Patent Number: 060318899
Section: description

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic cross sectional view of an acoustic delay line of a beam line according to an embodiment of the invention. This acoustic delay line is used, for example, in place of the vacuum duct 57 of the X-ray exposure system shown in FIG. 9. At the downstream of the mirror box 54 shown in FIG. 9, a vacuum duct 57 is connected, at the downstream of which a beam line large-diameter outer tube unit 1 is connected. An inner tube 2 is installed inside of the large-diameter outer tube unit 1. The inner tube 2 is used as an envelope of an optical path of radiated light. A radiated light output frame 3 is coupled to the tip of the inner tube 2 on the downstream side thereof. A flange 5 mounted at the downstream end of the large-diameter outer tube unit 1 and the radiated light output frame 3 are hermetically sealed by a vacuum bellows 4. Drivers 6.sub.1 and 6.sub.2 are mounted on the lower wall of the large-diameter outer tube unit 1 at opposite end portions. The drivers 6.sub.1 and 6.sub.2 drive the inner tube 2 in a vertical direction while supporting it. The inner tube 2 is driven synchronously with a pivotal motion of the mirror 55 (FIG. 9) to establish an optical path of radiated light. A plurality of partition plates 7 are disposed inside of the large-diameter outer tube unit 1 at a predetermined pitch along the axial direction. Each of these partition plates 7 is formed with an opening 7' at the central area of the plate, the opening 7' having a size not to obstruct the up/down motion of the inner tube 2. These juxtaposed partition plates 7 are coupled together by coupling bolts 8. A plurality of partition plates 9 are formed on the outer circumference of the inner tube 2 at positions corresponding to the partition plates 7. Each pair of the partition plates 7 and 9 is preferably disposed at a gap of 1 mm or smaller. The partition plates 7 and 9 divide the inner space of the large-diameter outer tube unit 1 into a plurality of partitioned spaces 10. A number of holes 2' are formed in the upper and lower walls of the inner tube 2 to communicate each partitioned space with the inner space of the inner tube 2. Although the number, size and shape of holes 2' is optional, it is preferable to set the total opening area of holes 2' in one partitioned space 10 larger than the opening area of the inner tube 2 in the cross section vertical to the center axis of the tube 2, and it is more preferable to set the former ten times larger than the latter. The inside of the large-diameter outer tube unit 1 is evacuated via a vacuum exhaust port D formed in the wall of the large-diameter outer tube unit 1 at generally the central partitioned space 10. The detailed structure of the beam line of this embodiment will be described with reference to FIGS. 2 to 4. FIG. 2 is a vertical cross sectional view of the beam line, taken along the center axis of the beam line, and FIGS. 3 and 4 are cross sectional views taken along respective one-dot chain lines A--A and B--B shown in FIG. 2. Each of the drivers 6.sub.1 and 6.sub.2 for the inner tube 2 is constituted of: a bearing case 13 with an internal linear guide bearing 12; a guide shaft 15 having a fork at its one end; a linear actuator 16 fixed to the bearing case 13; a coupling plate 17 for coupling the movable part of the actuator 16 and the guide shaft 15; and a vacuum bellows 18. The vacuum bellows 18 is coupled between the one end of the guide shaft 15 and the bearing case 13 to retain the vacuum degree of the inside of the large-diameter outer tube unit 1. The bearing cases 13 of the drivers 6.sub.1 and 6.sub.2 are mounted on flanges 11.sub.1 and 11.sub.2 provided at the lower wall of the large-diameter outer tube unit 1. Coupling plates 19 are fixed to the forks 14 of the inner tube 2. Each coupling plate 19 and corresponding fork 14 are coupled together by a pin 20. The radiated light output frame 3 has a disk-like shape, and a rectangular or arc-shaped window matching a cross section of a radiated light flux is formed in the frame 3 at its central area. The window is hermetically sealed with a beryllium thin film 21 which is welded or soldered to the output frame 3. The output frame 3 is coupled to the flange 5 of the large-diameter outer tube unit 1 via the vacuum bellows 4 and flanges 3' and 5'. As shown in FIGS. 3 and 4, the cross section of the inner tube 2 has a shape covering the radiated light flux. As shown in FIG. 2, one end of the inner tube 2 is mounted on a flange 3" of the radiated light output frame 3, and the other end thereof protrudes from the large-diameter outer tube unit into the upstream vacuum duct 5. The drivers 6.sub.1 and 6.sub.2 drive the inner tube 2 in the vertical direction and receive a force in the horizontal direction generated by a pressure difference between the atmospheric pressure applied to the radiated light output frame 3 and the vacuum pressure in the large-diameter outer tube unit 1. The drivers 6.sub.1 and 6.sub.2 are driven by a signal supplied from a synchronizing means 81, synchronously with the operation of the driver 56 shown in FIG. 9. As shown in FIG. 4, for the convenience of assembly, each partition plate 7 of the large-diameter outer tube unit 1 is divided into upper and lower pieces which are coupled together by coupling plates 22 with screws. After the inner tube 2 and partition plates 9 are assembled integrally, they are assembled in the large-diameter outer tube unit 1. A sensor head 23 of a vacuum gauge is mounted on the flange 5. The sensor head 23 measures the vacuum degree in the large-diameter outer tube unit 1 and supplies the measured data to the controller 80 (FIG. 9). The controller 80 monitors a change in the vacuum degree, and when the beryllium thin film is broken, it operates to actuate the high speed shutter valve 66 and shutter valve 65 (FIG. 9) at the upstream positions. It is therefore possible to prevent gas from entering the inside of the synchrotron. The size of the large-diameter outer tube unit constituting the acoustic delay line is about 400 mm in outer diameter and about 2 m in length. In the large-diameter outer tube unit 1 shown in FIG. 1, the two adjacent partitioned spaces 10 communicate with each other via the holes 2' formed in the upper and lower walls of the inner tube 2 and via the internal space of the inner tube 2. If the total opening area of holes 2' in one partitioned space 10 is ten times or more of the cross sectional area of the inner space of the inner tube 2, a resistance applied to the gas flowing between the inner space of the inner tube 2 and its partitioned space 10 is sufficiently small as compared to a resistance applied to the gas flowing through the inner space of the inner tube 2 along its axial direction. Therefore, the structure shown in FIG. 1 can be considered as substantially equivalent to the structure that the two adjacent partitioned spaces 10 communicate with each other via a hole having a cross sectional area of the inner space of the inner tube 2. If the inner tube 2 is not used, the partition plates 9 cannot be mounted so that the two adjacent partitioned spaces 10 communicate with each other via the opening 7'. The cross sectional area of the inner space of the inner tube 2 is smaller than the area of the opening 7'. Therefore, the resistance of the gas flowing in the axial direction increases, and a transport speed of the gas flowing in the large-diameter outer tube unit 1 in its axial direction can be lowered. Next, another embodiment will be described with reference to FIGS. 5 to 8. In the system shown in FIG. 1, the inside of the large-diameter outer tube unit 1 is divided into a plurality of partitioned spaces 10 by the partition plates 7 and 9 superposed at a small gap, and each pair of adjacent partitioned spaces 10 communicates via the inner space of the inner tube 2 and the holes 2' formed in the upper and lower walls of the inner tube 2. It takes, therefore, a long time to evacuate the gas in each partitioned space from the vacuum exhaust port D and obtain a predetermined vacuum degree, when the inside of the large-diameter outer tube unit 1 is evacuated at the initial running stage. FIG. 5 is a schematic cross sectional view of a large-diameter outer tube unit capable of increasing an evacuation speed, according to another embodiment. When the inside of the large-diameter outer tube unit 1 is to be evacuated, the partition plates 7 are driven by a driver 30 to move them in the axial direction of the large-diameter outer tube unit and broaden a gap between the partition plates 7 and 9. In this manner, the evacuation speed can be increased. The detailed structure of the large-diameter outer tube unit of this embodiment will be described with reference to FIGS. 6 to 8. FIG. 6 is a vertical cross sectional view of the large-diameter outer tube unit 1 taken along the center axis of the unit 1, and FIG. 7 is a cross sectional view taken along one-dot chain line C--C of FIG. 6. As shown in FIG. 6, the partition plates 7 are coupled together by a bolt 8. Two brackets 31 are mounted on the lower portion of each partition plate 7. Each bracket 31 has a roller 32 mounted rotatively. FIG. 8 is a perspective view showing the bracket 31 and roller 32. As shown in FIG. 7, the roller 32 becomes in contact with the inner circumference of the large-diameter outer tube unit 1 to movably support the partition plate in the axial direction. As the roller 32 rolls on the inner circumference of the large-diameter outer tube unit 1, the partition plate 7 can move in the axial direction. The driver 30 for moving the partition plates 7 has a similar structure to those of the drivers 6.sub.1 and 6.sub.2 of the inner tube 2 of the first embodiment. Specifically, the driver 30 is constituted of: a bearing case 35 with an internal linear guide bearing 34; a linear actuator 36 fixed to the bearing case 35; a coupling shaft 37 coupled to the outermost partition plate 7; a vacuum bellows 38 for vacuum sealing the space between the coupling shaft 37 and bearing case 35; and a coupling plate 39 for coupling the actuator 36 and coupling shaft 37. The bearing case 35 of the driver 30 is mounted on a flange 5' of the large-diameter outer tube unit 1. The linear actuator 36 has a function of making the motion of the partition plates stop at opposite ends of a motion stroke and a function of generating an electric interlock signal, which indicates the operating status of the beam line. In operation, prior to evacuating the inside of the large-diameter outer tube unit 1, the linear actuator 36 is driven to move the coupling shaft to the left as viewed in FIG. 6. The partition plates 7 therefore move to the left and a space to a corresponding partition plate 9 mounted on the outer circumference of the inner tube 2 is broadened as shown in FIG. 5. In this state, the gas in the large-diameter outer tube unit 1 is discharged from the vacuum exhaust port D, so that the vacuum degree of the inside of the large-diameter outer tube unit 1 can be set to an operating value in short time. After the vacuum degree of the inside of the large-diameter outer tube unit 1 is set to the operating value, the linear actuator 36 is again driven to move the coupling shaft to the right as viewed in FIG. 5 and set each partition plate 7 near to the corresponding partition plate 9. In a state that the partition plate is set near to the corresponding partition plate 9 to such an extent as shown in FIG. 1, an exposure process starts. In the above embodiments, since the inner tube 2 used as an envelope of a light beam flux is swung up and down by the drivers 6.sub.1 and 6.sub.2 synchronously with the up/down scan of the X-ray mirror, the opening of the radiated light output frame 3 can be made narrow. Accordingly, as compared to a conventional large opening, the strength of the beryllium thin film 21 is increased so that breakage thereof can be prevented. Even if the beryllium thin film 21 is broken, there is an increased flow resistance of gas because the cross sectional area of the passage from the opening of the radiated light output frame 3 directly to the upstream is made-small. Furthermore, the gas enters each partitioned space 10 from the holes 2' whose total area is larger than the cross sectional area of the passage, and the gas is trapped by the partitioned space 10, so that the essential function of an acoustic delay line can be provided sufficiently. Accordingly, a time taken to reach the high speed shutter valve can be prolonged, and the gas can be prevented from entering the inside of the synchrotron 50 (FIG. 9). In the embodiments shown in FIGS. 1 and 5, the movable partitions 9 are supported by the inner tube 2. In place of the inner tube 2, a solid support member may be used for supporting the movable partitions 9. FIG. 10 is a schematic cross sectional view of a beam line in which movable partition plates 9 are supported by a solid support member 2a. The support member 2a may be only the upper portion, lower portion, or side portion of the inner tube 2 shown in FIG. 4. With this arrangement, the same advantageous effects as the embodiment shown in FIG. 1 can be expected. The present invention has been described in connection with the preferred embodiments. The invention is not limited only to the above embodiments. It is apparent that various modifications, improvements, combinations, and the like can be made by those skilled in the art.