JP4351413B2 - Laser plasma X-ray generator - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention has a cylindrical side surface with good thermal conductivity for a cryo-target material that changes its state from liquefaction to solidification by cooling a chemically inert and gaseous cryo (low temperature) material at room temperature. The surface of the rotating body cooled to a very low temperature, such as the cylindrical side and bottom plane, is supplied by spraying to form a cryo-target layer, and the repetitively pulsed laser light with high peak power is focused on this cryo-target layer. The present invention relates to a laser plasma X-ray generator that generates pulse X-rays from plasma generated by irradiation.
[0002]
In particular, the amount of fine particles generated by the target material that is generated and scattered by the irradiation of repetitively pulsed laser light having a high peak power is limited to a small amount, and the fine particles are collected to continuously and stably generate high average output pulses. The present invention relates to a laser plasma X-ray generator capable of generating X-rays.
[0003]
[Prior art]
A pulse laser beam having a high peak power is focused on a point having a diameter of 100 μm or less and irradiated to a solid target to generate a high-temperature and high-density laser plasma. Has been known as a laser plasma X-ray since the 1970s. And the pulse energy of the laser beam is improved and the physical characteristics are being investigated.
[0004]
Regarding the application of laser plasma X-rays, many techniques have been disclosed as medical applications and as applications to light sources for X-ray lithography. Later, as part of laser fusion research, laser plasma X-rays were studied vigorously, revealing the laser wavelength, intensity dependence, or target element dependence of the X-ray spectral intensity. In particular, the total conversion efficiency from incident laser energy to X-ray energy was found to be extremely high, from several percent to 10 percent, and lasers such as the realization of high-energy pulsed YAG lasers capable of high repetition rates of several hundred Hz are possible. With the advancement of technology, development for practical use of laser plasma X-rays having high average output due to high repetition was carried out.
[0005]
US Pat. No. 4,700,371 (Oct. 13, 1987) discloses a target for generating plasma by focusing an incident laser. There are cylindrical rotating drum targets or tape targets. However, since these targets are solid materials mainly composed of metals such as copper (Cu), aluminum (Al), and gold (Au), the material in the vicinity of the condensing point evaporated by laser heating is in the surrounding chamber. There are problems such as deposition on the inner surface of the wall or the surface of an expensive X-ray mirror that collects the emitted laser plasma X-rays, and the scattered fine particles damage the surface of the X-ray mirror. The reason is that the solid material of the target material is deposited and adhered to the surface of the X-ray mirror and strongly absorbs X-rays and / or may become crystal fine particles and damage the surface of the X-ray mirror. This is because the reflectivity of the mirror decreases and the effective intensity of usable X-rays decreases with time. Therefore, it is necessary to periodically replace expensive X-ray mirrors.
[0006]
In addition, since the target to be used is repeatedly focused and irradiated with laser light, it has a short life due to evaporative wear and needs to be frequently replaced.
[0007]
Conventionally, in this type of laser plasma X-ray generator, as a method for solving the above-described problems, a liquid that is obtained by cooling a noble gas such as xenon (Xe) that is chemically inert and in a gaseous state at room temperature is used. A cryomaterial that has been solidified or solidified is formed and used in a cryotarget layer.
[0008]
For example, as shown in FIG. 13, an apparatus for continuously supplying a cryo target made of a cooled and liquefied or solid cryo material is disclosed in Japanese Patent Laid-Open No. 1-6349 (Japanese Patent No. 2614457). .
[0009]
  That is, figure13As shown in FIG. 2, a belt conveyor 102 having a continuously moving rotating endless belt is provided inside the vacuum chamber 101, and the liquefied or solidified cryomaterial is continuously supplied from the supply path 103 onto the surface of the rotating endless belt. The cryo target layer 104 is formed by being supplied and attached.
[0010]
On the other hand, the pulsed laser light enters the vacuum chamber 101 from the entrance, and forms a focused irradiation point 105 on the cryotarget layer 104 attached on the surface of the moving rotating endless belt. Accordingly, the cryomaterial of the cryotarget layer 104 is turned into plasma at the focused irradiation point 105 and emits pulse X-rays, and the pulse X-rays are extracted outside through the X-ray exit.
[0011]
Cryo material is continuously supplied from the cryo material supply path 103 onto the surface of the moving rotating endless belt, and the cryo target layer 104 is formed in the cryo target layer 104 which has been turned into plasma at the focused irradiation point 105 and has a hole. Restore.
[0012]
In the laser plasma X-ray generator that transports the cryo-target layer to the laser focusing point using the rotating endless belt described above, the rotating endless belt is cooled only when it comes into contact with a cryogenic rotating body. Due to the action of bending and stretching, there is a problem that the life of the rotating endless belt is shortened, and furthermore, it is difficult to keep the temperature of the attached surface of the cryomaterial supplied at a stable low temperature. There is.
