JPH0785439B2 - Bending electromagnet - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a structure of a superconducting deflection electromagnet in a storage ring as a charged particle accelerating and accumulating device for accelerating or accumulating charged particles by rotating them on a closed orbit. is there.

[Conventional technology]

Conventional synchrotrons and storage rings are manufactured for high-energy physics experiments (mainly experiments for interaction of elementary particles and collisions of electrons and positrons, protons and antiprotons, and discovery of new particles). And was generally large (tens of meters to tens of kilometers in diameter). As described above, the conventional accelerator is large in size and is composed of a large number of deflection electromagnets, and each deflection electromagnet has a substantially linear structure.

On the other hand, recently, SOR light emitted when electrons or positrons orbit is used for surface analysis such as photoelectron spectroscopy or semiconductor L
Attention has been paid to its use as a light source for X-ray lithography when manufacturing SI. In this semiconductor industry this SO
The introduction of the R light source requires a storage ring that is smaller and designed specifically than before. For this reason, attempts are being made worldwide to reduce the size of storage rings.

One effective direction for downsizing is to make the deflection electromagnet superconducting and deflect one electron by 180 degrees so that the orbit radius of the electron is on the order of several tens of centimeters. This is described, for example, in “Heuberga, Solid State Engineering, p. 93, 1986, February (A. Heuberger, Solid State Technology, p. 93, February.
1986) ”.

[Problems to be solved by the invention]

However, a specific magnet structure that secures a uniform magnetic field in a wide area of a plane perpendicular to the orbital axis through which electrons pass and at the same time can extract SOR light has not yet been realized.

Further, the conventional superconducting bending electromagnet is manufactured for the above-mentioned elementary particle experiment, and has a so-called cos θ winding coil structure with a linear structure and no space for SOR light extraction. For this reason, the collar and cryostat (insulating container) that support the electromagnetic force of the coil and prevent heat from entering from the outside are all wrapped around the entire coil, and the space for SOR light extraction cannot be taken freely. Has become.
Also, since the vacuum system is not at room temperature, the vacuum duct cannot be easily assembled and removed.

The present invention has been made in view of such a point, and the purpose thereof is, regarding the structure of the collar and the cryostat, a space for SOR light extraction can be freely set, and the vacuum system is set to room temperature. An object of the present invention is to provide a miniaturized SOR exposure apparatus that can be easily assembled and removed and is suitable for the semiconductor industry.

[Means for solving problems]

In order to achieve such an object, the present invention provides a bending electromagnet of a charged particle accelerator in which the horizontal cross section of the vacuum duct is substantially fan-shaped, and a pair of vacuum ducts are provided above and below the vacuum duct. To enclose the vacuum duct and the SOR light extraction pipe connected to this duct, in which a loop is formed so that currents in opposite directions flow inside and outside along the vacuum duct in order to generate a deflection magnetic field. And a heat insulating container surrounding the collar integrally formed with a non-magnetic material that supports the upper and lower exciting coils, and a vertical cross section along the vacuum duct of the collar and the heat insulating container is U-shaped with a groove open to the outside of the duct so that the extraction pipe can be fitted and removed freely, so that the duct and the extraction pipe can be installed in the groove. Those were.

[Action]

In the bending electromagnet according to the present invention, the vacuum duct can be easily accessed.

〔Example〕

First, the features of the present invention will be described. In the present invention, the charged particles are deflected by 180 degrees by a deflection electromagnet having one or a plurality of coils, and the orbit radius is reduced to about several tens of cm.
With a coil layout structure that was able to be made significantly smaller than the conventional circular acceleration storage device, the collar that supports the superconducting coil and the structure of the cryostat that prevents heat intrusion have been secured with an area for SOR light extraction. The main feature is that the structure facilitates access to the vacuum duct through which charged particles pass.

FIG. 1 is a perspective view showing an embodiment of a deflecting electromagnet according to the present invention. For easy understanding of the structure, the collar 1 is drawn with the upper half of the half and the exciting coil 2 with the upper half. . First
In the figure, 3 is a vacuum duct, 4 is a SOR light extraction pipe, 5 is SOR light, and S is an electron beam.

