JP6090896B2 - Insertion light source - Google Patents

Description

  The present invention relates to an insertion light source, and more particularly to an insertion light source that enables generation of radiation light having a wide frequency band and excellent polarization.

  Currently, synchrotron radiation experiments conducted around the world are roughly divided into an X-ray region having a photon energy of 4 keV or more and a VUV (vacuum ultraviolet) to SX (soft X-ray) region of 10 eV to 2 keV. Of these, the X-ray region of 4 keV to 20 keV has many users, and many synchrotron radiation facilities are designed to generate the synchrotron radiation in this region most efficiently. At present, a synchrotron radiation facility having a light source that generates X-rays of 4 keV to 20 keV by combining an electron storage ring having an energy of about 3 GeV and a vacuum-sealed undulator technology has become a global trend. Such 3GeV-class light sources operate in various parts of the world, and there are some that are currently under construction.

  On the other hand, although a VUV-SX ray light source is a minority in terms of the number of users, it is indispensable for research on electronic properties and the like, and is also an indispensable light source for a synchrotron radiation research facility.

  When this radiant light in the VUV-SX ray region is obtained by an undulator in the 3 GeV-class radiant light facility, the photon energy range is generally set to 200 eV to 2 keV by setting the period length of the undulator to 5 cm to 10 cm. Is. However, in recent years, with the development research on surface physics and environmental materials (Li batteries, green memory) at the top, research subjects using synchrotron radiation having energy of 50 eV or less have become increasingly important. For this reason, in one beam line, there is an increasing demand for using a wide range of radiated light with a photon energy range of 20 eV to 2 keV.

  That is, there is a first requirement to realize an insertion light source that can generate radiated light in a wide photon energy range.

  By the way, in order to generate low energy radiation using an undulator suitable for the X-ray region, a method of increasing the magnetic field by increasing the period length can be considered. However, this means that a large amount of harmonic components other than the required wavelength are radiated simultaneously. Thus, the increased radiation power becomes a heat load on the beam line optical element. The presence of this heat load can have a significant adverse effect on experiments in the VUV-SX ray region. This is because light in the same region has a very strong interaction with matter and does not pass through the atmosphere. When carrying out precision experiments in the same area, it is necessary to place all of the measurement equipment from the optical system in an ultra-high vacuum, but distortion caused by thermal loads such as mirrors that have received synchrotron radiation has a significant impact on this precision experiment. There is a possibility of effect.

  That is, in the experiment in the VUV-SX ray region, there is a second request to suppress the thermal load as much as possible.

  In the experiment in the VUV-SX ray region, the polarization characteristic of the emitted light is an important factor. Polarization switching experiments in which left and right circular polarization states are formed and switched to perform measurement are one of the important experimental techniques in synchrotron radiation science and are still widely used today. In recent years, in addition to this, a synchrotron radiation experiment using switching between horizontal and vertical linearly polarized light has become important.

  In other words, in addition to the first and second requirements, there is a need to develop an insertion light source that satisfies the third requirement to switch between horizontal and vertical linearly polarized light.

Japanese Patent Laid-Open No. 10-326700 JP-A-5-303000 JP 2000-206296 A JP-A-8-213199

  The problems described below have arisen in the course of the present inventor's earnest research in view of the above background.

  As an insertion light source that satisfies the above first to third requirements, two undulators (for low energy and high energy) with different period length and polarization are prepared and arranged in tandem (columns) and used exclusively. A way to do this is conceivable. This configuration will be described with reference to FIG.

  The tandem insertion light source 100 shown in FIG. 6 has a configuration in which two undulators 101 and 103 are arranged in series in the beam axis 105 direction. The undulator 101 is arranged so that the magnetic circuit is parallel to the horizontal plane. On the other hand, the undulator 103 is rotated 90 ° with respect to the undulator 101 so that the magnetic circuit is perpendicular to the horizontal plane. Thereby, a vertical magnetic field can be generated in the undulator 101 and a horizontal magnetic field can be generated in the undulator 103.

  Thus, by making the energy range to be handled differently by a plurality of undulators, it becomes possible to generate radiated light in a wide energy range as a whole insertion light source while narrowing the energy range to be handled by one undulator. As a result, it is not necessary to increase the magnetic field so much as compared with the case where the undulator handles radiation light in a wide energy range, and an effect of suppressing the generation of heat load to some extent can be expected.

  Further, each of the undulators 101 and 103 can be composed of magnetic circuits having different cycle lengths. The period length of the magnetic circuit constituting the undulator 101 and the magnetic circuit constituting the undulator 103 can be set independently of each other.

  As described above, the tandem insertion light source 100 satisfies the first and second requirements described above.

  In the tandem insertion light source 100, the vertical magnetic field orthogonal to the beam axis 105 and the horizontal magnetic field orthogonal to the beam axis 105 can be switched and used by maximizing the gap (interval between magnet rows) of one undulator. Is possible. Thereby, the third request is also satisfied. For example, by maximizing the gap of the undulator 101, the vertical magnetic field can be weakened and only the horizontal magnetic field can be generated. Conversely, by maximizing the gap of the undulator 103, the horizontal magnetic field can be weakened and only the vertical magnetic field can be generated.

  However, according to the configuration of FIG. 6, since it is necessary to install two undulators in one straight line portion, it is allowed per one undulator under the same installation space given to the insertion light source. The length is less than half. As a result, the emitted light intensity is halved. Also, in order to achieve the same level of synchrotron radiation intensity as can be achieved with one undulator, more than twice the installation space is required. Extremely difficult. That is, it is required to realize an insertion light source that can switch between a vertical magnetic field and a horizontal magnetic field while realizing equivalent radiated light intensity under a limited installation space. In other words, there is a fourth requirement not to install a plurality of undulators in tandem on a straight line. The configuration shown in FIG. 6 does not satisfy this requirement.

  As another insertion light source, a method is conceivable in which two undulators (for low energy and for high energy) having different period length and polarization are arranged in a cross shape and used exclusively with each other. This configuration will be described with reference to FIG.

  The cross-type insertion light source 110 shown in FIG. 7 is composed of two sets of undulators 101 and 103 each of which is a set of upper and lower and left and right magnetic circuits. The undulator 101 has a magnetic circuit arranged in parallel to a horizontal plane. On the other hand, the undulator 103 is rotated 90 ° with respect to the undulator 101 so that the magnetic circuit is perpendicular to the horizontal plane.

