JPH047600B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a circularly polarized light generating device that uses high-speed electrons in an electron storage ring to alternately and periodically obtain clockwise and counterclockwise circularly polarized light. be.

[Prior art]

In measurements that investigate the circular dichroism or magnetic circular dichroism of a substance, a circularly polarized light generator that periodically generates clockwise and counterclockwise circularly polarized light alternately is required as a light source. A circularly polarized light generator is also required to create spin-polarized electrons using the phenomenon of photoelectron emission from a single crystal.

Conventionally, the mainstream of devices that periodically generate clockwise and counterclockwise circularly polarized light alternately and periodically uses optical elements. Methods that utilize the photoelasticity of crystals have been adopted as the operating principle. For this reason, even if calcium fluoride, which has the shortest transmission wavelength, was used, it was not possible to create circularly polarized light with a wavelength shorter than about 1300 Å.

On the other hand, in this type of device, which has no wavelength limit in principle, a double helical coil is placed in the trajectory of high-speed electrons, and currents in opposite directions are applied to each coil. A helical type with a magnetic field transverse to the axis on the central axis, and the direction of the magnetic field rotating in a spiral along the axis.
There was something called a Wiggler. When high-speed electrons run along the central axis of this double helical coil, the electrons also move in a helical pattern due to the Lorentz force, emitting circularly polarized bremsstrahlung light in the forward direction. In addition, this synchrotron radiation interferes at a specific wavelength depending on the length of one period of the coil, so strong light can be obtained (BMKincaid, “A Short
−period Helical Wiggler as an Improved
Source of Synchrotronradiation” Journal of
Applied Physics.vol 48, No. 7, Jujy 1977,
p2684-2691, LRElias, et al. “Observation
of Stimulated Emission of Radiation by
Relativistic Electrons in a Spatially
Periodic Transverse Magnetic Field”
Physical Review Letters vol 36, No.13,
(See March 1976, p717-720, in which the literature confirms that circularly polarized light is generated from helical wigglers).

However, in such conventional devices, the direction of rotation of the helical motion of the electrons is uniquely determined by the way the double helical coil is wound, and therefore only one of clockwise or counterclockwise circularly polarized light can be obtained. Nakatsuta.

[Purpose of the invention]

This invention was made in consideration of the above points, and utilizes a high-speed electron beam of an electron storage ring.
It is an object of the present invention to provide a circularly polarized light generating device that can alternately and periodically obtain clockwise and counterclockwise circularly polarized light and can generate circularly polarized light that can be used up to extremely high frequencies.

[Embodiments of the invention]

In order to achieve the above-mentioned object, the present invention provides a plurality of magnets and electromagnets with different polarities alternately in a straight portion in the circumferential direction of an electron storage ring so as to be perpendicular to each other to create a helical magnetic field, thereby causing electrons to move in a helical manner. It is designed to generate polarized light. This invention will be explained below.

Before describing embodiments of the present invention, the basic operation of an electron storage ring will first be described with reference to FIG. In Figure 1, 1 is a bending electromagnet, 2 is a high frequency acceleration cavity that gives energy to electrons, 3 is a ring-shaped vacuum path through which high-speed electrons run, 4 is an inflector for electron injection from the outside, and 5 is an inflector. These make up an electron storage ring in the perturbator.

The outline of the operation will be explained below.

An electron beam E _b is injected into the electron storage ring having the above configuration using an injector such as a linear accelerator, and the electron beam E b is rotated in the ring-shaped vacuum path 3 for a long time.
It can accumulate 10 ¹⁰ to ^{10 11} electrons. The electrons running in this vacuum path 3 change direction due to the magnetic field at each bending electromagnet 1, and at this time, light (synchrotron radiation) is emitted by relativistic dipole radiation. The energy loss due to the emission of light is replenished into electrons by the high frequency acceleration cavity 2.
This is an overview of an electron storage ring.

FIG. 2 is a configuration block diagram showing one embodiment of the present invention, and 1 to 5 indicate the same things as in FIG.
6 is a straight portion of the vacuum path 3; 7 is a circularly polarized light generator that generates circularly polarized light, and is composed of a magnetic field generator 8 and an AC power source 9. Note that 10 is a left and right circularly polarized light extraction port. The details of the configuration and operation of the magnetic field generator 8 will be explained below with reference to FIGS. 3 and 4.

FIG. 3 shows the magnetic field generating section 8 in the embodiment shown in FIG.
is a perspective view showing the configuration of a pair of upper and lower magnets A ₁
creates a magnetic field in one direction, and similarly a pair of upper and lower magnets
A ₂ creates a magnetic field in the opposite direction to the magnetic field of magnet A ₁ . magnet
Since A ₁ and A ₂ must always maintain a magnetic field of the same strength and in one direction, they may be made of permanent magnets. Magnet A ₂
A plurality of pairs of electron beams E b and A ₂ are arranged in a straight line along the traveling direction M of the electron beam E _b as shown in FIG.
The spacing between two adjacent magnets should be equal. These series of magnets (A ₁ , A ₂ , A ₁ , A ₂ ...A ₁ , A ₂
) forms a magnetic field distribution in which the direction of the magnetic field is periodically reversed along the axis of the electron beam E _b . Next _{, a set of electromagnets B 1 and B 2 ( thus electromagnets} B ₁ and _{B 2}
The direction of the magnetic field is opposite to that of magnet A), and are shifted by 1/4 period length of the magnetic field period of magnet A, as shown in Figure 3.
Insert the magnets between A ₁ and A ₂ and between A ₂ and A ₁ (therefore, they will be lined up repeatedly in the order of A ₁ B ₁ A ₂ B ₂ A ₁ B ₁ A ₂ B ₂ ...). The magnetic field strengths of A ₁ , A ₂ , B ₁ , and B ₂ are all the same. Also, A ₁ , A ₂ ,
The number of each of B ₁ and B ₂ should also be the same. The larger the number, the better the intensity and coherence of the emitted light, but this number is determined depending on the conditions of use.

The distribution of the direction of the magnetic field generated by these magnets A (magnet group consisting of A ₁ and A ₂ ) and electromagnet B (electromagnet group consisting of B ₁ and B ₂ ) is distributed along the central axis M.
As shown in Figures a and b (the arrow indicates the direction of the magnetic field on the central axis M), it is rotating spirally. In the case of Fig. 4a, it is a clockwise spiral rotation, and if the flow of current supplied to electromagnets B ₁ and B ₂ is reversed, the directions of the magnetic fields of electromagnets B ₁ and B ₂ will be respectively In contrast, the direction of rotation of the magnetic field along the central axis M is counterclockwise as shown in FIG. 4b. In this way, by changing the flow direction of the current supplied to the electromagnets B ₁ and B ₂ , it is possible to switch between the clockwise helical magnetic field distribution and the counterclockwise helical magnetic field distribution. High-speed electrons passing through the central axis M of a space with such a magnetic field distribution are subjected to the Lorentz force, and in the case of Figure 4a, they run in a clockwise spiral, and in the case of Figure 4b, they move in a counterclockwise helical motion. I do. High-speed electrons in helical motion emit circularly polarized light (references above)
P.2685, refer to document P.718). Electrons that perform a clockwise helical motion emit counterclockwise circularly polarized light, and electrons that perform a counterclockwise helical motion emit clockwise circularly polarized light. When the speed of electrons is close to the speed of light, the circularly polarized light is strongly concentrated in the forward direction due to relativistic effects. Furthermore, the light emitted by the respective magnetic fields of magnet A and electromagnet B interfere with each other and strengthen each other at the wavelength λ ₁₀ (Å) shown in equation (1) below.

λ ₁₀ =λ ₀ (1+K ² )/2γ ² (1) where K=0.093×B ₀ ×λ ₀ and γ=E/0.51 (see the above reference).

Here, λ ₀ represents the length of one period (cm) of the magnetic field shown in FIG. 4a, B ₀ represents the strength of the magnetic field (K Gauss), and E represents the energy of the electron (Me V).

Next, based on the above equation (1), B ₀ = 2(K
Gauss), λ ₀ = 6 (cm), and E = 600 (MeV), the wavelength λ ₁₀ is found to be 470 Å. in this case,
The radius of rotation of a relativistic electron in helical motion is approximately
It was found that the pitch angle (the angle formed by the helical trajectory with respect to the central axis M) was approximately 1 mnradian.
Generally, as the number of magnets A and electromagnets B increases, the coherence improves and the intensity of emitted light increases. Also, the above
As is clear from equation (1) _, the interfering wavelength λ ₁₀ changes as the electron energy _E and magnetic field strength B ₀ change. , a clockwise rotation in which the wavelength λ ₁₀ is variable by continuously changing the energy of the electrons running in the electron storage ring or the strength of the magnetic field,
Left-handed circularly polarized light is obtained periodically.

Note that by making the switching cycle of the current of the AC power supply 9 supplied from the AC power supply 9 to the magnetic field generation unit 8 of the circularly polarized light generator 7 variable, the clockwise and counterclockwise repetition cycles of circularly polarized light can be easily changed. Needless to say.

〔Effect of the invention〕

As explained in detail above, this invention arranges magnets and electromagnets alternately and obtains a predetermined circularly polarized light by excitation of the electromagnets. Because it gives helical motion to the electrons in the ring and can easily change the direction of rotation periodically, it is possible to measure circular dichroism and magnetic circular dichroism of materials over a wide wavelength range from infrared to soft X-rays. It can generate left-right circularly polarized light with a wide range of applications and a high degree of freedom. It also has the advantage of contributing to the generation of spin-polarized electrons.

[Brief explanation of drawings]

Fig. 1 is a block diagram of the structure of an electron storage ring, Fig. 2 is a block diagram of an embodiment of the present invention, Fig. 3 is a schematic diagram of a magnetic field generating section applied to an embodiment of the invention, and Fig. 4 a and b are schematic diagrams showing electron beam trajectories. In the figure, 1 is a bending electromagnet, 2 is a high frequency acceleration cavity,
3 is a vacuum path, 4 is an inflator, 5 is a perturbator, 6 is a linear section, 7 is a circularly polarized light generator, 8 is a magnetic field generator, 9 is an AC power supply, 10 is a left and right circularly polarized light extraction port, E _b is an electron In the beam, A (A ₁ , A ₂ ,...) is a magnet, B (B ₁ , B ₂ ,...) is an electromagnet, and M is a central axis.

Claims (1)

[Claims] 1 A circularly polarized light generator using an electron storage ring that accumulates high-speed electrons, in which two sets of magnet rows A and B are arranged along the traveling direction of the electron beam, and one magnet row A has a constant strength. This magnet array A consists of two types of magnets A _{1 and 2} with opposite magnetic field directions.
A ₂ is arranged alternately at equal intervals in the circumferential direction of the electron storage ring, and the direction of the magnetic field is orthogonal to the circumferential direction of the electron storage ring, and the other magnet row B is Consisting of multiple electromagnets with magnetic fields of the same strength as magnet array A, magnet array B consists of two types of electromagnets with the magnetic field directions reversed.
B ₁ and B ₂ are alternately arranged in the circumferential direction of the electron storage ring at the same intervals as the magnet row A, and the direction of the magnetic field is relative to the circumferential direction of the storage ring and the magnetic field direction of the magnet row A. The magnets are arranged so as to be perpendicular to each other and shifted by 1/4 period with respect to the magnetic field distribution of the magnet row A, and are provided with an AC power source that simultaneously reverses the direction of the magnetic field of the electromagnet row B. A circularly polarized light generator characterized by: