JPS59143252A - Electric field generating apparatus - Google Patents

Abstract

PURPOSE:To enable electrodes to be installed within a narrow space and freely change distribution of electric field to be generated by generating electric field with line-shaped electrodes arranged on a pair of substrates. CONSTITUTION:A substrate is formed like a half-sector along the center path O of ion and on the opposing surfaces thereof, n pieces of electrodes A1-An (substrate 4) and B1-Bn (substrate 4') with concentric arc forms having the width of, for example 0.5mm. are respectively arranged at a pitch of 0.5mm.. With such a constitution, when a voltage is applied to the n-pairs of electrodes, an electric field is generated in the space surrounded by the electrodes. Within such electric field, an equal potential plane formed by connecting each pair of electrodes given the equal potential to each other can exist but such equal potential plane is influenced by the potential applied to the adjacent electrodes. Accordingly, an electric field having arbitrary distribution of potential can be formed in the space surrounded by the electodes.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electric field generator suitable for use in a mass spectrometer, particularly a superimposed field mass spectrometer.

In a superimposed field mass spectrometer, for example, as shown in FIG. It generates an electric field and creates a superimposed field. If an attempt is made to sweep the mass by electric field sweeping in a mass spectrometer that uses such a superimposed field as an analysis field, the focusing position of the ion beam will change. , c' must be changed in conjunction with the electric field sweep. However, in the conventional device using concentric cylindrical electrodes as shown in FIG. 1, the electric field distribution is uniquely determined by the electrode shape, and c and c' cannot be changed. 3.3' is a correction electrode called a Matsuyama plate used for this purpose, and by changing the DC voltage applied to the electrodes 3 and 3', the constant C1C' of the toroidal electric field can be changed.

Generally, in a mass spectrometer, it is desired that the magnetic field strength be high in terms of resolution or measurement range, and for this purpose, the magnetic pole spacing must be as narrow as possible. However, in the conventional device described above, there is a limit to how narrow the space can be made because the electrodes 2, 2' and the correction electrodes 3, 3' must be placed between the magnetic poles. Also, the constants c and c are determined by the correction electrode.
,' can be changed, but the further away from the center of the field, the greater the deviation from the ideal toroidal electric field, which also has the drawback of increasing higher-order aberrations.

The present invention has been made in view of the points related to -, and an object of the present invention is to provide an electric field generating device that can be installed and covered even in a narrow gap, and that can arbitrarily change the electric field distribution. There is.

The present invention comprises a plurality of pairs of concentric arc-shaped linear electrodes arranged vertically symmetrically across the center plane on a pair of parallel planes located at equal distances between the center plane, and the plurality of pairs of wire electrodes. It is characterized by being comprised of a storage means for storing information regarding the potential to be applied to the pair of shaped electrodes, and a power supply means for applying a predetermined potential to each electrode pair based on the information read from the storage means. There is. An embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 2 shows the configuration of an embodiment of the present invention.
1, 1' are magnetic poles similar to those in FIG. Between the magnetic poles, thin insulating substrates 4,4' are placed in parallel at equal distances from the central plane through which ions pass.

As shown in FIG. 3, the substrate is given an arcuate shape along the central path O of ions, and on its opposing surface are arranged concentric arcuate electrodes A1 of n trees with a non-width of 0.5, for example. ~
A.

(Substrate 4), B+ ~ Bn (Substrate 4') is 0.51
They are arranged at a pitch of 1m. This electrode pattern can be created, for example, by pattern exposure and etching techniques in the same manner as the substrates 1 to 1 used in ordinary electronic equipment. The two substrates are arranged so that the patterns are symmetrical with respect to the central plane Iυ, in other words, A1, B+, An
and Bn are arranged to face directly across the central plane, and the lead wires drawn out from each electrode of each substrate are connected as a pair to a pair of directly facing electrodes, and a power source 5 is connected to each rough corner. It is connected to the. A memory 6 stores voltages to be applied for n sets. The information stored in the memory 6 is successively read out by a read control circuit 7 and supplied to the power source 5 as voltage information for each coarse angle.

In the above configuration (\), when a voltage is applied to 0 sets of electrodes, an electric field is generated in the space between the electrodes. Within that electric field, each month's electrodes given the same potential There is an equipotential surface that connects the electrodes, but the equipotential surface is affected by the potentials applied to adjacent electrodes.Therefore, what kind of voltage is applied to each electrode, and what kind of electric field is generated at j? By determining whether or not an electric field is formed, it is possible to avoid generating an electric field with an arbitrary distribution in the space between the electrodes.

Here, when it is assumed that an electric field φ is formed in the space between the electrodes, the potential of the 0th set of electrodes will be considered using FIG. 4.

Now, considering the electric field φ to be an axially symmetrical electric field with respect to the central axis of ion rotation q, the electric potential at any position within the electric field is shown in Figure 4. If we write φ(X, y) in x-y coordinates, the following equation holds true.

Δφ(x, y) =O (1) where ρ0 is the radius of rotation of the ion center path, and Φ is the potential at an arbitrary point <x, y>.

From the above equation, the following equation can be obtained as a general form of φ(X, V).

φ(X,V)=-Eoρ0Σgroup(nho5...(3)4
．． 3! Here, a no J is a coefficient, and Eo is the central orbit of the ion Jx=y=
is the electric field strength at o.

If the distance between the electrodes is 21, then each electrode exists on the plane of y=±h, so if we set y=h in equation (3) and substitute the value of X according to the position of each electrode, we get It can be seen that the potential of each electrode can be determined. Conversely, if the potential determined in this way is applied to each electrode in a different manner, a toroidal electric field will be generated in the space between the electrodes. Note that field disturbance occurs at the short edge e of the electric field, but the distance 2h between the electrodes is made sufficiently larger than the width W of the electrodes (
), the disturbance in the field near the ion center path can be ignored.

Here, to actually find the potential of each electrode, the coefficient 827
(recurs
ion formula) is obtained.

(j +1) aL, 1t2 +aj+1. ．． j+z
+ (j + 2) az, z, z +al-t3.
j-0-(3) Here a4 = 01f, J ≧Or” Al.

Furthermore, since the potentials of directly facing electrodes are equal, the electric field is symmetrical about the central plane, and therefore the coefficient of the odd term of the power of y is 0'C.

Combining these things, the coefficient a i7 of the term containing y representing the field outside the central plane where j = 0 is calculated by Liebe (
Coefficient ai0 (1≧1)C of terms that do not include y in the central plane
'It can be expressed. An example of ζ for coefficients up to the fourth order is as shown in the above equation.

a02"' -ago a20...(
5) a+z=a+o azo a3o -<6
) az 2 =-28+o-1-2a 2
o -a 3 o -a 4
Q...(7) ao4=ato-a2o+2a3o+a4゜...(8
) In the end, the third-order magnification that is actually required in a mass spectrometer
W+n is alo, azo, a3o.

If the four coefficients of a40 are given, the voltage (voltage 1 sill) to be applied to each electrode can be given with respect to an arbitrary triidal electric field using equations (3) and (4).

In order to find the four coefficients alo, a2 (1, a30, a40), for example, use a computer to actually substitute numerical values for each coefficient, and in a specific electric field (for example, an electric field with a specific constant 01), 1 is enough to select a combination with a small number of
Using the value of o+a3ona40 and data on the position of each electrode, the voltage should be applied to each electrode Δ1 to An (including 81 to Bn connected to each other) according to equations (5) to (8) and equation (3) above. Potential information V++ to VIT+ is calculated for an electric field of a certain constant C. Information on the potential applied to each electrode V21 to Vzn, V3t>V3n for various electric fields with completely different constants Cz, C3, ...
, *** and apply a voltage to each electrode based on the respective information, it is possible to generate an electric field of each constant.

In the embodiment shown in FIG. 2, the memory 6 stores a plurality of pieces of information obtained as described above, and the readout control circuit 7
When any information is read out from the information and supplied to the power source C, the power source 5 applies a voltage based on the information to each electrode. Therefore, an electric field is generated in the space between the electrodes according to the information stored in the memory.

In addition, in the above example, r is 1 to l.'' Although we have taken the idal electric field as an example, any electric field C can be generated as long as the electric field is symmetrical with respect to the central plane, as long as information about that electric field is obtained. It goes without saying that there is.

Further, the substrates 4.4' may be attached to the magnetic poles 1.1', respectively, and it goes without saying that the magnetic poles are not necessary if the generation of an electric field alone rather than a superimposed field is avoided.

As described in detail below, according to the present invention, the electric field is generated by the linear electrodes installed on the two substrates, so the conventional electric field 14i2.2' is not required, and it can be installed even in a narrow gap. becomes possible. Furthermore, it is possible to arbitrarily change the distribution of the electric field to be avoided.

[Brief explanation of the drawing]

Fig. 1 is a diagram for explaining a conventional example, Fig. 2 is a diagram showing the configuration of an embodiment of the present invention, Fig. 3 is a diagram for explaining a substrate and a linear electrode, and Fig. 4 is a diagram for explaining a linear electrode. FIG. 4 is a diagram showing the relationship between the shaped electrode and the x-y coordinates. 4.4': Substrate, 5: Power supply, 6: Memory, 7: Readout control circuit, A, B: Linear electrode. Patent applicant JEOL Ltd. Representative Ito-husband

Claims (1)

[Claims] A plurality of pairs of concentric arc-shaped linear electrodes arranged vertically symmetrically across the central plane on a pair of parallel planes located at equal distances across the central plane; An electric field generating device comprising storage means for storing information regarding the applied potential, and power supply means for applying a predetermined potential to each electrode pair based on the information read from the storage means.