JPH05121022A - Electron gun - Google Patents

Abstract

PURPOSE:To adjust the intensity of electron beams easily, and reduce an electric power supply capacity connected to a cathode and pulse voltage impressed upon an anode wire. CONSTITUTION:An insulating material 20 is arranged between an electrically conductive extraction grid 11 and an ionization chamber wall 4, and a bias voltage source 21 is also connected between the electrically conductive extraction grid 11 and the ionization chamber wall 4. This bias voltage source 21 is arranged to produce an electric potential difference between the electrically conductive extraction grid 11 and the ionization chamber wall 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high power electron gun,
In particular, the present invention relates to an electron gun improved so that the electron beam intensity can be changed efficiently and easily.

[0002]

2. Description of the Related Art In recent years, an electron beam has been used in many fields of advanced materials such as chemical reaction, microscopy, analysis, welding, etc., and an electron gun is used as a source of this electron beam. FIG. 3 shows an example of an electron gun conventionally used. That is, the electron gun is composed of an ionization chamber 3 in which an anode wire 1 is penetrated through an insulator 2 and a high voltage chamber 5 communicating with the ionization chamber 3 via a conductive extraction grid 11 described later. It is configured. Also, the ionization chamber 3
Has an exit window 10 that is transparent to electrons on the side opposite to the high voltage chamber 5, and has a conductive portion of a voltage substantially equal to the voltage of the exit window 10 at the connection portion with the high voltage chamber 5. A sex extraction grid 11 is formed.

On the other hand, a cathode 7 having a high negative bias voltage is accommodated in the high voltage chamber 5 while being supported by an insulator 8, and a voltage introducing terminal 9 from the cathode 7 to the outside of the high voltage chamber 5.
Has been withdrawn. Further, the high voltage chamber 5 is provided with an exhaust port 12 and is connected to an exhaust device (not shown) so that the pressures in the ionization chamber 3 and the high voltage chamber 5 can be controlled. There is.

Both the ionization chamber 3 and the high voltage chamber 5 contain a gas having an extremely low pressure capable of achieving ionization, and usually helium of 10 to 50 millitorr is used. In addition, the wall 4 of the ionization chamber 3 and the high voltage chamber 5
Both walls 6 are at ground potential. Further, when performing ionization, a pulse voltage of 10 to 20 kilovolts is applied to the anode wire 1.

On the other hand, the cathode 7 is a high voltage supply source (not shown).
A negative bias voltage (e.g., -150 kilovolts) is constantly maintained through a voltage introduction terminal 9 connected to. Also, the exit window 10 is constructed of a somewhat thin sheet that is transparent to high energy. The sheet can be made of a metal such as aluminum or titanium and has a thickness of tens of micrometers. Furthermore, as this window width, many application examples,
Especially in applications relating to the treatment of materials by irradiation, window widths in excess of 1 cm are required.

In the conventional electron gun constructed as described above, electrons serving as an electron beam source are emitted as described below. That is, when a pulse voltage is applied to the anode wire 1 penetrating the ionization chamber 3 under a low pressure, a discharge occurs between the anode wire 1 and the wall 4 of the ionization chamber at the ground potential,
Plasma is generated in the ionization chamber 3. On the other hand, the cathode 7 arranged in the high voltage chamber 5 extracts cations from the plasma diffused from the ionization chamber 3 toward the conductive extraction grid 11.

The cations penetrate into the high voltage chamber 5 through the conductive extraction grid 11 arranged between the ionization chamber 3 and the high voltage chamber 5 and hit the cathode 7. Then, on the surface of the cathode 7, electrons are emitted by the impact of the cations. The electrons thus emitted travel in the opposite direction to the cations, are accelerated toward the conductive extraction grid 11, pass through the ionization chamber 3 and exit window 10.
And is supplied as an electron beam source.

Here, ignoring the initial energy of positive ions in the vicinity of the conductive extraction grid 11, and assuming that the negative bias voltage is VHT and the charge amount of positive ions is e, the positive ions are (single charged ions). Can be considered to reach the cathode 7 with energy equal to e · VHT. Further, on the surface of the cathode 7, the electrons secondary-emitted by the impact of the cations extracted from the extraction grid are accelerated toward the conductive extraction grid 11, where the electrons reach the energy of e · VHT. To do. Under these conditions, one cation and an electron emitted by this cation have substantially overlapping orbits corresponding to the same electric field line.

The electron gun as described above is mainly constructed by replacing the electron gun with a gas laser or a magnet hydrodynamic generator by electronic excitation, and by replacing the exit window 10 with an X-ray generating target. It is applicable to a generator.

By the way, the intensity required for the electron beam generated by the electron gun remarkably depends on the object to be applied (for example, a gas laser by electron excitation). Therefore, conventionally, an electron gun as shown in FIG. 4 has been proposed as a measure against the above beam intensity. That is, the ionization chamber 3
By installing apertures 13 at both ends of the ionization chamber, the density of plasma generated in the ionization chamber 3 is increased and the number of cations extracted from the ionization chamber is changed, whereby the number of electrons emitted by cation impact on the cathode surface is increased. To control the electron beam intensity.

It should be noted that the apertures 1 are provided at both ends of the ionization chamber 3.
3, except that the electron gun shown in FIG. 3 is provided, and the wall 4, the aperture 13 and the wall 6 of the high voltage chamber 5 of the ionization chamber 3 are all at the ground potential.

In the conventional electron gun constructed as described above, electrons serving as an electron beam source are emitted as described below. That is, when a pulse voltage is applied to the anode wire 1 penetrating the ionization chamber 3 under a low pressure, a discharge is generated in the space surrounded by the wall 4 of the ionization chamber at the ground potential and the apertures 13 at both ends of the ionization chamber. Then, plasma is generated in the ionization chamber 3. On the other hand, the cathode 7 arranged in the high voltage chamber 5 extracts positive ions from the plasma.

The cations enter the high voltage chamber 5 through the conductive extraction grid 11 arranged between the ionization chamber 3 and the high voltage chamber 5 and hit the cathode 7. Then, on the surface of the cathode 7, electrons are emitted by the impact of the cations. In this way, the emitted electrons travel in the opposite direction to the cations, are accelerated towards the conductive extraction grid 11, pass through the ionization chamber 3 and exit window 1
It reaches 0 and is supplied as an electron beam source.

[0014]

However, the conventional electron gun as described above has the following problems to be solved. That is, in order to change the electron current,
As described above, the number of cations reaching the cathode surface, that is, the number of cations in plasma diffused in the direction of the conductive extraction grid 11 may be changed.
As this means, apertures 13 are provided at both ends of the ionization chamber 3.
By adopting a method of increasing the plasma density generated in the ionization chamber 3, a method of varying the pulse voltage applied to the anode wire, or a method of varying the high voltage applied to the cathode. Was there.

However, these methods cannot easily adjust the intensity of the electron beam, increase the capacity of the power source connected to the cathode, and reduce the pulse voltage applied to the anode wire. There wasn't.

The present invention has been proposed in order to solve the above-mentioned drawbacks of the prior art, and the purpose thereof is to easily adjust the intensity of the electron beam and to connect it to the cathode. Another object of the present invention is to provide a highly efficient electron gun capable of reducing the capacity of the power supply and the pulse voltage applied to the anode wire.

[0017]

According to a first aspect of the present invention, there is provided an exit window that is transparent to electrons and a conductive extraction grid provided on the opposite side of the exit window, and ionization is performed at a low pressure. Gas to be ionized, an ionization chamber equipped with a wire for ionizing the gas to generate cations, and the ionization chamber is communicated via the conductive extraction grid, and a cathode is housed at a position facing the conductive extraction grid. In the electron gun including the high voltage chamber, an insulator is disposed between the conductive extraction grid and the wall of the ionization chamber, and between the conductive extraction grid and the wall of the ionization chamber, and between the both. It is characterized in that a bias voltage source for making a potential difference is connected.

The invention according to claim 2 further comprises an exit window permeable to electrons, a conductive extraction grid provided on the opposite side, and a gas to be ionized at a low pressure. , An ionization chamber equipped with a wire for ionizing this gas to generate cations, and an aperture electrically connected to the walls of the ionization chamber at both ends of the ionization chamber, and ionized through the conductive extraction grid. In an electron gun comprising a high voltage chamber communicating with the chamber and containing a cathode at a position facing the conductive extraction grid, an insulator is provided between an aperture provided in the ionization chamber and a wall of the ionization chamber. , A bias voltage source for establishing a potential difference between the aperture and the wall of the ionization chamber is connected.