FIG. 2 is a cross-sectional view in the yz plane including the z-axis of FIG. 1, showing an air-core type bending electromagnet. In FIG. 2, 1 is a collar, 2 is an exciting coil, 3 is a vacuum duct, 4 is a SOR light extraction pipe, 6 is a cryostat, 7 is a vacuum part of the cryostat 6, 8 is a groove, 8a is an opening, and 9 is a leg. It is a department.

In FIG. 2, a collar 1 is an upper and lower exciting coil 2
The magnetizing coil 2 is made of a non-magnetic material and is integrally formed. The exciting coil 2 forms a loop so that currents in opposite directions flow inward and outward along the vacuum duct 3 to generate a deflection magnetic field in the vacuum duct 3. They are formed and placed above and below with the vacuum duct 3 interposed therebetween. The vacuum duct 3 has a substantially fan-shaped horizontal cross section. The cryostat (heat insulating container) 6 has a structure surrounding the collar 1, and a groove 8 is formed in the collar 1 and the cryostat 6. The bending electromagnet is composed of a collar 1, an exciting coil 2, a cryostat 6 and a leg portion 9. The vacuum duct 3 and the SOR light extraction pipe 4 connected to the vacuum duct 3 are installed in the groove 8. The electron beam S travels in the vacuum duct 3 in the direction of the arrow (see FIG. 1), and the SOR light 5 is extracted from the SOR light extraction pipe 4 to the outside of the fan-shaped vacuum duct 3. In addition, there are collars 1 above and below the fan-shaped portion of the vacuum duct 3,
There is no collar above or below the straight line (see Figure 1). Similar collars 1 are provided above and below a fan-shaped vacuum duct (not shown) on the opposite side of the straight line portion.

Further, FIG. 3 is a cross-sectional view in, for example, the yz plane including the z-axis of FIG. 1, showing a deflection electromagnet with a return yoke, except that the return yoke 10 is added to the deflection electromagnet. Is the same as.

2 and 3 each have a structure corresponding to a magnetic field strength of 3.5 T, an accumulated energy of 550 MeV, and an orbital radius of 52.38 cm. The features of the color 1 and the cryostat 6 will be described below.

The cross section of the stainless steel collar 1 that holds down the exciting coil 2 is U-shaped as shown in FIG. 2, and a U-shaped cryostat 6 is provided around it. Because of the U-shape, the magnetic field can be easily measured and the vacuum duct 3 can be easily accessed. That is, since the vacuum system is at room temperature,
It can be designed independently including the vacuum duct, and can be inserted into the groove 8 of the bending electromagnet later, and at that time, it is cooled by He flowing in the innermost space layer of the cryostat 6 (the space layers two more inside than the vacuum part 7). There is no need to cancel. Vacuum duct 3
The same is true when removing. Therefore, the degree of freedom of the SOR light extraction space is also increased. Such a structure is called a warm bore structure.

Regarding the manufacturing process, since the exciting coil is directly wound around the mold of the collar 1 as shown in FIG. 1, the winding can be performed while measuring the position (thickness) of the exciting coil. Therefore, the accuracy of the position of the exciting coil can be easily obtained. Assembly is
For example, the collar is divided into parts, the exciting coil is wound around the lower collar, and the collar is press-welded to embed the exciting coil inside to form an integrated structure. In this case, since the collar 1 presses down, the electromagnetic force can also be supported.

In the structure of the present embodiment, although initial cooling takes time, in the steady state, its own weight (about 4 tons in the case of stainless steel) should be thermally insulated from room temperature, and the consumption amount of liquid He is extremely small. . In addition, all electromagnetic force is suppressed by the structure. Moreover, if an Al alloy or the like, which has recently been used as a low temperature structural material, is used, the specific gravity is small and the thermal conductivity is extremely high, so that the own weight becomes about 1.5 tons and the cooling time becomes short.

