JPH0552639B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention relates to a charged particle device, and more specifically, it relates to a charged particle device, and more specifically, a method for accelerating a charged particle beam such as an electron beam by creating a circular equilibrium trajectory. The present invention relates to a charged particle device having a charged particle device.

[Conventional technology]

Although the charged particle device of the present invention is applicable to both a synchrotron and a storage ring, the following description will be made with an electron beam storage ring in mind.

FIG. 3 shows a charged particle device according to the applicant's earlier application, in which the storage ring 10 is connected to the electron beam 1.
first to seventh inflectors 2a to 2g sequentially provided in the introduction section, a circular equilibrium orbit 3 around which the electron beam 1 revolves, a rectangular pump electromagnet 6a arranged in the introduction section, and a rectangular pump electromagnet 6a arranged in the equilibrium orbit 3. The electron beam 1 consists of a fine-tuning pump electromagnet 6b, a first high-frequency cavity 7a, a second high-frequency cavity 7b, etc.
The beam passes through an intersection 9 between the magnetic field boundary 4 and the radial direction 8 and enters the first inflector 2a at a predetermined angle θ with the tangent 5 of the magnetic field boundary 4.

The storage ring 10 configured as described above allows a high-energy electron flux to orbit along the equilibrium orbit 3 and continues to hold the high-energy electron flux with its kinetic energy for a period of several hours to several tens of hours. functions. One application of the storage ring 10 is as a light source for VLSI exposure that utilizes synchrotron radiation, which is emitted when a high-energy electron flux orbits the balanced orbit 3.

Usually, an accelerator such as a well-known linear accelerator or synchrotron is provided upstream of the storage ring 10, and the electron beam 1 is sent from the upstream accelerator. The electron beam 1 has a predetermined angle θ between it and the tangent line 5, for example, about 30 degrees,
It is introduced into the storage ring 10 through the intersection 9 of the radial direction 8 and the magnetic field boundary 4 via the first inflector 2a to the seventh inflector 2g, and is made parallel to the equilibrium orbit 3 by the rectangular pump electromagnet 6a. ,
The center of the cross section of the electron beam 1 gently oscillates around the equilibrium orbit 3.

This oscillation occurs at the point where the center of the cross section of the electron beam 1 intersects the equilibrium orbit 3 for the first time after the electron beam is incident.
The bump is removed by the fine adjustment bump electromagnet 6b which makes the angle between the bump and the equilibrium orbit 3 zero. Thus, the center of the cross section of the electron beam 1 coincides with the equilibrium trajectory 3.

Although it depends on the kinetic energy of the electron beam 1, for example, when the kinetic energy is about 800 MeV and the diameter of the equilibrium orbit 3 is about 1.6 m, the synchrotron radiation loss per revolution is about 45 keV. In order to make the quantum lifetime sufficiently long with such high radiation loss, it is necessary to increase the accelerating voltage generated in the radio frequency cavity, and this high voltage may be difficult to achieve with a single radio frequency cavity. In the conventional example shown in Fig. 3, assuming such a case,
First high frequency cavity 7a and second high frequency cavity 7
b is installed.

FIG. 4 shows the magnetic field distribution 17 in the direction of the axis of symmetry on the central plane of the storage ring 10 and an example of coil arrangement for forming the magnetic field distribution 17. 11 is a horizontal axis of coordinates with 13 as the origin, which is the radial direction 8 in FIG. 12 is a vertical axis, which indicates relative arrangement dimensions for coil arrangement, and relative magnetic field strength for magnetic field distribution. The position of the equilibrium trajectory 3 is also shown on the horizontal axis 11. If this balanced orbit 3 has a predetermined dimension, an upper large coil 14a, a lower large coil 14b, an upper medium coil 15a, a lower medium coil 15b, and an upper small coil 16, which form a coil thread for forming a magnetic field.
The arrangement dimensions of each of the coils a and the lower small coil 16b may also be considered in relative proportion. The example shown in FIG. 4 is an example in which the magnetic field for the storage ring 10 is formed by an air-core coil thread, and depending on the required magnetic field strength and the diameter of the balanced orbit 3, a superconducting coil may be used. Normally conducting coils are sometimes used.

The magnetic field boundary 4 is shown in Fig. 4, and there is a positive magnetic field part inside the magnetic field boundary 4, and in particular, a weakly convergent magnetic field is formed near the equilibrium orbit 3, and the magnetic field is and to prevent the divergence of electron flux in the vertical direction. Regarding the path of the electron beam 1 in the part of the negative magnetic field outside the magnetic field boundary 4, an appropriately selected magnetic shield (not shown) is installed to create a weak magnetic field that can be ignored. .

The first to seventh inflectors 2a to 2g each have a center of curvature on the balanced track 3 side. Third
In the case of the figure, the inflectors 2a to 2g are in a magnetic field, and the direction of the center of curvature is determined by the direction of the magnetic field. The voltage is applied in the direction in which the radius of curvature of the electron beam 1 increases. In this sense, the function of the inflectors 2a to 2g is to prevent the electron beam 1 introduced at the intersection point 9 from being excessively deflected by the magnetic field, and to introduce it into the circular equilibrium trajectory 3 at a gentle angle. Here, the number of inflectors is appropriately selected depending on the strength of the magnetic field of the storage ring 10 and the magnitude of the kinetic energy of the electron beam 1.

The electron flux stably orbiting on the balanced orbit 3 emits synchrotron radiation light (not shown), and is also lost due to synchrotron radiation light in the first high-frequency cavity 7a and the second high-frequency cavity 7b. It continues to orbit for several hours to several tens of hours while being supplemented with energy.