[0019]

According to the electron gun of claim 1, an insulator is provided between the conductive extraction grid and the wall of the ionization chamber, and a bias voltage is applied between the conductive extraction grid and the wall of the ionization chamber. Can be applied to lower the potential of the conductive extraction grid below the potential of the walls of the ionization chamber. As a result, the positive ions in the plasma generated in the ionization chamber can be attracted to the conductive extraction grid with a stronger attractive force than before, and the ionization efficiency in the ionization chamber can be significantly increased.

According to the electron gun of the second aspect, an insulator is arranged between the apertures provided at both ends of the ionization chamber and the wall of the ionization chamber, and a bias is provided between the aperture and the wall of the ionization chamber. By applying the voltage, the potential of the aperture can be made lower than the potential of the wall of the ionization chamber. As a result, the electrons generated in the ionization chamber receive a stronger repulsive force than the conventional one due to the aperture, and are confined in the ionization chamber, whereby the ionization efficiency in the ionization chamber can be remarkably increased.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be specifically described below with reference to FIGS. The same members as those of the conventional type shown in FIGS. 3 and 4 are designated by the same reference numerals, and the description thereof will be omitted.

(A) First Embodiment In the present embodiment, as shown in FIG. 1, an insulator 20 is provided between the conductive extraction grid 11 and the wall 4 of the ionization chamber, and the conductive material is used. A bias voltage source 21 is connected between the sex extraction grid 11 and the wall 4 of the ionization chamber.
This bias voltage source 21 is provided to create a potential difference between the conductive extraction grid 11 and the wall 4 of the ionization chamber. Other configurations are similar to those of the conventional type shown in FIG.

In the electron gun of this embodiment having such a structure, the intensity of the electron beam can be easily adjusted as described below. That is, when a pulse voltage is applied between the anode wire 1 arranged in the ionization chamber 3 and the wall 4 of the ionization chamber 3, the gas in the ionization chamber 3 is ionized by the pulse discharge and plasma is generated. In this case, in the plasma generated by the pulse discharge, the cations diffused toward the conductive extraction grid 11 have a negative potential with respect to the wall 4 of the ionization chamber by the bias voltage source 21. Receives a stronger electric attraction than the conventional method. As a result, the number of cations passing through the conductive extraction grid 11 is significantly increased. That is, the number of cations reaching the cathode surface increases, and the number of electrons secondary-emitted by the cations also increases.

Therefore, when it is necessary to greatly increase the electron beam intensity, the pulse voltage applied to the anode wire 1 is increased and the conductivity extraction is performed by applying a negative bias voltage, as in the conventional case. By equipping the grid 11, the number of cations extracted into the high voltage chamber can be increased, and the electron beam intensity can be efficiently increased.

On the other hand, even in the case where the electron beam intensity similar to the conventional one is required, by installing the conductive extraction grid 11 to which a negative bias voltage is applied, the positive diffusion diffused in the direction of the conductive extraction grid. Since the number of ions can be increased, the pulse voltage applied to the anode wire 1 can be reduced. Furthermore, anode wire 1
Since the pulse voltage applied to the pulse generator can be reduced, it is suitable for increasing the pulse repetition rate and the life of the pulse generator can be extended.

(B) Second Embodiment In this embodiment, as shown in FIG.
Insulators 22 are provided between the apertures 13 provided at both ends of the inside and the wall 4 of the ionization chamber.
A bias voltage source 23 is connected between 3 and the wall 4 of the ionization chamber. The bias voltage source 23 is provided to create a potential difference between the aperture 13 and the wall 4 of the ionization chamber. Other configurations are the same as those of the conventional type shown in FIG. In the electron gun of this embodiment having such a configuration, the intensity of the electron beam can be easily adjusted as described below. That is, when a pulse voltage is applied between the anode wire 1 disposed in the ionization chamber 3 and the wall 4 of the ionization chamber 3, the ionization chamber 3 is pulse-discharged.
The gas is ionized and electrons are generated.