With the structure as in the present embodiment, the axial electromagnetic force of the outer coil (upper and lower exciting coils on the right side of FIG. 2) (air core type and entire half circumference)
The deflection of the opening 8a (see Figs. 2 and 3) is about 0.5 mm or less in two-dimensional calculation when 135 tons and 66 tons of half circumference with return yoke are added. According to the calculation, in order to obtain the uniformity of 2 × 10 ⁻³ in the air-core type bending electromagnet, the position accuracy of the exciting coil should be −11.9 to 21.1 mm. Therefore, the above-mentioned degree of deflection has little effect on the magnetic field homogeneity. The calculation of electromagnetic force and the calculation of deflection will be described later in detail.

A drawback of the air core structure is that it takes a long time for initial cooling, but the use of an Al alloy or the like enables light and quick cooling. Furthermore, if the indirect forced circulation cooling method is adopted, the amount of liquid He required can be greatly reduced.

Next, the calculation of the electromagnetic force applied to the exciting coil will be described. When a current is passed through the exciting coil, an electromagnetic force attracting the outer exciting coil is generated, and this electromagnetic force tries to narrow the U-shaped groove 8. 4 and 5 show the calculation results of the electromagnetic force applied to the exciting coil 2 which is the basis of the calculation of the deflection. 4 shows the air-core type, and FIG. 5 shows the electromagnetic force with the return yoke. In FIGS. 4 and 5, the coil at the transition between the inner coil and the outer coil is jumped up by 30 degrees. Although the electromagnetic force applied to the coil at this transition can be calculated, it is not shown here because it is not necessary for the calculation of the two-dimensional strain and stress shown in the subsequent calculation. Further, each numerical value indicates the hoop force acting in the radial direction indicated by the arrowhead, and the axial force acting in the vertical direction (z direction) indicated inside the exciting coil 2. In these calculations, a continuous current having a volume is analytically solved according to Biot-Savart's law, and the electromagnetic force applied to each element of the exciting coil is calculated by Maxwell's stress.

It can be seen that in the case with the return yoke, the hoop force is averaged and the values are almost the same in the θ direction when the coordinate system is the r, θ coordinate system. Regarding the axial force, the value with the return yoke is less than 1/2 that of the air core type.

Based on the above detailed calculation, the total axial force acting on the outer coil is calculated to be 135 × 2 = 270 tons for the air core type and 66 × 2 = 132 tons for the return yoke type. This value was used as input data for the deflection calculation described below.

Next, the calculation of the deflection will be described. The deflection was two-dimensionally calculated using the axial force of the outer coil described in the calculation of the electromagnetic force as input data. In detail, three-dimensional calculation must be performed including the coil of the transition part,
Two-dimensional calculation was performed to see the order of deflection. FIG. 6 shows a cylindrical two-dimensional model. Regarding the bending electromagnet having the structure shown in FIGS. 2 and 3, the dimension R is as shown in FIG. 6 (a).
(Distance between z-axis and outer excitation coil), r (distance between z-axis and groove), T (width of excitation coil), H (thickness of collar 1) Pressure shall be applied. Since color 1 is rotating around the z axis,
Using the two-dimensional cylindrical model (thickness H) of FIG. (B), the pressure p applied inside is approximated by the pressure p from above, and the sixth
As shown in FIG. 6 (c), the deflection was approximated and calculated by the difference in the uniformly distributed loads.

Fig. 7 (a) shows the parameters of the 3.5T air-core type bending electromagnet of Fig. 2 (R = 73.5cm, T = 12cm, total axial force P = 270 tons, r =
Stress distribution (Fig. 7 (b)) and deflection distribution (Fig. 7 (c)) in the radial direction calculated using 42.5 cm, H = 20 cm are shown. In Figures 7 (b) and (c), S1 is the radial stress σr, S2 is the θ stress σθ, S3 is the amount of deflection when collar 1 is stainless steel, and S4 is the case when collar 1 is an Al alloy. Is the amount of deflection.

