JP3242576B2 - Wigler for two-dimensional scanning - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wiggler for generating radiation by inserting it into a storage ring or the like, and more particularly to a new multipole wiggler for generating radiation two-dimensionally.

[0002]

2. Description of the Related Art Synchrotron radiation, which is generated by inserting a wiggler into a linear portion such as a storage ring, has the characteristics of being variable in wavelength over a wide wavelength range and having high brightness, and is therefore useful for treatment and diagnosis. Applications, industrial uses such as chemical synthesis / purification separation, evaporation and melting, and use in scientific research have been made, and more active uses are being developed. In many cases, such radiation needs to be irradiated over a wide range, for example, when performing image processing such as angiography, or in chemical synthesis or weather measurement. However, in the conventional apparatus, the main magnet of the wiggler is disposed so as to face in one of the horizontal and vertical directions, and the radiated light is emitted in one plane. Therefore, the irradiation direction is limited to the one-dimensional direction. Had been.

[0003] In response to such a demand for two-dimensional irradiation, conventionally, a reflecting mirror is used to two-dimensionally scan radiated light, or an object to be irradiated is moved vertically with respect to a light beam. Thus, a method of obtaining a two-dimensional image has been adopted.
In addition, a method of scanning the emitted light by changing the orbit of the electron beam by controlling the magnetic field by inserting an orbit changing electromagnet system before and after the wiggler, or expanding the width of the emitted light by using the asymmetry of the spectroscope A method is also conceivable. further,
Japanese Patent Application Laid-Open No. Hei 7-236632 discloses a configuration in which the natural opening angle of emitted light is used in angiography (cardiac coronary angiography system) utilizing the wavelength selectivity of emitted light. In this method, since the distance between the synchrotron radiation generator and the irradiation target is large, it is necessary to make the entire apparatus large. Each of these methods requires expensive accessory equipment,
The whole apparatus became large-scale, and the economic difficulty was great. In particular, a system for changing the trajectory of an electron beam becomes complicated and expensive as the energy of the electron beam is high. Further, it has been impossible with these methods to irradiate the emitted light at high speed in two dimensions.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a two-dimensional radiated light without attaching an expensive device to a wiggler. In particular, it is an object of the present invention to provide a new wiggler in which the radiation itself emitted from the wiggler scans two-dimensionally.

[0005]

In order to solve the above-mentioned problems, a two-dimensional scanning wiggler of the present invention has a plurality of main magnet pairs periodically arranged so that a magnetic field alternates. A plurality of pairs of sub-magnets generating a magnetic field in a direction substantially perpendicular to the magnetic field formed by the main magnets are arranged at substantially equal intervals between the main magnets, and two-dimensional scanning of emitted light is performed. And It is more preferable to dispose the magnetic field generated by the main magnet row and the magnetic field generated by the sub magnet row so that the primary integral along the electron trajectory becomes substantially zero. In addition, the sub-magnet array imparts a large deflection angle to the electron beam with the first magnet pair, and deflects in the opposite direction in a stepwise manner with the subsequent magnet pairs, and compensates for the difference from the original magnetic field strength with the last magnet pair. Thus, it is preferable that the first-order integral value of the magnetic field formed by the sub-magnet row along the electron trajectory becomes substantially zero. Further, the main magnet and the sub magnet are preferably electromagnets. More preferably, the main magnet is a superconducting electromagnet. Furthermore, in order to solve the above-mentioned problem, the method of generating emitted light according to the present invention is characterized in that an emitted electron beam in a multipole wiggler is periodically meandered in one direction and simultaneously scanned in a direction perpendicular to the meandering direction. Is generated two-dimensionally.