[0013]
In addition, since it is difficult to obtain uniformity in the thickness along the surface of the cryo target layer that is supplied from the cryo material supply path and adhered to the rotating endless belt, laser light in the normal direction of the surface of the cryo target layer is obtained. There is also a problem that the relative position of the condensed irradiation point may deviate from a predetermined position depending on the location of the surface, and the intensity of the generated X-rays is not stable.
[0014]
  In order to solve such a problem, it is disclosed in, for example, Japanese Patent Application Laid-Open No. 2001-015296 instead of a belt conveyor using a rotating endless belt.14There is an apparatus for continuously supplying a cryo target made of a cryo material that can be liquefied or solidified when cooled.
[0015]
That is, the illustrated laser plasma X-ray generator has a rotating body 111 inside a vacuum chamber 110, and the rotating body 111 has a thermal conductivity as a surface of a rotating shaft 112 and a cryo-target rotated by a rotation driving mechanism. The cryogenic fluid 113 is circulated through the rotating shaft 112 to cool the side surface to a cryogenic temperature.
[0016]
On the other hand, the target supply mechanism 120 supplies, for example, xenon (Xe), which is chemically inert and is liquefied or solidified by cooling and gaseous at room temperature, from the supply path 121 to the surface of the rotating body 111 as a cryotarget material. A cryotarget layer 122 having a predetermined thickness is formed.
[0017]
In the laser plasma X-ray generator, a focused pulsed laser beam 131 having a high peak power is focused and irradiated on the focused irradiation point 130 of the cryo target layer 122, and a pulsed X-ray 132 is generated from the plasma generated here. To do.
[0018]
Thus, the cryo target layer 122 regenerated by rotating the rotating body 111 can be continuously supplied to the focused irradiation point 130 of the pulse laser beam 131. Therefore, when the rotator 111 with good thermal conductivity is cooled to a very low temperature to form the cryo target layer 122 on the surface, the rotation speed of the rotator 111, the temperature of the rotator surface, the cryomaterial supplied to the rotator surface The thickness of the cryo target layer 122 can be appropriately set by setting the supply amount and the like. Further, since the position of the focused irradiation point 130 of the pulse laser can be sequentially moved by the rotation of the rotating body 111, damage to the rotating body 111 due to the plasma generated at the focused point of the pulse laser can be prevented.
[0019]
Further, as shown in the figure, a fixed wall 150 is provided that surrounds the rotating body 111 with a gap and receives and confines cryogenic material in the gap, and rotates by setting environmental conditions including the speed of the rotating body 111 and the ambient temperature. The cryomaterial attached to the cylindrical surface of the rotating body 111 is formed to have a substantially uniform thickness to form a cryotarget layer 122. Accordingly, a liquefied or solidified cryo-target layer can be stably formed on the surface of the rotating body 111, and plasma is always generated at the focused irradiation point 130 of the pulse laser beam 131 under the same stable condition. be able to.
[0020]
However, as shown in FIG. 15, in the case where the focused irradiation point 130 is irradiated with 0.7 J / 20 ns pulsed laser light 131 with the cryotarget layer 122 formed on the surface of the rotating body 111 described above, the cryotarget layer High-temperature and high-pressure plasma is formed on the surface of 122 within 30 ns and pulsed X-rays 132 are generated. At the same time, a shock wave driven by the generated plasma propagates inside the cryo-target layer 122, and after passing through the shock wave, the gas 134 and the crushed fine particles in which the cryo-material that has become the cryo-target is evaporated from 1 μs to almost 100 μs. 135 diffuses to form a crater 136 in the cryo-target layer 122 having a predetermined thickness. When xenon (Xe) is used as a cryotarget material, the crater 136 reaches a depth of 150 μm and a diameter of 400 μm. Incidentally, the volume of the cryo-target material required for emitting pulsed X-rays by the formation of plasma is the product of the area of the focused spot diameter of 100 μm and the depth of 20 μm.
[0021]
[Problems to be solved by the invention]
  Figure above14In the laser plasma X-ray generator described with reference to FIG. 5, the cryotarget material (Xe) diffuses an amount reaching a depth of 150 μm and a diameter of 400 μm with respect to a focused irradiation with a diameter of 100 μm. Therefore, these generated substances diffuse into the vacuum chamber without damaging the components in the vicinity of the focused irradiation point where the diffusing gas and fine particles rotate. Furthermore, this generated substance increases rapidly by staying in the vacuum chamber, and there is a high risk of deteriorating the function of the apparatus. To eliminate this, figure14The generated material can be collected and regenerated by using an exhaust means such as the exhaust device 140 shown in FIG. 1, but since the diffusion amount increases rapidly, this requires a large exhaust amount.