Fig. 8 shows the parameters (R = 73.5 cm, T = 10 cm, total axial force P = 132 tons, r = 42.5) with the 3.5T return yoke in Fig. 3.
cm, H = 15 cm) shows the radial stress distribution (Fig. 8 (b)) and the flexure distribution (Fig. 8 (c)).
8 (b) and 8 (c), S1 to S4 are the same stress and deflection amount as S1 to S4 in FIGS. 7 (b) and 7 (c).

In calculating the numerical values shown in FIGS. 7 and 8, the Young's modulus E of the Al constitutional value E = 7500 kg / mm ² and the stainless steel value E = 19700 kg / mm ² were used, and the Poisson's ratio ν was 0.3 for both.
And The total axial force P is P = pS, where p is the pressure per unit area and S is the area. This area S is
7 (a) and 8 (a), it is calculated by the following equation.

S = π (R + T) ² −πR ^{2 From the} above calculation result, the deflection is about 0.5 mm or less, and there is almost no influence on the magnetic field homogeneity. Moreover, the stress is well within the elastic limit, and there is no problem.

Note that the above calculation is a calculation when there is no filling material between the SOR light extraction pipes 4, but a filling material may be packed between the SOR light extraction pipes 4, in which case both the amount of deflection and the stress are further reduced. .

〔The invention's effect〕

As described above, according to the present invention, in order to generate a deflection magnetic field in the vacuum duct, exciting coils having loops formed so that currents in opposite directions flow inward and outward along the vacuum duct are vertically arranged with the vacuum duct interposed therebetween. A groove is provided in the collar that is placed above one pair and supports the upper and lower excitation coils and is integrated with a non-magnetic material, and the heat insulating container that surrounds this collar.The vacuum duct and the SOR light extraction pipe connected to the vacuum duct are placed in the groove. By installing it, you can connect the SOR light extraction pipe to the vacuum duct and fit it in the collar,
Assembling the vacuum duct has a high degree of spatial freedom in the vacuum duct.
There is an effect that it is possible to provide a small-sized SOR exposure apparatus suitable for the semiconductor industry that can be easily removed.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of a deflection electromagnet according to the present invention, FIG. 2 is a sectional view when the deflection electromagnet of FIG. 1 is an air core type, and FIG. 3 is a deflection electromagnet of FIG. FIG. 4 is a cross-sectional view of the case with a return yoke, FIG. 4 is an explanatory view showing the hoop force and axial force of the exciting coil of the air-core type deflection electromagnet, and FIG. 5 is the hoop force and axial force of the exciting coil of the deflection electromagnet with return yoke. FIG. 6 is an explanatory view showing a cylindrical two-dimensional model in which deflection is calculated, and FIGS. 7 (a), (b), and (c) are dimensions and pressures in the air-core type deflection electromagnet. An explanatory diagram and a graph showing radial deflection and stress distribution in the air-core type deflection electromagnet, and FIGS. 8A, 8B, and 8C show dimensions and pressure in the deflection electromagnet with a return yoke. Figure and bending magnet with return yoke Is a graph showing the distribution of radial deflection and stress. 1 ... Color, 2 ... Excitation coil, 3 ... Vacuum duct,
4 …… SOR light extraction pipe, 5 …… SOR light.

Claims (2)

[Claims] 1. A deflection electromagnet for a charged particle accelerator, wherein a horizontal cross section of a vacuum duct is substantially fan-shaped, in order to generate a deflection magnetic field in the vacuum duct, which is provided in a pair above and below the vacuum duct. Exciting coils that form loops so that current flows in the opposite directions inside and outside along the vacuum duct, and the upper and lower exciting coils that are provided so as to enclose the vacuum duct and the SOR light extraction pipe connected to this duct. A collar integrally formed of a non-magnetic material and a heat insulating container surrounding the collar, and a vertical cross section along the vacuum duct of the collar and the heat insulating container is such that the fitting and removal of the duct and the extraction pipe are It has a U-shape with a groove open to the outside of the duct so that the duct and the extraction pipe can be installed in the groove. Bending magnet to butterflies. 2. The deflection electromagnet according to claim 1, wherein the pair of exciting coils arranged above and below are superconducting coils.