JPS58169857A - Charged particle filter - Google Patents

Abstract

PURPOSE:To easily realize a focusing condition in accordance with a charged particle desired to selectively pass, by applying different potential to at least one of the pair of electrodes between its central part and both end parts along the direction of the magnetic field. CONSTITUTION:The second electrode plate 8 is divided into three electrode elements 8a, 8b, 8c. The elements 8a, 8c are connected to a voltage divided point T2 of a divider resistor 7, and potential -V1 is applied to the both elements 8a, 8c. While the element 8b is connected to another voltage divided point T3 of the resistor 7 and applied with potential -V2. A position of the point T3 is changed to adjust the potential V2 and V1. This adjustment is actually performed in such a manner, for instance, that a sectional shape of a beam passing through a pin hole (not shown in the drawing) arranged immediately below an incident axis (z) is projected onto a fluorescent plate and observed and the position of the point T3 is adjusted to form said sectional shape to a true circle.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is directed to a predetermined 11
The charged particles of 100% and 100% weight are sorted and separated into 56 charged particles.

A charged particle filter (WIEN) that selectively passes only heavy particles with a predetermined amount of energy and energy using an intersecting electric field and an electric field. ), it is also called Wien-Neurta. Some improvements were made to this Wien filter, and in 1972, it was
, l-, Seliger) announced an improved version of the early Wien filter, which had a focusing effect only in the direction of the magnetic field, but also had a focusing effect in the direction of the electric field. , Appl, Phys, , ,
Vol, 43. May 1972. r), 2
352) Figure 1 (a) is for explaining this conventional charged particle Noirta. In the figure, 1a is an electrode plate on which a positive charge L12 is applied, and on this electrode plate 1a, a flat 1j is applied. An electrode plate 1b to which a negative potential is applied is arranged.The electric field formed between the two electrodes is shown by electric lines of force in the figure, and a magnetic field approximately perpendicular to this electric field is generated. A magnetic pole piece of 28.2N is provided.The opposing end faces of this magnetic pole piece are not parallel, but have an opening angle that corresponds to the conditions described below), so the magnetic field is as shown by the lines of magnetic force G. It becomes.

That is, as shown in FIG. 1(b), the positive charge incident perpendicularly to the paper surface from the back side to the front side of the paper surface is expressed as the l-axis, and the entrance direction of the front electron beam 1 is the l-axis. The direction of the electric field is the y-axis, and the weight is on the l-axis and the y-axis! If the l-axis is taken as the X-axis, near the l-axis, which is the path of charged particles, the
x, Iy, Ez) are uniform, but the magnetic field B
(Bx, By, BZ) in the X direction and in the X direction, but in the above formula (Eo, Bo are constants, F'o
, Bo is the mass part m of the charged particles that go straight through the filter and are selectively detected after passing through the pinhole provided directly under the
It is set so that the relationship (2) holds true. Also, rQl specific charge Y)Ee, is the microton radius of a charged particle expressed as rO==v, /ηRO using m.

By the way, if the coordinates of a charged particle are expressed as (X, ~., 2), then the motion of the former I particle passing through an electromagnetic field is generally expressed as Equation 1, but by substituting equation (1) into this equation, Assign l, -iN
The following two equations can be derived using .

Ji: -Leavev1oe2X------
C) Yu. -'z? ? ”B:j -------(
5) From these equations (4) and (5), when the trajectory of a charged particle traveling straight through an electromagnetic field departs from the two axes, a force proportional to the amount of departure in the direction of pulling it back acts equally in the X direction and the X direction. Charged particles are focused in the X and V directions.

Now, in such a conventional device, a pair of magnetic pole pieces 2
Since the angle formed by the end face of N, 28 is uniquely determined according to the cycle of the charged particle trying to avoid selective passage [1 ton radius 1'Q=, V7, 'ηBO, In order to change the angle, the angle formed by the end faces of both magnetic pole pieces must be changed, but the magnetic pole piece is connected to a yoke etc.
Therefore, it is difficult to mechanically move the charged particles due to the presence of the charged particles, and therefore it is practical to adjust the focusing conditions according to the charged particles that are to be selectively passed through.

Furthermore, because the gradient of the magnetic field changes due to the hysteresis of one pole piece, the focusing condition is no longer satisfied even if the setting is made to satisfy the focusing condition for specific charged particles.
Therefore, it is difficult to maintain a good focus all the time.

The present invention has been developed in view of these conventional drawbacks.
The basic analogy of the present invention will be explained below. As shown below, it is assumed that the magnetic field B is uniform but the electric field has a specific gradient.

(11(3)
) by substituting equation (6) into equation i = -vtE6x/2 - +1 komago
-1) Evening 2 desks (6, (10, y/2y',) -B, z
) -----(7-2) Z = YLB, y----(
7-3) Yell. Therefore, if we integrate the equation (7-3>), then =
qBog-, y, )+v However, since we are considering the problem of convergence of isomorphism with the incident axis being the l-axis, the initial coordinate Vo of the charged particle in the above equation is set as O. That is, C′, the formula of J is (7
-2) Substituting into the equation yields 1 work. (10:)/72 seasons-B, (4 snakes, y10v>
);RetEo-VBo-mBI-Mi. /2) y15. For the charged particle of interest, equation (2) holds true.
Since j, the above formula is λ ri knee + 1 rei. j -----(g).