In the two-dimensional scanning wiggler of the present invention, since the electron beam meanders due to the main magnet row in which the magnetic field alternates,
Radiation light that reciprocally scans in a direction crossing the magnetic field is emitted in the traveling direction of the electron beam. Further, the traveling direction of the electron beam is stepwise deflected by the magnetic field generated by the sub-magnet row in a direction perpendicular to the reciprocating scanning direction, so that the irradiation direction of the radiation light changes two-dimensionally, and the radiation from the wiggler is performed. The emitted light scans two-dimensionally to have a substantially rectangular cross section. Therefore, when the radiation light generated by the two-dimensional scanning wiggler of the present invention is used, the radiation light can be directly scanned without a device for scanning the radiation light two-dimensionally or a special moving device for moving the irradiation target two-dimensionally. To a predetermined area of the object to be irradiated. Therefore, there is a great effect when applied to various application fields of synchrotron radiation, such as image processing in disease diagnosis and environmental observation, and promotion of chemical reactions in a wide range. In addition, although it is necessary to add an auxiliary magnet row to the wiggler magnet row, there is no need to attach an accessory device outside the wiggler, and the apparatus as a whole can be reduced in size, which is economically excellent.

It is to be noted that the arrangement is such that the primary integral value of the magnetic field generated by the main magnet row and the magnetic field generated by the sub-magnet row along the electron trajectory becomes almost zero. Since the set electron trajectory returns to the position before the wiggler is inserted, it becomes easy to properly maintain the electron trajectory of the storage ring or the like into which the wiggler is inserted. In addition, the secondary magnet array gives the electron beam a large deflection angle first, then gradually deflects it in a stepwise manner on the opposite side, and finally returns to the original electron trajectory, making full use of the wiggler's aperture It is possible to obtain good radiated light having a fine scanning line interval and to easily adjust the magnetic field distribution. Further, when the main magnet and the sub magnet are electromagnets, there is an advantage that the magnetic field can be easily adjusted and can be performed after assembly. If the main magnet is a superconducting electromagnet, a strong magnetic field is generated, so that short-wavelength, high-brightness two-dimensional scanning radiation can be obtained.

Further, according to the method for generating radiation light of the present invention, the radiation beam is periodically meandered in one direction and simultaneously scanned in a direction perpendicular to the meandering direction in the multipole wiggler, whereby the radiation light is generated in two directions. Since the light is emitted in a two-dimensional manner, the radiation itself emitted from the wiggler becomes a versatile light beam having a rectangular cross-sectional area, and special accessories are not required. The magnetic field applied for scanning in the direction perpendicular to the meandering direction may be continuous or stepwise.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a two-dimensional scanning wiggler according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a drawing showing a magnet arrangement in one embodiment of a two-dimensional scanning wiggler of the present invention, FIG. 2 is a magnetic field distribution diagram in this embodiment, FIG. 3 is an electron beam orbit displacement diagram, and FIG. FIG. 5 is a perspective view showing the trajectory of the electron beam in the wiggler of the present invention, and FIG. 6 is a drawing showing the trajectory scanned by the emitted light from the two-dimensional scanning wiggler of the present invention.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The two-dimensional scanning wiggler of the present embodiment shown in the drawings is a horizontal wiggler, in addition to a main magnet row which generates an alternating magnetic field in a vertical direction with respect to an electron beam orbit in a beam duct provided in a normal wiggler. And a sub-magnet row for generating a magnetic field in the horizontal direction. FIG. 1 is a vertical sectional view showing the magnet arrangement in the present embodiment. The main magnet row for generating a vertical magnetic field in this embodiment includes 21 odd-pole main magnet pairs M1 to M21 arranged at equal intervals of 7 cm, an inlet side magnet pair Min and an outlet side magnet pair. Mot
Consists of An alternating magnetic field having a magnetic field strength of 3T and a period of 14 cm is generated along the electron orbit EB by the main magnet pair. The field strength is 3.5T near the magnet and superconducting coils are used. The intensity of the magnetic field generated by the side magnet pair is selected to be approximately half that of the main magnet pair, so that the first-order integral value of the vertical magnetic field along the electron trajectory becomes zero. The sub-magnet row for horizontal magnetic field generation is provided on the outermost side with 22 electromagnet pairs S1 to S22 provided so as to be orthogonal to the middle of each magnet pair of the main magnet row for vertical magnetic field generation. It consists of a pair of side pole magnets Sin and Sot. The directions of the magnetic fields generated by the electromagnet pairs S1 to S22 are the same, the magnetic field intensity is 0.13T, and the period length is 7 cm. Side magnet vs. Si
n, the direction of the magnetic field generated by Sot is the magnet pair S1 to S
In the opposite direction to that of 22, the magnetic field strength is such that the first-order integral of the horizontal magnetic field along the electron trajectory is zero.