  Unlike the tandem insertion light source 100 shown in FIG. 6, the cross-type insertion light source 110 has an undulator 101 and an undulator 103 installed in the vicinity of each other, and a single closed space is formed by both undulators. Thereby, since two undulators are not installed in a line in one straight line portion, space saving can be achieved as compared with the tandem insertion light source 100 shown in FIG. That is, the fourth request is satisfied.

  Also in the cross-type insertion light source 110, as in the tandem insertion light source 100 shown in FIG. 6, the period length of each undulator can be changed, and the magnetic field derived from the undulator can be increased by widening the gap of one undulator. The influence can be eliminated. Thereby, the 1st-3rd request | requirement can be satisfied.

  However, according to the configuration of FIG. 7, the mutual undulators 101 and 103 form a closed space over the entire length of the magnetic circuit. This configuration poses difficulties for undulator design and construction.

  When actually designing and constructing an undulator, it is important to secure an opening in the horizontal plane of the electron trajectory by arranging the magnet rows only in the vertical direction of the electron beam axis. When the magnet rows are formed not only in the vertical direction in the vertical direction but also in the horizontal direction in the left and right directions like the cross-type insertion light source 110, it becomes difficult to perform magnetic field measurement and magnet replacement / adjustment that are indispensable for undulator development. In other words, the fifth requirement that engineering does not limit the opening in the horizontal plane of the electron trajectory (no undulator is disposed in the horizontal direction perpendicular to the beam axis direction) is required. The cross-type insertion light source 110 cannot satisfy the fifth requirement.

  Further, by arranging the magnet rows in the left and right horizontal directions, a large installation space is required in the horizontal direction, which is also a problem in terms of space saving.

  In addition, the structure of patent documents 1-4 mentioned above is also an insertion light source designed for the purpose different from the purpose which this invention assumes, and all do not satisfy the 1st-5th request | requirement simultaneously. Absent.

  Patent Document 1 discloses an insertion light source for holding and fixing each magnet row to a holder without using an adhesive in a configuration in which three rows are arranged only in the vertical direction of the electron beam axis. It is disclosed. In this insertion light source, three magnet rows are constituted by a central vertical magnetic field magnet row and horizontal magnetic field magnet rows on both sides thereof, and the three magnet rows face each other in the vertical direction. Then, the three magnet rows are set as a pair and are opposed to each other through a gap so that the gap length can be adjusted. Further, the magnet rows on both sides of the pair of upper and lower magnet rows and the center magnet row are configured to be movable relative to the beam axis direction.

  In this configuration, the central magnet row generates a vertical magnetic field, and the magnet rows on both sides generate a horizontal magnetic field. Then, the horizontal magnetic field is adjusted by moving the magnet rows on both sides relative to the central magnet row in the direction parallel to the beam axis. However, in this configuration, since the vertical magnetic field orthogonal to the beam axis cannot be canceled out, it cannot be used while switching between horizontal and vertical linearly polarized light, and the third requirement is not satisfied. Furthermore, since the purpose of generating radiated light in a wide photon energy range is not assumed, and because the period length of the central magnet row and the magnet rows on both sides must be the same, the first and second It is not configured to satisfy the request of 2.

  FIG. 8 is a conceptual diagram showing the insertion light source disclosed in Patent Document 1. As shown in FIG. The insertion light source 130 shown in FIG. 8 includes three rows of magnetic circuits 131, 132, and 133 that are arranged in parallel to the beam axis 105, and three rows of magnetic circuits 134 and 135 that are also arranged in parallel to the beam axis 105. 136. The magnetic circuits 131, 132, and 133 are opposed to the magnetic circuits 134, 135, and 136 in the vertical direction. On the right side of the figure, a graph showing the distribution of the horizontal magnetic field and the vertical magnetic field in the beam moving direction is shown.

  In FIG. 8A, when the magnetic circuits 131, 132, and 133 are completely opposed to the magnetic circuits 134, 135, and 136, the horizontal magnetic field Bx perpendicular to the direction of the beam axis 105 is canceled. It can be seen that a vertical magnetic field By perpendicular to the direction of the beam axis 105 appears. By moving the magnetic circuits 132, 133, 135, and 136 arranged on both sides in the beam axis direction, a horizontal magnetic field Bx appears (FIGS. 8B and 8C). However, the perpendicular magnetic field By perpendicular to the direction of the beam axis 105 cannot be canceled out.

  Patent Document 2 discloses an insertion light source for generating radiated light having an arbitrary polarization characteristic in a wide wavelength region from visible light to an X-ray region without limiting the horizontal aperture of the electron beam. It is disclosed. That is, it can be said that the first, second, and fifth requests are assumed.

  FIG. 9A is a conceptual diagram showing an insertion light source disclosed in Patent Document 2. FIG. The insertion light source 120 shown in FIG. 9A includes four rows of magnetic circuits 111, 112, 113, and 114 arranged in parallel to the beam axis 105. One set of magnetic circuits 111 and 112 is located above, and another set of magnetic circuits 113 and 114 is located below. By moving one set of magnetic circuits in the longitudinal direction (direction parallel to the beam axis 105) relative to the other set, horizontal polarization (vertical magnetic field), vertical polarization (horizontal magnetic field), elliptical polarization ( It is possible to switch between the vertical and horizontal magnetic field modes. FIG. 9B is a graph showing the displacement of the horizontal / vertical magnetic field with respect to the beam axis direction in each magnetic field mode obtained by moving the magnet array, where (a) is a vertical magnetic field, (b) is a horizontal magnetic field, and (c). Indicates an elliptically polarized mode. Therefore, the third to fifth requirements are satisfied.

  However, in the configuration of Patent Document 2, the periodic lengths of the vertical magnetic field and the horizontal magnetic field are the same. For this reason, it is not possible to generate radiation light in a wide energy range by one insertion light source by separately handling radiation light in different energy ranges, and the first and second requirements are satisfied. Absent.

  In Patent Document 3, the gap length between the upper and lower sides is reduced in a configuration in which two sets of magnet rows each having three rows of magnet rows arranged in parallel to the beam axis are arranged to face each other. An insertion light source aimed at suppressing the deflection of the magnet array caused by doing so is disclosed.

  In this insertion light source, a first main magnet row in which magnets magnetized in the vertical direction and magnets magnetized in the horizontal direction are alternately arranged in a row (parallel to the beam axis direction), and the first main magnet Magnets magnetized in the vertical direction and magnets magnetized in the horizontal direction are alternately arranged in a row with a gap in the vertical direction, and the vertical magnetization direction is the same as that of the first main magnet row. A second main magnet array having a horizontal magnetization direction opposite to the first main magnet array is provided. Furthermore, a first auxiliary magnet row is provided on both sides of the first main magnet row, and a second auxiliary magnet row is provided on both sides of the second main magnet row. In the first auxiliary magnet row, magnets magnetized in the vertical direction and magnets magnetized in the horizontal direction are alternately arranged in a row. The second auxiliary magnet row is provided with a gap in the vertical direction from the first auxiliary magnet row, and magnets magnetized in the vertical direction and magnets magnetized in the horizontal direction are alternately arranged in a row. At the same time, the vertical magnetization direction is opposite to that of the first auxiliary magnet row and the horizontal magnetization direction is the same as that of the first auxiliary magnet row. With this configuration, the attractive force acting between the first and second main magnet rows is canceled out by the repulsive force acting between the first and second auxiliary magnet rows, thereby obtaining an effect of suppressing deflection deformation. is there.

  However, the insertion light source disclosed in this document cannot be used while switching between horizontal and vertical linearly polarized light as well as that disclosed in Patent Document 1, and does not satisfy the third requirement. Further, the purpose of generating radiated light in a wide photon energy range is not assumed, and the first and second requirements are not satisfied. In patent document 3, the structure where the period length of each magnet row | line is equal is assumed.

  Patent Document 4 discloses an insertion light source for the purpose of reducing the influence of a thermal load derived from harmonics generated in a linear undulator that generates linearly polarized light. However, the solution is to set the period length of the vertical undulator to twice the period length of the horizontal undulator and rotate the electron beam alternately forward and backward in the shape of figure 8 when viewed from the axial direction. This suppresses the generation of harmonics in In other words, it is not a configuration in which the cycle length can be freely selected, and is not a configuration that satisfies the first and second requirements. In addition, since it cannot be used while switching between horizontal and vertical linearly polarized light, the third requirement is not satisfied.

  The present invention has been made for the purpose of providing an insertion light source that can satisfy various requests of a user while realizing space saving by satisfying all of the above first to fifth requirements. .

  The insertion light source according to the present invention, which has been made to solve the above problems, has the following characteristics.

  A first magnet magnetized in a first direction, a second magnet magnetized in a second direction orthogonal to the first direction, and a third magnet magnetized in a direction to cancel the magnetization of the first magnet in the first direction And a magnet array formed by repeatedly arranging one unit in which a fourth magnet magnetized in a direction to cancel the magnetization in the second direction of the second magnet is arranged in series in the first direction. The configuration has six rows.

  The magnet array includes a first magnet array, a second magnet array, a third magnet array, a fourth magnet array, a fifth magnet array, and a sixth magnet array, and the first magnet array and the fourth magnet array. Of the magnets constituting the row, at least the first magnet and the third magnet, the second magnet and the fourth magnet have the same length in the first direction, and the second magnet row, Of the magnets constituting the third magnet row, the fifth magnet row, and the sixth magnet row, at least the first magnet and the third magnet, and the second magnet and the fourth magnet according to the first direction. The lengths are the same.

  That is, the first magnet row and the fourth magnet row have the same length (period length) in the first direction as one unit. Similarly, the second magnet row, the third magnet row, the fifth magnet row, and the sixth magnet row have the same length (period length) in the first direction of one unit that is repeated.

  The second magnet row and the third magnet row are arranged on both sides of the first magnet row in the third direction orthogonal to the first direction and the second direction, and the first magnet row On the other hand, the fourth magnet row is disposed apart from the second direction, and the fifth magnet row and the sixth magnet row are disposed on both sides of the fourth magnet row in the third direction.

  And at least one of the first magnet row and the fourth magnet row is movable in the first direction with respect to the other, and the set of the second magnet row and the third magnet row and the At least one of the set of the fifth magnet row and the sixth magnet row is configured to be movable in the first direction with respect to the other set.

  By comprising in this way, the magnetization direction which concerns on a said 2nd direction between the 1st magnet row | line | column and a 4th magnet row | line | column can be cancelled | released, and cancellation | release of this cancellation can be performed. Thereby, a magnetic field can be generated or canceled in the second direction.

  Similarly, the magnetization direction in the third direction can be canceled and the cancellation canceled between the second magnet row and the third magnet row and between the fifth magnet row and the sixth magnet row. Thereby, a magnetic field can be generated or canceled in the third direction. That is, the first direction is the traveling direction of the electron beam, the second direction is the vertical direction orthogonal to the traveling direction of the electron beam, and the third direction is the horizontal direction orthogonal to the traveling direction of the electron beam. The vertical magnetic field can be switched.

The period lengths of the first magnet array and the fourth magnet array (hereinafter referred to as λ _y ) and the period lengths of the second magnet array, the third magnet array, the fifth magnet array, and the sixth magnet array (hereinafter, λ _x represents a configuration that can be set independently of each other.

  Therefore, it is possible to generate radiated light having a wide energy range as the entire insertion light source while narrowing the energy range to be handled. Further, since the magnet arrays are not arranged in series with each other, the installation space can be saved.

  Furthermore, since the first, second, and third magnet rows and the fourth, fifth, and sixth magnet rows are arranged with a gap in the second direction, they are separated from each other. The emitted light can be generated by advancing the electron beam in the first direction in the region. That is, no magnet row is arranged in the horizontal direction (third direction) perpendicular to the beam axis direction, and there is no problem of difficulty in work such as magnetic field measurement and magnet replacement / adjustment.

  Further, in the above configuration, the first magnet row and the fourth magnet row are such that the second magnet row and the fourth magnet row face each other in the second direction, and the second magnet row and the fifth magnet row. , And the third magnet row and the sixth magnet row, the first magnet and the third magnet face each other in the second direction, the second magnet row, the third magnet row, and the first magnet row, respectively. The five magnet row and the sixth magnet row assume a magnet arrangement state in which the second magnet and the fourth magnet face each other in the third direction.

  Under the magnet arrangement state, a state in which the magnetic fields in the second direction and the third direction are both canceled is realized.

The length of the first magnet row in the first direction of the unit is λ _y , the length of the unit of the second magnet in the first direction is λ _x , and the natural number is n Then, at least one of the first magnet row and the fourth magnet row can move by a distance of (2n−1) λ _y / 2 from the initial state to the first direction with respect to the other. And at least one of the set of the second magnet row and the third magnet row and the set of the fifth magnet row and the sixth magnet row is in an initial state with respect to the other set. It is configured to be movable in the first direction by a distance of (2n−1) λ _x / 2.

By moving at least one of the first magnet row and the fourth magnet row from the magnet arrangement state by a distance of (2n−1) λ _y / 2 in the first direction with respect to the other, It becomes possible to cause a magnetic field in the second direction to appear. In addition, from the initial state, at least one set of the set of the second magnet row and the third magnet row and the set of the fifth magnet row and the sixth magnet row is initially set with respect to the other set. By moving from the state in the first direction by a distance of (2n−1) λ _x / 2, it is possible to cause the magnetic field in the third direction to appear.

  By adopting such a configuration, the three states of the state where both the magnetic fields in the second direction and the third direction are canceled, the state where the magnetic field in the third direction is canceled, and the state where the magnetic field in the second direction is canceled Transition between is possible. This transition between states may be performed in any order.

  According to the present invention, an insertion light source that satisfies all the above first to fifth requirements, that is, an insertion light source that can meet various user requirements while realizing space saving is realized.

It is a schematic diagram of the magnetic circuit with which the insertion light source of this invention is provided. It is the schematic diagram which expand | deployed the state of FIG. It is a graph which shows distribution of the horizontal magnetic field and vertical magnetic field regarding the beam moving direction in the state of FIG. 1A. It is a schematic diagram of the magnetic circuit in a perpendicular magnetic field mode. It is the schematic diagram which expand | deployed the state of FIG. It is a graph which shows distribution of the horizontal magnetic field and vertical magnetic field regarding the beam moving direction in the state of FIG. 2A. It is a schematic diagram of the magnetic circuit in a horizontal magnetic field mode. It is the schematic diagram which expand | deployed and illustrated the state of FIG. 3A planarly. It is a graph which shows distribution of the horizontal magnetic field and vertical magnetic field regarding the beam moving direction in the state of FIG. 3A. It is a typical block diagram of the drive means for performing switching of a magnetic field mode. It is a typical block diagram of another drive means for performing switching of a magnetic field mode. It is a graph which shows distribution of the horizontal magnetic field and the vertical magnetic field in the Example of a perpendicular magnetic field mode. It is a graph which shows distribution of the horizontal magnetic field and the vertical magnetic field in the Example of a horizontal magnetic field mode. It is a conceptual diagram which shows the structure of a tandem type insertion light source. It is a conceptual diagram which shows the structure of a cross-type insertion light source. It is the conceptual diagram which shows the structure of the insertion light source disclosed by patent document 1, and the graph which shows distribution of the horizontal magnetic field and vertical magnetic field regarding a beam moving direction. It is a conceptual diagram which shows the structure of the insertion light source of patent document 2. FIG. 10 is a graph showing horizontal and vertical magnetic field distributions in the beam movement direction in the insertion light source described in Patent Document 2.

  An embodiment of an insertion light source according to the present invention will be described with reference to the drawings. In the following drawings, the actual dimensional ratio and the dimensional ratio on the drawing do not necessarily match.

[Magnetic circuit]
FIG. 1A is a schematic diagram of a magnetic circuit included in the insertion light source. FIG. 1B is a schematic diagram illustrating the two rows of the three rows of magnetic circuits shown in FIG. 1A in a plan view.

  Moreover, in FIG. 1B, in each magnet row group, the magnet rows constituting the magnet row group are illustrated as if they are arranged with a gap in the horizontal direction. This is a measure for securing a space for attaching a reference numeral. Actually, as shown in FIG. 1A, the magnet rows may be arranged close to each other in the horizontal direction.

  The magnetic circuit 1 includes six rows of magnets formed by arranging a plurality of magnets adjacent to each other in a direction parallel to the beam axis 5. In the following, the direction parallel to the beam axis 5 is referred to as the Z direction, the vertical direction orthogonal to the Z direction (upward in the drawing) is referred to as the Y direction, and the horizontal direction orthogonal to the Z direction is referred to as the X direction. More specifically, the moving direction of the electron beam is defined as the + Z direction, the direction from the magnet group 20 to the magnet group 10 is defined as the + Y direction, and the direction from the magnet group 12 to the magnet group 13 is defined as the + X direction (see FIG. 1A). ). Moreover, in the following drawings, the arrow shown in each magnet has shown the magnetization direction.

  In the following, when the positive and negative directions are distinguished from each other, they are expressed as + X direction, + Y direction, + Z direction, etc. Y direction, Z direction and the like are expressed. In FIG. 1B, “N” is applied to the magnet magnetized in the + Y direction, “S” is applied to the magnet magnetized in the −Y direction, and “right arrow” is applied to the magnet magnetized in the + Z direction. "A left-pointing arrow" is added to the magnet magnetized in the -Z direction.

  Although each magnet can use what was comprised by the Nd-Fe-B type | system | group magnet, in this invention, it is not limited to the magnet comprised by these materials.

  In the magnetic circuit 1, the two magnet array groups 10 and 20 are arranged apart from each other in the Y direction. The electron beam passes through the space formed by this separation.

  The first magnet array group 10 includes a first magnet array 11, a second magnet array 12, and a third magnet array 13. The second magnet array group 20 includes a fourth magnet array 21, a fifth magnet array 22, and a sixth magnet array 23. The lengths of the magnets constituting the first magnet row 11 and the fourth magnet row 21 in the Z direction are the same. Moreover, the length which concerns on the Z direction of each magnet which comprises the 2nd magnet row | line | column 12, the 3rd magnet row | line | column 13, the 5th magnet row | line | column 22, and the 6th magnet row | line | column 23 is the same.

As shown in FIG. 1B, the first magnet array 11 includes a magnet 11a magnetized in the vertical direction (−Y direction), a magnet 11b magnetized in the horizontal direction (−Z direction), and magnetized in the vertical direction (+ Y direction). The four magnets composed of the magnet 11c and the magnet 11d magnetized in the horizontal direction (+ Z direction) are set as a unit, and these are repeatedly arranged in the Z direction. The length in the row direction (Z direction) of the magnet row constituting one unit is called a period length. Here, the periodic length of the first magnet array is defined as λ _y . The period length λ _y of the first magnet row 11 is defined by the length of each magnet constituting the first magnet row in the Z direction.

The second magnet row 12 includes a magnet 12a magnetized in the vertical direction (+ Y direction), a magnet 12b magnetized in the horizontal direction (+ Z direction), a magnet 12c magnetized in the vertical direction (−Y direction), and the horizontal direction. The four magnets composed of the magnets 12d magnetized in the (-Z direction) are regarded as one unit and are repeatedly arranged in the Z direction. The period length of the second magnet array 12 is defined as lambda _x. Here, λ _x is different from λ _y . The periodic length λ _x of the second magnet row 12 is defined by the length of each magnet constituting the second magnet row in the Z direction.

The third magnet array 13 includes a magnet 13a magnetized in the vertical direction (−Y direction), a magnet 13b magnetized in the horizontal direction (−Z direction), a magnet 13c magnetized in the vertical direction (+ Y direction), and a horizontal Four magnets composed of magnets 13d magnetized in the direction (+ Z direction) are set as one unit, and these are repeatedly arranged in the Z direction. Period length of the third magnet array 13 is the same lambda _x the period length of the second magnet array 12.

  The second magnet array group 20 is arranged to be spaced downward (−Y direction) from the first magnet array group 10. This separation distance Gap (see FIG. 1A) is set to a predetermined value, and this value is fixed during normal operation. Of course, the Gap value may be changed according to the use conditions. However, as will be described later, when used as an insertion light source according to the present invention, it is basically unnecessary to change the Gap value.

The fourth magnet row 21 includes a magnet 21a magnetized in the vertical direction (+ Y direction), a magnet 21b magnetized in the horizontal direction (−Z direction), a magnet 21c magnetized in the vertical direction (−Y direction), and a horizontal Four magnets composed of magnets 21d magnetized in the direction (+ Z direction) are regarded as one unit, and these are repeatedly arranged in the Z direction. The periodic length of the fourth magnet array is λ _y that is the same as the periodic length of the first magnet array.

The fifth magnet row 22 includes a magnet 22a magnetized in the vertical direction (+ Y direction), a magnet 22b magnetized in the horizontal direction (−Z direction), a magnet 22c magnetized in the vertical direction (−Y direction), and a horizontal Four magnets composed of magnets 22d magnetized in the direction (+ Z direction) are regarded as one unit, and these are repeatedly arranged in the Z direction. Period length of the fifth magnet array 22 is the same lambda _x the period length of the second magnet array 12 and the third magnet array 13.

The sixth magnet array 23 includes a magnet 23a magnetized in the vertical direction (−Y direction), a magnet 23b magnetized in the horizontal direction (+ Z direction), a magnet 23c magnetized in the vertical direction (+ Y direction), and the horizontal direction. The four magnets composed of the magnets 23d magnetized in the (-Z direction) are regarded as one unit, and these are repeatedly arranged in the Z direction. Period length of the sixth magnet array 23, a second magnet array 12, the third magnet rows 13, and the same lambda _x and fifth magnet array 22.

  In the state of FIG. 1A and FIG. 1B, the magnet magnetized in the Y direction existing in the first magnet array 11, and the magnetized in the Y direction existing in the fourth magnet array 21 at a position facing this magnet in the Y direction. The magnetized direction is opposite to the magnet. In other words, the magnetic fields are arranged in directions that cancel each other in the Y direction.

  In the state of FIGS. 1A and 1B, the third magnet row 13 in the position facing the magnet 12a magnetized in the + Y direction existing in the second magnet row 12 in the X direction has a −Y direction. A magnet 13a magnetized is disposed. For this reason, a magnetic flux that moves from the magnet 13a in the gap in the -X direction to the magnet 12a between the magnets 12a-13a may conceptually occur. However, at positions facing these magnets in the Y direction, a magnet 22a magnetized in the + Y direction is present in the fifth magnet array 22, and a magnet 23a magnetized in the -Y direction is present in the sixth magnet array 23. Exists. As a result, a magnetic flux that moves from the magnet 22a in the + X direction in the gap toward the magnet 23a between the magnets 22a-23a may conceptually occur. That is, the magnetic flux generated between the second magnet row 12 and the third magnet row 13 with respect to the magnets 12a and 13a, and the magnetic flux generated between the fifth magnet row 22 and the sixth magnet row 23 with respect to the magnets 22a and 23a, Occurs in the direction of canceling each other.

  By the same reason, the magnetic flux generated between the second magnet row 12 and the third magnet row 13 with respect to the magnets 12c and 13c, and between the fifth magnet row 22 and the sixth magnet row 23 with respect to the magnets 22c and 23c. Magnetic fluxes are also generated in directions that cancel each other. As a result, the horizontal magnetic field generated between the second magnet row 12 and the third magnet row 13 and the horizontal magnetic field generated between the fifth magnet row 22 and the sixth magnet row 23 cancel each other. In other words, the magnetic field is arranged in the direction that cancels out in the X direction.

  From the above, it can be seen that in the states of FIGS. 1A and 1B, no magnetic field is generated in the X direction and the Y direction, that is, neither a horizontal magnetic field nor a vertical magnetic field is generated. This state is called “zero magnetic field mode”. FIG. 1C is a graph showing the distribution of the horizontal magnetic field Bx and the vertical magnetic field By in the Z direction in this state.

  In the present embodiment, one of the first magnet row 11 and the fourth magnet row 21 is configured to be relatively movable in the Z direction with respect to the other. That is, of the first magnet row 11 and the fourth magnet row 21, only the first magnet row 11 may be configured to be movable in the Z direction, and only the fourth magnet row 21 is movable in the Z direction. It may be configured. Of course, both of them may be configured to be movable in the Z direction. In addition, at the time of this movement, it is the structure which can move independently, without affecting the position of the other magnet row | line | column 12, 13, 22, and 23, ie, with respect to these magnet row | line | columns.

