JPH07114159B2 - Undulator device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The disclosed technology belongs to the technical field of generation of synchrotron radiation and free electron laser light (FEL) used in macroscopic nuclear industry, microscopic semiconductor-related industry and the like.

[0002]

2. Description of the Related Art As is well known, the rise of industrial society, as well as civil society, is owed largely to the highly developed physical sciences. Technology There are electro technologies such as semiconductor integrated circuits, but such technologies require high-intensity light and X-rays, and the wavelengths thereof range from the micron unit to the angstrom unit.

Thus, as shown in FIG. 5, in a synchrotron radiation (SR light) generator 1 which originally applies a synchrotron as a high energy particle beam generator used for physics research. , Charged particles from the generation source are circulated around the equilibrium orbit 3 having the RF cavity 2 and the like via bending magnets 4, 4 and the like, and the electron beam is meandered by the undulator 5 inserted in the straight portion of the orbit to obtain high brightness. An undulator light generation mechanism that can extract synchrotron light has been developed and used for process technology such as lithography technology for integrated circuits and fine circuits of semiconductors, and for structural analysis and physical property analysis of various materials. It is expected that it will be used not only in research technology but also in industrial applications in the near future.

Thus, in the above-mentioned state of the art,
Only for research purposes, since undulator light, which extracts various wavelengths with high brightness and has a wider range of applications than synchrotron radiation (SR light), leads to the development of industrial technology. Not only is there a strong demand for the development of an undulator light device that has a wide wavelength range that can be selected for industrial use and that can extract high-luminance light.

[0005]

Thus, the undulator (wiggler) gives a meandering effect to the electron beam that is incident and passes by changing the magnetic force lines in the direction intersecting with the electron beam. Lights generated at the meandering points overlap and interfere with each other, and undulator light of extremely high brightness is generated at a certain specific wavelength.

In order to change the wavelength of the undulator light in a wide range, a method of changing the energy of the electron beam, a method of changing the magnetic field intensity of the undulator, and
There are three methods of changing the period length of the magnetic field of the undulator.

However, the above-mentioned first method of changing the energy of the electron beam is not possible in the operation of the electron accelerator which is the electron beam supply device, or the user who uses the synchrotron radiation from the same electron accelerator. In cases such as when there is a child, it is usually not allowed.

Further, in the method of dealing with this by changing the magnetic field intensity of the second undulator, if the magnetic field intensity is raised too high to obtain undulator light of a long wavelength, the electron beam is largely bent by the magnetic force, and The coherence of light generated at the meandering point of the electron beam becomes small, and undulator light having a desired spectrum cannot be obtained. On the other hand, if the magnetic field intensity is lowered too much to obtain undulator light of a short wavelength, the undulator light Since the power of the undulator light is proportional to the square of the magnetic field strength, the power of the undulator light is lowered and the undulator light has a high brightness, and thus the original usefulness of the undulator light is reduced.

Therefore, the method of changing the period length of the magnetic field of the third undulator is the best method for changing the wavelength of the undulator light in a wide range and maintaining good spectral characteristics and high brightness. There is.

Therefore, as an example of development based on the prior art, in a linear polarization undulator device, magnetic pole rows having different period lengths (that is, different magnetic pole pitches) are previously attached to each surface of a pair of tetrahedrons to rotate the tetrahedrons. A so-called revolver-type linear polarization undulator device has been developed and put into practical use in which the period length of the magnetic field of the undulator is changed by doing so.

By the way, as described above, in recent advanced industries, electronic technologies such as semiconductor integrated circuits play a great role, but it is extremely important to analyze the physical properties of semiconductors and magnetic materials used for them. Therefore, it is becoming more and more important to study the analysis of material properties and electronic properties.

Measurement using circularly polarized light is remarkably effective for the analysis of the physical properties of the electrons. For example, the states of the electrons responsible for the magnetic moment of the magnetic substance can be determined by measuring the clockwise circularly polarized light and the counterclockwise circularly polarized light of various wavelengths. The effectiveness of the method of measuring from the difference between the scattering and absorption intensity of polarized light is well known.

As is well known, light has various polarization characteristics. For example, when circularly polarized light having different magnetic characteristics due to different circular polarization directions such as clockwise rotation and counterclockwise rotation is used, a semiconductor or the like is magnetized. It is remarkably effective as a means of experiment and theoretical analysis because physical properties such as the degree of scattering differing depending on the direction can be measured.
It is also extremely important as an industrial prototype SR device.

Therefore, even with respect to the undulator light having a characteristic that the brightness is extremely high at a certain specific wavelength, such circularly polarized undulator light has been particularly attracting attention.

Therefore, there is a rapidly increasing need for an apparatus that can set a specific wavelength in a wide wavelength range and generate circularly polarized undulator light without reducing the power of light.

However, in reality, such a circular polarization undulator device having a wide wavelength range (variable period length) has not been developed, and its appearance is strongly desired.

Various trial-and-error methods have been used to realize the undulator device that makes the magnetic field period length of the circularly polarized light undulator having such strong needs variable, that is, realizes highly polarized circularly polarized light over a wide wavelength range. Although various theories and experiments have been researched and developed, a technology which is sufficiently satisfied and has a possibility of being industrially applicable has not yet been developed.

In the so-called revolver type undulator that has been put into practical use, the magnetic field period length can be changed, but the undulator light generated is only linearly polarized light, and circularly polarized light cannot be obtained.

Further, in the evolved Nikitin type undulator as shown in FIG. 6, magnets having different magnetic poles 7 and 7 '... Adjacent to each other are arranged opposite to each other, and further, a phase adjusting magnet 8 is arranged in the traveling direction of the electron beam. , 8'is installed in multiple stages in the traveling direction of the electron beam, that is,
A mode in which two linear polarization undulators are joined via a phase adjuster is used. In such a mode, the degree of polarization can be freely changed, circularly polarized light can be obtained, and the revolver type linear system can be used as a mechanism for varying the magnetic field period length. Although a mechanism similar to the polarization undulator can be used, the requirement for the electron beam to obtain circularly polarized light with this type of undulator is very strong and impossible in reality, and is only theoretically studied. .

On the other hand, as an undulator device capable of obtaining circularly polarized light although the period length is not variable, as shown in FIG. 7, the traveling direction of the electron beam in the undulator is z, and the direction orthogonal to this is x, If y, along the traveling direction z of the electron beam, electromagnets 7, 7 ... Having mutually different polarities in the traveling direction, and magnetic poles 7 ', 7'. , 8 ', 8'in the x direction whose phase is changed by 90 ° with respect to the magnetic poles facing each other in the y direction, are different from each other in the traveling direction z, and are opposite to each other. Make it polar, and
A so-called orthogonal delay magnetic field type circular polarization undulator has been developed in which the magnetic fields are rotated by shifting the magnetic poles in the x and y directions by half poles.

However, in the orthogonal delay magnetic field type circular polarization undulator, although there is a technique of a theoretical idea, in reality, there are some points that cannot be realized in an actual design such as an arrangement of magnetic poles and a set of relays. is there.

Therefore, as shown in FIG. 8, a revolver type linear polarization undulator 11 in which magnetic pole rows having different period lengths in the above-mentioned linear polarization undulator are attached to each surface of a pair of tetrahedra to rotate the tetrahedron. , 11,
And 11 ', 11' pair units up and down, and
A compound revolver-type circular polarization undulator that is arranged in combination in the left-right direction is theoretically possible as a variable-cycle-length circular polarization undulator.

However, the revolver pair units 11, 11 of the revolver type linear polarization undulator described above are used.
Alternatively, each 1'unit of 11 'and 11' has a large weight, and in this embodiment, two pair units are combined, so that one undulator device is extremely heavy and occupies a large space. Considering the prevention of bending of each revolver 11 and 11 'during operation, the support mechanism and the rotation drive device are extremely complicated, and the control becomes complicated, so that they cannot endure actual use, and the opposing magnetic poles are There is a Masnas point that the magnetic field strength cannot be increased because the magnetic circuit cannot be assembled by connecting with the yoke.

Further, in the orthogonal delay magnetic field type circular polarization undulator, a method of changing the connection by using a magnet for generating a magnetic field as an electromagnet and changing the connection to change the magnetic polarity of a part of the electromagnets and change the magnetic field period length is also conceivable. For example, when the mode shown on the left side of FIG. 9 is changed to the mode shown on the right side, the magnetic field cycle length doubles.

However, in such a mode, the number of current contacts (relays) for changing the connection of the exciting coil of the electromagnet is remarkably increased, the electric circuit structure is complicated, and the undulator for inverting the polarity of circularly polarized light at a high speed. In order to realize the operation mode, the inductance of the excitation circuit of the electromagnet must be reduced and the current value flowing in the excitation coil must be increased considerably. There is the inconvenience that the cost increases and maintenance and maintenance becomes complicated.