FIG. 2 is a diagram showing a magnetic field distribution generated along the electron trajectory by the above-mentioned magnet array. The horizontal axis represents the distance of the electron orbit in the direction of the wiggler axis, and the vertical axis represents the magnetic field strength.
The dotted line represents the distribution of the vertical magnetic field, and the solid line represents the distribution of the horizontal magnetic field. The vertical magnetic field is determined by the side magnet pair M on the entrance side.
In, a sine curve is drawn in the negative direction at the entrance of the wiggler by about 1.5T, and the polarity is changed alternately. Then, the pair of side magnets at the outlet swings in a sine curve by approximately 1.5 T in the same direction as the inlet and returns to zero. The deviation for a half cycle caused by the main magnet rows M1 to M21 is two side magnet pairs Min,
The first-order integral of the vertical magnetic field along the electron trajectory from the entrance to the exit of the wiggler is offset by the mot, and becomes zero. In addition, the horizontal magnetic field is generated by the side magnet pair Sin at the entrance.
After a large swing in the negative direction, 22 peaks having a peak value of 0.13T in the positive direction are formed at equal intervals by the 22 electromagnet pairs S1 to S22, and the exit side magnet pair Mo is formed.
Due to t, it swings largely in the same direction as the inlet side and returns to zero. As for the horizontal magnetic field, the magnetic field generated by the electromagnet arrays S1 to S22 and the magnetic field generated by the two side magnet pairs Sin and Sot cancel each other out, and the first-order integral value of the horizontal magnetic field along the electron trajectory becomes zero. At this time, if the secondary integral values of the vertical and horizontal magnetic fields along the electron trajectory from the wiggler entrance to the exit are adjusted to be zero, not only the position of the electron beam passing through the wiggler but also the motion Since the direction also matches the original electron orbit, it is easy to maintain the orbit in the storage ring.

FIG. 3 is a diagram showing the trajectory displacement of the electron beam in the wiggler. The horizontal axis represents the distance in the wiggler axis direction, the vertical axis represents the displacement from the original position of the electron trajectory, and the dotted line is caused by the vertical magnetic field. The horizontal displacement and the solid line represent the vertical displacement due to the horizontal magnetic field. The horizontal displacement of the electron beam is biased to one side by the negative magnetic field generated at the entrance side magnet pair Min, and then reciprocates in a substantially sinusoidal manner by the main magnet arrays M1 to M21, and the exit side magnet pair. It is returned to the original orbital position by the mot. The maximum displacement during this time reaches approximately 0.6 mm. The electrons meandering by the magnetic field emit light in the tangential direction of the trajectory having an intensity inversely proportional to the square of the radius of curvature of the trajectory. On the other hand, the displacement in the vertical direction is
After receiving a strong acceleration force downward by in, the electromagnet row S1
~ S22 receives the force in the direction of returning upward step by step,
Finally, the side magnet array Sot returns to the original trajectory, and a parabola is drawn as a whole. It has the largest displacement at the center of the wiggler, with a deviation from the original orbit of about 2.3 mm.

FIG. 4 is a chart showing a change in the deflection angle of the electron beam in this embodiment. The horizontal axis represents the distance in the wiggler axis direction, and the vertical axis represents the deflection angle of the electron beam. The dotted line represents the electron beam deflection angle in the horizontal direction, and the solid line represents the deflection angle in the vertical direction. The horizontal deflection angle of the electron beam describes a periodic shape close to eleven sine waves between the entrance and the exit of the wiggler according to the change in the tangential direction of the electron orbit. The deflection angle amplitude is about 10
mrad. On the other hand, the vertical deflection angle undergoes strong deflection of about 5 mrad by the side magnet pair Sin at the entrance, and then the deflection is eliminated stepwise in the opposite direction by the electromagnet rows S1 to S22, and at the substantially central position of the wiggler. After passing the position where the deflection angle is zero and going too far to 5 mrad, the exit side magnet array Sot returns to the position where the deflection angle is zero.