From Equations (7-1) and (8), it can be seen that a charged particle is 46 in the 7th axis, and the charged particle is 46 in the X direction and the axis in the X direction. It can be seen that the force acting on the pullback ψ is the same as the one in the example. From this, J in equation (6), the magnetic field B is assumed to be uniform, and the electric field F is given a specific gradient. X direction and y direction for charged particles
It can be understood that the focusing effect works in the direction.

゛ The present invention is based on the above-mentioned idea, and includes a pair of electrodes and a magnetic pole for forming a magnetic field in a direction perpendicular to the electric field between the pair of electrodes. In the charged particle filter that separates electrical particles, at least one of the electrodes (#1) is connected to its center along the direction of the magnetic field. It is characterized in that different Iζ potentials are applied to both ends, and one embodiment of the present invention will be described in detail below based on the drawings.

In FIG. 2 showing an embodiment of the present invention, 3N and 3
S1. , t7Tt, and their end faces are parallel to 1.
The magnetic field shown in Equation (6) is formed between the two magnetic pole pieces. In the gap between the magnetic pole pieces, is equipped with a first electrode plate 5 made of metal., 61J IJJ variable power source (reed), this variable power source 6 is connected to raw fish grounded and molecules +11
(The resistor 7 is connected in series. Since the electrode plate 55 is connected to the voltage dividing point T1 of this resistor 7, it is given a voltage (11) of V. 8 is connected to the first electrode Mj 5. Flat tr
This is a second electrode plate 8 which is mounted on a supporting member 9 made of an insulating material in a lateral direction. The second electrode plate 8 has three electrodes 8a and 8.
It is divided into b and 8c. Electrode piece 8a.

80 is connected to the voltage dividing point T2 of the Ff resistor 7, and both electrodes) i'8a and 8c have % (, +, 'j) of -V1. Also, the electrode piece 8b is It is connected to the other pressure point T3 of the piezoresistor 7, and the potential -V2 is λ.V2V) is adjusted by changing the position of the voltage dividing point T3.
The gradient of the electric field in the vicinity of the l-axis, which is unique to the suite in which charged particles are incident, is such that the gradient of the electric field in the vicinity of Equation (6)-0 is expressed. , this node 'a' is actually observed by projecting the cross-sectional shape of the beam passing through a pinhole (not shown) placed directly below the incident axis 2 onto a fluorescent screen, and confirming that this cross-sectional shape is a perfect circle. To adjust the partial pressure J:λT3 (O position) so as to match the J.

It will be done.

With this configuration, an electric field with a gradient as shown in the space between the electrode plates 5. In order to obtain a particle that can be easily received by the target, the heavy particles incident on the Z axis are focused in the X and Y directions, pass through the pinhole, and are sorted out with an extremely high resolution.

In addition, in the embodiment described in 1-1, the electrode plate 8 is divided and different voltages II'/ are applied to the central electrode piece and the electrode pieces at both ends, or the rKKi plate 5 is divided and the central electrode Make sure that the potential of the electrode pieces at both ends is higher than the potential of the electrode pieces.

Alternatively, both electrode plates may be divided and different potentials applied to the center and both ends of the electrode plates.

Sentence, the number of divisions of the electric root is m at most more than 3,
Instead of using a good conductor such as a metal as the electrode plate, by using one electrical resistor, the center part and both ends (with different potentials) can be connected along the surface of the electrode plate without dividing it into parts. Even if it is bestowed.

As is clear from the above explanation, the present invention (3)
By adjusting the potential applied to the electrode piece (the electric field gradient near the input axis l is adjusted as shown in equation (6), the charged particle beam is focused in the X direction and the yh direction. However, the electric current ◇ shifted to the electrode can be easily adjusted by moving the contact point of the voltage dividing resistor. It is possible to realize the condition.

In addition, since there is no hysteresis in the electric field formed between the two, it is possible to obtain a good focusing condition (charged particles) by adjusting the opposite direction.

[Brief explanation of the drawing]

Figure 1(a) is a diagram for explaining a conventional filter.
FIG. 1(b) is a diagram for explaining the coordinate axes, and FIG. 2 is a diagram for explaining one embodiment of the present invention. 1a, 1b: %i electrode plates 2N, 28.3N, 3S
: Magnetic pole C, 4.9: Pot 1" 1 member, 5, 8: Electrode plate, 6
:b] Transformer power supply, 7;' Voltage dividing resistor, 8a, 8b, 8c:
Electrode J-11. Patent applicant JEOL Ltd. Representative Tadao Kase

Claims (1)

[Claims] It is equipped with a pair of electrodes and a magnetic pole for forming a magnetic field in the j-j directions perpendicular to the electric field between the pair of electrodes, and the charged particles having a predetermined energy and mass are selected by the orthogonal electric and magnetic fields. At least the -h electrode of the pair of electrodes, the central part and both ends of the charged particle in the direction of the magnetic field, and the charged particle noirta (") are given LJ. Charged particles characterized by: