs. Emittance curves and the brightness vs. cathode current density curves for the simulated results of FIG. 14, wherein the brightness is 10⁵ A/cm²sr and the Emittance is μmrad, and the cathode current density is A/cm².

FIG. 16 is a simulated result for the model in FIG. 11, wherein the cathode temperature is 300 K and the laser photon energy minus photocathode work function is 0.2 eV, and wherein the cathode radius: Rc is varied.

FIG. 17 is the brightness vs. Emittance curves and the brightness vs. cathode current density curves for the simulated results of FIG. 16, wherein the brightness is 10⁵ A/cm²sr and the Emittance is μmrad, and the cathode current density is A/cm².

FIG. 18 is electron beam trajectories for the Pierce type electron gun and electrons are started ±45 degree from the normal to the surface.

FIG. 19 is the electron beam trajectories for the non Pierce type electron gun and the electrons are started ±45 degree from the normal to the surface.

FIG. 20 is the electron beam trajectories for the non Pierce type electron gun and the electrons are started normal to the surface, wherein the cathode temperature is 300 K and the laser photon energy minus photocathode work function is 0.2 eV

FIG. 21 is comparison between the electron gun with a convex beam drawing electrode and the conventional convex cathode electron gun, wherein the cathode temperature is 300 K and the laser photon energy minus photocathode work function is 0.2 eV, and wherein the cathode radius: Rc is varied.

FIG. 22 is the brightness vs. Emittance curves and the brightness vs. cathode current density curves for the simulated results of FIG. 21, wherein the brightness is 10⁵ A/cm²sr and the Emittance is μmmrad, and the cathode current density is A/cm².

FIG. 23 is simulated results for the model in FIG. 11, wherein the cathode temperature is 300 K and laser photon energy minus photocathode work function is 0.2 eV, and wherein the wehnelt angle is varied.

FIG. 24 is the brightness vs. Emittance curves and the brightness vs. cathode current density curves for the simulated results of FIG. 23, wherein the brightness is 10⁵ A/cm²sr and the Emittance is μmmrad, and the cathode current density is A/cm².

FIG. 25 is the simulated result for the model in FIG. 11, wherein the cathode temperature is 1800 K and the cathode work function is 2.35 eV, and wherein the cathode radius is varied.

FIG. 26 is the brightness vs. Emittance curves and the brightness vs. cathode current density curves for the simulated results of FIG. 25, wherein the brightness is 10⁵ A/cm²sr and the Emittance is μmmrad, and the cathode current density is A/cm².

FIG. 27 is the simulated results for the model in FIG. 11, wherein the distance between the cathode and the anode is 1 mm, and wherein the cathode radius is varied.

FIG. 28 is the brightness vs. Emittance curves and the brightness vs. cathode current density curves for the simulated results of FIG. 27.

FIG. 29 is the simulated result for the model in FIG. 11, wherein the distance between the cathode and the anode is 3 mm, and wherein the cathode radius is varied.

FIG. 30 is the brightness vs. Emittance curves and the brightness vs. cathode current density curves for the simulated results of FIG. 29, wherein the brightness is 10⁵ A/cm²sr and the Emittance is μmmrad, and the cathode current density is A/cm².

FIG. 31 is the emission current which give the maximum brightness or the maximum Emittance as a function of Rc.

FIG. 32 is the emission currents which give the maximum brightness or the maximum Emittance as a function of Rc, where Rc is smaller than 120 μm.

FIG. 33 is the simulated result for the model in FIG. 11, wherein the cathode radius is 15 μm, and the distance between the anode and the cathode: Dac is varied.

FIG. 34 is the brightness vs. Emittance curves and the brightness vs. cathode current density curves for the simulated results of FIG. 33, wherein the brightness is 10⁵ A/cm²sr and the Emittance is μmmrad, and the cathode current density is A/cm².

FIG. 35 is the simulated results for the model in FIG. 11, wherein the cathode radius is 960 μm, and the distance between the anode and the cathode: Dac is varied.

FIG. 36 is the brightness vs. Emittance curves and the brightness vs. cathode current density curves for the simulated results of FIG. 35, wherein the brightness is 10⁵ A/cm²sr and the Emittance is μmmrad, and the cathode current density is A/cm².

FIG. 37 is the simulated result for the model in FIG. 11, wherein the cathode radius is 120 μm, and the distance between the anode and the cathode: Dac is varied.

FIG. 38 is the brightness vs. Emittance curves and the brightness vs. cathode current density curves for the simulated results of FIG. 37, wherein the brightness is 10⁵ A/cm²sr and the Emittance is μmmrad, and the cathode current density is A/cm².

FIG. 39 is the emission currents which give the maximum brightness or the maximum Emittance as a function of 1/Dac.

