JPH04324300A - Undulator - Google Patents

Abstract

PURPOSE:To obtain emitted light of high intensity by a specific wavelength by improving accuracy of a periodic magnetic field on a beam passing axis, formed by a parmanent magnet, and increasing an interference effect of the undulator emitted light. CONSTITUTION:A structure of plane type undulator is provided. That is, a plurality of permanent magnets 12 for forming a periodic magnetic field are arranged in both sides of a beam duct 11 and held by magnetic holders 13(non- magnetic) to hold each plurality of these magnetic holders 13 by holder fixing beds 14(formed of magnetic material). The holder fixing beds 14 is mounted to a mount base 15. Of the permanent magnets 12, in a magnet position in a magnetizing direction orthogonal to the duct 11, a through hole 20 of passing through the magnetic holder 13 and the holder fixing bed 14 is drilled to insert a magnetic flux adjusting bolt 21, consisting of magnetic material, retractably into this through hole 20. In a position of the through hole 20 in the mount base 15, an adjusting hole 22 is drilled.

Description

[Detailed description of the invention]

[Object of the invention]

0002

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an undulator installed in an accelerator or the like that utilizes synchrotron radiation, and more particularly to an undulator having a structure in which a plurality of permanent magnets are arranged along an electron beam duct.

0003

2. Description of the Related Art It is known that high-energy electrons emit various electromagnetic waves when they undergo circular motion or vibration, and one of these types of radiation is synchrotron radiation. This synchrotron radiation occurs when electrons are accelerated to a high energy state of hundreds of millions of electron volts (several hundred MeV) and propagate in vacuum at almost the speed of light, and when their trajectory is bent by a deflecting magnetic field, it occurs in the tangential direction of their trajectory This is a phenomenon in which light called synchrotron radiation is emitted. This synchrotron radiation is generally
In a circular accelerator, the deflecting magnetic field of the deflecting electromagnet is implemented by accelerating the accelerated electron beam in a direction perpendicular to the electron trajectory.

The synchrotron radiation is continuous light with a wavelength ranging from several angstroms to several thousand angstroms, and the integrated radiation power is extremely large. However, since light at wavelengths other than those used can damage the irradiated object, there is a demand for spectroscopy in a narrow wavelength range. If the wavelength is shortened to meet this demand, the intensity of the emitted light will decrease, and a high-brightness light source will not be obtained. Therefore, in order to satisfy the demands for shorter wavelengths and higher brightness, undulator radiation using an undulator (electronic meandering device), which is one of the insertion type light sources, has been studied and used.

FIGS. 5 and 6 show an example of a conventional undulator. The undulator shown in these figures is a so-called planar type, and is undulated in the y-axis direction of the vacuum duct 1 (see Fig. 5,
A plurality of permanent magnets 2...2 arranged adjacent to each other on both sides (with the z-axis direction being the beam passing direction), and the permanent magnets 2
Magnet holders 3...3 made of non-magnetic material such as aluminum alloy, which individually hold magnet holders 3...2, and bolts (not shown) each consisting of a plurality (for example, 20) of these magnet holders 3...3. ) and a plurality of holder fixing bases 4...4 held by bolts (not shown);
It is provided with frames 5, 5 on both sides of the vacuum duct 1. Frame 5
, 5 are fixed to each other via studs (not shown), so that the permanent magnets 2...2 maintain a predetermined gap on both sides of the vacuum duct 1 against the strong magnetic attraction force.

The size of the permanent magnets 2...2 is, for example, 1 cm (
y axis direction) x 1 cm (z axis direction) x 10 cm (x axis direction: depth), and the permanent magnets 2... ) are arranged 90 degrees apart. FIG. 6 shows the magnetic field strength distribution on the beam passing axis in the z-axis direction, which is formed by this magnet arrangement. The positions A to E in FIG. 5 correspond to the points A to E in FIG. 6, respectively. A in Figure 5
Due to the upper and lower permanent magnets 2 and 2 at the position C, the magnetic field is directed from the upper side to the lower side in the figure, whereas at the C position, the magnetic field is oppositely directed from the lower side to the upper side. Most of them cancel out and become zero. Further, the E position is the same as the A position, and the above magnetic field direction is repeated, and the permanent magnet 4
form one period. In other words, the magnetic field strength distribution from position A to position D becomes a periodic magnetic field with a cosine distribution as shown in FIG.
cm. Since the length of the entire undulator in the z-axis direction is, for example, approximately 2 m, the above-mentioned periodic magnetic field is also repeated for that length with a high-intensity magnetic force.