[0022]
An object of the present invention is to solve such a problem in a laser plasma X-ray generator using a rotating body as a substrate of a cryo-target layer, and to evaporate or diffuse upon receiving focused irradiation of laser light. Limit the amount of cryo-target material to be as small as possible to reduce the capacity of the exhaust means for collecting the generated material, and collect the generated material as much as possible to reduce the cost of equipment and its operation It is to provide a laser plasma X-ray generator capable of performing the above.
[0023]
[Means for Solving the Problems]
  The laser plasma X-ray generator according to the present invention is chemically inert, gaseous at room temperature, and when cooledLiquefy and furtherliquidStatusFrom solidChange to stateThe cryotarget material is supplied to the surface of the side surface or bottom surface of the rotating body having a rotation axis and rotating around the rotation axis and having a cylindrical surface with good thermal conductivity and being cooled to a cryogenic temperature. A cryo-target layer having a predetermined thickness is formed as a cryo-target, and pulse X-rays are generated from plasma generated by condensing and irradiating the cryo-target with a pulsed laser beam having high peak power. is there.
[0024]
One of the features is that the circuit has a width and thickness of a size that can secure a minimum amount of cryo-target material necessary for generating X-rays by generating plasma when focused with pulsed laser light. The above cryotarget is provided with a belt-like circle formed in a ring shape on the surface of the rotating body. Such a cryo-target band may be formed with a thickness on the surface of the rotator or may be formed by a groove having a depth on the surface of the rotator. Of course, the cryo-target band may be formed on a shallow groove.
[0025]
The cryotarget material supply port in this case is a cryotarget that is cooled in advance and ejects a cryotarget material having a concentration close to the liquid state onto the surface of the rotating body and immediately solidifies on the surface of the rotating body to form a cryotarget band in the form of crystal particles. A target supply nozzle is desirable.
[0026]
In addition, the cryo-target band may be formed on the surface of the rotator so as to be parallel to the rotation axis direction on the side surface and concentric on the bottom surface. In addition, a feature added to this is that the cryo-target material is fixedly arranged with respect to the cryo-target belt of the rotating body that rotates and adheres to the surface of the rotating body and adheres to the surface of the rotating body in the vicinity of the cryo-target band. And a pressure collecting wall for creating a cryotarget band having a predetermined size.
[0027]
Moreover, the amount of the cryo target material that evaporates while being focused and irradiated by the pulse laser beam is, for example, about 20 μm to 30 μm in thickness for xenon (Xe). Thus, by setting the width and thickness or depth of the cryo-target band to a value suitable for the amount of transpiration by condensing irradiation of laser light, that is, the condensing spot diameter and the transpiration depth, The transpiration of the material is limited in the width direction of the target groove and is not expanded on the surface of the rotating body substrate. In particular, when the width direction dimension is limited by using the pressure collecting wall, no extra transpiration in the width direction occurs.
[0028]
In addition, the opening part of the cryo target groove is wide with respect to the central part and has a concave cross section so that the high temperature plasma particles scattered at the part where the cryo target groove is in contact with the surface of the rotor substrate will not be damaged. It is desirable to be formed.
[0029]
Furthermore, in order to avoid damage to the rotor substrate due to the plasma, a gas serving as a buffer layer, such as carbon dioxide (CO 2)₂) From liquefaction to solidification to form a buffer layer on the surface of the rotator, and a cryo-target material such as xenon (Xe) can be minimized. In this case, the buffer material supply nozzle that supplies the gas serving as the buffer layer is disposed at a position upstream of the cryotarget material supply nozzle.
[0030]
Another feature is that the crystal fine particles of the cryomaterial ejected from the focused irradiation point by the focused irradiation of the pulse laser beam and the vaporized gas from the focused irradiation point to the rotating body rotation direction and the cryo target. It is further provided with an exhaust nose for collecting and exhausting on the belt. This feature is preferably combined with the above feature, but can also be effective independently. In particular, fine particles that scatter in a direction substantially perpendicular to the surface of the rotating body from the focused irradiation point are naturally collected by an exhaust nose that is arranged obliquely in the rotating direction of the rotating body, that is, in the tangential direction of the circular cryotarget band. It will be possible. Therefore, the recovery of the cryotarget material is facilitated, and the residual of the cryotarget material gasified inside the vacuum chamber can be greatly reduced.
[0031]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described with reference to the drawings. The shape or shape of the figure, or relative dimensions, etc., are prepared to help understand the explanation, so please refer to them only.
[0032]
FIG. 1 is an explanatory longitudinal sectional schematic view showing an embodiment of the present invention.
[0033]
In the laser plasma X-ray generator of FIG. 1, a vacuum chamber 10, a cylindrical rotating body 11, a rotating shaft 12 of the rotating body 11, and a cryogenic fluid 13 that cools the rotating body 11 inside form a main structure. To do. A target material supply unit 20 that supplies a cryomaterial serving as a laser beam target has a cryotarget material supply nozzle 21 that supplies a cryomaterial to the surface of the rotating body 11, and the cryomaterial is a cryotarget layer on the surface of the rotating body 11. 22 is formed.
[0034]
The pulsed laser light 31 is condensed at a condensing irradiation point 30 in the cryo target layer 22 on the surface of the rotator 11 to generate plasma, and a pulse X-ray 32 is emitted. An X-ray mirror 33 is provided in order to make the radiation of the pulse X-ray 32 parallel light in the output direction. The cryogenic gas generated in the vacuum chamber 10 due to the impact of plasma generation is collected by the exhaust device 40 and collected in the collection layer 41. The fixed wall 50 is provided to have a gap with the surface of the rotating body 11 and receives and confines the cryo material injected into the gap. As disclosed in the above-mentioned publication, the surface of the rotating body 11 is fixed. A cryotarget layer 22 having a stable thickness in a liquefied state or a solidified state is formed thereon.
[0035]
Further, the feature of the present invention is that the cryo target material supply nozzle 21 for supplying the cryo material injects the cryo material onto the surface of the rotating body 11 and immediately solidifies the cryo material on the surface. It is made to adhere in a crystal fine particle state. Furthermore, a target groove 51, a pressure collecting wall 52, and an exhaust nose 53 are provided. Here, it is assumed that the cryo target material supply nozzle 21, the pressure collecting wall 52, and the exhaust nose 53 are fixed to the fixed wall 50. The target groove 51 is formed by embedding a cryo material therein to form the above-described cryo target band. The fixed wall 50 is necessary for isolating the spray portion having a relatively high pressure and the periphery of the cryo target band from the vacuum in order to maintain the high degree of vacuum of the vacuum chamber 10.
[0036]
In the figure, a rotary bearing, a rotation drive mechanism and an axial drive mechanism for driving the rotation and movement of the rotating body 11, an introduction pipe and an exhaust pipe for the cryogenic fluid 13, and the like are shown. Accordingly, for example, the axial drive mechanism can form a plurality of the above-described cryotarget bands by moving the rotating body 11 stepwise in the axial direction.
[0037]
Next, the function of each component will be described with reference to FIG.
[0038]
Inside the vacuum chamber 10, there is provided a rotating body 11 having a cylindrical surface and having a thermal conductivity that is hollow and serves as a cooling tank, with a rotating shaft 12 perpendicular to the horizontal plane. The rotary shaft 12 is supported by a rotary bearing provided in the vacuum chamber 10. The rotating shaft 12 is preferably made of a material having a small thermal conductivity coefficient.
[0039]
The rotating shaft 12 is an upper portion, and an introduction pipe for introducing a low-temperature liquefied gas such as liquid nitrogen, liquid argon, or liquid helium from the outside into the hollow interior of the rotating body 11 as a cryogenic fluid 13, and a cryogenic fluid. The exhaust pipes for discharging and collecting 13 vaporized gases are coaxially provided. Accordingly, the cryogenic fluid 13 is accumulated as a liquid in the hollow inside the rotating body 11, and the surface of the rotating body 11 is made below the liquefaction temperature of the cryomaterial that becomes the cryo target layer 22 using the heat conduction of the rotating body 11. Cooling.
[0040]
On the other hand, the cryomaterial is, for example, xenon, and is a target material that is an object of focused irradiation of the laser beam 31 that generates laser plasma. The cryomaterial is fluidized and replenished to the recovery tank 41 from the outside and stored inside. The cryomaterial is jetted and supplied at a concentration close to the liquid state around the target groove 51 provided on the surface of the cooled rotator 11 by the temperature-controlled cryotarget material supply nozzle 21. In this state, the inside of the target groove 51 is filled, and the cryo target layer 22 is formed on the surface of the rotating body 11.
[0041]
Here, the target groove 51 shown in FIG. 1 and the cryo target layer 22 formed on the surface thereof will be described with reference to FIGS. 2 and 3 together with FIG.
[0042]
The rotating body 11 uses, for example, copper (Cu) whose surface is covered and protected by a high melting point metal tungsten alloy or the like, is a cylindrical target substrate, and has a sufficient thickness to fill the depth of the target groove 51. have.
[0043]
As shown in FIG. 2, the target groove 51 shown in FIG. 1 has a ring shape centered on the rotation axis on a plane perpendicular to the rotation axis 12. It is preferable that the formation of the cryo target layer and the generation of the pulse X-ray are alternately generated during one rotation of the rotating body 11 so that the pulse X-ray 32 can be continuously generated. However, if necessary, the target groove 51 can form a plurality of parallel lines in the direction of the rotating shaft 12 in combination with the axial drive mechanism described above on the cylindrical side surface of the cylindrical rotating body 11. Furthermore, another target groove | channel can also be provided in the circular bottom face of a cylindrical or disk-shaped rotary body. In this case, the plurality of target grooves form a plurality of concentric circles around the rotation axis.
[0044]
The cross-sectional size of the target groove 51 may be, for example, a depth of 100 μm and a width of 150 μm at a deep portion, and a depth of 15 μm and a width of 300 μm at a shallow portion. The size of the target groove 51 is a transpiration phenomenon in which the pulse laser beam 31 is directly heated, and has a volume that does not damage the rotating body 11 that is the substrate material.
[0045]
Therefore, the cryomaterial injected from the cryotarget material supply nozzle 21 fills the target groove 51 of the rotor 11 having a good thermal conductivity cooled to a very low temperature and, for example, a cryotarget having a thickness of 10 μm on a cylindrical surface. Layer 22 will be formed. In this case, the thickness of the cryo target layer 22 can be appropriately formed by setting environmental conditions such as the rotational speed of the rotating body 11, the temperature of the cylindrical surface, and the supply amount of the cryomaterial supplied to the cylindrical surface.
[0046]
The target groove 51 is formed in two steps of a shallow portion and a deep portion so that the substrate material is not damaged at the portion where the target groove 51 and the substrate surface of the rotating body 11 are in contact with each other. For example, the cross section may have a funnel shape or a semicircular shape.
[0047]
That is, when the cross-section of the target groove is not a stepped shape as shown in the figure, the concave structure is formed because the reflected shock wave reflected on the inner surface of the target groove is converged on the center of the target groove. It is desirable because it does not diffuse into the surroundings and the surrounding target material is not detached or peeled off in a wide range.
[0048]
Here, returning to FIG. 1, the description will be continued.
[0049]
As will be described later, since the pressure collecting wall 52 embeds the cryotarget material in the target groove 51, it is desirable that the cryomaterial is in a crystalline fine particle state on the surface of the rotating body 11. Accordingly, the cryomaterial is supplied by spraying the cryomaterial onto the surface of the cooled rotating body 11 by the cryotarget material supply nozzle 21 controlled at a low temperature, thereby rapidly generating crystal particles. In addition, since the tip of the cryotarget material supply nozzle 21 is located inside the pressure collecting wall 52, the sprayed cryomaterial can be prevented from scattering over a wide range on the surface of the rotating body 11. As a result, the efficiency of forming the cryotarget band is improved.
[0050]
Also, the cryomaterial that has become gaseous when the cryotarget layer 22 is turned into plasma is discharged and collected out of the vacuum chamber 10 by the exhaust device 40, sent to the cryomaterial recovery tank 41, and cooled again to a low temperature. Then, it is supplied to the surface of the rotating body 11 in the vacuum chamber 10 via the cryo target material supply nozzle 21. Further, the exhaust device 40 has a 133 × 10 6 inside the vacuum chamber 10.^-3It operates so as to maintain the pressure at Pa or lower.
[0051]
On the other hand, the pulse laser beam 31 is irradiated from the laser incident port of the vacuum chamber 10 through the condensing mechanism and reaches the condensing irradiation point 30 of the cryo target layer 22. Next, the pulse X-ray 32 generated from the plasma generated at the focused irradiation point 30 is shaped into parallel light by the X-ray mirror 33 and emitted from the X-ray exit.
[0052]
Next, as shown in FIGS. 4 and 5, the pressure collecting wall 52 is positioned in front of the focused irradiation point 30 in the rotational travel direction of the rotating body 11 above the target groove 51. The exhaust nose 53 is located on the upper side of the target groove 51, in the rotational travel direction of the rotating body 11, and in the tangential direction of the circular target groove 51, ahead of the focused irradiation point 30. The exhaust nose 53 is coupled to the exhaust device 40 as shown, and the collected exhaust material is recovered in the recovery tank 41.
[0053]
In the example shown in FIG. 4, the pressure collecting wall 52 and the exhaust nose 53 are fixed to a fixed wall 51 that surrounds the cylindrical rotating body 11 with a gap inside the vacuum chamber 10. However, it goes without saying that the pressure collecting wall 52 and the exhaust nose 53 may be directly fixed to the vacuum chamber 10 itself. FIG. 4 is a view showing a cross section perpendicular to the rotating shaft 12 and is removed from the target groove 51 portion.
