JPS586257B2 - ion source device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in an ion source device with a backflow electronic damper.

In a high-energy ion source, electrons are secondarily generated between electrodes that electrostatically extract and accelerate ions, but these electrons are accelerated while flowing backwards because their charge is opposite to that of positive ions.

Among these backflow electrons, the electrons that can pass through without colliding with the accelerating electrode are made to collide with and absorbed by a backflow electron damper placed opposite to the acceleration electrode.

By the way, the energy carried by the backflow electrons is extremely large, and when they collide with the backflow electron damper, it imparts a thermal load to the damper.

For this reason, copper or the like with good thermal conductivity is used as the main material of the backflow electronic damper.

However, this type of device has the following problems.

In other words, electrons incident on a solid produce secondary electrons, some of which include primary electrons that are scattered elastically or inelastically, and the energy of these reflected primary electrons is smaller than the energy of the incident electrons. There is almost no energy loss.

Therefore, high-energy reflected primary electrons are emitted from the damper due to the backflow electrons colliding with the backflow electron damper.

Then, the reflected primary electrons collide again with the accelerating electrode for accelerating ions, and load all or part of the energy onto the accelerating electrode.

Therefore, the load heat of the accelerating electrode increases, leading to problems such as shortening the life of the accelerating electrode.

The present invention has been made in consideration of the above circumstances, and its purpose is to reduce the load heat on the accelerating electrode caused by reflected primary electrons emitted from the backflow electron damper due to electron collision. An object of the present invention is to provide an ion source device that can extend the life of an accelerating electrode.

That is, the present invention aims to achieve the above object by forming the electron collision surface of the backflow electron damper from a metal member that emits less reflected primary electrons.

Here, the reflected electron gain increases as the primary electron energy that provides the maximum value of the gain increases.

Therefore, the primary electron energy that gives the maximum value of electron collision electron emission gain on the electron emission surface is low, generally 400 [
ev] By forming the accelerating electrode using the following metal members, the heat load on the accelerating electrode can be reduced.

Hereinafter, details of the present invention will be explained with reference to illustrated embodiments.

The figure is a schematic cross-sectional view showing a schematic configuration of an embodiment of the present invention.

In the figure, 1 is a cylinder with a bottom made of stainless steel, for example.
A cylindrical body 3 is attached to the open end of the bottomed cylindrical body 1 with an annular insulator 2 interposed therebetween.

A backflow electronic damper 4 is disposed inside the bottomed cylindrical body 1.

This damper 4 is made of aluminum, for example, and is cooled by a cooling pipe 5 attached to its upper surface.

On the other hand, an accelerating electrode system 7 is attached to the lower end of the cylindrical body 3 via an annular insulator 6.

The accelerating electrode system 7 consists of three accelerating electrodes 7a, 7b, 7c, and these accelerating electrodes 7a, 7b,
7c are arranged in the above order from the damper 4 side and are insulated from each other.

A positive voltage of about 100 [KV] is applied to the accelerating electrode 7a, and a positive voltage of about -5 [KV,
) is applied, and the acceleration electrode 7c is grounded.

Furthermore, a hollow cathode (not shown) or the like is disposed between the backflow electron damper 4 and the accelerating electrode system 7.

Then, a working gas is passed through the cathode, and a discharge is started between the cathode and the cylindrical body 3 to generate plasma.

With this configuration, positive ions (indicated by ■ in the figure) are electrostatically extracted from the plasma generated in the space between the backflow electron damper 4 and the acceleration electrode system 7 and accelerated. At the same time, electrons (indicated by e in the figure) are generated secondarily between the accelerating electrodes 7a, 7b, and 7c.

Some of these electrons collide with the accelerating electrode 7a, but the electrons that have passed without colliding with the accelerating electrode 7a flow backward in the direction opposite to the flow of positive ions and collide with the backflow electron damper 4.

Here, since the electron damper 4 is constructed of the above-mentioned members, the number of reflected primary electrons emitted from the damper 4 due to the collision of the reverse flow electrons is small.

Therefore, the thermal load on the accelerating electrode system 7 caused by the reflected primary electrons is reduced.

In this way, in this device, the backflow electron damper 4 that absorbs backflow electrons is formed of a metal member such as aluminum that has a small reflected electron gain. can be reduced.

Therefore, the thermal load on the accelerating electrode system 7 can be reduced, and the life of the accelerating electrode system 7 can be extended.

Further, since the cooling pipe 5 is provided, there are also advantages such as being able to prevent heat generation due to electron collision in the backflow electronic damper 4.

Note that the present invention is not limited to the embodiments described above.

For example, the metal member forming the backflow electron damper is not limited to aluminum, but may also be made of iron, molybdenum, niobium, palladium, rubidium, titanium, zircodium, or the like.

Furthermore, any metal member may be used as long as it has a low primary energy that provides the maximum electron collision electron emission gain, generally 400 (eV) or less.

Further, only the surface (electron collision surface) of the backflow electron damper may be formed of the metal member.

In addition, various modifications can be made without departing from the gist of the present invention.

[Brief explanation of the drawing]

The figure is a schematic cross-sectional view showing a schematic configuration of an embodiment of the present invention. 4... Backflow electronic damper, 5... Cooling pipe, 6... Insulator, 7... Accelerating electrode system, 7
a, 7b, 7c...accelerated electric expansion,

Claims (1)

[Scope of Claims] 1. An ion device comprising an accelerating electrode that extracts and accelerates ions from a plasma, and a backflow electron damper that absorbs electrons that are secondarily generated in the vicinity of the accelerating electrode and flow backward in the direction in which the ions are extracted. An ion source device characterized in that the entire or surface of the backflow electron damper is made of a metal with low primary electron energy that provides a maximum value of electron collision electron emission gain. 2. The entire or surface of the backflow electron damper is
The ion source device according to claim 1, wherein the ion source device is formed of a metal having a voltage of 0.0 0 (eV) or less. 3. The ion source according to claim 2, wherein any one of aluminum, iron, molybdenum, niobium, palladium, rubidium, titanium, or zirconium is used as the metal forming the backflow electron damper. Device.