JP2012004060A - X-ray source and adjusting apparatus and method for the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an X-ray tube in which an opening portion of an NA aperture can be adjusted while keeping a focus size without opening a vacuum container.SOLUTION: An X-ray source has a vacuum container 11 provided with a transmission target 37. An electron source 16 for generating an electron beam 44 is mounted in the vacuum container 11. A convergent lens for converging the electron beam 44 generated by the electron source 16 is mounted in the vacuum container 11. An aperture 38, which has an opening portion 39, sets an open angle of the electron beam 44 converged by the convergent lens 18, and allows the electron beam 44 to be incident to the transmission target 37, is disposed so as to be movable with respect to the vacuum container 11. The X-ray source has a position adjusting mechanism 43 capable of adjusting the position of the opening portion 39 of the NA aperture 38 in a radial direction through an operation from the outside of the vacuum container 11.

Description

  Embodiments described herein relate generally to an X-ray source including an aperture for setting an opening angle and a current amount of an electron beam converged by an electron optical system, an adjustment apparatus, and an adjustment method thereof.

  A general X-ray source having a micro focus has already been commercialized as a micro focus X-ray source, and is widely used in a non-destructive inspection apparatus for inspecting a micro area of an object with high resolution. In this X-ray source, an electron beam emitted from an electron source is converged by an electromagnetic lens, converged and incident on a narrow area of the target surface in the order of μm or less, and X-rays emitted there The structure which permeate | transmits and discharge | releases is taken.

  In order to focus the electron beam on a small spot with a certain amount of current value, it is important to design the electron source and the electromagnetic lens with matching, but at present, by making various efforts. A microfocus X-ray source approaching 0.1 μm has been achieved.

  Here, an X-ray source that performs transmission imaging of an inspection object with high resolution is required to have the above-mentioned micro focus in order to ensure spatial resolution. On the other hand, high contrast is ensured. Therefore, it is important to be able to emit X-rays having appropriate energy. This is because when the X-ray energy used is too high when performing transmission imaging of a micro area of the inspection site, the captured image does not have sufficient contrast (shading), and it is impossible to determine the presence or absence of defects. .

  Most current microfocus X-ray sources are driven at a high voltage of 70 kV or higher or 150 kV or higher to emit high-energy X-rays. However, when the object to be inspected is a small sample of several tens of μm, or the constituent element is a light element having a small X-ray attenuation rate, particularly an organic substance, the X-ray energy to be used is 30 keV or less. In some cases, it is necessary to use a soft X-ray region of 5 keV or less. Furthermore, in recent years, there has been an increasing demand for high-resolution inspections for product fields that make heavy use of organic materials, pharmaceutical fields, and minute objects composed of light elements that lead to cells. The practical application of a microfocus X-ray source capable of emitting low-energy X-rays covering the soft X-ray region of the industry is very suitable for industrial needs.

JP 2009-26600 A

  However, the micro focus X-ray source compatible with the current high energy cannot be maintained simply by operating with a reduced drive voltage, and the design has been changed so that it can be used for low voltage drive without changing its configuration. By doing so, it is not easy to keep the focus size limit that can be achieved within a satisfactory range.

  Therefore, although an X-ray tube to which an electron optical system using an electrostatic lens having a simple configuration as described in Patent Document 1 is effective, in the case of the configuration described in Patent Document 1, Since the beam trajectory and the profile correction mechanism are not provided, it is important to make the eccentricity and inclination accuracy of each electrode constituting the electrostatic lens as high as possible. In particular, the NA aperture for determining the spread (opening angle) and current amount of the electron beam incident on the target is provided with a hole (opening) having a diameter of 0.1 to 0.2 mm, for example. It must be mounted with sufficient accuracy (generally within an allowable eccentricity ± 10 μm) so that the center and the center axis of the electron beam coincide.

  In the conventional microfocus X-ray tube having a small and sealed tube structure configured as described above, in order to guarantee the basic performance of the focus size and the amount of electron beam current incident on the target, the electron gun unit It is most important to maintain the axial accuracy of the X-ray tube. However, in general, an X-ray tube is subjected to a thermal cycle by baking at a high temperature to suppress the amount of released gas, so the amount of eccentricity before and after the baking treatment It is not easy to completely eliminate. If the amount of eccentricity exceeds the specified range, an operation of opening the tube and repairing the electron gun unit is required, which requires a lot of labor.