FIG. 40 is the emission currents which give the maximum brightness or the maximum Emittance as a function of 1/Dac, wherein the emission current is smaller than 8 mA.

FIG. 41 is a schematic electron gun model in the second invention.

FIG. 42 is the simulated results of the model in FIG. 41, wherein the cathode radius is varied.

FIG. 43 is the brightness vs. Emittance curves and the brightness vs. cathode current density curves for the simulated results of FIG. 42.

FIG. 44 is the electron beam trajectories for the case when the brightness is smaller than Langmuir limit.

FIG. 45 is the electron beam trajectories for the case when the brightness is larger than Langmuir limit.

FIG. 46 is an electron gun model with an electrostatic lens.

FIG. 47 is the simulated result for the model in FIG. 46, wherein a lens exciting voltage is varied.

FIG. 48 is the brightness vs. Emittance curves and the brightness vs. cathode current density curves for the simulated results of FIG. 47, wherein the brightness is 10⁵ A/cm²sr and the Emittance is μmmrad, and the cathode current density is A/cm².

FIG. 49 is the electron beam trajectories for the case when the brightness is larger than Langmuir limit, and a positive voltage is applied in the electrostatic lens.

FIG. 50 is the electron beam trajectories for the case when the brightness is larger than Langmuir limit, and a negative voltage is applied in the electrostatic lens.

FIG. 51 is the simulated result for the model in FIG. 46, wherein a wehnelt angle is varied.

FIG. 52 is the brightness vs. Emittance curves and the brightness vs. cathode current density curves for the simulated results of FIG. 51.

FIG. 53 is the simulated result for the model in FIG. 46, wherein the cathode radius: Rc is varied, and wherein the brightness is 10⁵ A/cm²sr and the Emittance is μmmrad, and the cathode current density is A/cm².

FIG. 54 is the brightness vs. Emittance curve and the brightness vs. cathode current density curve for the simulated results of FIG. 53, wherein the brightness is 10⁵ A/cm²sr and the Emittance is μmmrad, and the cathode current density is A/cm².

FIG. 55 is the simulated result for the model in FIG. 46, wherein the distance from the cathode to the anode: Dac is varied.

FIG. 56 is the brightness vs. Emittance curves and the brightness vs. cathode current density curves for the simulated results of FIG. 55, wherein the brightness is 10⁵ A/cm²sr and the Emittance is μmmrad, and the cathode current density is A/cm².

FIG. 57 is the simulation result of the model in FIG. 1, wherein the cathode temperature is varied.

FIG. 58 is the brightness vs. Emittance curves and the brightness vs. cathode current density curves for the simulated results of FIG. 57, wherein the brightness is 10⁵ A/cm²sr and the Emittance is μmmrad, and the cathode current density is A/cm².

FIG. 59 is the simulated results of the model in FIG. 46, wherein a magnetic lens is added at the position of the electrostatic lens, and lens exciting AT is varied.

FIG. 60 is the brightness vs. Emittance curves and the brightness vs. cathode current density curves for the simulated results of FIG. 59.

FIG. 61 is the electron beam trajectories for the case when the brightness is larger than Langmuir limit, and the magnetic lens is operated.

FIG. 62 is an electron gun model with the photocathode in this invention.

FIG. 63 is electron optics with a high brightness electron gun in this invention.

FIG. 64 is a primary electron optics with the high brightness electron gun in this invention.

FIG. 65 is the simulated result of the model in FIG. 46, wherein the cathode radius of curvature is varied.

FIG. 66 is the brightness vs. Emittance curves and the brightness vs. cathode current density curves for the simulated results of FIG. 65, wherein the abscissa is brightness (10⁵ A/cm²sr) and the ordinate is the Emittance (μmmrad), or the cathode current density (A/cm²).

FIG. 67 is the simulated results of the gun with the photo cathode, wherein the cathode radius is varied.

FIG. 68 is the brightness vs. Emittance curves and the brightness vs. cathode current density curves for the simulated results of FIG. 67, wherein the abscissa is the brightness (10⁵ A/cm²sr) and the ordinate is an Emittance (μmmrad), or the cathode current density (A/cm²).

FIG. 69 is the simulated result of the gun with the photo cathode, wherein the cathode radius is varied and Dac is 2.5 mm.

FIG. 70 is the brightness vs. Emittance curves and the brightness vs. cathode current density curves for the simulated results of FIG. 69, wherein the abscissa is the brightness (10⁵ A/cm²sr) and the ordinate is the Emittance (μmmrad), or cathode current density (A/cm²).

FIG. 71 is the simulated results of the gun with the photo cathode, wherein the cathode radius is varied and Dac is 0.8 mm.