  Furthermore, in the present embodiment, a set of the second magnet row 12 and the third magnet row 13 (hereinafter referred to as “first set”), and a set of the fifth magnet row 22 and the sixth magnet row 23 ( Hereinafter, one set of “second set” is configured to be relatively movable in the Z direction with respect to the other set. That is, of the first set and the second set, only the first set may be configured to be movable in the Z direction, or only the second set may be configured to be movable in the Z direction. Of course, both sets may be configured to be movable in the Z direction. In addition, at the time of this movement, it is the structure which can move independently, without affecting the position of the other magnet row | line | columns 11 and 21, ie, with respect to these magnet row | line | columns.

[Change method of magnetic field]
[Vertical magnetic field mode]
2A and 2B show a state where the first magnet row 11 is moved in the + Z direction by a half cycle (λ _y / 2) from the state of FIGS. 1A and 1B. At this time, the relative relationship between the second magnet row 12 and the third magnet row 13 and the relative relationship between the fifth magnet row 22 and the sixth magnet row 23 do not change from the states of FIGS. 1A and 1B. That is, the horizontal magnetic field is in the same state as the zero magnetic field mode.

  On the other hand, the relative relationship between the first magnet row 11 and the fourth magnet row 21 is changed by moving the first magnet row 11 by a half cycle. More specifically, the −Y direction existing in the fourth magnet row 21 is located at the position facing the Y magnet in the −Y direction magnetized in the first magnet row 11 and opposed to the magnet (11a). Is magnetized (21c). Further, a magnet (21a) magnetized in the + Y direction existing in the fourth magnet array 21 at a position facing the magnet (11c) magnetized in the + Y direction existing in the first magnet array 11 in the Y direction. Exists. That is, the flow of magnetic flux of magnet 11a → gap → magnet 21c → magnet 21d → magnet 21a → gap → magnet 11c → magnet 11b → magnet 11a is generated. This magnetic flux flow is generated at each location between the first magnet array 11 and the fourth magnet array 21, and as a result, a magnetic field in the Y direction (vertical magnetic field) is generated. In FIG. 2A, the direction of the magnetic field is indicated by a thick arrow in the gap region.

  Therefore, in the state of FIGS. 2A and 2B, a magnetic field in the X direction is not generated, but a magnetic field in the Y direction is generated. That is, it can be seen that a horizontal magnetic field is not generated but a vertical magnetic field is generated. This state is called “vertical magnetic field mode”. FIG. 2C is a graph showing the distribution of the horizontal magnetic field Bx and the vertical magnetic field By in the Z direction in this state.

2A and 2B, from the state shown in FIGS. 1A and 1B, the first magnet row 11 is moved in the + Z direction by a half cycle (λ _y / 2) to shift from the zero magnetic field mode to the vertical magnetic field mode. To do. However, in view of the fact that one unit constituted by four magnets each having a different magnetization direction is repeatedly arranged, one of the first magnet row 11 and the fourth magnet row 21 is set to the other. It can be seen that it is only necessary to move in the Z direction by (2n−1) λ _y / 2 (where n is a natural number).

[Horizontal magnetic field mode]
3A and 3B show a state in which the fifth magnet row 22 and the sixth magnet row 23 are moved in the −Z direction by a half cycle (λ _x / 2) from the state of FIGS. 1A and 1B. At this time, the relative relationship between the first magnet row 11 and the fourth magnet row 21 does not change from the state of FIGS. 1A and 1B. That is, the vertical magnetic field is the same state as the zero magnetic field mode.

  On the other hand, by moving the fifth magnet row 22 and the sixth magnet row 23 by a half cycle, the relative relationship between the second magnet row 12 and the fifth magnet row 22, and the third magnet row 13 and the sixth magnet row 23, respectively. It has changed.

  More specifically, the magnet (12a) magnetized in the + Y direction existing in the second magnet array 12 is magnetized in the -Y direction existing in the fifth magnet array 22 at a position facing the Y direction. Magnet (22c) is present. Further, a magnet (22a) magnetized in the + Y direction existing in the fifth magnet row 22 is located at a position facing the magnet (12c) magnetized in the -Y direction existing in the second magnet row 12 in the Y direction. ) Exists.

  Similarly, the magnet (13a) magnetized in the -Y direction existing in the third magnet array 13 and the magnet magnetized in the + Y direction (in the sixth magnet array 23) at a position facing the magnet (13a). 23c). Further, a magnet (23a) magnetized in the −Y direction existing in the sixth magnet array 23 at a position opposite to the magnet (13c) magnetized in the + Y direction existing in the third magnet array 13 in the Y direction. ) Exists.

  Under this state, a magnetic flux is generated between the magnet 12a in the second magnet row 12 and the magnet 13a in the third magnet row 13 in the −X direction from the magnet 13a toward the magnet 12a. Then, at positions facing these magnets in the Y direction, a magnet 22c magnetized in the −Y direction in the fifth magnet array 22 and a magnet 23c magnetized in the + Y direction in the sixth magnet array 23. Exists. As a result, a magnetic flux is generated between the magnets 22c-23c from the magnet 23c in the gap in the -X direction and directed toward the magnet 22c. That is, a magnetic field in the −X direction is generated at this gap position.

  By the same reason, with respect to the magnets 12c and 13c, the magnetic flux generated between the second magnet row 12 and the third magnet row 13 is in the + X direction, and the magnets 22a installed at positions facing these magnets in the Y direction. And 23a, the magnetic flux generated between the fifth magnet row 22 and the sixth magnet row 23 is also in the + X direction. Therefore, a magnetic field in the + X direction is generated at this gap position.

  From the above description, in the state of FIGS. 3A and 3B, a magnetic field in the Y direction is not generated, but a magnetic field in the X direction is generated. That is, it can be seen that a vertical magnetic field is not generated but a horizontal magnetic field is generated. This state is called “horizontal magnetic field mode”. FIG. 3C is a graph showing the distribution of the horizontal magnetic field Bx and the vertical magnetic field By in the Z direction in this state.