Further, in such a mode, it is more difficult to increase the magnetic field strength because it is not possible to form a magnetic circuit by connecting mutually facing magnetic poles with a yoke.

Therefore, in the mode shown on the left side of FIG.
It is also conceivable that the magnetic fields are arranged so that the upper and lower magnetic poles and the left and right magnetic poles facing each other are connected by a yoke.

In this case, the magnetic field cycle length can be changed by, for example,
By changing the wiring of the excitation coil of the electromagnet,
The magnetic field cycle length can be tripled by changing from the mode shown on the left side of 0 to the mode shown on the right side.

However, as is clear from the example of the mode on the right side of FIG. 10, there is a disadvantage that a short period component is mixed in the magnetic field waveform in the traveling direction of the electron beam.

Therefore, in such a mode, there occurs a problem that the original feature of the undulator that selectively generates light of a certain specific wavelength with high brightness is lost.

Furthermore, in order to deal with such a problem, as shown in FIG. 11, a predetermined number of quadrupole electromagnets capable of selectively generating magnetic fields in the x-direction and the y-direction by changing the connection of the exciting coil. A combined xy-direction magnetic pole wire connection changing type orthogonal delay magnetic field type undulator is conceivable, and the magnetic field cycle length is, for example, as shown in the left side of FIG. Change it to vertical, vertical,
Horizontal, horizontal, ... Excitation makes it possible to double the intensity, and it is also possible to obtain linearly polarized light. There are almost no moving parts, the structure is simple and compact, Although there is a merit that the large mixing of the short-period component as described above can be avoided, it has a demerit that an irregular magnetic field is induced by a dummy pole (a pole that is not excited).

Further, although a helical undulator using a spiral coil has been developed as an undulator capable of obtaining circularly polarized light although the magnetic field period length is not variable, the pitch of the spiral coil wound very many times has been proposed. It is unlikely that a mechanism that can change all of them with high accuracy will be available.

[0033]

By the way, in the quadrature undulator of the above-mentioned aspect, the magnetic poles are arranged so as to provide a horizontal magnetic field and a vertical magnetic field intersecting at 90 ° in a plane orthogonal to the traveling direction of the electron beam. Therefore, the cycle length of the magnetic field (the length of the direction required for the magnetic field vector to make one rotation about the traveling direction of the electron beam as the axis) is calculated by dividing one rotation of 360 ° by 90 °. It was determined by multiplying the magnetic pole pitch.

Therefore, to change the magnetic field cycle length,
There is no choice but to change the magnetic pole pitch and, for example, it is necessary to adopt a mechanism such as a bellows type, and it is theoretically possible to use such a bellows mechanism mechanically in a quadrature delay undulator. There was a net that it was extremely difficult in terms of design, and it was almost impossible to realize it.

Since the magnetic pole pitch cannot be adjusted and changed as a result, in each plane of the undulator along the traveling direction of the electron beam, the in-plane orthogonal to the traveling direction of the electron beam is obtained. If it is possible to change the magnetic field direction at, the angular difference in the magnetic field direction between adjacent parts can be
When θ is set, the cycle length is (magnetic pole pitch) × (360 /
Δθ), the magnetic field cycle length can be adjusted by adjusting Δθ of the angular difference.

From the point that the angle difference (Δθ) can be changed, the above-mentioned orthogonal delay undulator of the x and y direction magnetic pole connection change type can be regarded as this special design mode.

Therefore, as shown in FIG. 1, assuming a spiral plane P having an arbitrary periodic length with respect to the traveling direction z of the electron beam, each undulator portion along the traveling direction z of the electron beam is assumed. By adjusting the direction w of the magnetic field along the spiral plane P by using the magnetic field direction rotation control function of each part of the undulator, the period length can be changed, that is, the brightness of the obtained light is reduced. It is possible to realize a circularly polarized light undulator having a wide wavelength range that does not have a good spectral characteristic.

[0038]

OBJECT OF THE INVENTION The object of the invention of this application is to solve the problem of the magnetic field line control method in the orthogonal delay magnetic field type undulator and the helical undulator which have been basically studied as the circular polarization undulator based on the above-mentioned prior art. The magnetic field is rotated along the traveling direction of the electron beam at an arbitrary cycle length, which allows circularly polarized light of an arbitrary wavelength in an arbitrary wide wavelength range to be generated, and is highly feasible in design. Since the structure can be simple and compact and the magnetic field strength can be changed, the power of the generated light can also be changed as desired, and a wide wavelength range can be achieved without reducing the brightness of circularly polarized light. An excellent undulator device that enables the generation of undulator light and benefits the field of optical technology utilization in various advanced industries. It is intended to provide cents.