The electron flux orbiting in this way is 10 ^-9 ~
Although it is in a vacuum of 10 ^-11 Torr, when the circulating current increases to, for example, several hundred mA or more, positive ions in the vacuum accumulate in the electron flux,
The collision between the electron flux and positive ions becomes impossible to ignore. This means that the electron flux orbiting on the balanced orbit 3 is lost, and there is a limit to the amount of current of the electron flux into the storage ring 10, and it is used as a synchrotron radiation light source for the purpose of increasing the intensity. This becomes a major obstacle when it is desired to significantly increase the circulating current.

[Problem that the invention seeks to solve]

In the conventional charged particle devices as described above, no measures are taken against positive ions produced by a flux of electrons orbiting in a balanced orbit. Therefore, as the accumulated current increases, there is a problem in that the circulation time of the accumulated current is inevitably shortened due to positive ions being trapped in the electron flux.

This invention was made to solve these problems, and by adding a means to remove positive ions generated by the collision of electron flux with gas in vacuum, it is possible to maintain an equilibrium orbit. The purpose of this invention is to obtain a charged particle device in which the circulating time of a circulating electron flux is extended.

[Means for solving problems]

In the charged particle device according to the present invention, a plurality of cathode/anode pairs are disposed with a balanced trajectory in between, and the polarities of adjacent cathode/anode pairs are opposite to each other.

[Effect]

In this invention, only the positive ions are removed due to the energy difference and electrical properties between the positive ions and the electron beam, and the direction of displacement applied to the electron beam is also alternately reversed.

〔Example〕

FIG. 1 and FIG. 2 show an embodiment of this invention,
In the figure, 18a and 18b are a first cathode and a first anode pair for removing positive ions from the electron flux moving along the equilibrium orbit 3, which sandwich the equilibrium orbit 3 from above and below. are placed opposite each other. Similarly, 19a and 19b, 20a and 20
b, 21a and 21b and 22a and 22b are respectively a second negative/anode pair, a third negative/anode pair, a fourth negative/anode pair, and a fifth negative/anode pair,
are arranged sequentially.

The rest of the configuration is the same as that shown in FIG. 3, and the explanation will be omitted. Next, regarding the operation,
The first negative/anode pair 18a, 18b will be explained as an example. For example, a voltage of several kV is applied between the first cathode 18a and the first anode 18b, and a corresponding electric field is formed between the two electrodes 18a, 18b. Within the electric field, positively charged particles are accelerated toward the cathode 18a, and negatively charged particles are accelerated toward the anode 18b, thereby obtaining predetermined energy. Since the positive ions existing along the electron flux between the electrodes 18a and 18b have low kinetic energy, it depends on the distance and length between the electrodes 18a and 18b.
The first cathode 18a is accelerated toward the first cathode 18a.
It collides with and is neutralized. The kinetic energy of each electron in the electron flux passing between the two electrodes 18a, 18b is very large compared to the energy obtained by the electron from the electric field formed between the two electrodes 18a, 18b. negative and anode pair 18a,
In many cases, the influence of passing between 18b and 18b can be ignored. Therefore, the set first anode/anode pair 18a, 18b only serves to remove positive ions, and has little effect on stable movement of the electron flux.

Here, since the electron flux often orbits the equilibrium orbit 3 more than tens of thousands of times, if it is necessary to pass through many pairs of cathodes and anodes as shown in the figure, the Even if the influence of two negative/anode pairs is small, their superimposed effects may not be negligible. In this embodiment, in order to suppress the above-mentioned superimposition effect, adjacent cathode/anode pairs, for example, the first cathode 18a and the second anode 19b, or the first anode 18b and the second cathode 19b, By arranging them adjacent to each other, the structure is such that the electron flux can stably orbit the equilibrium orbit 3 many times.

In the above example, the structure of the cathode and anode was not mentioned, but the structure of both electrodes is as follows.
Possible examples include a flat plate, a conductor with a curved surface, and a plate-like structure with a conductor provided on the surface of an insulator.

Furthermore, there are cases where it is desired to prevent eddy currents induced on the electrode surface due to interaction with the electron flux, and in such cases, a mesh-like electrode structure may be considered.

〔Effect of the invention〕

As is clear from the above explanation, by arranging multiple cathode/anode pairs with the equilibrium orbit in between, and by making the polarities of adjacent cathode/anode pairs opposite to each other, the positive ion and electron beams are Due to the energy difference and electrical properties, only positive ions are removed and the direction of displacement applied to the electron beam is alternately reversed, so the influence of positive ions on the stable movement of the electron beam is reduced as much as possible.
The reduction in the accumulation time of the electron beam, that is, the number of revolutions, can be minimized, and a high-performance charged particle device can be realized.

[Brief explanation of the drawing]

FIG. 1 is a side view of the main part of an embodiment of the present invention, FIG. 2 is a plan view of the main part, FIG. 3 is a schematic plan view of the main part of a conventional charged particle device, and FIG. 4 is a schematic plan view of the main part of the conventional charged particle device. It is an arrangement|positioning and magnetic field distribution diagram. 1...Electron (charged particle) beam, 2a to 2g...1st to 7th inflectors, 3...Equilibrium orbit, 18
a, 18b, 19a, 19b, 20a, 20b,
21a, 21b, 22a, 22b...first to fifth negative/positive electrode pairs. In each figure, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] 1. Sequentially disposing a plurality of inflectors each having a center of curvature on the side of the equilibrium orbit at the introduction portion of the charged particle into the equilibrium orbit around which the charged particle circulates;
In a charged particle device in which a circular equilibrium trajectory is formed with a weakly focused magnetic field distribution, a plurality of cathode/anode pairs are arranged across the equilibrium trajectory, and the polarity of adjacent cathode/anode pairs is A charged particle device characterized in that the directions are opposite to each other.