Beam source

Abstract

This beam source generates a beam containing atoms or molecules in metastable excited states and comprises: an emission unit for emitting the atoms or the molecules; an irradiation unit for irradiating the atoms or the molecules with an electron beam; and a generation unit for generating a magnetic field in a space in which the atoms or the molecules are present and at least a part of the trajectory of the electron beam is generated. The irradiation unit comprises a cathode and an anode sandwiching said space. A first direction of the electrical flux line generated in said space by the irradiation unit or the opposite direction thereof coincides with a second direction of the magnetic flux line generated in said space by the generation unit. The emission unit comprises a wall which is provided between the cathode and the anode and has a first hole for emitting the atoms or the molecules toward the anode. A third direction in which the emission unit emits the atoms or the molecules coincides with the first direction or the opposite direction thereof. The anode comprises a portion projecting toward the cathode and having a second hole at the tip. The cathode, the first hole, and the second hole are aligned along a substantially straight line in the first direction. The beam is emitted from the second hole.

Description

beam source

[0001] The present invention relates to a beam source.

[0002] Atoms or molecules in a metastable excited state can be generated by discharge in a vacuum. Non-Patent Documents 1 and 2 are known methods for efficiently generating atoms or molecules in a metastable excited state. In Non-Patent Document 1, He is emitted from a nozzle into a vacuum, and an electron beam is irradiated onto the He from the same direction as the He is emitted. This generates metastable excited He. An electron beam is generated from a cathode in the nozzle, and the He is excited to a metastable excited state by electron impact with a skimmer, which is an anode. Unnecessary electronically excited neutral particles and charged particles are separated further downstream.

[0003] T. Horio et al., Journal of Scientific Instruments 123 (19), 194308 (2005)A. Kohlhase et al., Journal of Chemical Physics 57 (12), pp 2925-2928 (1986)

[0004] However, even when the methods of Non-Patent Documents 1 and 2 are used, the efficiency of generating atoms or molecules in a metastable excited state is not sufficient.

[0005] An object of the present invention is to provide a beam source capable of improving the efficiency of generating atoms or molecules in a metastable excited state.

[0006] A beam source according to an embodiment of the present invention is a beam source that generates a beam containing atoms or molecules in a metastable excited state, and includes: an emitter that emits the atoms or molecules; an irradiator that irradiates the atoms or molecules with an electron beam; and a generator that generates a magnetic field in a space where the atoms or molecules are present and where at least a part of a trajectory of the electron beam occurs. The irradiator includes a cathode and an anode that sandwich the space, and the irradiator generates electric field lines in a first direction or a direction opposite to the first direction in the space, and the generator generates electric field lines in the space. a third direction in which the atoms or molecules are emitted from the emitter and a wall having a first hole at a tip thereof; the cathode, the first hole, and the second hole are arranged in a substantially straight line in the first direction; the emitter is provided between the cathode and the anode and includes a wall having a first hole through which the atoms or molecules are emitted from the cathode side to the anode side; a third direction in which the atoms or molecules are emitted from the emitter and a wall having a first hole at a tip thereof; the cathode, the first hole, and the second hole are arranged in a substantially straight line in the first direction;

[0007] According to the present invention, it is possible to improve the efficiency of generating atoms or molecules in a metastable excited state.

[0008] FIG. 1 is a cross-sectional view of a beam source in the first embodiment. FIG. 2 is a cross-sectional view showing an apparatus having a beam source according to the first embodiment. FIG. 3 is a side view showing details of a beam head. FIG. 4 is a cross-sectional view of a beam head attached to an anode. FIG. 5 is a view showing simulation results for sample A. FIG. 6 is a view showing simulation results for sample B. FIG. 7 is a view showing simulation results for sample C. FIG. 8 is a view showing simulation results for sample D. FIG. 9 is a perspective view showing simulation results for sample C. FIG. 10 is an enlarged view of FIG. 9. FIG. 11 is a cross-sectional view of a beam source in the second embodiment. FIG. 12 is a cross-sectional view of a beam source in the third embodiment. FIG. 13 is a cross-sectional view of a beam source in the first embodiment.

