JPS63231862A - Superimposed field energy analyzer with projection on electrode - Google Patents

Abstract

PURPOSE:To make the electric field distribution and the magnetic field distribution at an edge section equal and correct the uneven electric field caused by inclined magnetic poles by making the gap between electrodes and the gap between the inclined magnetic poles equal and providing projections with specified different widths on the right and left electrode faces. CONSTITUTION:Magnetic poles 11, 12 are inclinatorily provided, electrodes 13, 14 with different widths are arranged on the left and right between them, and the gap Sm between the magnetic poles 11, 12 and the gap Se between the electrodes 13, 14 are made almost equal. The widths of the electrodes 13, 14 are made De, Dr, and projections 15, 16 are provided in front of them. The widths of the projections are made t1, t2 respectively, the widths of electrode top faces except the projections De-2t1, Dr-2t2 are made equal, and the widths of the projections are made 0.05Se-0.2Se. Accordingly, the electrode gap and the inclined magnetic field gap are made equal, the electric field distribution and the magnetic field distribution at the edge section are made equal, and the projections with different widths are provided in front of the right and left electrodes, thereby the uneven electric field caused by the inclined magnetic poles is corrected.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an energy analyzer using a type of filter that superimposes an electric field and a magnetic field, and particularly relates to an energy analyzer that uses a filter that superimposes an electric field and a magnetic field, and in particular provides a protrusion on an electrode to satisfy the straight-line traveling condition of charged particles. The present invention relates to a superimposed field energy analyzer as described above.

[Conventional technology]

BACKGROUND ART Conventionally, an analyzer called a Wien filter in which uniform electric and magnetic fields are superimposed is known as an energy analyzer for electron beams and ion beams. Wien filters have excellent properties such as high-resolution analysis and the fact that the beam travels in a straight line within the filter. It is suitable for analyzing energy, etc., as it can monochromate the energy and simplify the optical system.

In such a Wien filter, uniform electric and magnetic fields are applied in directions perpendicular to each other, and an electron beam is incident in a direction perpendicular to these fields. In such a Wien filter, the orthogonal uniform electric field E and magnetic field B are Ew = 2πU o / L + B w = E w
/V.

As the Vienna condition, Vo=L mouth lever/m) Positive 7 Under the B=E/V.

When the following conditions are met, the beam travels straight. Here, UO
is the energy of the incident beam, 0 is the velocity of the particle, L is the length of the filter, Ew, Bw are the electric fields that satisfy the Wien condition,
It is a magnetic field. Now, when an electron with an energy such as U=Uo±ΔU is incident, it deviates from the straight-line propagation condition and is bent in the direction of the electric field E.

Therefore, at the exit of the filter, the beam is dispersed depending on the energy level and can be used as an energy analyzer.

FIG. 3(a) is a perspective view of the Wien filter, and FIG. 3(b) is a sectional view. In the figure, 1.2 is a magnetic pole and 3.4 is an electrode.

Although such a Wien filter is thought to satisfy the above-mentioned straight-line condition, it has hardly been realized in practice. The reason for this is that most superimposed field devices have electrodes inserted into the magnetic pole gap as shown in Figure 3, and in order to maintain high uniformity of the magnetic and electric fields, the magnetic pole gap Sm
This is due to the fact that the structure is much larger than the electrode gap Se. In such a case, the electric field and magnetic field distribution at the beginning or end of the magnetic pole or electrode is as shown in Figure 4, where the change in the magnetic field (solid line in the figure) is gradual, and the change in the electric field (broken line in the figure) is ) becomes abrupt, and the condition B = E/V o does not hold at the edge.

Furthermore, in the combination of magnetic poles and electrodes as shown in FIG. 3, there is a lens effect in the X direction and the electron beam converges, but there is no lens effect in the X direction and the beam diverges. To avoid this, By=Bo (1+x/Ro
), Ro=4Uo/Ew.

It has been proposed to create a gradient group of EW=2πUO/L (L: filter length).

Therefore, a case will be described in which the electrode spacing and the magnetic pole spacing are made approximately equal in order to equalize the distribution of the electric field and the magnetic field at the edge, and in which tilted magnetic poles are used to provide a lens effect also in the X direction.

Figure 5 is a diagram showing a Wien filter when using gradient magnetic poles and electrodes with different widths on the left and right sides, Figure 6 is a diagram showing the electric field in the X direction in Figure 5, 11.12 is a gradient magnetic pole, 1
3 is a narrow electrode, 14 is a wide electrode, Se is the electrode gap, Sm is the magnetic pole gap, and Se=Sm=10 m.

In such a magnetic pole and electrode arrangement, when a voltage is applied between the electrodes 13 and 14 and the gradient magnetic poles 11 and 12 are set at ground potential, the electric field distribution Ex (x) in the X direction is as shown in FIG. By tilting the magnetic pole, a component F, x = a x (a > 0) is created in the electric field distribution, but
By making the width of the electrode plate asymmetrical (D r > De) with De at the electrode work 3 and Dr at the right electrode 14, Ex=
It is possible to create an opposite electric field gradient bx (b<Q), and as a result - both can cancel. However, in the case of the electromagnetic pole arrangement shown in Figure 5, as can be seen from Figure 6, the minimum value of the electric field is
= -2.5 mm, and at the same time, Ex shows a change proportional to X2. This means that the electrode gap Se is Se=10m
This depends on the fact that m has a larger value than De and Dr. In order to create a uniform field, the electrode height D is usually
This is because D>2Se must be satisfied, but in this case Se>D must be satisfied due to the requirement to increase Se.

The present invention is intended to solve the above-mentioned problems, and provides a superimposed field energy analyzer in which the electric field and magnetic field at the edge are approximately equalized and protrusions are provided on the electrodes to obtain a uniform electric field distribution. The purpose is to provide.

[Means for solving problems]

For this purpose, the superimposed field energy analyzer of the present invention in which protrusions are provided on the electrodes is such that, in the superimposed field energy analyzer using gradient magnetic poles, the electrode gap Se and the gradient magnetic pole gap Dm are made equal, and the opposing electrode surfaces are mutually connected to each other. It is characterized by having protrusions of different widths.

[Effect]

The superimposed field energy analyzer in which protrusions are provided on the electrodes of the present invention equalizes the electric field and magnetic field distribution at the edge by making the electrode gap and the gradient magnetic pole gap equal, and furthermore, the left and right electrode surfaces are provided with a width that is different from each other. By providing protrusions with different numbers, it is possible to correct the non-uniformity of the electric field due to the gradient magnetic pole and achieve uniformity of the electric field.

〔Example〕

Examples will be described below based on the drawings.

FIG. 1 is a diagram showing the structure of a Wien filter in a superimposed field energy analyzer in which an electrode is provided with a protrusion according to the present invention;
FIG. 2 is a diagram showing the electric field distribution in the case of FIG. 1, and the same numbers as in FIG. 4 indicate the same contents. In the figure, 15.1
It is a 6-bar protrusion.

In the figure, the magnetic pole gap Sm and the electrode gap Se are made equal, and a protrusion 15.16 is provided on the front surface of the electrode 13.14. In this example, the width of this protrusion is 1. ．． 12, the width of the top surface of the electrode excluding the protrusion De-2tl, D
The case where jl and j2 are changed so that r 2 tz is made equal is shown. In this way, the width of the protrusion t1
, t2 between the left and right electrodes, it is possible to compensate for one component of X in Ex (x) shown in FIG.

In the distribution shown in Figure 2, the electric field uniformity at X=±21 is Δ
It was possible to reduce E/E to within 5%.

As a result of various experiments, this electric field uniformity was determined by adjusting the thickness of the protrusion to 0.05Se≦1. ．． It was confirmed that better results could be obtained in the range of 12≦0.2Se.

〔Effect of the invention〕

As described above, according to the present invention, the electric field and magnetic field distribution of the edge field are made equal by making the electrode gap and the gradient magnetic pole gap equal, and furthermore, protrusions with different widths are provided on the left and right electrode surfaces. This makes it possible to correct the electric field non-uniformity due to the tilted magnetic poles and realize electric field uniformity. In particular, by setting the shape of this protrusion in the range of 0°05Se<t<0.2Se, it is possible to improve the uniformity of the electric field distribution.

[Brief explanation of drawings]

Fig. 1 is a diagram showing an embodiment of a superimposed field energy analyzer in which an electrode is provided with a protrusion according to the present invention, Fig. 2 is a diagram showing the electric field distribution in the case of Fig. 1, and Fig. 3 is a diagram of a conventional Wien filter. Figure 4 is a diagram showing the distribution of the edge fields of electric and magnetic fields, Figure 5 is a diagram showing the configuration of a Wien filter using gradient magnetic poles with equal magnetic pole gap and electrode gap,
FIG. 6 is a diagram showing the electric field distribution in the case of FIG. 11.12... Gradient magnetic pole, 13.14... Electrode, 1
5.16... Protrusion.

Claims (2)

[Claims] (1) In a superimposed field energy analyzer using gradient magnetic poles, an electrode is characterized in that the electrode gap Se and the gradient magnetic pole gap Dm are made approximately equal, and protrusions with mutually different widths are provided on both opposing electrode surfaces. Superimposed field energy analyzer equipped with protrusions. (2) A superimposed field energy analyzer in which an electrode is provided with a protrusion according to claim 1, wherein the width t of the protrusion satisfies 0.05Se<t<0.2Se.