JPH0442988A - Wiggler for free electron laser - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention "Industrial Application Field" The present invention is directed to a free electron laser wiggler for applying a periodic magnetic field to an electron beam in order to obtain 17-ther light or synchrotron radiation in a nonchlotron or linear accelerator. Regarding.

``Prior art'' Wiggler for free electron lasers generates synchrotron radiation by meandering the flight direction of electrons accumulated in a synchrotron or linear accelerator, and at the same time generates laser oscillation by resonance between the synchrotron and a magnetic field. For example, Nuclear
I instruments and Metbods i
n Physics Research A25
0 (1986), pages 120 to 124, as shown in Figure 7, electronic It is disclosed that a periodic magnetic field is generated for the beam.

Also, on pages 100 to 109 of the above-mentioned document, there is
As shown in the figure, it is disclosed that a periodic magnetic field is generated for an electron beam by alternately arranging permanent magnets and magnetic poles so that the different poles of each magnet face each other. There is.

[Problems to be Solved by the Invention] As can be seen from FIGS. 7 and 8, the conventional wiggler for free electron lasers has a structure in which the trajectory of the electrons is sandwiched between them.
Rectangular magnet 10 extending in a direction perpendicular to the orbit
It has a configuration in which 0 is arranged. Therefore, the cross-sectional shapes of the magnets 100 on the opposing surfaces 102 of the upper and lower magnetic poles 101 sandwiching the electron orbit are each rectangular, and in the extending direction of each magnet 100 (corresponding to part a in the park), the b direction of the magnet 100 The dimensions were constant. Therefore, the magnetic field strength was constant over the a direction of each magnet 100.

Therefore, as shown in the simulation of the electron beam trajectory in Figure 9, the incident position of the electron beam (thus, the electron beam jumps out of the wiggler, causing the problem that laser oscillation is not formed1,1). In addition, each wavy line shown in Figure 9 represents the flight trajectory of the electron, and as shown in the direction C, depending on the incident position of the electron, the electron beam may easily deviate from the wiggler as described above. be.

The present invention has been made to solve these problems, and an object of the present invention is to provide a wiggler for a free electron laser in which the formed electron beam does not deviate from the wiggler and laser oscillation is performed.

[Means for Solving the Problems] The present invention provides a wiggler for free electron lasers, in which a vacuum duct is provided between two facing magnetic poles that generate a magnetic field, and an electron beam is formed within the vacuum duct. , magnetic material magnetic poles arranged at appropriate intervals in the traveling direction so that the magnetic field direction and magnetic force intensity distribution are different in the direction perpendicular to the traveling direction of the electrons, and the magnetic material magnetic poles sandwiching the magnetic material magnetic pole. Each of the magnets includes a permanent magnet that magnetizes the magnetic poles so as to generate the magnetic field direction and magnetic force intensity distribution.

[Operation] With this configuration, the magnetic poles form magnetic fields whose magnetic field directions and magnetic force intensity distributions are opposite to each other. Therefore, the magnetic pole acts to prevent the flying electrons from scattering, thereby suppressing the formation of the electron beam.

[Example] In FIG. 1 showing an example of the wiggler for free electron lasers of the present invention, a cylindrical vacuum duct l in which an electron beam is formed in the cavity center has a flat surface 2a. Sandwiched between two magnetic poles 2. At this time, the surface 2a
are installed so as to be in contact with the outer peripheral surface of the vacuum duct l and to be parallel to each other. Such magnetic poles 2 have a rectangular cross-sectional shape, and each of the magnetic poles 2 is U-shaped and fixed to the bottom surface 3b of a recess 3a of a support 3 made of a non-magnetic material. Incidentally, the surface 2a of the magnetic pole 2 does not protrude from the recess 3a, and the vacuum duct 1 is located approximately in the center of each surface 2a, and the magnetic pole 2 is located approximately in the center of the recess 3a. established in