[0007] Since the length of the entire undulator in the z-axis direction is long, for example, 2 m, as described above, each holder fixing base 4 is divided into blocks for convenience of assembly.

When an electron beam enters the periodic magnetic field thus formed from the z-axis direction in FIG.
It is subjected to a Lorentz force in the axial direction (perpendicular to the plane of the paper), and it meanderes while drawing an almost cosine-distributed trajectory, similar to a periodic magnetic field. Undulator synchrotron radiation is generated with each meandering motion, and these synchrotron radiations interfere with each other, resulting in a radiation spectrum with a sharp peak waveform in which only the light intensity of a specific wavelength is significantly greater than that of synchrotron radiation. can get.

[0009]

[Problems to be Solved by the Invention] As mentioned above, undulator radiation utilizes the interference effect between the synchrotron radiation of each meander, so in order to give light of a certain wavelength a sharp peak, it is necessary to The phase and amplitude of each meandering motion must match with high precision. That is, the precision of the periodic magnetic field must be high. However, the variation in the magnetic properties of the permanent magnets is large, and the accuracy of the periodic magnetic field is reduced, so that it may not be possible to obtain undulator synchrotron radiation of sufficient intensity.

The present invention has been made in view of the problems of the prior art, and it is possible to appropriately correct the accuracy of a periodic magnetic field even when there are large variations in the magnetic properties of permanent magnets.
The object of the present invention is to provide an undulator that can ensure sufficient intensity of undulator radiation using a highly accurate periodic magnetic field. [Structure of the invention]

[0011]

[Means for Solving the Problems] In order to achieve the above object, in the present invention, electron beams are arranged along the path of the electron beam with their arrangement directions shifted so as to form a periodic magnetic field in the path of the electron beam. A plurality of permanent magnets, a magnet holder that holds each of the permanent magnets individually and is made of a non-magnetic material, a holder fixing base that holds a plurality of the magnet holders and is made of a magnetic material, and this holder. a pedestal for holding a fixed pedestal, and a through hole coaxially penetrating the holder fixing pedestal and the magnet holder is bored in a permanent magnet that generates a magnetic field orthogonal to the beam passage path among the permanent magnets. A magnetic flux adjustment member made of a magnetic material was inserted into this through hole so that it could move forward and backward with respect to the permanent magnet.

0012

[Operation] If the magnetic flux adjusting member made of a magnetic material is sufficiently retracted to the mount side, the magnetic resistance of the gap between the permanent magnet and the magnetic flux adjusting member is large, and the magnetic flux is not divided from the permanent magnet to the magnetic flux adjusting member side. However, as the magnetic flux adjustment member enters the permanent magnet side and approaches the permanent magnet, the magnetic resistance gradually decreases, and a part of the magnetic flux of the permanent magnet is transferred to the magnetic flux adjustment member.
A closed magnetic circuit is constructed via a holder fixing base made of a magnetic material and an adjacent magnetic flux adjustment member. The number of magnetic fluxes passing through this magnetic circuit changes depending on the advancing and retreating distance of the magnetic flux adjusting member. In other words, by adjusting the advancing and retreating distance of the magnetic flux adjustment member in the through hole, the magnetic field strength and phase of the electron beam path can be adjusted arbitrarily, increasing the distribution precision of the entire periodic magnetic field formed by multiple permanent magnets. It is within the allowable value.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 1 to 4.