[0009] Hereinafter, embodiments of the present invention will be described with reference to the drawings. The following embodiments are examples for embodying the technical ideas of the invention, and the present invention is not limited to the described configurations and numerical values. In the drawings, components having the same functions are given the same reference numerals, and redundant descriptions may be omitted. Partial substitution or combination between different embodiments and configuration examples is possible. The size, positional relationship, etc. of each component shown in each drawing may be exaggerated to facilitate understanding of the invention.

[0010] (First embodiment) A beam containing atoms or molecules in a metastable excited state can be generated by discharge in a vacuum. The generation efficiency of atoms or molecules in a metastable excited state is proportional to the frequency of collisions between electrons and atoms or molecules in the ground state. The frequency of collisions is determined by the relative speeds of the atoms or molecules and electrons and the flight time of the electrons. Therefore, applying a magnetic field to the electrons causes the electrons to move in a spiral motion. This increases the frequency of collisions between atoms or molecules and electrons, thereby improving the generation efficiency of atoms or molecules in a metastable excited state.

[0011] 1 is a cross-sectional view of a beam source according to a first embodiment. The direction of emission of atoms or molecules is defined as the X direction. As shown in FIG. 1, the beam source 100 includes a chamber 10, a cathode 12, an anode 14, and a magnet 16.

[0012] The chamber 10 has a first wall 10a and a second wall 10b. The first wall 10a surrounds the cathode 12 and the region 17 and is, for example, cylindrical. The second wall 10b has a first hole 11 penetrating the second wall 10b. The first hole 11 is located approximately at the center of the second wall 10b. The diameter of the first hole 11 is, for example, 0.1 mm to 5 mm, and is, for example, 1 mm. The shape of the first hole 11 is, for example, circular. The chamber 10 is made of an insulating and non-magnetic material.

[0013] The cathode 12 is located approximately at the center of the second wall 10b. The cathode 12 is, for example, cylindrical. The anode 14 is provided in the +X direction from the chamber 10. The anode 14 has portions 14a and 14b. The portion 14a is conical, and the portion 14b is disk-shaped. A second hole 15 is provided at the tip of the portion 14a. The diameter of the second hole 15 is, for example, 0.1 mm to 10 mm, and is, for example, 1 mm. For example, the shape of the second hole 15 is circular. The distance between the tip of the cathode 12 and the tip of the portion 14a is D0. The cathode 12 and the anode 14 are made of a conductive material. The cathode 12, the first hole 11, and the second hole 15 are arranged in the X direction.

[0014] The magnet 16 is provided on the first wall 10a. The magnet 16 generates a magnetic field in a space 19, which is at least a part of the space between the cathode 12 and the anode 14. A region 17 is an area surrounded by the magnet 16. The north and south poles of the magnet 16 are arranged in the X direction. The distance between the tip of the cathode 12 and the region 17 is D1. A negative value of the distance D1 means that the cathode 12 penetrates into the region 17.

[0015] A gas of atoms or molecules is introduced into space 30a within chamber 10. Space 30b between chamber 10 and anode 14 has a lower pressure than space 30a. Space 30c on the +X side of anode 14 has a lower pressure than space 30b. As a result, atoms or molecules are emitted from first hole 11 in direction 51 toward second hole 15. Second wall 10b functions as an emission section that emits atoms or molecules in the X direction. The emission section may have other configurations.

[0016] For example, the pressure in the space 30a is 1 to 100 Torr, for example, 40 Torr. The pressure in the space 30b is 1×10 －２ ~1 x 10 －６ Torr, for example, 1×10 －４ When no gas is introduced into the space 30a, the pressure in the space 30b is, for example, 1×10 －５ Torr or less, for example, 1×10 －６ Torr, where 1 Torr is 130 Pa.

[0017] To release atoms or molecules from space 30a to space 30b, the pressure in space 30a is preferably 100 times or more, more preferably 1000 times or more, the pressure in space 30b. The pressures in spaces 30b and 30c may be approximately the same. To release atoms or molecules from space 30b to 30c, the pressure in space 30c is preferably lower than the pressure in space 30b.