3A and 3B, the zero magnetic field is obtained by moving the fifth magnet row 22 and the sixth magnet row 23 in the −Z direction by a half period (λ _x / 2) from the state of FIGS. 1A and 1B. The mode was changed to the horizontal magnetic field mode. However, in view of the fact that one unit composed of four magnets with different magnetization directions is repeatedly arranged, the second magnet row 12 and the third magnet row 13 (first set), Of the group (second group) of the five magnet array 22 and the sixth magnet array 23, one group is moved by (2n-1) λ _x / 2 (where n is a natural number) in the Z direction with respect to the other group. You can see that

That is, according to the configuration of the present embodiment, the insertion light source can be used while switching between the zero magnetic field mode, the vertical magnetic field mode, and the horizontal magnetic field mode. The period length λ _y of the magnet array (11, 21) for generating the vertical magnetic field and the period length λ _x of the magnet array (12, 13, 22, 23) for generating the horizontal magnetic field are independent of each other. It is possible to set. For this reason, the period length can be freely set according to the photon energy to be generated, and an insertion light source having a high degree of freedom can be realized.

  In addition, according to this structure, since it is the structure which moves each magnet row | line | column to a Z direction (beam axis direction), when changing a magnetic field mode, it is not necessary to change a gap space | interval to a Y direction. In order to erase one magnetic field by moving the magnet array in the vertical direction and changing the gap interval, it is usually necessary to move a distance of several hundred mm or more. This means that much time is required for switching and the drive mechanism becomes large. On the other hand, according to this configuration, it is sufficient to move the magnet array in the Z direction by a half of the cycle length at a minimum, and switching of the magnetic field can be realized with a moving distance of about 20 mm at most. Thereby, shortening of switching time and size reduction of a drive mechanism are realizable.

〔Drive system〕
FIG. 4A and FIG. 4B are drawings schematically showing driving means for switching the above-described magnetic field modes. The driving means shown in any of the drawings is installed outside the magnet array groups 10 and 20 in the Z-axis direction, and can move the magnet array in the Z-axis direction. In each of these drawings, the drive shaft is hatched, and the non-hatched portion is constituted by, for example, a holding portion for fixing the position of the magnet row.

  The drive means 30A shown in FIG. 4A includes drive shafts 31 and 32. The first magnet row 11 can be moved in the Z direction by the drive shaft 31, and the fifth magnet row 22 and the sixth magnet row 23 can be simultaneously moved in the Z direction by the drive shaft 32. Accordingly, the first magnet row 11 can be moved in the Z direction with respect to the fourth magnet row 21 by the drive shaft 31, and the set of the second magnet row 12 and the third magnet row 13 (by the drive shaft 32 ( With respect to the first set), the set (second set) of the fifth magnet row 22 and the sixth magnet row 23 can be moved in the Z direction.

  Note that the positions of the second magnet row 12 and the third magnet row 13 are fixed by the holding portion 33, and the position of the fourth magnet row 21 is fixed by the holding portion 34.

  The drive means 30B shown in FIG. 4B includes drive shafts 35 and 36 in addition to the drive shafts 31 and 32. The first magnet row 11 can be moved in the Z direction by the drive shaft 31, and the fifth magnet row 22 and the sixth magnet row 23 can be simultaneously moved in the Z direction by the drive shaft 32. Further, the second magnet row 12 and the third magnet row 13 can be moved in the Z direction by the drive shaft 35, and the fourth magnet row 21 can be moved in the Z direction by the drive shaft 36.

According to this configuration, the degree of freedom of movement of the magnet array is further increased than that of the driving unit 30A, and various magnetic fields can be generated. For example, when the period length λ _y of the vertical magnetic field magnet array and the period length λ _x of the horizontal magnetic field magnet array are set to 1: 2, the vertical magnetic field and the horizontal magnetic field having different period lengths are switched and used. In addition to the usage mode, it is possible to realize a function as an 8-shaped undulator. In addition, by setting λ _y = λ _x , a function as a circularly polarized undulator can be realized.

[Theoretical explanation]
The arrangement state in the zero magnetic field mode shown in FIG. 1B is an initial state. With respect to this initial state, the displacement phase in the Z direction of the first magnet row 11 is θ _u , the displacement phase in the Z direction of the second magnet row 12 and the third magnet row 13 is φ _u , and the Z phase of the fourth magnet row 21 is Z. The displacement phase in the direction is defined as θ _d , and the displacement phase in the Z direction of the fifth magnet row 22 and the sixth magnet row 23 is defined as φ _d . _Assuming that the magnitudes of the vertical magnetic field and horizontal magnetic field at the reference point Z = 0 are B _y0 and B _X0 , the vertical magnetic field and horizontal magnetic field magnitudes B _y (z) and B _x (z) at Z = z are respectively Is represented by the number 1

    When the above formula 1 is expanded and put together, it is expressed as the following formula 2.

Assuming that λ _x and λ _y are arbitrary according to Equation 2 and φ _u −φ _d = ± π, B _x (z) = 0 and a vertical magnetic field mode (horizontal polarization) is realized. Further, if λ _x and λ _y are arbitrary and θ _u −θ _d = ± π, B _y (z) = 0 and a horizontal magnetic field mode (vertical polarization) is realized.

Note that a circular (elliptical) polarization undulator is realized by setting λ _x = λ _y and θ _u = θ _d = ± π / 2. Furthermore, an 8-shaped undulator is realized by setting λ _x = 2λ _y , θ _u = θ _d = 0, and φ _u = φ _d = 0.

  In the above-described embodiment, the lengths in the Z direction of the magnets constituting the first magnet row 11 and the fourth magnet row 21 are the same. However, among the magnets constituting these magnet arrays, at least the magnets (11a, 11c, 21a, 21c) magnetized in the Y direction have the same length in the Z direction and are magnetized in the Z direction. The magnets (11b, 11d, 21b, 21d) may have the same length in the Z direction.

  Similarly, in the above-described embodiment, the lengths in the Z direction of the respective magnets constituting the second magnet row 12, the third magnet row 13, the fifth magnet row 22, and the sixth magnet row 23 are the same. It was. However, among the magnets constituting these magnet arrays, at least the magnets magnetized in the Y direction (12a, 12c, 13a, 13c, 22a, 22c, 23a, 23c) have the same length in the Z direction, In addition, the magnets magnetized in the Z direction (12b, 12d, 13b, 13d, 22b, 22d, 23b, 23d) may have the same length in the Z direction.