In this case, among the electrons generated by the pulse discharge, the electrons that move in the longitudinal direction of the anode wire 1 are
The aperture 13 having a negative potential with respect to the wall 4 of the ionization chamber by the bias voltage source 23 receives an electrically stronger repulsive force than that of the conventional method, and is confined in the ionization chamber. As a result, collision with gas atoms is further promoted, ionization efficiency is increased, and plasma density is also high.

Thus, the positive ions in the plasma generated by the discharge are accelerated toward the cathode 7 in the high voltage chamber 5, pass through the extraction grid 11 and hit the cathode 7. That is, the number of cations reaching the cathode surface increases, and the number of electrons secondary-emitted by the cations also increases.

Therefore, when it is necessary to greatly increase the electron beam intensity, the negative bias voltage V applied to the cathode 7 is increased and the pulse voltage applied to the anode wire 1 is increased as in the conventional case. Furthermore, by equipping the aperture 13 to which a negative bias voltage is applied to improve the ionization efficiency in the ionization chamber, the electron beam intensity can be efficiently increased.

On the other hand, even in the case where the electron beam intensity similar to the conventional one is required, the ion current can be increased by equipping the aperture 13 to which the negative bias voltage is applied, so that the cathode 7 can be provided. The negative bias voltage V to be applied and the pulse voltage to be applied to the anode wire 1 can be reduced, and the power supply capacity can be reduced. Further, since the pulse voltage applied to the anode wire 1 can be reduced, it is suitable for increasing the pulse repetition rate and the life of the pulse generator can be extended.

[0031]

As described above, according to the present invention, insulation is provided between the conductive extraction grid and the wall of the ionization chamber, or between the apertures provided at both ends of the ionization chamber and the wall of the ionization chamber. By arranging an object and connecting a bias voltage source for making a potential difference between the two, it is possible to easily adjust the intensity of the electron beam.
It is possible to provide a highly efficient electron gun capable of reducing the capacity of the power supply connected to the cathode and the pulse voltage applied to the anode wire.

[Brief description of drawings]

FIG. 1 is a sectional view showing a first embodiment of an electron gun of the present invention.

FIG. 2 is a sectional view showing a second embodiment of the electron gun of the present invention.

FIG. 3 is a sectional view showing an example of a conventional electron gun.

FIG. 4 is a sectional view showing another example of a conventional electron gun.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Anode wire 2 ... Insulator 3 ... Ionization chamber 4 ... Ionization chamber wall 5 ... High-voltage chamber 6 ... High-voltage chamber wall 7 ... Cathode 8 ... Insulator 9 ... Voltage introduction terminal 10 ... Exit window 11 ... Conductivity Extraction grid 13 ... Aperture 20, 22 ... Insulator 21, 23 ... Bias voltage source

Claims (2)

[Claims] 1. An exit window permeable to electrons, and a conductive extraction grid provided on the opposite side of the exit window, the gas to be ionized at a low pressure, and the cation by ionizing the gas. And an ionization chamber having a wire for generating an electric field, and an electron gun including a high voltage chamber communicating with the ionization chamber via the conductive extraction grid and containing a cathode at a position facing the conductive extraction grid. An insulator is arranged between the extraction grid and the wall of the ionization chamber, and a bias voltage source for establishing a potential difference between the conductive extraction grid and the wall of the ionization chamber is connected between the two. An electron gun characterized by that. 2. An exit window permeable to electrons, and a conductive extraction grid provided on the opposite side of the exit window, the gas to be ionized at a low pressure and the cation by ionizing the gas. Is equipped with an ionization chamber equipped with a wire for generating, and an aperture electrically connected to the walls of the ionization chamber at both ends of the ionization chamber, and is communicated with the ionization chamber via the conductive extraction grid, and a conductive extraction grid In an electron gun consisting of a high voltage chamber containing a cathode at a position opposite to, an insulator is disposed between the aperture provided in the ionization chamber and the wall of the ionization chamber, and the aperture and the wall of the ionization chamber are An electron gun characterized in that a bias voltage source for establishing a potential difference between the two is connected therebetween.