FIG. 5 is a perspective view showing a trajectory of an electron beam in the wiggler of the present invention. The electron beam is incident on the wiggler, deflected vertically downward, and then proceeds while reciprocating horizontally in the vertical alternating magnetic field. Then, during this period, a force gradually returning vertically upward is received for each cycle, so that a parabolic arc is drawn as a whole to reach the exit of the wiggler. In order to maintain the orbit in the storage ring, the position and orientation of the electron beam at the exit of the wiggler must be restored to the same state as when the wiggler is not inserted into the storage ring. The trajectory of the electron beam formed in this manner is a sine wave having an amplitude of about 0.6 mm and a band having a maximum droop of about 2.3 mm. The radiation emitted from the electron beam fluctuates in the horizontal direction by a deflection angle of 10 mrad, and the deflection angle in the vertical direction changes from -5 mrad to +5 mrad during the period from when the electron beam enters the wiggler until the electron beam exits. .

Therefore, the projection trajectory of the radiated light observed at a position appropriately distant from the wiggler scans a rectangular plane as shown in FIG. That is, the deflection angle of the electron beam incident on the wiggler is changed at the entrance position of the wiggler by the entrance side electromagnet Sin of the sub-magnet row for generating the horizontal magnetic field, and the irradiation position of the emitted light is vertically downward from the origin O in the drawing. Kick and move to point A in the figure at the center of the lower side of the irradiation surface. Next, the irradiation position of the radiated light is kicked in the horizontal direction by the pair of entrance-side side magnets Min of the main magnet row for generating a vertical magnetic field, and moves to a point B in the drawing, which is one end point of the lower side of the irradiation surface. Furthermore, while the electron beam is kicked in the opposite horizontal direction by the main magnet row, the deflection angle is changed in the vertical direction by the electromagnet row S1 of the sub-magnet row, so that the irradiation position is the other end point on the lower side of the irradiation surface in the figure. Move to point C. In the same manner, in the same manner, the laser beam moves upward and downward from the bottom while reciprocating horizontally within the irradiation surface.
The irradiation position moved from point U, which is one end point of the upper side of the irradiation surface, to point W at the center of the upper side is set as the exit side magnet pair Sot.
As a result, the scanning is kicked from the point W to the origin O, and one scan is completed. In this way, the emitted light can scan a substantially rectangular plane within a very short time after passing through the wiggler.

Accordingly, by using the two-dimensional scanning wiggler of the present invention, it is possible to directly perform extremely high-speed planar scanning, and to radiate the object from the wiggler when it is necessary to irradiate the object in a planar manner. There is no need to deflect the emitted light with a two-dimensionally oscillating reflecting mirror or to drive the irradiation target two-dimensionally. Further, when the scanning mechanism of this embodiment is used together with a means for changing the wavelength of the emitted light, the two wavelengths sandwiching the K-absorption edge of iodine are switched at about 2 ms to irradiate the two-dimensional scanning surface, so that the iodine is changed. Angiography of the coronary artery of the heart utilizing the large difference in the mass absorption coefficient of the X-ray before and after the K absorption edge can be easily obtained. Although the emitted light has a natural spread angle, the trajectory of the center of the emitted light is displayed in FIG. 6 ignoring the spread angle.

Although the above embodiment has been described based on a multi-period wiggler having a main magnet row composed of 21 electromagnet pairs, it does not depend on the number of magnet pairs in light of the technical idea of the present invention. It is clear. Although the wiggler using a superconducting electromagnet as the main magnet has been described, it goes without saying that the wiggler using a normal electroconductive magnet, a permanent magnet, or a hybrid magnet as the main magnet and the sub magnet can be applied without any change. Nor. In this embodiment, the horizontal wiggler has been described. However, it is needless to say that the same effect can be obtained by equipping the sub-magnet row perpendicularly to the main magnet row in the case of the vertical wiggler. Although the mode in which the horizontal magnetic field is changed stepwise by discretely disposing the sub magnet pairs has been described, the magnetic field may be changed continuously. In addition, the magnetic field distribution by the sub-magnet array is set to be point-symmetric with respect to the center of the wiggler, but the point is that the deflection angle only needs to gradually change in the sub-scanning direction. It is also possible to adopt a configuration in which the inner side magnet pair cancels out and the exit side magnet pair is omitted. In the present embodiment, the two-dimensional scanning wiggler is inserted into the storage ring and used.
The same effect can be obtained even when applied to a linac.