As shown in FIG. 2, these two upper and lower magnetic poles 2 have a trapezoidal cross-sectional shape on the surface 2a so that the widths are different in the direction perpendicular to the traveling direction of the electrons forming the electron beam. Magnetic poles 4 made of a magnetic material and permanent magnets 5 having an appropriate thickness and parallel to the side surface of the magnetic material magnetic pole 4 on the electron beam direction side are alternately provided. The adjacent magnetic poles 4 are arranged such that their trapezoidal cross-sectional shapes on the surface 2a are reversed by 180 degrees. Also, the first
The part of the magnetic pole 2 indicated by A in the figure corresponds to the part indicated by A in FIG. Further, in the upper and lower magnetic poles 2 that sandwich the vacuum duct 1, both magnetic poles 2 are provided so that the magnetic body magnetic poles 4 face each other and the permanent magnets 5 face each other, and the magnetic column body magnetic poles 4 and 7 that face each other are provided. The direction of the magnet 5 is the same.

In other words, in the opposing upper and lower magnetic poles 4, the narrow portions 4a are opposed to each other, and the wide portions 4h are opposed to each other.

By sandwiching the magnetic pole 4 between the permanent magnets 5 in this manner, the magnetic pole 4 is magnetized. Further, the adjacent permanent magnets 5'+17 have different magnetic poles. (
77' Also in the magnetic poles 4 magnetized by the permanent magnet 5, the adjacent ones and the magnetic poles 51 are different from each other. Further, the opposing upper and lower magnetic poles 4 and permanent magnets 5 are also arranged so as to have different magnetic poles.

In this way, in each of the magnetic poles 4, the width of the magnetic pole 4 is changed in the direction perpendicular to the traveling direction of electrons, so that the width of the magnetic pole 4 is narrow as shown in FIG. The magnetic field strength increases from the portion 4a toward the wide portion 4b. In addition, in FIG. 4, the portion indicated by X=0 approximately corresponds to the electron PJ formation position (position A/2) shown in FIG. Therefore, the magnetic field strength is no longer constant in the direction (width direction) of the magnetic poles 4, and the magnetic field strength distribution is reversed in the adjacent magnetic poles 4. Therefore, the magnetic field strength distribution in the narrow part 4a and the wide part 4h of the magnetic pole 4 is alternately strong and weak in the direction of movement of electrons, and The magnetic field strength in the vicinity of any of the magnetic poles 4 is averaged. Therefore, even if some electrons try to escape in the width direction of the wiggler, they can be focused on the widthwise center of the magnetic pole 4.

Therefore, since the electron beam can be formed at the center of the wiggler in the width direction, laser oscillation can be generated. Furthermore, it has been confirmed that the electron beam converges in the Simico 1 nosion of the electron beam trajectory, as shown in FIG. 5, regardless of the position of incidence of the electrons on the wiggler.

FIG. 6 shows another embodiment of the wiggler for a free electron 1 noser according to the present invention. Yoke+
They are connected at o-+, u+-2, and to3- (representatively referred to as yoke 10) and are integrally formed.

The yoke 10 has a C-shape as shown in Fig. 6, and is constant except for the facing part 11-4. It depends on the thickness. The opposing portion +1 is formed such that the width of the outer surface 11a of the yoke 10 is greater than the width of the inner surface 111 of the yoke 10, and the horizontal cross-sectional shape of the opposing portion 11 is trapezoidal as shown in the figure. It is. Opposing part 11- which has such a shape
1 and 1l-2 have opposing surfaces 11c and lld that face each other horizontally and in parallel at the center of the yoke lO.

In the yokes 10-1, 10-2, and 10-2 having such a shape, as shown in the figure, in the adjacent yokes 10, each column part 10a is distributed to the left and right, and each opposing part 11 is arranged in the same row. They are placed in such a way that they line up. Moreover, the opposing surfaces 11c and lId of the adjacent yoke 10 are
The facing surface portion of the yoke 10 formed by the yoke 10 and the permanent magnet 5 formed by the permanent magnet 5 and the corrugated iron 1° sandwiched between the permanent magnet 5 formed with the same thickness and the same surface as the above-mentioned first implementation. Similar to the example, the trapezoidal cross section as shown in FIG. The yoke 10 and the permanent magnet 5 are supported by suitable supports (not shown), and each yoke 10 has a column 1 (10a has a conductor 14).
is wound. By energizing the conducting wire 14, the facing portion 11 of each yoke 10 becomes a magnetic pole. In addition, the adjacent opposing part 1
1 and 1] Connect the conductor wires 1 so that they have different magnetic poles.
4 is energized.