The undulator shown in these figures is of the so-called planar type. First, the overall configuration will be explained based on FIGS. 3 and 4. A plurality of permanent magnets 12 . , magnet holders 13...13 made of non-magnetic material such as aluminum alloy, which individually hold the permanent magnets 12...12, and magnet holders 13...
A plurality of holder fixing bases 14 . . . 14 each made of a magnetic material and holding a plurality of holders (for example, 20 pcs.) as one block with bolts (not shown);
14 with bolts 14a...14a
5. As shown in FIG. 4, the pedestal 15 has upper and lower plates that are U-shaped when viewed from the z-axis direction, and the upper and lower plates are fixed to each other via studs 16...16. A predetermined distance between the top and bottom is maintained against strong magnetic attraction.

The permanent magnets 12...12 are arranged so that the magnetic pole directions of adjacent ones (in the figure, the direction of the arrow indicates the direction of magnetization) are shifted by 90 degrees as in the conventional configuration described above (however, (those in the y-axis direction are in phase), and as a result, a periodic magnetic field is formed on the beam passing axis as in FIG. 6 above. Note that the electron beam propagates in the vacuum duct 11 in the z-axis direction.

On the other hand, as shown in FIGS. 1 and 2, at each position of every other permanent magnet 12 . Holder fixing base 14 along the same orthogonal axis
and a through hole 20 passing through the magnet holder 13. In other words, each through hole 20 opens in the permanent magnet 12 and the upper and lower plates of the pedestal 15, respectively. The inner peripheral surface of this through hole 20 is threaded. A magnetic flux adjusting bolt (magnetic flux adjusting member) 21 made of a magnetic material and having a predetermined length is inserted into each of the through holes 20 . . . 20 so as to be movable forward and backward.

Further, adjustment holes 22 that reach the respective through holes 20 are bored from the outside in the upper and lower plates of the pedestal 15. This adjustment hole 22 has a larger diameter than the through hole 20 in order to insert an adjustment jig therein.

Next, the effects of this embodiment will be explained.

The electron beam entering the periodic magnetic field formed by the permanent magnets 12...12 from the z-axis direction inside the vacuum duct 11 is directed from the periodic magnetic field in the x-axis direction (direction perpendicular to the plane of the paper).
It is subjected to the Lorentz force and meandering along a trajectory similar to the distribution of a periodic magnetic field. Undulator radiation is generated for each meandering motion, and these radiations interfere with each other, causing the light intensity of only a certain wavelength to become significantly large.
A radiation spectrum with a sharp peak waveform is obtained. Note that this synchrotron radiation is emitted at all angles in the traveling direction of the electron beam, but usually, interference light with high intensity emitted in the z-axis direction is used.

Further, the adjustment operation for the above-mentioned periodic magnetic field will be explained. If the magnetic flux adjustment bolt 21 is sufficiently retracted to the upper and lower plates of the mount 15 and the gap between the permanent magnet 12 and the bolt 21 is large, the magnetic resistance is also large, and a part of the magnetic flux generated by the permanent magnet 12 detours to the bolt 21 side. No problem. In other words,
In this state of high magnetic resistance, the periodic magnetic field formed by the permanent magnet 12 is not affected in any way.

On the other hand, when the magnetic flux adjustment bolt 21 is turned through the adjustment hole 22 from the upper and lower plate sides of the frame 15 and the bolt 21 is gradually brought closer to the vacuum duct 11 side, the gap between the permanent magnet 12 and the bolt 21 is As the air gap becomes smaller, the magnetic resistance gradually decreases as well. As the magnetic resistance decreases, a part of the magnetic flux forming the periodic magnetic field is divided into a closed magnetic path and detoured, for example, as shown by the imaginary line H in FIG. That is, a part of the magnetic flux enters the adjacent permanent magnet 12 via the permanent magnet 12, the air gap, the bolt 21, the holder fixing base 14, the adjacent bolt 21, and the air gap. Therefore, the strength of the central magnetic field in the periodic magnetic field between the permanent magnets 12, 12 is reduced by the amount of the shunt of magnetic flux. In this way, the amount of divided magnetic flux increases as the amount of insertion of the magnetic flux adjustment bolt 21 increases, and the strength of the periodic magnetic field between the permanent magnets 12 and 12 changes according to the amount of divided magnetic flux.

Therefore, even if there are large variations in the magnetic properties of the permanent magnets 12...12 and the accuracy of the periodic magnetic field is degraded, the magnetic flux adjusting bolts 21 provided every other permanent magnet 12...12. By suitably fine-tuning , the precision (phase, intensity) of the magnetic field distribution on the beam passing axis along which the electron beam passes can be easily kept within a predetermined precision. By improving the precision of the periodic magnetic field in this way, the interference effect of the synchrotron radiation generated with each meandering of the electron beam increases, and the intensity of the undulator radiation of a certain specific wavelength can be sufficiently increased.

Further, according to the configuration of this embodiment, the holder fixing base 14 has a holding function of holding the magnet holders 13...13 block by block, and is actively made of a magnetic material to have a function for adjusting the magnetic flux. Because it also functions as part of a magnetic closed circuit, the overall structure is simple and compact.

[0024] The undulator according to the present invention is not limited to the planar undulator as described in the above embodiments, but may also include a hybrid type undulator that combines a permanent magnet and high permeability steel, or two sets of undulators. The present invention can be similarly applied to an orthogonal delay magnetic field polarization undulator in which planar undulators are arranged orthogonally to each other, or an orthogonal series polarization undulator in which a plurality of sets of planar undulators are arranged in series and orthogonal to each other.

Furthermore, the number of magnetic flux adjusting members in the x-axis direction (depth direction) in the present invention is as described in the above embodiments.
The number is not limited to one per permanent magnet, but may be an appropriate number taking into consideration the magnetization strength and depth of the permanent magnet.

[0026]

As explained above, according to the present invention, there are provided a plurality of permanent magnets that form a periodic magnetic field on the beam passing axis of an electron beam passing path, and a non-magnetic magnet holder that individually holds the permanent magnets. , a magnetic holder fixing base for holding a plurality of the magnet holders, and a mount for holding the holder fixing base, and among the permanent magnets, a permanent magnet that generates a magnetic field orthogonal to the beam passage path. A through hole was drilled coaxially through the holder fixing base and the magnet holder, and a magnetic flux adjusting member made of a magnetic material was inserted into this through hole so that it could move forward and backward with respect to the permanent magnet. By changing the distance and adjusting the magnetic resistance, the amount of magnetic flux divided from the permanent magnet to the magnetic flux adjustment member side can be changed from zero to an appropriate value, and the strength and phase of the periodic magnetic field on the beam passage axis can be appropriately corrected. The accuracy of the periodic magnetic field can be kept within the permissible value. In this way, although it is a correction mechanism with a relatively simple structure, the highly accurate periodic magnetic field after correction allows
The interference effect of the undulator radiation light is significantly enhanced, and high-intensity radiation light having a specific wavelength can be obtained.

[Brief explanation of drawings]

FIG. 1 is a partial side view (partially cut away) of a planar undulator according to an embodiment of the present invention.

FIG. 2 is a partial sectional view taken along line II-II in FIG. 1;

FIG. 3 is a side view (partially omitted) showing the overall configuration of a planar undulator.

FIG. 4 is a right side view of the undulator in FIG. 4.

FIG. 5 is a partial side view of a conventional planar undulator.

FIG. 6 is a graph explaining a periodic magnetic field.

[Explanation of symbols]

11 Vacuum duct 12 Permanent magnet 13 Magnet holder 14 Holder fixing base 15 Mount 20 Through hole 21 Magnetic flux adjustment bolt

Claims (1)

[Claims] Claim 1: A plurality of permanent magnets arranged along a passage of an electron beam with their arrangement directions shifted so as to form a periodic magnetic field in the passage, and each of the permanent magnets being held individually. A magnet holder made of a non-magnetic material, a holder fixing base made of a magnetic material and holding a plurality of the magnet holders, and a pedestal for holding the holder fixing base. , a through hole coaxially penetrating the holder fixing base and the magnet holder is bored in a permanent magnet that generates a magnetic field orthogonal to the beam passage path, and a magnetic flux adjusting member made of a magnetic material is inserted into the through hole. An undulator characterized by being inserted into a permanent magnet so that it can move forward and backward.