[0054]
Next, a main operation procedure according to the present invention will be described with reference to FIGS. 4 to 8 in FIG.
[0055]
First, after the cylindrical surface of the rotator 11 is cooled to a temperature sufficient to sufficiently crystallize the cryomaterial, the cryomaterial is supplied to the surface including the target groove 51 of the rotator 11 from the cryotarget material supply nozzle 21. Be injected. As a result, the cryo material is immediately solidified on the surface of the rotator 11 to form crystal particles. As shown in FIG. 4, the cryo target layer 22 made of the crystal materialized cryo material is formed in the rotational traveling direction of the rotating body 11. The cryo target layer 22 is formed on the surface of the rotating body 11 with a thickness of 10 μm to 50 μm, for example.
[0056]
Next, as shown in FIGS. 5 and 6, the pressure collecting wall 52 slides on the surface of the rotator 11, scrapes the crystal particulate cryomaterial of the cryotarget layer 22 deposited on the surface, and the target groove 51. The cryo-target band 23 is formed by stuffing and compressing.
[0057]
The light source of the pulsed laser light 31 incident on the cryotarget band 23 is a high peak power and high repetition type pulsed laser light source, and the pulsed laser light 31 is about a focused irradiation point 30 on the surface of the cryotarget band 23. Condensed and irradiated with a spot diameter of 100 μm. In this case, the laser intensity on the surface of the cryo-target band 23 is about 10¹²W / cm²It becomes.
[0058]
Plasma 24 is generated in the cryo-target band 23 around the focused irradiation point 30 by focused irradiation of the pulse laser beam 31. After the generated plasma is extinguished, the cryomaterial generates a vaporized gas 34 and generates fine particles (debris) 35. After this, a crater-like trace 36 is generated in the cryo-target zone 23. This trace 36 exposes the target groove 51 around the focused irradiation point 30. However, the thickness of the cryomaterial directly scattered as plasma by the pulsed laser beam 31 having a focused spot diameter of about 100 μm is an ablation rate type that is experimentally measured in the case of a cryotarget material made of xenon (Xe). From this, the depth is up to about 30 μm. The fact that craters with a depth greater than this actually occur is due to conduction heating by plasma and shock waves. Therefore, if the thickness of the cryotarget layer remaining after the cryotarget material is vaporized as plasma is sufficiently thick against the shock wave, the surface of the copper covered with, for example, a tungsten alloy of the rotating body 11 as the substrate material is damaged. Not receive.
[0059]
On the other hand, to obtain a stable pulse X-ray 32 by operating the pulse laser at a repetition frequency of 300 Hz to 6000 Hz, it is necessary to irradiate the surface of the new cryo-target band 23 for each pulse. Therefore, the number of rotations per minute is obtained as the rotational speed of the rotating body 11 from the distance from the focused irradiation point 30 to the next focused irradiation point on the surface of the cryotarget band 23 and the radius and angular velocity of the rotating body 11. It is done.
[0060]
That is, the above-described trace 36 is replenished with cryomaterial from the cryotarget material supply nozzle 21 for re-use. Therefore, in the relationship between the time required for replenishment and the number of cryotarget material supply nozzles 21 on one circumference of the cryotarget groove 51, if necessary, not only the rotating body 11 is rotated by the rotating shaft but also the axis of rotation. By reciprocating in the direction, the same location on the surface of the cryo-target band 23 is overlapped within a short time so that the pulse laser beam 31 is not irradiated. That is, a plurality of target grooves 51 are formed on the side surface of the rotating body 11 shown in the figure. The apparatus is configured to spray the cryomaterial from the cryotarget material supply nozzle 21 onto the crater-like trace 36 during the rotation of the rotating body 11 and immediately repair the trace 36.
[0061]
Further, as shown in FIG. 7, the surface velocity υ (= ω × r) of the cryo-target band 23 is obtained from the product of the angular velocity ω of the rotating body 11 and the radius r to the surface. On the other hand, the speed υ is perpendicular to the surface of the rotating body 11 by the irradiation of the pulse laser beam 31._DThe fine particles (debris) diverging at (_D ²+ Υ²)^1/2  Therefore, it moves inclining in the direction of the surface speed υ.
[0062]
On the other hand, the exhaust nose 53 opens at this position. That is, the gas amount Q that can be exhausted is equal to the product of the exhaust speed S and the degree of vacuum (pressure) P, but as described above, the pressure in the vacuum chamber 10 is 10^-3The order must be less than Torr. On the other hand, the pressure in the exhaust nose 53 is 10^-2Since the exhaust device 40 shown in FIG. 1 sucks air, the particulates and gas sucked into the exhaust nose 53 are efficiently exhausted.