[0018]

As described in detail above, the two-dimensional scanning wiggler of the present invention directly generates radiation for two-dimensional scanning at a high speed, and therefore requires irradiation which requires radiation spread in a plane. It can be applied to objects. Also, the two-dimensional scanning wiggler of the present invention can be manufactured relatively economically because it is constituted by a magnet array incorporated in the wiggler itself without using any special accessories, and is easily used industrially. .

[Brief description of the drawings]

FIG. 1 is a diagram showing a magnet arrangement in an embodiment of a two-dimensional scanning wiggler of the present invention.

FIG. 2 is a magnetic field distribution diagram in a wiggler in the present embodiment.

FIG. 3 is an orbital displacement diagram of an electron beam in the present embodiment.

FIG. 4 is a drawing showing a deflection angle of an electron beam in the present embodiment.

FIG. 5 is a perspective view showing a trajectory of an electron beam in a wiggler of the present invention.

FIG. 6 is a view showing a trajectory scanned by light emitted from a two-dimensional scanning wiggler of the present invention.

[Explanation of symbols]

Min Inlet side magnet pairs of the main magnet row for generating a vertical magnetic field M1 to M21 Main magnet pairs of the same main magnet row Mot Outlet side magnet pairs of the same main magnet row Sin Sin On the inlet side of the sub magnet row for horizontal magnetic field generation Magnet pair S1 to S22 Electromagnet pair of sub-magnet row as above Sot Outlet side magnet pair of sub-magnet row as above

Continuation of the front page (56) References JP-A-4-267100 (JP, A) JP-A-60-68539 (JP, A) JP-A-5-242999 (JP, A) JP-A-60-146500 (JP, A) JP-A-5-217696 (JP, A) JP-A-60-180100 (JP, A) JP-A-8-138988 (JP, A) JP-A-63-226899 (JP, A) 4-36698 (JP, A) JP-A-4-204300 (JP, A) JP-A-4-42988 (JP, A) JP-A-7-236632 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H05H 13/04 G21K 1/093 H05H 7/04

Claims (4)

(57) [Claims] 1. A multi-pole wiggler having a plurality of main magnet pairs periodically arranged so that magnetic fields alternate, and a sub-polar wiggler for generating a magnetic field in a direction substantially perpendicular to a magnetic field generated by a row of the main magnet pairs. A plurality of magnet pairs are arranged at substantially equal intervals between the main magnets.
Wherein the main magnet row has an electronic trajectory of a generated magnetic field.
Arranged so that the first-order integral along the road is almost zero,
In addition, the sub-magnet row is enlarged by the first magnet pair to the electron beam.
To provide a large deflection angle, followed by multiple pairs of magnets in opposite steps
To compensate for the difference with the last magnet pair.
1 along the electron trajectory of the magnetic field generated by the sub magnet array.
Arrangement is made so that the next integral value becomes substantially zero, and the electron beam is sub-scanned in a direction substantially perpendicular to the meandering surface by the sub-magnet pair while meandering by the row of the main magnet pairs. Is a two-dimensional scanning wiggler that allows two-dimensional scanning. 2. A two-dimensional scanning wiggler according to claim 1, wherein the main magnet and the auxiliary magnet is an electromagnet. 3. A 2-dimensional scanning wiggler according to claim 1 or 2, wherein said main magnet is an electromagnet with a superconducting winding. 4. The radiation beam is two-dimensionally generated by periodically meandering an electron beam in a multipole wiggler in one direction and by sub-scanning in a direction perpendicular to the meandering direction. The sub-scanning is largely deflected first, then deflected stepwise in the opposite direction, and finally deflected until it compensates for the difference from the initial direction. A method of generating emitted light, comprising returning to a direction.