  The present invention has been made in view of the above points, and provides an X-ray source capable of adjusting the position of the aperture opening without opening the vacuum vessel while maintaining the focal spot size, and an adjustment device and adjustment method thereof. For the purpose.

  The X-ray source of the embodiment includes a vacuum container provided with a transmission target. The X-ray source has an electron source that is housed in a vacuum vessel and generates an electron beam. Further, the X-ray source has an electron optical system that is housed in a vacuum vessel and converges an electron beam generated by the electron source. The X-ray source has an aperture, is movably arranged with respect to the vacuum vessel, and has an aperture that sets an opening angle of the electron beam converged by the electron optical system and makes it incident on the transmission target. Furthermore, the X-ray source has a position adjustment mechanism that can adjust the position of the opening of the aperture in the radial direction by an operation from the outside of the vacuum vessel.

It is explanatory drawing of the X-ray source which shows 1st Embodiment. It is explanatory drawing of the adjustment apparatus of an X-ray source same as the above. It is explanatory drawing of the adjustment apparatus of the X-ray source which shows 2nd Embodiment.

  The configuration of the first embodiment will be described below with reference to the drawings.

  FIG. 1 is an explanatory diagram of the X-ray source.

  An X-ray tube 10 which is an X-ray source has a vacuum container 11 in which the inside is held in vacuum. It is an X-ray tube having a holding part 13 and a deformable structure 14 that holds the holding part 13 with respect to the vacuum vessel body 12. Further, inside the vacuum vessel 11, an electron source 16, an extraction electrode 17, and a converging lens 18 which is an electron optical system are housed.

  The vacuum vessel main body 12 includes a cylindrical vessel portion 21 having a holding portion 13 connected to one end side via a deformable structure 14, and the other end side of the vessel portion 21 via an insulating cylinder 22 that is an insulator. A metal plate part 23 as a connection part is connected to the other end side of the metal plate part 23 via an insulating cylinder 24 as an insulator, and the metal plate part 25 is connected to the metal plate part 25 as a connection part. A metal plate portion 27 that is a connecting portion is connected to the other end side via an insulating cylinder 26 that is an insulator, so that a substantially bottomed cylindrical shape is formed. In addition, introduction terminals 28 and 28 are disposed on the metal plate portion 27, and the introduction terminals 28 and 28 are electrically connected to the drive power supply 29 together with the metal plate portions 23, 25 and 27.

  The container part 21 is formed with a grounding part 31 for setting the container part 21 to the ground potential.

  The holding portion 13 is integrally provided with a substantially cylindrical holding portion main body 33 and a flange portion 34 that extends outward from the entire periphery of the peripheral portion of the holding portion main body 33. The holding portion 13 is movable in the radial direction by an alignment (positioning) screw 35 that is a plurality of screws screwed into the container portion 21 of the vacuum vessel main body 12 of the vacuum vessel 11.

  The holding part main body 33 has an X-ray emission window 36 opened at the center on one end side, and a transmission target 37 such as tungsten is attached and held in the X-ray emission window 36. Further, an NA (variable aperture) aperture 38 as an aperture is attached to the other end side of the holding portion main body 33 at a position facing the X-ray emission window 36. The NA aperture 38 has an opening 39 at the center.

  Each of the alignment screws 35 is arranged along, for example, four locations on the top, bottom, left, and right as viewed from the axial direction, that is, along two directions (X direction and Y direction) that intersect (orthogonal) each other. Each of the formed screw holes 40 is screwed, and the proximal end side is located outside the container portion 21, that is, the vacuum vessel 11, and the distal end side is inserted inside the container portion 21, that is, the vacuum vessel 11, and the flange portion of the holding portion 13 It is in contact with the outer periphery of 34. Further, these alignment screws 35 can be moved back and forth along the radial direction intersecting (orthogonal) with the axial direction of the vacuum vessel 11 (X-ray tube 10) by rotating. 13 and NA aperture 38 (and transmission target 37) are configured to move in the radial direction.

  Further, the deformable structure 14 is obtained by joining the flange portion 34 of the holding portion 13 and the holding portion connecting portion 41 formed inwardly projecting to one end side of the container portion 21 of the vacuum vessel main body 12. 11 is configured to maintain the internal airtightness. The deformable structure 14 is a member that can be bonded to the surrounding vacuum vessel body 12 and can withstand high temperatures during baking, such as a deformable (easily deformable) metal such as copper. It is formed in a cylindrical shape by a member, and is configured to absorb the movement distance of the holding portion 13 moved by the alignment screw 35 by deformation. The deformation structure 14 has a limit of about ± 50 μm so that the deformation for absorbing the moving distance of the holding unit 13 does not cause a crack or the like and impair the airtightness of the vacuum vessel 11. . Then, with this deformable structure 14, each alignment screw 35, and the holding portion 13, the position adjustment that can adjust the radial position of the NA aperture 38 (and the transmission target 37) by an operation from the outside of the vacuum vessel 11 A mechanism 43 is configured.

  On the other hand, the electron source 16 generates an electron beam 44, and is generally used as an electron source for an electron microscope, such as a TFE (Thermal Field Emission) electron source as a typical example. There is something that has been. The electron source 16 has an emitter 45 as a main component, and the emitter 45 has a configuration in which an emitter tip 45b joined to the tip of a filament 45a is covered with a cylindrical suppression electrode 46.

  Further, the electron source 16 is fixed to the converging lens 18 via a flange portion 47 as an electron source fixing portion connected around the suppression electrode 46. This flange portion 47 protrudes in the radial direction with respect to the suppression electrode 46 and is connected to a cylindrical mounting flange 52 as a lens mounting portion for mounting in the converging lens 18 via an insulating tube 51 as an insulator. Has been. Further, the flange portion 47 is electrically connected to the metal plate portion 27 via an energization rod 53 as an energization member. Therefore, the suppression electrode 46 is electrically connected to the drive power supply 29 via the energizing rod 53 and the metal plate portion 27, and is configured to receive a predetermined current and voltage from the drive power supply 29. The suppression electrode 46 is capable of suppressing the emission of electrons from the peripheral portion other than the tip of the emitter chip 45b when a negative voltage is applied from the drive power supply 29.

  In addition, the extraction electrode 17 is joined to one end side of the built-in flange 52. Further, the built-in flange 52 is electrically connected to the metal plate portion 25 via an energizing rod 55 as an energizing member.

  Further, the extraction electrode 17 is connected between the emitter 45 via the insulating cylinder 51. Therefore, the extraction electrode 17 is electrically connected to the drive power supply 29 via the built-in flange 52, the energizing rod 55, and the metal plate portion 25, and is supplied with a predetermined current and voltage from the drive power supply 29. It is configured. Therefore, a positive voltage is applied to the emitter 45 from the drive power supply 29 to the extraction electrode 17 so that electrons emitted from the tip of the emitter tip 45b are extracted as an electron beam 44. The extraction electrode 17 is formed in an annular shape, and the center of the extraction electrode 17 is aligned with high accuracy with respect to the tip of the emitter tip 45b. The electron source 16, the flange portion 47, the suppression electrode 46, the built-in flange 52, the extraction electrode 17, and the like constitute an integral unit portion 58.

  The converging lens 18 converges, deflects, and corrects the aberration of the electron beam 44 extracted by the extraction electrode 17, and transmits through the opening 39 of the NA aperture 38 that sets the opening angle and current amount of the electron beam 44. An annular first lens electrode 62 serving as a first electrode is supported by a lens housing 61 that is a cylindrical lens body serving as a support member and is incident on the target 37. In addition, an annular lens second electrode 64 as a second electrode is supported at one end of the lens housing 61 via an insulating cylinder 63 as an insulator, and a tube is provided outside the insulating cylinder 63. A cylindrical built-in portion 65 is formed so as to protrude, and an annular lens third electrode 66 as a third electrode is supported at one end of the built-in portion 65. An attachment portion 69 is disposed on the other end of the lens housing 61 via an insulating cylinder 68 as an insulator, and a unit portion 58 is provided on the attachment portion 69 via a fixing screw 70 as a fixing member. It is fixed. Therefore, only the lens second electrode 64 is supported while being insulated from the other electrodes 62 and 66. Further, the lens housing 61 (unit part 58) is fixed to an attached part 72 that is formed to project from the container part 21 of the vacuum container body 12 of the vacuum container 11 via an attachment screw 71 as an attachment member. Yes.