[0063]
Next, an embodiment different from the above will be described with reference to FIGS. 9 and 10 together.
[0064]
The difference between this embodiment and that described above is the rotating body 61 having no target groove and the pressure collecting wall 62 having a notch at the tip. The pressure collecting wall 62 slides on the surface of the rotating body 61, scrapes and compresses the crystal particulate cryomaterial of the cryotarget layer 22 deposited on the surface, and compresses to form the cryotarget band 63. Therefore, the inner wall of the pressure collecting wall 62 has a shape that narrows toward the notch at the tip, and the shape of the notch determines the cross-sectional shape of the cryotarget band 63.
[0065]
As described above, the molded cryo-target band 63 has at least the width of the condensing spot diameter of the laser beam and the thickness commensurate with the amount of the cryo-target material that evaporates and diffuses due to the plasmatization. Further, the cryo-target band 63 is formed by the pressure collecting wall 62 so that the cross section thereof is a small mountain having a base that can minimize the gasification of the cryo material.
[0066]
Here, the shape in which the rotor substrate has no target groove has been described, but it is desirable to form a cryotarget layer by providing a shallow target groove in order to form a stable cryotarget band.
[0067]
Further, as explained when referring to FIG. 8 above, if the thickness of the cryotarget layer left after the cryotarget material is vaporized as plasma is sufficiently thick against the shock wave, the rotating body that is the substrate material Although the surface of 11 is not damaged, it is conceivable that a buffer material is further inserted into the surface of the rotating body 11 if necessary.
[0068]
Next, an embodiment different from the above using a cushioning material will be described with reference to FIGS. 11 and 12 together.
[0069]
A fundamental difference between this embodiment and the above-described one is that a gas, for example, carbon dioxide gas (for example, carbon dioxide gas) is used between the surface of the rotator 71 and the cryotarget band 74 to avoid damage to the substrate of the rotator 71 due to plasma. CO₂) From a liquefied state to a solid state to form a buffer layer 73 of dry ice. As a result, since the amount of the cryotarget material such as xenon (Xe) that becomes the cryotarget band 74 can be minimized, it is possible to suppress the amount of gasification and micronization of the cryotarget material by transpiration. Therefore, the generated pulse X-ray 32 is not attenuated in the vacuum chamber.
[0070]
That is, as shown in the drawing, the buffer material supply nozzle 70 that supplies the gas that becomes the buffer layer 73 is disposed on the cryotarget band 74 at a position upstream of the cryotarget material supply nozzle 21.
[0071]
In addition, a target groove 72 having a concave cross section is formed on the surface of the rotating body 71 so that the buffer layer 73 can form a thickness between the cryotarget band 74 and the substrate surface of the rotating body 71. .
[0072]
Further, the pressure collecting wall 75 slides on the surface of the rotating body 71, scrapes and compresses the crystal particulate cryomaterial of the cryotarget layer 74 deposited on the surface, and compresses to form the cryotarget band 76. The inner wall of the pressure collecting wall 76 has a shape that narrows toward the notch at the tip, and the shape of the notch determines the cross-sectional shape of the cryotarget band 76. The cryo-target band 76 has a small mountain structure in which the cross section has a skirt as described above.
[0073]
The gas material used as the buffer layer 73 has a liquefaction and solidification temperature greatly different from that of a cryomaterial such as xenon, so that the separation of both is easy.
[0074]
In the above description, the plurality of cryotarget bands are provided in parallel to the rotation axis direction on the side surface of the rotator and concentrically around the rotation axis on the bottom surface. However, the cryotarget bands may be spiral. In this case, the positions of the pressure collecting wall and the exhaust nose tip are fixed or moved and adjusted in the axial direction of the rotating body or in the direction perpendicular to the axis.
[0075]
Thus, in the above description, the appropriate conditions are shown and described with reference to the drawings. However, the configuration and combination such as the shape size and the mutual position shown and described are related to each other together with environmental conditions. However, the present invention is not limited to the above description as long as the functions described above are satisfied.
[0076]
【The invention's effect】
As described above, according to the present invention, a cryo-target band is formed by scraping and pushing a crystal target cryo-target material by a pressure collecting wall on the surface of a rotating body with good heat conduction efficiency cooled by a cryogenic fluid or the like. In addition, a focused irradiation point of the pulse laser beam is placed at the center. Since the cryo-target zone has such a size that the plasma generated inside does not damage the wall of the rotor substrate, only the cryo-target material forming the cryo-target zone is transpiration and scatter. Accordingly, it is possible to avoid transpiration and scattering of the cryotarget material more than necessary due to conduction heating by plasma and shock waves.