FIG. 72 is the brightness vs. Emittance curves and the brightness vs. cathode current density curves for the simulated results of FIG. 71, wherein the abscissa is the brightness (10⁵ A/cm²sr) and the ordinate is the Emittance (μmmrad), or the cathode current density (A/cm²).

FIG. 73 is the simulated result of the gun with the photo cathode, wherein the cathode radius is varied and Dac is 2.5 mm, wherein the brightness is 10⁵ A/cm²sr and the Emittance is μmmrad, and the cathode current density is A/cm², and wherein said cathode is cooled to a 77 degree Kelvin.

FIG. 74 is the brightness vs. Emittance curves and the brightness vs. cathode current density curves for the simulated results of FIG. 73, wherein the abscissa is the brightness (10⁵ A/cm²sr) and the ordinate is the Emittance (μmmrad), or the cathode current density (A/cm²).

FIG. 75 is the relationship between the cathode work function and the photo electron limiting wavelength.

FIG. 76 is the simulated result of the beam trajectories for the normal brightness.

FIG. 77 is the simulated result of the beam trajectories for the high brightness.

FIG. 78 is the simulated result of the beam trajectories for the very high brightness.

FIG. 79 is the simulated result of the gun, wherein the cathode temperature is 1800 K, the lens excitation is 12.5 kV, the Dac is 2.5 mm, and the cathode work function is 2.35 eV, the wehnelt angle: θw is 90.5 degree, and the cathode radius is varied.

FIG. 80 is the brightness vs. Emittance curves and the brightness vs. cathode current density curves for the simulated results of FIG. 79, wherein the abscissa is the brightness (10⁵ A/cm²sr) and the ordinate is the Emittance (μmmrad), or the cathode current density (A/cm²).

FIG. 81 is the simulated result of the electron gun, wherein the cathode radius Rc is varied, and the distance between the cathode and the anode: Dac is 0.8 mm.

FIG. 82 is the brightness vs. Emittance curves and the brightness vs. cathode current density curves for the simulated results of FIG. 81, wherein the abscissa is the brightness (10⁵ A/cm²sr) and the ordinate is an the Emittance (μmmrad), or the cathode current density (A/cm²).

FIG. 83 is the simulated result of the electron gun with a small aperture at a back surface of the anode, wherein the cathode radius Rc is varied and the distance between the cathode and the anode: Dac is constant and 2.5 mm.

FIG. 84 is the brightness vs. Emittance curves and the brightness vs. cathode current density curves for the simulated results of FIG. 83, wherein the abscissa is the brightness (10⁵ A/cm²sr) and the ordinate is the Emittance (μmmrad), or the cathode current density (A/cm²).

FIG. 85 is the emission currents which give the maximum brightness as a function of the cathode radius.

FIG. 86 is an objective lens model.

FIG. 87 is the simulated results of the gun in FIG. 11, wherein the distance between the cathode and the anode: Dac is constant: 5 mm and the cathode radius Rc is varied from 1.5 mm to 3 mm with a increment of 0.5 mm.

FIG. 88 is the brightness vs. Emittance curves and the brightness vs. cathode current density curves for the simulated results of FIG. 87, wherein the abscissa is the brightness (10⁵ A/cm²sr) and the ordinate is the Emittance (μmrad), or the cathode current density (A/cm²).

FIG. 89 is the simulation result of the gun in FIG. 11, wherein the distance between the cathode and the anode: Dac is constant: 3 mm and the cathode radius Rc is varied from 1 mm to 3 mm with a increment of 0.5 mm.

FIG. 90 is the brightness vs. Emittance curves and the brightness vs. cathode current density curves for the simulated results of FIG. 89, wherein the abscissa is the brightness (10⁵ A/cm²sr) and the ordinate is the Emittance (μmrad), or the cathode current density (A/cm²).

FIG. 91 is the simulated result of the gun in FIG. 11, wherein the distance between the cathode and the anode: Dac is constant: 4 mm and the cathode radius Rc is varied from 1.5 mm to 3 mm with a increment of 0.5 mm.

FIG. 92 is the brightness vs. Emittance curves and the brightness vs. cathode current density curves for the simulated results of FIG. 91, wherein the abscissa is the brightness (10⁵ A/cm²sr) and the ordinate is the Emittance (μmrad), or the cathode current density (A/cm²).

FIG. 93 is the emission currents which give the maximum brightness or the maximum Emittance as a function of the cathode radius, for the Dac of 5 mm.

FIG. 94 is the emission currents which give the maximum brightness as a function of the (cathode radius)³: Rc³ for the Dac of 3 and 4 mm.

FIG. 95 is the simulated results of the electron gun with a small aperture at the backside of the anode, wherein the brightness is 10⁵ A/cm²sr and the Emittance is μmmrad, and the cathode current density is A/cm².