[0018] The cathode 12 and the anode 14 function as an irradiation unit that irradiates an electron beam. The voltage applied to the cathode 12 is, for example, −50 to −1000 V, and is, for example, −400 V, relative to the anode 14. The distance D0 between the cathode 12 and the anode 14 is, for example, 10 to 100 mm, and is, for example, 25 mm. The irradiation unit may be configured in a manner other than the cathode 12 and the anode 14.

[0019] The magnet 16 functions as a generator that generates a magnetic field in the space 19 between the cathode 12 and the anode 14. The generator may be configured in a manner other than the magnet 16. The magnetic flux density in the space 19 is, for example, 50 mT to 500 mT, and is, for example, 100 mT or 160 mT.

[0020] According to the first embodiment, the magnet 16 generates a magnetic field in the space 19. Here, atoms or molecules exist in the space 19, and at least a part of the trajectory of the electron beam is generated. This bends the traveling direction of the electrons traveling as the electron beam. This lengthens the path of the electrons from the cathode 12 to the anode 14, and increases the flight time of the electrons. This increases the frequency of collisions between the electrons and atoms or molecules, and increases the efficiency of generating atoms or molecules in a metastable excited state. Furthermore, the velocity direction of the electron beam forms a larger angle with the velocity direction of the atoms or molecules.

[0021] At this time, it is preferable that the direction 52A (first direction) of the electric field lines generated in the space 19 by the cathode 12 and the anode 14, or the direction opposite to the direction 52A, coincide with the direction 54 (second direction) of the magnetic field lines generated in the space 19. This causes the electrons to spiral, lengthening the flight time of the electrons. This increases the frequency of collisions between the electrons and atoms or molecules, thereby increasing the efficiency of generating atoms or molecules in a metastable excited state. The directions 52A and 54 do not have to coincide.

[0022] It is preferable that the direction 51 (third direction) in which atoms or molecules are emitted coincides with the direction 52A of the electric field lines generated in the space 19 or the opposite direction to the direction 52A. This increases the space in which atoms or molecules and electrons coexist, making it easier for atoms or molecules and electrons to collide with each other. This increases the frequency with which electrons collide with atoms or molecules. The directions 51 and 52 do not have to coincide with each other.

[0023] Here, "the directions coincide" does not necessarily mean that they coincide in the strict sense. For example, "the second direction coincides with the third direction" means that the angle between the second direction and the third direction is preferably 20° or less, and more preferably 10° or less.

[0024] The cathode 12 and the anode 14 are arranged to sandwich all or part of the space 19. The direction from the cathode 12 toward the anode 14 is direction 52 (fourth direction). This generates electric field lines in the space 19 in a direction 52A opposite to direction 52, allowing the electron beam to be irradiated. The irradiated electron beam is bent by the magnetic field, increasing the frequency with which the electrons collide with atoms or molecules.

[0025] The magnet 16 is provided so as to surround the space 19, with its north and south poles aligned in a direction 52. This allows the direction 54 of the magnetic field lines 53 of the magnetic field generated by the magnet 16 within the space 19 to be the direction 52. If the north and south poles of the magnet 16 are reversed, the direction 54 will be opposite to the direction 52. The magnet 16 may be a permanent magnet or an electromagnet. Furthermore, there may be a single magnet 16 or multiple magnets 16.

[0026] The second wall 10b is provided between the cathode 12 and the anode 14 and has a first hole 11 for emitting atoms or molecules from the cathode 12 side to the anode 14 side. This allows the atoms or molecules to be emitted from the first hole 11 in a direction 52.

[0027] The anode 14 has a second hole 15. The first hole 11 and the second hole 15 are arranged in a direction 52. That is, the cathode 12, the first hole 11, and the second hole 15 are arranged on a straight line. As a result, electrons and atoms or molecules that have passed through the first hole 11 travel toward the second hole 15, and then the electrons are captured by the anode 14 near the second hole 15. As a result, in the space 30c, the atoms or molecules traveling in the direction 51 contain almost no charged particles.

[0028] The anode 14 has a portion 14a that protrudes toward the cathode 12, and the second hole 15 is located at the tip of the portion 14a. As a result, electrons move toward the second hole 15 located at the tip of the portion 14a. Therefore, the electrons and atoms or molecules that have passed through the first hole 11 travel toward the second hole 15.

[0029] (Example of Apparatus Having Beam Source of First Embodiment) As an example of an apparatus using a beam source, an apparatus using a beam of He in a metastable excited state will be described. FIG. 2 is a cross-sectional view showing an apparatus having a beam source according to the first embodiment. As shown in FIG. 2, the apparatus 102 includes chambers 31 to 33. The chambers 31 and 32 are separated by an anode 14. The chambers 32 and 33 are separated by a partition plate 34. The anode 14 has a second hole 15, and the partition plate 34 has a hole 35. The pressure in chamber 33 is lower than the pressure in chamber 32, and the pressure in chamber 32 is lower than the pressure in chamber 31.

[0030] A beam head 104 and a pipe 20 are provided in the chamber 31. He gas is supplied to the pipe 20. Ground-state He atoms supplied from the pipe 20 into the beam head 104 are emitted into the chamber 31 through the first hole 11 (see FIG. 1). The ground-state He atoms are converted into metastable excited He atoms by a discharge between the cathode 12 and the anode 14. ＊ (2 １ S, 2 ３ S). He ＊ (2 １ S, 2 ３ S) passes through the second hole 15 and is emitted into the chamber 32 as a metastable excited He beam 38.

[0031] A quench lamp 36 is provided in the chamber 32. The quench lamp 36 quenches the He in the metastable excited He beam 38. ＊ (2 １ S, 2 ３ By applying infrared light energy to He ＊ (2 １ S) was deactivated, and He ＊ (2 １ S) and He ＊ (2 ３ Metastable excited He(2S) ３ S) beam 38a. He ＊ (2 ３ The lifetime of the metastable excited He beam 38a is approximately 4200 seconds. The metastable excited He beam 38a passes through the hole 35 and is emitted into the chamber 33.

[0032] In the chamber 33, the metastable excited He beam 38a is irradiated onto the target 37. If the target 37 is a neutral atom or molecule, the atom or molecule can be subjected to Penning ionization. Penning ionization has different characteristics from ionization using an electron beam or synchrotron radiation. Therefore, it can be used for measurements such as electron spectroscopy or mass spectrometry, which have different capabilities.

[0033] The metastable excited He beam 38a can also be used as a beam in which the wavelength of the matter wave (so-called de Broglie wave) is equal to or greater than the interatomic distance. Furthermore, the metastable excited He beam 38a can be used for microfabrication exceeding atomic resolution. For example, the metastable excited He beam 38a can be used in semiconductor processing, semiconductor device manufacturing, or medical equipment.

[0034] The metastable excited He beam 38a is neutral and does not have electrostatic repulsion between particles, so it can be easily made into a parallel beam, making it easy to utilize wave properties such as interference effects. Furthermore, because atoms or molecules in a highly excited state are highly sensitive to electric fields, it is also possible to control the traveling direction of the metastable excited He beam 38a using a non-uniform electric field.

[0035] As the atom or molecule in the metastable excited state, in addition to He, rare gas atoms such as Ar, Ne, Kr, etc. can be used. As the atom or molecule in the metastable excited state, atoms other than rare gases or N ２ It may also be a molecule such as

[0036] Fig. 3 is a side view showing the beam head in detail. Fig. 4 is a cross-sectional view of the beam head attached to the anode. As shown in Figs. 3 and 4, the beam head 104 includes a block 21 and a pipe 23 in addition to the components shown in Fig. 1. The block 21 has members 21a and 21b. The member 21b is arranged to surround the chamber 10 and the pipe 20. The member 21a is arranged to cover the chamber 10 and the magnet 16. The members 21a and 21b are fastened together, for example, by screws. This fixes the magnet 16 to the chamber 10.

[0037] The second wall of the chamber 10 is exposed from the tip of the member 21a in the +X direction. The tip of the pipe 20 in the +X direction is inserted into the chamber 10. A cable 18 electrically connected to the cathode 12 is provided inside the pipe 20. A pipe 23 is wound around the member 21b. It is sufficient that the member 21b and the pipe 23 are in contact with each other, and the pipe 23 may be provided inside the member 21b.

[0038] A pillar 22 is fixed to the anode 14. A beam head 104 is provided inside the pillar 22. The beam head 104 is fixed to the pillar 22 by a fixing member 24. In this way, the beam head 104 is fixed to the anode 14.

[0039] The He gas supplied into the pipe 20 is introduced into the chamber 10 and emitted from the first hole 11 as a He beam 38. A cable 18 applies a negative voltage to the cathode 12. Liquid nitrogen, for example, is supplied into the pipe 23 to cool the interior of the chamber 10. This prevents the temperature of the magnet 16 from exceeding its heat-resistant temperature, and controls the speed of the He.

[0040] An example of the material of each component is shown below: The chamber 10 is made of boron nitride. The cathode 12 is made of tantalum. The anode 14 is made of stainless steel. The magnet 16 is a samarium-cobalt magnet. The pipe 20 is made of glass. The block 21 is made of copper. The pillar 22 is made of aluminum.

[0041] (Simulation) The flight of electrons from the cathode 12 to the anode 14 was simulated. The cathode 12 was cylindrical, with a diameter of 4 mm and a length in the X direction of 18 mm. The portion 14a of the anode 14 was conical, with a 60° apex angle and a length in the X direction of 15 mm. The diameter of the second hole 15 was 1 mm. The portion 14b was disk-shaped, with a diameter of 49 mm and a thickness in the X direction of 8 mm. The distance D0 between the cathode 12 and the anode 14 was 25 mm. 0 V was applied to the anode 14, and -400 V was applied to the cathode 12. The magnet 16 was ring-shaped, with an outer diameter of 22 mm, an inner diameter of 14 mm, and a width in the X direction of 8 mm. The magnetic flux density at the center of the magnet 16 was 160 mT. The simulator used was SIMION 3D VERSION 7.0, which can calculate the flight time of electrons.

[0042] The simulation was performed for four samples A to D. Sample A is a sample without a magnet 16. Sample B is a sample with a magnet 16, and the distance D1 in the X direction between the cathode 12 and the magnet 16 is 0 mm. Sample C is a sample with a magnet 16, and the distance D1 is 3 mm. Sample D is a sample with a magnet 16, and the distance D1 is 7 mm.

[0043] Figure 5 shows the simulation results for sample A. Two magnets 16 are shown in the X direction, but this is to represent the north and south poles; in reality, there is only one magnet. As shown in Figure 5, in sample A, the electron trajectory 42 is approximately linear from the cathode 12 to the anode 14. The length of the electron trajectory 42 is 25.1 mm, and the electron flight time is 4.22 ns.

[0044] 6 is a diagram showing the simulation results for sample B. As shown in Fig. 6, in sample B, the electrons curl up immediately after passing through region 17 surrounded by magnet 16, and do not travel in the X direction and do not reach anode 14.

[0045] Fig. 7 is a diagram showing the simulation results for sample C. As shown in Fig. 7, in sample C, electrons travel in a spiral motion within region 17 surrounded by magnet 16 before reaching anode 14.

[0046] 8 is a diagram showing the simulation results for sample D. As shown in Fig. 8, in sample D, electrons curl up in front of region 17 surrounded by magnet 16, travel in the -X direction, and do not reach anode 14.

[0047] FIG. 9 is a perspective view showing the simulation results for sample C. FIG. 10 is an enlarged view of FIG. 9. In FIG. 10, the magnet 16 is omitted from the illustration to make the electron trajectories 42 easier to see. As shown in FIGS. 7, 9, and 10, electrons undergo spiral motion in region 17 surrounded by magnet 16. The number of spirals is particularly dense near the center of region 17 in the X direction. This is thought to be because the magnetic flux density is greatest at the center of region 17. The number of spiral rotations is low between region 17 and portion 14a. This is thought to be because the magnetic flux density is low and the electron speed is high.

[0048] 7, 9, and 10, in sample C, the number of rotations of electron trajectory 42 is 10.5. Furthermore, the radius of rotation of trajectory 42 is approximately 0.3 mm. Therefore, the increase in electron flight distance due to electron rotation is estimated to be 2π × 0.3 mm × 10.5 = 19.8 mm. Since the electron flight distance in sample A is 25.1 mm, the increase in flight distance due to the provision of magnet 16 is approximately 79%. The electron flight time in sample C increased by approximately 62% compared to the flight time in sample A. Because the increase in flight time is greater than the increase in flight distance, the electron speed in sample C is also improved compared to sample A.

[0049] By providing the magnet 16, the component of the electron velocity perpendicular to the X direction can be increased, the effective electron velocity can be improved, and the electron flight time can be lengthened. This increases the frequency of collisions between electrons and atoms or molecules, thereby improving the efficiency of generating atoms or molecules in a metastable excited state.

[0050] In the simulation, when the width of magnet 16 in the X direction is 8 mm, electrons do not travel from cathode 12 to anode 14 when D1 = 0 mm or 7 mm. When D1 = 3 mm, electrons travel from cathode 12 to anode 14. For this reason, the position of the end of cathode 12 facing anode 14 is preferably located on the opposite side of region 17 from anode 14, and distance D1 is preferably ¼ or more of the width of magnet 16 in the X direction. Furthermore, distance D1 is preferably ¾ or less, and more preferably ½ or less, of the width of magnet 16 in the X direction. Note that the arrangement of cathode 12 may be other than the above, depending on conditions such as the arrangement position of magnet 16, distance D0, and the voltage applied to cathode 12.

[0051] In the beam source 100 of the first embodiment, as shown in FIG. 1 , the direction 52A (first direction) of the electric field lines or the direction opposite to the direction 52A coincides with the direction 54 (second direction) of the magnetic field lines. The chamber 10 has a first hole 11 that emits the atoms or molecules from the cathode 12 side to the anode 14 side. The direction 51 (third direction) in which the first hole 11 emits the atoms or molecules coincides with the direction 52A or the direction opposite to the direction 52A. The anode 14 has a portion 14a that protrudes toward the cathode 12 and has a second hole 15 at its tip. The cathode 12, the first hole 11, and the second hole 15 are arranged in a substantially straight line in the direction 52A. The beam of atoms or molecules that passes through the second hole 15 is emitted from the second hole 15.

[0052] In this way, by aligning the direction 52A (or the opposite direction) of the electric field lines with the direction 54 of the magnetic field lines and aligning the direction 52A (or the opposite direction) with the direction 51 of atom or molecule emission, the space in which atoms or molecules and electrons coexist becomes larger, making it easier for atoms or molecules to collide with electrons. This increases the frequency of collisions between electrons and atoms or molecules. By arranging the cathode 12, the first hole 11, and the second hole 15 in a substantially straight line in the direction 52A, it is possible to align the direction 52A (or the opposite direction) of the electric field lines with the direction 51 of atom or molecule emission, and to emit a beam from the second hole 15.

[0053] The phrase "arranging the cathode 12, the first hole 11, and the second hole 15 in a straight line (or approximately in a straight line) in the direction 52A" does not necessarily mean that they are arranged in a straight line in the strict sense. For example, the angle between the line connecting the cathode 12 and the first hole 11 and the line connecting the first hole 11 and the second hole 15 is preferably 20° or less, and more preferably 10° or less.

[0054] Second Embodiment FIG. 11 is a cross-sectional view of a beam source according to a second embodiment. The direction 52 from the cathode 12 to the tip of the portion 14a of the anode 14 (i.e., the direction of the electric field lines) is defined as the X direction. As shown in FIG. 11 , in the beam source 106 of the second embodiment, the position X17- in the X direction of the end of the magnet 16 on the cathode 12 side is located on the negative X side of the position X12 in the X direction of the end 12A of the cathode 12 on the anode 14 side. The position X17+ in the X direction of the end of the magnet 16 on the anode 14 side is located on the positive X side of the position X15 in the X direction of the second hole 15. Thus, the region between the end 12A of the cathode 12 and the second hole 15 is included in the region 17 surrounded by the magnet 16. In this case, the direction 52 of the electric field lines and the direction of the magnetic field lines 53 coincide throughout most of the area between the end 12A of the cathode 12 and the second hole 15. In this arrangement, the cathode 12 discharges with the magnet 16 rather than near the second hole 15, causing the electron beam to diffuse. This may result in a decrease in the efficiency of generating metastable excited atoms or molecules. Furthermore, the space between the first hole 11 and the second hole 15 is shielded by the magnet 16, which may reduce pumping efficiency and deactivate excited atoms. However, this does not exclude the second embodiment as long as it is possible to suppress the discharge between the cathode 12 and the magnet 16 and increase pumping efficiency. A synergistic effect with the pointed anode 14 may be obtained.

[0055] Third Embodiment Fig. 12 is a cross-sectional view of a beam source according to the third embodiment. As shown in Fig. 12, in the beam source 108 of the third embodiment, position X17- in the X direction of the end of magnet 16 on the cathode 12 side is located on the +X side of position X12 in the X direction of end 12A of cathode 12 on the anode 14 side. Position X17+ in the X direction of the end of magnet 16 on the anode 14 side is located on the -X side of position X15 in the X direction of second hole 15.

[0056] Thus, position X12 of end 12A of cathode 12 is located on the opposite side of anode 14 from region 17 surrounded by magnet 16. This reduces the area in which direction 52 of electric field lines and direction 53 of magnetic field lines coincide. This prevents electrons in the electron beam from being scattered in unintended directions, improving the frequency of collisions between electrons and atoms or molecules. This improves the efficiency of generating atoms or molecules in a metastable excited state. The distance D1 between position X12 and position X17- in the X direction is preferably 1 / 12 or more of the distance D0 between position X12 and position X15 in magnet 16. Because magnetic field lines 53 spread out from the end of magnet 16, it is preferable to prevent the spread of magnetic field lines 53 from interfering with cathode 12.

[0057] If position X12 is located on the -X side of position X17-, and distance D1 is too large, electrons will not enter region 17, as in sample D in Figure 8. From this perspective, distance D1 is preferably ¾ or less of the width of magnet 16 in the X direction under the magnetic flux density conditions in Figure 8. Furthermore, distance D1 is preferably ⅓ or less of distance D0.

[0058] Furthermore, position X15 of second hole 15 is located closer to anode 14 than region 17 surrounded by magnet 16. This reduces the area where direction 52A of the electric field lines and direction 53 of the magnetic field lines coincide. This prevents electrons from scattering in unintended directions, increasing the frequency of collisions between electrons and atoms or molecules. This improves the efficiency of generating atoms or molecules in a metastable excited state. The distance D2 between position X15 and position X17+ in the X direction is appropriately adjusted so that magnetic field lines 53 do not interfere with second hole 15 while maintaining the condition in which no discharge occurs between cathode 12 and magnet 16.

[0059] Either the end 12A of the cathode 12 or the second hole 15 may be located within the region 17 surrounded by the magnet 16. In this case, it is preferable to arrange them so that no discharge occurs between the cathode 12 and the magnet 16.

[0060] 13 is a cross-sectional view of a beam source according to Embodiment 1. As shown in Fig. 13, in the beam source 100 according to the first embodiment, the position X17+ in the X direction of the end of the magnet 16 on the anode 14 side is located on the -X side of the position X11 in the X direction of the first hole 11.

[0061] As described above, the position X11 of the first hole 11 is located closer to the anode 14 than the region 17 surrounded by the magnet 16. This reduces the area where the direction of the electric field lines 52 and the direction of the magnetic field lines 53 coincide compared to the third embodiment shown in FIG. 12 . This prevents the cathode 12 from discharging with the magnet 16 rather than near the second hole 15, thereby preventing the electron beam from diffusing. This improves the efficiency of generating atoms or molecules in a metastable excited state. The distance D3 between the position X11 and the position X17+ in the X direction is preferably at least 1 / 20, more preferably at least 1 / 10, of the distance D4 between the position X12 and the position X11. This prevents the electron beam from being diffused by the magnetic field lines 53 and directs the electron beam toward the anode 14 via the electric field lines, thereby improving the efficiency of generating atoms or molecules in a metastable excited state.