[0039]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the structure of the invention of this application, which is based on the above-mentioned object, has the synchrotron radiation (SR light) generation device. The wavelength range of the undulator light is widened at the undulator light generation part in
The period length can be freely and selectively changed, and the power of the light is not reduced and the magnetic field strength is not changed. When the undulator light is circularly polarized by rotating the magnetic field intersecting with the traveling direction of the electron beam around the traveling direction of the electron beam, an arbitrary period assumed along the traveling direction of the electron beam A means is provided to provide a mechanism for electrically or mechanically rotating the magnetic poles so that each portion has an arbitrary rotation angle so as to generate a magnetic force line along a long spiral surface. Or, the initial set arrangement of the magnetic poles is determined, and further, the rotation period of the magnetic field is made different so that the wavelength of the circularly polarized undulator light can be freely set in a wide wavelength range. In addition, it is possible to selectively polarize and generate undulator light having a desired degree of polarization and spectral characteristics. Moreover, the magnetic field strength is independent of the magnetic field cycle length and the magnetic field rotation direction. Since it can be set arbitrarily, it is possible to generate undulator light with desired intensity, and it is possible to obtain undulator light with the optimum characteristics for analyzing and analyzing the magnetic properties of objects to be applied. It is a technical measure that was adopted.

[0040]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of the invention of this application is shown in FIGS.
The explanation is based on the following.

The same parts as in FIG. 4 and subsequent figures will be described using the same reference numerals.

The embodiment shown in FIG. 2 is a mode in which the direction w of the magnetic force lines shown in FIG. 1 is electrically controlled along the spiral plane P, and a ring shape is formed at a predetermined pitch along the traveling direction z of the electron beam. A predetermined number of pole pieces 13, 13, ... Are formed on the yoke 12 in the circumferential direction, and a predetermined number of units having coils 14, 14 for exciting are arranged, and a current flowing through each coil at each unit angle is arranged. By controlling the rotation angle of the magnetic field generated at each unit center point around the electron beam traveling direction z, the spiral plane P along the electron beam traveling direction z of FIG. 1 is controlled.
The magnetic field crossing angle (Δ) which is an important point of the invention of this application
θ) can be adjusted to change the magnetic field cycle length, that is, the wavelength of the undulator light, and in this aspect, the wavelength can be changed without changing the magnetic field intensity, so that the power of light is not reduced. It is a fixed yoke type circular polarization undulator device capable of adjusting the wavelength.

In the mode of this embodiment, although there are some restrictions depending on the number of pole pieces formed on the yoke,
The magnetic field cycle length, that is, the wavelength of the undulator light can be continuously varied, and furthermore, the magnetic field control by the current value control can be performed considerably freely to adjust the cycle length of the undulator light, that is, the wavelength. This is a kind of fixed multipole undulator control system that enables control of circularly polarized undulators.

In the mode of the embodiment, although the period is slightly limited depending on the number of divisions of the pole pieces formed on the yoke, the period length of the magnetic field, that is, the wavelength of the undulator light can be continuously changed, and the current With value control, control can be performed quite freely.

Next, the embodiment shown in FIG. 3 is a rotary magnetic pole type circular polarization undulator control system. In this embodiment, two pole pieces 1 are attached to each ring-shaped yoke 12 '.
By providing 3'and 13 'facing each other and appropriately rotating the yoke 12' mechanically, the structure is extremely simple and compact, and it is a highly feasible mode. As for the embodiment of the mechanical design example, for example, as shown in FIG. 4, a rotation system can be adopted, and the roller bearings 16, 16 ... Are provided in the V-shaped groove provided in the bearing base 15. The yoke 12 'is rotatably set, the yoke 12' is rotatably mounted on the bearing rollers 16 and 16, and the worm gear 17 is formed on the outer peripheral surface of the yoke 12 'so as to be integrated with the bearing base 15. The worm 21 provided on the output shaft 20 of the stepping motor 19 provided on the provided bracket 18 is attached to the yoke 1
By engaging the worm gear 17 of 2'and rotating each stepping motor 19 in a predetermined manner, the pole piece 13 is rotated through the rotation of the yoke 12 'to rotate the magnetic force line, that is, the magnetic field, and each yoke 12' is rotated. , 12 '... Can be set in a predetermined manner so that the magnetic force lines are along the spiral surface P.

Of course, the embodiment of the invention of this application is not limited to the above-mentioned embodiments. For example, the turning direction of the magnetic field can be selectively changed over time by switching control of current or the like. Also, it is possible to change the wavelength and polarization direction of the undulator light temporally by passing alternating currents with different frequencies and phases in the coils of each yoke, and also for each yoke in the traveling direction of the electron beam. Various modes such as undulator light with the optimum spectrum shape and polarization characteristics can be obtained by freely changing the rotation direction and rotation angle of the magnetic poles to form a complicated magnetic field distribution. Is.

Further, in terms of design modification, the magnet may be a permanent magnet or an electromagnet, and it is needless to say that the rotation cycle of the magnetic field may be fixed or selectively changed, which is a range of choice for those skilled in the art. .

Of course, the number of pole pieces is also within the scope of design changes.

[0049]

As described above, according to the invention of this application, basically, in the conventional circular polarization undulator device, the wavelength of the light is changed by changing the magnetic field intensity, so that the power of the output light is reduced. However, in the invention of this application, the period length of the magnetic field can be freely changed, and the wavelength of the undulator can be changed according to the purpose of use and the conditions, and the undulator light having polarization characteristics can be used without lowering the power. The excellent effect that it can be obtained freely is exhibited.

Therefore, the invention of this application provides a very advantageous means for analyzing and demonstrating the electronic properties of a magnetic substance and the like, and can also obtain the original circularly polarized undulator light.
The excellent effect of making full use of the optical characteristics of the undulator light is also achieved.

Further, the device according to the invention of this application is basically limited to the conventional circular polarization undulator, but compared with the device which can be basically developed with the function of changing the period length. Therefore, it is possible to provide a simple and compact undulator, the number of current contacts such as relays can be reduced, it is easy to process the device parts, and not only the initial cost, but also the running cost and maintenance cost are low. There is also an effect that the durability of the undulator can be sufficiently improved.

Then, in the device according to the invention of this application,
Unlike the above-mentioned conventional circular polarization undulator that has a limited period length variable function, a magnetic field period length variable function is provided by changing the magnetic flux line crossing angle with respect to the electron beam traveling direction, instead of changing the magnetic pole pitch. Therefore, the cycle length variability and the degree of freedom in device design are extremely high, and there is an advantage that it can be applied to various application fields and advanced application forms.

The degree of superiority or inferiority of each method in the above-mentioned control is shown in Table 1. For example, the rotating magnetic pole type is the best in each effect, and there is no overall mutual evaluation. It is high and has the effect that it can be designed and installed immediately.

[0054]

[Table 1]

[Brief description of drawings]

FIG. 1 is a schematic perspective view of a principle aspect of the invention of this application.

FIG. 2 is a partially enlarged schematic perspective view of one embodiment.

FIG. 3 is a partially enlarged schematic perspective view of another embodiment.

FIG. 4 is a partial cutaway perspective view of the specific embodiment of FIG.

FIG. 5 is a schematic plan view of a synchrotron radiation (SR light) generator.

FIG. 6 is a schematic perspective view of a Nikitin type evolutionary undulator.

FIG. 7 is a partially cutaway schematic perspective view of an orthogonal delay type undulator of a basic mode of a circular polarization undulator.

FIG. 8 is an enlarged schematic perspective view of a composite revolver undulator.

FIG. 9 is one of schematic mode diagrams of a unidirectional magnetic pole connection change type of an orthogonal delay undulator.

FIG. 10 is a schematic perspective view of another mode of the one-way magnetic pole connection change type of the orthogonal delay circular polarization undulator.

FIG. 11 is a schematic perspective view of an x- and y-direction magnetic pole wire connection changing type of an orthogonal delay undulator.

[Explanation of symbols]

 12 'yoke 13' magnetic pole (pole piece)

Claims (3)

[Claims] 1. An undulator device in which undulator light is circularly polarized by arranging a magnetic field for the electron beam around the direction of travel of the electron beam sequentially at an angle, in the direction of travel of the electron beam. The magnetic field generation portion of the undulator device in which the angle of the direction of the intersecting magnetic field lines has an arbitrary phase difference for each portion in the traveling direction of the electron beam is divided into a large number of segments, and the magnetic field strength of each segment is constant or arbitrary. The undulator device is provided with a mechanism capable of providing an angle change that is constant in time or changes in time in the direction of the magnetic force line. 2. The undulator device according to claim 1, wherein the angle change of the magnetic field is mechanically applied. 3. The undulator device according to claim 1, wherein the angle change of the magnetic field is electrically applied.