JPS5826616B2 - Takiyokujiba Souchi - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic field device for improving the convergence of particle beams in particle beam optical systems such as particle beam microscopes, charged particle analyzers, mass spectrometers, and electron beam analyzers. be.

In order to improve the convergence from the first order to the higher order of the particle beam optical system,
The shapes of the electrodes and magnetic poles of the particle beam analysis unit, as well as the inclinations and curved surfaces of their end faces, are usually modified.

However, in a high-resolution particle beam optical system, it is necessary to make further corrections in addition to the above-mentioned corrections each time the settings of the magnetic field and electric field are changed due to the magnetic properties of the magnet.

However, in order to perform correction smoothly, primary, secondary...
...(N-1) depending on the convergence, 4 poles and 6 poles, respectively.
Pole: It is effective to use a magnet with 2N magnetic poles.

However, a magnet with a large number of poles is difficult to machine and assemble, and it also has the disadvantage that a multi-pole magnet is required depending on the convergence of each order.

Therefore, the present invention aims to provide a highly suitable composite multipole magnetic field device to solve the above-mentioned problems.

Next, embodiments of the present invention will be described with reference to the drawings.

Figure 1 shows an 8-pole field generated on the inner surface of a rectangular yoke 1.
Coils 2' to 9' are arranged, and 4-pole field coils 2 to 5 are arranged on top of these 8-pole field coils 2' to 9' to create a single yoke with multiple multi-pole coils. This is an embodiment showing a composite multipole magnetic field device in which a field is formed.

Figure 2 shows an example in which the yoke cross section is a right-angled rhombus, and six coils 2'' to 7'' generate a hexapole field on the inner surface of the yoke 1.
This is an embodiment in which four-pole field coils 2 to 5 are placed on top of these six-pole field coils 2" to 7" to form a composite multi-pole field.

Note that the means for forming a composite multipolar field shown in Figs. 1 and 2 is one in which coils are arranged in a stacked manner.
As shown in the figure, they may be distributed and mixed vertically in the same space.

In addition, the structure of the magnetic field device is such that all the coils are integrally molded with a resin having good thermal conductivity on a yoke made of pure iron or equivalent low carbon steel.

However, it is not necessarily limited to this structure.

As described above, the magnetic field device of the present invention has a structure in which multiple coils are arranged on each side of a yoke with a polygonal cross section to generate an even number of multipole fields such as a 4-pole field, a 6-pole field, an 8-pole field, etc. It is possible to arbitrarily generate a single or multiple multipole fields in the yoke of the yoke.
It is possible to generate an ideal magnetic field in a large space considering the external shape of the magnet, and because the leakage magnetic flux from the magnetic poles is significantly reduced, it is possible to make the yoke thinner and make the entire magnet lighter and smaller. , this tendency is more pronounced as the number of poles increases.

Therefore, the magnetic field device of the present invention is suitable for the capabilities of conventional multipole electromagnets, and has an extremely compact structure, so when it is used to improve the focusing performance of particle beam optical systems, it can be used to improve resolution. This has the effect of significantly improving the

The above effects are particularly remarkable when the present magnetic field device is a superconducting electromagnet.

[Brief explanation of drawings]

Figures 1 to 3 of the drawings are examples of the composite multipole magnetic field device of the present invention, and Figure 1 is a longitudinal cross-section of the magnetic field device of the present invention in which a 4-pole field and an 8-pole field are generated inside a yoke with a rectangular frame shape. Front view, 2nd
The figure shows a vertical cross-sectional view of the magnetic field device of the present invention in which a four-pole field and a six-pole field are generated inside a frame-like yoke with a right-angled rhombus cross section, and Figure 3 is a cross-sectional view showing another embodiment of a composite multipole field. be. Figure 4 is an explanatory diagram of a conventional multipole electromagnet, where a is a four-pole field, and b is a four-pole field.
The figure shows the 6-pole field, and the 0 figure shows the 8-pole field. 1... Yoke, 2, 3, 4, 5... 4-pole field coil,
2', 3', 4', 5', 6', 7', 8
', 9'...8-pole Yang coil, 2", 3", 4", 5
", 6", 7"...6-pole field coil.

Claims (1)

[Claims] 1 A yoke with a polygonal frame-like cross section is provided with multiple coils that generate even-numbered multi-pole magnetic fields such as 4-pole field, 6-pole field, 8-pole field, etc., and a single magnet or multiple even-numbered A composite multipolar magnetic field device for improving the focusing property of a particle beam optical system, which is characterized by generating a multipolar magnetic field.