[0077]
As a result, the amount of gas released from the cryomaterial in the vacuum chamber is greatly reduced, so that the generated X-rays are absorbed. As a result, the power of the exhaust device can be greatly reduced, resulting in a great economic effect. In particular, fine particle recovery immediately after the generation of plasma X-rays further improves such an effect.
[Brief description of the drawings]
FIG. 1 is a diagram showing an embodiment of an outline of a longitudinal section in the present invention.
2 is a view showing an embodiment of a groove portion on a side surface of a rotating body in FIG. 1. FIG.
FIG. 3 is a diagram showing an embodiment of a partial cross section in FIG. 2;
FIG. 4 is a diagram showing an embodiment of a cross section of a main part of a rotating body in FIG.
5 is a diagram showing an embodiment of a development plane and its cross section in the vicinity of the focused irradiation point in FIG. 4; FIG.
6 is a view showing an embodiment of a transverse section and a front section according to the pressure collecting wall of FIG. 5;
7 is a view showing an embodiment according to the exhaust nose of FIG. 5; FIG.
FIG. 8 is a diagram showing an embodiment of the description relating to the process of X-ray generation according to the present invention.
9 is a diagram showing an embodiment of a development plane and its cross section in the vicinity of a focused irradiation point different from FIG.
10 is a diagram showing an embodiment of a transverse section and a front section according to the pressure collecting wall of FIG. 9;
11 is a diagram showing an embodiment of a cross section of a main part of a rotating body different from FIG.
12 is a diagram showing an embodiment of a cross section in the cryo-target band portion of FIG. 11. FIG.
FIG. 13 is a perspective view showing an example of the prior art.
FIG. 14 is a diagram showing an example of a conventional vertical cross-sectional outline.
FIG. 15 is a diagram illustrating an example of a description relating to a conventional X-ray generation process;
[Explanation of symbols]
10 Vacuum chamber
11, 61, 71 Rotating body
12 Rotating shaft
13 Cryogenic fluid
20 Target material supply section
21 Cryotarget material supply nozzle
22, 74 Cryotarget layer
23, 63, 76 Cryo target zone
30 Focusing point
31 Pulsed laser beam
32 Pulse X-ray
33 X-ray mirror
34 Vaporized gas
35 Fine particles (debris)
36 Traces
40 Exhaust system
41 Recovery tank
50 fixed wall
51, 72 Cryo target groove
52, 62, 75 Pressure collection wall
53 Exhaust nose
70 Buffer material supply nozzle
73 Buffer layer

Claims (4)

A cryo-target material that is chemically inert, gaseous at room temperature, liquefied when cooled, and changes from a liquid state to a solid state in a gaseous state, has a rotation axis, and rotates around the rotation axis. In addition, a cryo-target layer that has a cylindrical shape with good thermal conductivity and is supplied to and attached to the surface of a rotating body that is cooled to a very low temperature and has a predetermined thickness on the surface has high peak power. It has a width that is equal to or larger than the spot size when repeatedly irradiating pulsed laser light, and a thickness that secures an amount that is equal to or more than the amount of the cryotarget material that evaporates and scatters when focused and irradiated with the pulsed laser light. In the laser plasma X-ray generator, which is one or a plurality of ring-shaped cryotarget bands that form a circle on the surface of the rotating body ,
The cryo-target material of the rotating body that rotates is fixedly arranged with respect to the surface of the rotating body and scrapes the cryo-target material attached to the surface of the rotating body around the cryo-target band to form a predetermined shape. A laser plasma X-ray generator, further comprising a pressure collecting wall that is pushed in to create the cryotarget band.   2. The cryotarget material according to claim 1, wherein the cryotarget material supply port ejects the cryotarget material having a concentration close to a liquid state, which has been cooled in advance, to the surface of the rotating body to form the cryotarget band in a crystalline fine particle state. A laser plasma X-ray generator characterized by being a supply nozzle.   The buffer material according to claim 1, wherein the buffer material is a buffer layer between the cryotarget band and the surface of the rotator, which is gaseous at room temperature and is liquefied when cooled and further changes from a liquid state to a solid state. A laser plasma X-ray generator, further comprising a buffer material supply nozzle that is supplied to and attached to the surface of the substrate.   The tangential direction of the cryotarget band according to claim 1, wherein the cryotarget material ejected from the focused irradiation point by the focused irradiation of the pulsed laser light is based on the rotation direction of the rotating body from the focused irradiation point. A laser plasma X-ray generator, further comprising an exhaust nose that collects and exhausts at an upper portion.

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