  Further, the second lens electrode 64 is electrically connected to the metal plate portion 23 via an energizing rod 73 as an energizing member. Therefore, the second lens electrode 64 is electrically connected to the drive power source 29 via the energizing rod 73 and the metal plate portion 23, and is configured to receive a predetermined current and voltage from the drive power source 29. Yes.

  Then, the hole centers of the other electrodes 62 and 66 are aligned and joined to the hole center of the second lens electrode 64 with high accuracy. Similarly, the center of the opening of the mounting portion 69 and the built-in portion 65 is processed with high accuracy with respect to the axial center (reference axis A) of the electrodes 62, 64, 66.

  Specifically, the tip of the emitter chip 45b and the centers of the extraction electrode 17, the lens first electrode 62, the lens second electrode 64, and the lens third electrode 66 are, for example, 100 μm or less with respect to the reference axis A, If a general high-precision processing technique is applied, it becomes possible to give an accuracy of 50 μm or less, for example.

  FIG. 2 shows an adjusting device 75 for the X-ray tube 10.

  The adjusting device 75 performs an alignment operation of the NA aperture 38 while measuring the intensity of the X-ray 76 emitted from the X-ray tube 10, and includes an X-ray shielding cover 77 covering the X-ray tube 10, An X-ray intensity meter 78 for detecting the intensity of X-rays 76 emitted from the X-ray tube 10 and a plurality of alignment jigs as operation mechanisms for operating the alignment screws 35 from the outside of the X-ray shielding cover 77, respectively. 79 and.

  The X-ray intensity meter 78 is disposed opposite to the X-ray tube 10 at a position separated from one end side of the X-ray tube 10 inside the X-ray shielding cover 77.

  Each alignment jig 79 is inserted into the X-ray shielding cover 77 through an opening 81 having a tip 79a formed in the X-ray shielding cover 77, and is fitted to each alignment screw 35. At the same time, the base end 79 b is located outside the X-ray shielding cover 77. These alignment jigs 79 can rotate the alignment screw 35 by operating the base end 79b.

  Next, the operation of the X-ray tube 10 will be described.

  As shown in FIG. 1, when the X-ray tube 10 is assembled, the mounting flange 52 of the electron source 16 and the mounting portion 69 of the converging lens 18 are fitted and assembled with high accuracy. The unit 58 is completed by fixing the electron source 16 and the converging lens 18 combined in such a configuration and procedure using the fixing screw 70.

  The unit portion 58 is attached and fixed to the inside of the vacuum vessel 11 by an attachment screw 71. In this state, the center of the unit portion 58 and the center position of the opening 39 of the NA aperture 38 held by the holding portion 13 are aligned with high accuracy. Thereafter, the inside of the vacuum vessel 11 is evacuated and sealed until the ultimate vacuum necessary for the operation of the unit 58 is reached. Furthermore, in the X-ray tube 10, the vacuum vessel 11 is baked at a predetermined temperature to suppress the amount of released gas.

  A drive power supply is supplied to the emitter 45 inside the X-ray tube 10 and the electrodes 62, 64, 66 of the converging lens 18 via the introduction terminals 28, 28 of the X-ray tube 10 and the metal plate portions 23, 25, 27. A predetermined voltage and current are supplied from 29. By this operation, the electron beam 44 emitted from the emitter 45 and extracted by the extraction electrode 17 is converged by the converging lens 18 to form a focal point (convergence spot) on the surface of the transmission target 37, from which the X-ray 76 is converted into the X-ray. It is emitted to the outside of the X-ray tube 10 through the emission window 36.

  When adjusting the X-ray tube 10, the X-ray tube 10 is attached to the adjusting device 75, and then the X-ray tube 10 covered with the X-ray shielding cover 77 is operated to focus the surface of the transmission target 37 ( The X-ray 76 is measured by the X-ray intensity meter 78 while the X-ray 76 is emitted from the convergence spot).

  Then, by adjusting the radial position of the NA aperture 38 (and the transmission target 37) together with the holding unit 13 using the alignment jig 79 so that the intensity measured by the X-ray intensity meter 78 is maximized, the NA The center of the aperture 38 is aligned with the center of the mounting flange 52 with high accuracy.

  In the micro-focus type X-ray tube 10 having a small and sealed tube structure configured as described above, in order to guarantee the basic performance of the focus size and the amount of current of the electron beam 44 incident on the transmission target 37, the unit It is most important to maintain the axial accuracy of the part 58 and the NA aperture 38. However, since a thermal cycle by baking is added to this, the accuracy is lowered due to deformation caused by thermal expansion, and before and after the treatment. It is difficult to completely eliminate the amount of eccentricity. Further, when the amount of eccentricity exceeds the specified range, an operation of opening the vacuum vessel 11 and repairing the positions of the unit portion 58 and the NA aperture 38 is required, which requires a lot of labor.

  Therefore, according to the first embodiment, when a sufficient amount of the electron beam 44 cannot pass through the opening 39 of the NA aperture 38 due to the application of the thermal cycle of baking, or the shape of the focal point is uniform. In the case where the shape has changed from a circle to an ellipse, the center of the opening 39 of the NA aperture 38 inside the X-ray tube 10 is corrected and adjusted to the specified position from the outside of the vacuum vessel 11 of the X-ray tube 10. The predetermined performance can be achieved. That is, even when the eccentricity exceeding the specified value occurs in the baking heat cycle, the aperture 39 of the NA aperture 38 is not opened without opening the vacuum vessel 11 (X-ray tube 10) while maintaining the fine focal spot size. The position can be adjusted easily.

  In addition, since the center of the opening 39 of the NA aperture 38 can be corrected and adjusted in this way, the predetermined performance of the X-ray tube 10 can be achieved.

  Further, the intensity of the X-ray 76 emitted from the transmission target 37 is measured by an X-ray intensity meter 78, and the position is adjusted from the outside of the X-ray shielding cover 77 so that the measured intensity of the X-ray 76 becomes the maximum value. By operating the mechanism 43 and adjusting the radial position of the opening 39 of the NA aperture 38, the position of the NA aperture 38 can be easily adjusted to an optimum point.

  Next, a second embodiment will be described with reference to FIG. In addition, about the structure similar to the said 1st Embodiment, the same code | symbol is attached | subjected and the description is abbreviate | omitted.

  In the second embodiment, the adjusting device 75 performs the same alignment operation of the NA aperture 38 of the X-ray tube 10 as in the first embodiment while observing the X-ray focal point shape of the emitted X-ray 76. To implement.

  In other words, the adjustment device 75 uses the test chart 85 for determining the X-ray focal shape and the X-ray imaging unit 86 as an X-ray detector capable of monitoring the transmitted image, so that the X-ray focal shape is uniform. So that the adjustment can be made.

  The X-ray imaging unit 86 outputs a monitor 88 disposed outside the X-ray shielding cover 77 and an image signal corresponding to the detected X-ray 76 disposed inside the X-ray shielding cover 77 to the monitor 88. And an X-ray detection unit 89.

  The test chart 85 is irradiated with X-rays 76 emitted from the transmission target 37 of the X-ray tube 10 while the electron beam 44 is emitted by operating the X-ray tube 10 and focused on the transmission target 37. The transmitted image is detected by the X-ray detector 89 and output to the monitor 88 as an image signal. The operator adjusts the center position of the opening 39 of the NA aperture 38 using the alignment jig 79 so that the X-ray focus shape is uniform while monitoring the X-ray focus shape with the monitor 88.

  In this way, the position adjustment mechanism from the outside of the X-ray shielding cover 77 so that the uniformity of the focal shape of the X-ray 76 in the transmission image of the test chart 85 by the X-ray 76 emitted from the transmission target 37 is the best. By operating 43 and adjusting the radial position of the opening 39 of the NA aperture 38, the position of the NA aperture 38 can be easily adjusted to an optimum point.

  According to each of the embodiments described above, the position of the NA aperture 38 is adjusted to an optimum point, and the intensity of the X-ray 76 emitted from the X-ray tube 10 and the uniformity of the focal shape are adjusted to be favorable. It becomes possible.

  In addition, since the position adjustment of the opening 39 of the NA aperture 38 is performed while emitting the X-ray 76, the position adjustment can be performed by the alignment jig 79 from the outside of the X-ray shielding cover 77. Even during the operation of the X-ray tube 10, it is possible to perform a position adjustment operation to align the center of the opening 39 of the NA aperture 38 with the orbital center of the electron beam 44, and this position adjustment becomes easier.

  In each of the above embodiments, the transmission target 37 may be provided at a place other than the holding unit 13 as long as the holding unit 13 holds at least the NA aperture 38.

10 X-ray tube as an X-ray source
11 Vacuum container
13 Holding part
14 Deformation structure
16 electron source
18 Convergent lens, an electron optical system
35 Alignment screw which is a screw
37 Transmission target
38 Aperture NA aperture
39 opening
43 Position adjustment mechanism
44 Electron beam
75 Adjustment device
76 X-ray
77 X-ray shielding cover
78 X-ray intensity meter
79 Jig for alignment as an operation mechanism
85 Test chart
86 X-ray imaging unit as an X-ray detector

Claims (6)

A vacuum vessel with a transmission target;
An electron source housed in the vacuum vessel and generating an electron beam;
An electron optical system that is housed in the vacuum vessel and converges an electron beam generated by the electron source; and
An aperture that includes an opening, is movably disposed with respect to the vacuum vessel, and sets an opening angle of an electron beam converged by the electron optical system to be incident on the transmission target;
An X-ray source comprising: a position adjusting mechanism capable of adjusting a position of an opening of the aperture in a radial direction by an operation from the outside of the vacuum vessel. The position adjustment mechanism
A holding part to which an aperture is attached and which constitutes a part of the vacuum vessel;
A deformable structure that is formed by a deformable member, constitutes a part of the vacuum vessel, and movably supports the holding portion;
The proximal end side is located outside the vacuum vessel, the distal end side is inserted into the vacuum vessel and abuts against the holding portion in the radial direction, and the deformation structure is deformed by advancing and retreating with respect to the vacuum vessel. The X-ray source according to claim 1, further comprising a screw that varies a position of the holding portion in a radial direction. X-ray source according to claim 1 or 2,
An X-ray shielding cover covering the X-ray source;
An operation mechanism for operating the position adjustment mechanism of the X-ray source from the outside of the X-ray shielding cover;
An apparatus for adjusting an X-ray source, comprising: an X-ray intensity meter that detects the intensity of X-rays emitted through a transmission target of the X-ray source. X-ray source according to claim 1 or 2,
An X-ray shielding cover covering the X-ray source;
An operation mechanism for operating the position adjustment mechanism of the X-ray source from the outside of the X-ray shielding cover;
An X-ray source comprising: an X-ray detector capable of detecting X-rays emitted through a transmission target of the X-ray source and outputting an image corresponding to the detected X-rays Adjustment device. A vacuum container provided with a transmission target, an electron source housed in the vacuum container and generating an electron beam, an electron optical system housed in the vacuum container and converging the electron beam generated by the electron source, and An aperture having an opening, movably disposed with respect to the vacuum vessel, and having an opening angle of an electron beam converged by the electron optical system to be incident on the transmission target; and a position of the opening of the aperture An X-ray source adjustment method comprising a position adjustment mechanism that can be adjusted in the radial direction by an operation from the outside of the vacuum vessel,
Covering the X-ray source with an X-ray shielding cover, and emitting the X-rays through the transmission target, the position adjusting mechanism is arranged from the outside of the X-ray shielding cover so that the X-ray intensity reaches a maximum value. Adjusting the radial position of the aperture of the aperture by operating. A method of adjusting an X-ray source. A vacuum container provided with a transmission target, an electron source housed in the vacuum container and generating an electron beam, an electron optical system housed in the vacuum container and converging the electron beam generated by the electron source, and An aperture having an opening, movably disposed with respect to the vacuum vessel, and having an opening angle of an electron beam converged by the electron optical system to be incident on the transmission target; and a position of the opening of the aperture An X-ray source adjustment method comprising a position adjustment mechanism that can be adjusted in the radial direction by an operation from the outside of the vacuum vessel,
Covering the X-ray source with an X-ray shielding cover and emitting X-rays through the transmission target, so that the X-ray focus shape uniformity in the transmission image of the test chart by the X-rays is the best. An X-ray source adjustment method, wherein the position adjustment mechanism is operated from the outside of the X-ray shielding cover to adjust the radial position of the opening of the aperture.

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