〔Example〕
As a magnet row (first magnet row 11 and fourth magnet row 21) in the center, an Nd-Fe-B magnet having a width of 40 mm, a height of 40 mm, and a thickness of 15 mm (manufactured by Hitachi Metals, Ltd., material name: NMX-46CH) ) Are arranged in the Z direction. Moreover, as both side parts (the 2nd magnet row | line | column 12, the 3rd magnet row | line | column 13, the 5th magnet row | line | column 22, the 6th magnet row | line | column 23), it is Nd-Fe-B type | system | group magnet of width 40mm, height 40mm, and thickness 30mm. A magnet composed of (manufactured by Hitachi Metals, Ltd., material name: NMX-46CH) was formed in the Z direction. Here, “width” refers to the length in the X direction, “height” refers to the length in the Y direction, and “thickness” refers to the length in the Z direction.

At this time, the period length λ _y of the magnet array for vertical magnetic field is λ _y = 15 mm × 4 = 6 cm, and the period length λ _x of the magnet array for vertical magnetic field is λ _x = 30 mm × 4 = 12 cm. In this embodiment, the central portion is configured with 10 cycles, and both side portions are configured with 5 cycles. That is, the total length of the Z-direction magnet row was set to 60 cm. Note that the gap in the Y direction between the two magnet row groups was 21 mm, and the distance between the central magnet row and the magnet rows on both sides in the X direction was 1 mm.

At this time, FIG. 5A shows a graph relating to the distribution of the horizontal magnetic field Bx and the vertical magnetic field By in the Z direction when the vertical magnetic field mode is formed by moving the magnet array by the method described above. Similarly, FIG. 5B shows a graph relating to the distribution of the horizontal magnetic field Bx and the vertical magnetic field By in the Z direction when the horizontal magnetic field mode is formed. It can be seen that the horizontal magnetic field is canceled in FIG. 5A and the vertical magnetic field is canceled in FIG. 5B. In the present embodiment, the maximum magnetic field By _max = 0.68T in the vertical magnetic field mode and the maximum magnetic field Bx _max = 0.37T in the horizontal magnetic field mode, both of which realize sufficiently high magnetic field formation.

1: Magnetic circuit provided in the insertion light source according to the present invention
5: Beam axis
10: First magnet array group
11: 1st magnet row
11a, 11b, 11c, 11d: Magnets in the first magnet row
12: Second magnet row
12a, 12b, 12c, 12d: Magnets in the second magnet row
13: Third magnet row
13a, 13b, 13c, 13d: Magnets in the third magnet row
20: Second magnet array group
21: Fourth magnet row
21a, 21b, 21c, 21d: magnets in the fourth magnet row
22: Fifth magnet row
22a, 22b, 22c, 22d: magnets in the fifth magnet row
23: Sixth magnet row
23a, 23b, 23c, 23d: magnets in the sixth magnet row
30A, 30B: Driving means
31, 32: Drive shaft
33, 34: holding part
35, 36: Drive shaft 100: Tandem type insertion light source 101: Undulator 103: Undulator 105: Beam axis 110: Cross type undulator 111, 112, 113, 114: Magnetic circuit 130: Conventional insertion light source 131, 132, 133, 134 , 135, 136: magnetic circuit

Claims (4)

A first magnet magnetized in a first direction, a second magnet magnetized in a second direction orthogonal to the first direction, and a third magnet magnetized in a direction to cancel the magnetization of the first magnet in the first direction And a magnet array formed by repeatedly arranging one unit in which a fourth magnet magnetized in a direction to cancel the magnetization in the second direction of the second magnet is arranged in series in the first direction. A configuration having six rows,
The magnet row includes a first magnet row, a second magnet row, a third magnet row, a fourth magnet row, a fifth magnet row, and a sixth magnet row. The first magnet row and the fourth magnet row are Among the constituting magnets, at least the first magnet and the third magnet, the second magnet and the fourth magnet have the same length in the first direction, and the second magnet row and the third magnet are the same. Of the magnets constituting the magnet row, the fifth magnet row, and the sixth magnet row, at least the lengths of the first magnet and the third magnet, and the second magnet and the fourth magnet in the first direction. Are the same,
The second magnet row and the third magnet row are arranged on both sides of the first magnet row in a third direction orthogonal to the first direction and the second direction, and the first magnet row is arranged with respect to the first magnet row. The fourth magnet row is arranged apart from the second direction, and the fifth magnet row and the sixth magnet row are arranged on both sides of the fourth magnet row in the third direction,
At least one of the first magnet row and the fourth magnet row is movable in the first direction with respect to the other, and the set of the second magnet row and the third magnet row and the fifth At least one set of the magnet row and the sixth magnet row is configured to be movable in the first direction with respect to the other set ,
In the first magnet row and the fourth magnet row, the second magnet and the fourth magnet face each other in the second direction, the second magnet row, the fifth magnet row, and the third magnet. The first magnet row and the sixth magnet row are arranged so that the first magnet and the third magnet face each other in the second direction, the second magnet row, the third magnet row, the fifth magnet row, and the fifth magnet row. The six-magnet array is based on the magnet arrangement state in which the second magnet and the fourth magnet face each other in the third direction.
The length of the first unit of the first magnet row in the first direction is λ _y , the length of the unit of the second magnet in the first direction is λ _x , and the natural number is n. When at least one of the first magnet row and the fourth magnet row is movable in the first direction by a distance of (2n−1) λ _y / 2 relative to the other , the second magnet At least one of the set of the row and the third magnet row and the set of the fifth magnet row and the sixth magnet row is (2n−1) λ _{x in} the first direction with respect to the other set. Insertion light source characterized in that it can be moved by a distance of 1/2 On the basis of the magnet arrangement state, at least one of the first magnet row and the fourth magnet row can move a distance of λ _y / 2 in the first direction with respect to the other, and the second A distance of λ _x / 2 in the first direction with respect to at least one of the group of magnets and the group of third magnets and the group of the fifth magnets and the sixth magnets in the first direction The insertion light source according to claim 1 , wherein the insertion light source is configured to be movable. A first magnet row group comprising the first magnet row, the second magnet row, and the third magnet row; and a second magnet comprising the fourth magnet row, the fifth magnet row, and the sixth magnet row. 3. The insertion light source according to claim 1, wherein an electron beam passes through a gap provided between the row group in the first direction. 4. A first drive unit for moving at least one of the first magnet row and the fourth magnet row by a predetermined distance relative to the other in the first direction;
At least one of the set of the second magnet row and the third magnet row and the set of the fifth magnet row and the sixth magnet row is relatively set in the first direction with respect to the other set. The insertion light source according to any one of claims 1 to 3, further comprising a second driving unit for moving the predetermined distance.

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