[0062] The chamber 10 (wall) includes a first wall 10a that surrounds the space 19 and at least a portion of the cathode 12, and a second wall 10b that separates the space 19 from another space 30b located closer to the second hole 15 than the first hole 11 and has the first hole 11. This allows the range within the chamber 10 to be defined as a range in which the direction of the electric field lines 52 and the direction of the magnetic field lines 53 coincide. The pressure in the space 19 is higher than the pressure in the space 30b. Therefore, in the space 19, where the probability of atoms or molecules existing is high, the direction of the electric field lines 52 and the direction of the magnetic field lines 53 can be made to coincide, thereby increasing the frequency of collisions between electrons and atoms or molecules. Meanwhile, in the space 30b, where the probability of atoms or molecules existing is low, the magnetic field lines 53 can be reduced, thereby suppressing electron scattering in unintended directions. This improves the efficiency of generating atoms or molecules in a metastable excited state.

[0063] Furthermore, by providing the magnet 16 on the first wall 10a, the range of the magnetic field lines 53 can be reduced. This reduces the spread of the magnetic field lines 53.

[0064] The above describes in detail preferred embodiments, but the present invention is not limited to the above-described embodiments, and various modifications and substitutions can be made to the above-described embodiments without departing from the scope of the claims.

[0065] This application claims priority from basic patent application No. 2024-051123, filed with the Japan Patent Office on March 27, 2024, the entire contents of which are incorporated herein by reference.

[0066] 10: Chamber 10a: First wall 10b: Second wall 11: First hole 12: Cathode 14: Anode 14a, 14b: Part 15: Second hole 16: Magnet 17: Area 18: Cable 19: Space 51, 52, 54: Direction 53: Magnetic field lines

Claims

1. A beam source for generating a beam containing atoms or molecules in a metastable excited state, comprising: an emitter that emits the atoms or molecules; an irradiation unit that irradiates the atoms or molecules with an electron beam; and a generator that generates a magnetic field in a space where the atoms or molecules are present and where at least a part of the trajectory of the electron beam occurs; the irradiation unit has a cathode and an anode that sandwich the space, and a first direction of electric field lines generated in the space by the irradiation unit or a direction opposite to the first direction coincides with a second direction of magnetic field lines generated in the space by the generator; the emitter is provided between the cathode and the anode and comprises a wall having a first hole that emits the atoms or molecules from the cathode side to the anode side; a third direction in which the emitter emits the atoms or molecules coincides with the first direction or the direction opposite to the first direction; the anode has a portion that protrudes toward the cathode and has a second hole at its tip; the cathode, the first hole, and the second hole are arranged in a line approximately in a straight line in the first direction; The beam is emitted from the second aperture.

2. A beam source according to claim 1, wherein the generating unit is a magnet arranged to surround the space and having north and south poles arranged in a fourth direction from the cathode toward the anode.

3. A beam source according to claim 2, wherein the end of the cathode on the anode side is positioned closer to the cathode than the area surrounded by the magnet.

4. A beam source according to claim 3, wherein the distance between the position of said end and said region is not more than 3 / 4 of the width of said magnet in said fourth direction.

5. A beam source according to any one of claims 2 to 4, wherein the second hole is located closer to the anode than the area surrounded by the magnet.

6. A beam source according to any one of claims 2 to 4, wherein the first hole is located closer to the anode than the area surrounded by the magnet.

7. A beam source according to claim 3, wherein the first hole is located on the anode side of the region surrounded by the magnet.

8. A beam source as described in claim 7, wherein the wall comprises a first wall surrounding the space and at least a portion of the cathode, and a second wall having the first hole and isolating the space from another space on the second hole side of the first hole.

9. The beam source of claim 8, wherein the pressure in said space is higher than the pressure in said other space.

10. The beam source of claim 8, wherein the magnet is mounted on the first wall.

11. A beam source according to any one of claims 1 to 4, wherein the atoms or molecules are noble gas atoms.

12. A beam source according to any one of claims 1 to 4, wherein the atoms or molecules are He atoms.

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