First, a vacuum duct 1 (not shown) is installed along the opposing surfaces in the space 13 sandwiched between the opposing surfaces, and the electrons fly through the vacuum duct 1. is formed.

In the wiggler in the second embodiment configured as described above, since the opposing portion I11 has a trapezoidal cross-sectional shape, the magnetic force intensity generated in the opposing portion 11 is controlled in the direction of movement of electrons, as in the first embodiment. The electron beam formed as described above can be changed in the direction perpendicular to the facing part 1.
It can be made to converge at the width direction center part of 1.

Furthermore, in this embodiment, by controlling the current or voltage supplied to the conductor 14 wound around each yoke 10, each yoke IO
It is possible to control the magnetic field strength generated at each time. Therefore, it is possible to form a desired magnetic field distribution along the direction of electron travel.

This produces the following effects. That is, the electrons traveling through the wiggler gradually lose energy due to the generation of light, so the wavelength of the light generated by the electrons changes. Therefore, in order to always obtain light of the same wavelength, it is necessary to lower the strength of the magnetic field as the energy of the electrons decreases. As described above, in this embodiment, it is possible to control the magnetic field distribution formed in the facing portion 11 of the yoke 10 by controlling the current or voltage supplied to the conductor wire 14 of each yoke 10. Light of the same wavelength can be obtained over the entire length of the wiggler, making it possible to improve the efficiency of the laser.

[Effects of the Invention] As detailed above, according to the present invention, a magnetic pole is formed by forming a magnetic field such that the magnetic field direction and magnetic force intensity distribution are different in the direction perpendicular to the traveling direction of electrons. The electron beam does not deviate from the wiggler, and the electron beam can be focused in a direction perpendicular to the direction in which the electrons travel, making it easy to perform laser oscillation.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the structure of a first embodiment of the wiggler for free electron lasers of the present invention, FIG. 2 is a plan view showing the structure on the surface of the magnetic pole shown in FIG. 1, and FIG. Figure 4 is a graph showing the magnetic field distribution at the magnetic pole shown in Figure 1, Figure 5 is a graph simulating the state of electron beam formation by the wiggler shown in Figure 1, Figure 6 is a side view of the magnetic pole shown in the figure. A perspective view showing the structure of a second embodiment of the wiggler for free electron lasers of the present invention, FIG. 7 is a perspective view showing the magnetic poles constituting the conventional wiggler, and FIG. 8 shows the magnetic poles constituting the conventional wiggler. The plan view and FIG. 9 are graphs simulating the formation state of an electron beam formed by a conventional wiggler. Fig. 6 2...Magnetic pole, 4...Magnetic material magnetic pole, 5...Permanent magnet, I
O.Yoke, 14...Conductor.

Claims (3)

[Claims] (1) A wiggler for free electron lasers, in which a vacuum duct is provided between two facing magnetic poles that generate a magnetic field, and an electron beam is formed within the vacuum duct, with the direction of the magnetic field perpendicular to the traveling direction of the electrons. and magnetic material magnetic poles arranged at appropriate intervals in the traveling direction so as to have different magnetic force intensity distributions, and generating the magnetic field direction and magnetic force intensity distribution in each of the magnetic material magnetic poles with the magnetic material magnetic poles sandwiched therebetween. A wiggler for free electrons, comprising: a permanent magnet that magnetizes the magnetic pole of the magnetic material. (2) The magnetic poles include a first magnetic pole that forms a magnetic field with different magnetic strengths in a direction perpendicular to the traveling direction of the electron beam, and a direction opposite to the direction of the magnetic field formed by the first magnetic pole. 2. The wiggler for a free electron laser according to claim 1, further comprising a second magnetic pole that forms a magnetic field and a magnetic strength distribution opposite to that formed by the first magnetic pole. (3) The two facing first magnetic poles and the second magnetic poles are separately formed integrally with a yoke, and a conducting wire is wound around the yoke in order to generate a magnetic field. The wiggler for a free electron laser according to claim 2.