FIG. 96 is the brightness vs. Emittance curves and the brightness vs. cathode current density curves for the simulated results of FIG. 95, wherein the abscissa is brightness (10⁵ A/cm²sr) and the ordinate is the Emittance (μmrad), or the cathode current density (A/cm²).

Claims

1. An electron gun consists of a cathode, a convex anode or a beam drawing electrode, and a truncated cone wehnelt, wherein; a distance between the cathode and the anode or the beam drawing electrode is Dac (mm) and an emission current Ie (mA) is controlled in the following range; 0.388/Dac−0.046≦Ie≦92.8/Dac+9.28, where Dac≧3 mm, or0.388/Dac−0.046≦Ie≦22/Dac+32.7, where Dac<3 mm.

2. The electron gun of claim 1, wherein said emission current is controlled in the following range; 0.388/Dac−0.046≦Ie≦17.8/Dac−1.51.

3. The electron gun of claim 1, wherein said emission current is controlled in the following range; 17.3/Dac−1.99≦Ie≦92.8/Dac+9.28, where Dac≧3 mm, or17.3/Dac−1.99≦Ie≦22/Dac+32.7, where Dac<3 mm.

4. The electron gun of claim 1, wherein said emission current is controlled in the following range; 0.388/Dac−0.046≦Ie≦117/Dac−8.35, where Dac≧4 mm, or0.388/Dac−0.046≦Ie≦12/Dac+17.8, where Dac<4 mm.

5. The electron gun of claim 1, wherein said emission current is controlled in the following range; 0.388/Dac−0.046≦Ie≦17.3/Dac−1.99.

6. The electron gun of claim 1, wherein the anode hole size is smaller than the beam size at the anode hole position, andthe alignment between the wehnelt and the anode is estimated by the transmission efficiency of the anode.

7. The electron gun of claim 1, wherein said wehnelt is designed as follows, suppose a first cone which has a top at a cross point an optical axis and the anode surface, and a bottom coincide with the cathode edge; and a second cone whose cone angle is 69.4 degrees larger than that of the first cone, and its cathode side coincide with the first cone. Outside of the second cone the wehnelt is deposited.

8. An electron gun consist of a cathode of which radius is Rc (μm), a flat anode or beam drawing electrode and a wehnelt, wherein an emission current Ie (mA) is controlled in the range as follows, 0.4+0.0064Rc≦Ie≦0.116Rc, where Rc≦120 μm, or0.4+0.0064Rc≦Ie≦10.5+0.0296Rc, where Rc>120 μm.

9. The electron gun of claim 8, wherein an electric field between the cathode and the anode is from 1.6 to 5.53 kV/mm.

10. The electron gun of claim 8, wherein said emission current Ie is controlled in the range as follows, 2.6+0.0254Rc≦Ie≦10.5+0.0296Rc, where Rc>120 μm, or2.6+0.0254Rc≦Ie≦0.116Rc, where Rc≦120 μm.

11. The electron gun of claim 8, wherein said emission current Ie is controlled in the range as follows, 0.4+0.0064Rc≦Ie≦2.6+0.0254Rc.

12. The electron gun of claim 8, wherein Said cathode radius is larger than 20 μm and smaller than 500 μm.

13. The electron gun of claim 8, wherein said cathode is flat or convex or concave spherical shape whose radius of curvature is larger than 1.5 mm, and wherein the cathode radius is from 20 to 500 μm, and a distance from the cathode to the anode is from 0.8 to 3 mm.

14. An electron gun consist of a concave cathode of which radius of curvature is Rcc (mm), a convex anode or beam drawing electrode of which radius of curvature is Rac (mm), wherein a distance from the cathode to the anode: Dac (mm) satisfy the following relation; that is, 1.1Dac≦Rcc≦0.933(Dac+Rac).

15. The electron gun of claim 14, wherein an emission current Ie (A) is controlled in the range as, 0.733Rc−0.5−Ie≦0.159Rc3+0.35, where Rc≦2.5 mm, or0.733Rc−0.5≦Ie≦0.255Rc3−1.17, where Rc>2.5 mm.

16. The electron gun of claim 14, wherein an emission current is controlled in the range as, 0.733Rc−0.5≦Ie≦0.132R3−0.059

17. The electron gun of claim 14, wherein trajectories started normally from the central part of the cathode don't cross to the optical axis from the cathode to a minimum beam diameter.

18. The electron gun of claim 14, wherein the anode or the beam drawing electrode traps more than 70 percent of the emission current.

19. The electron gun of claim 14, wherein Said cathode is a photo cathode whose work function is Φw, wherein said cathode is excited by the laser beam and wherein hλ/C−Φw≦0.2 eV.

20. The electron gun of claim 14, wherein said wehnelt is a truncated double cone shape or a truncated cone and a flat plate.