JPH05258697A - Electron gun - Google Patents

Abstract

PURPOSE:To facilitate the regulation of electron beam strength in an electron gun. CONSTITUTION:A heater 20 for heating a conductive extract grid 4 is arranged near the conductive extract grid 4. The heater 20 is supported by an insulating material 21 mounted on the wall 3 of an ionizing chamber, and the current supply to the heater 20 is conducted from the outside.

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 easily changed.

[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. 2 shows an example of an electron gun conventionally used. That is, the electron gun is composed of an ionization chamber 2 in which an anode wire 1 is arranged, and a high voltage chamber 6 which communicates with the ionization chamber 2 via a conductive extraction grid 4 described later. Further, the ionization chamber 2 is provided with an exit window 11 that is transparent to electrons on the side opposite to the high voltage chamber 6, and the exit window 11 is provided at the connection with the high voltage chamber 6. A conductive extraction grid 4 is formed with a voltage approximately equal to the voltage.

On the other hand, a cathode 5 having a high negative bias voltage is accommodated in the high voltage chamber 6 supported by an insulator 8, and a high voltage introducing terminal 9 is provided from the cathode 5 to the outside of the high voltage chamber 6. Has been withdrawn. Further, the high voltage chamber 6 has an exhaust port 10
Is provided and is connected to an exhaust device (not shown) so that the pressures in the ionization chamber 2 and the high voltage chamber 6 can be controlled.

Both the ionization chamber 2 and the high voltage chamber 6 contain a gas having an extremely low pressure capable of achieving positive ionization, and usually helium of 10 to 50 millitorr is used. The wall 3 of the ionization chamber 2 and the wall 7 of the high voltage chamber 6 are both at the ground potential. Further, when performing ionization, the anode wire 1 and the wall 3 of the ionization chamber are
And a pulse voltage of 10 to 20 kilovolts is applied.

On the other hand, the cathode 5 is constantly maintained at a negative bias voltage (for example, -150 kilovolts) through a high voltage introduction terminal 9 connected to a high voltage supply source (not shown). . The exit window 11 is also composed of a somewhat thin sheet that is transparent to high energy.
This sheet can be made of a metal such as aluminum or titanium and has a thickness of tens of micrometers. Furthermore, this window width requires a window width of more than 1 cm in many applications, especially those relating to the treatment of materials by irradiation.

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 arranged in the ionization chamber 2 under a low pressure, a wire discharge occurs between the anode wire 1 and the wall 3 of the ionization chamber at the ground potential, and the anode wire in the ionization chamber 2 Plasma is generated between the walls of the ionization chamber.

On the other hand, the cathode 5 arranged in the high voltage chamber 6
Cations are extracted from the plasma that has diffused from the ionization chamber 2 toward the conductive extraction grid 4. The cations penetrate into the high voltage chamber 6 through the conductive extraction grid 4 arranged between the ionization chamber 2 and the high voltage chamber 6 and collide with the cathode 5. Then, on the surface of the cathode 5, electrons are emitted by the impact of the cations.

The electrons thus emitted travel in the opposite direction to the cations and are accelerated toward the conductive extraction grid 4, and further pass through the ionization chamber 2 to reach the exit window 11 and the electron beam. Supplied as a source.

Here, ignoring the initial energy of cations in the vicinity of the conductive extraction grid 4, and assuming that the negative bias voltage at the cathode 5 is VHT and the charge amount of cations is e, the cations (single It can be considered that the cathode 5 reaches the cathode 5 with energy equal to e · VHT. Also,
Electrons secondary emitted on the surface of the cathode 5 by the impact of the cations extracted from the extraction grid are accelerated toward the conductive extraction grid 4, where the electrons are e · VHT.
Reach the energy of. Under these conditions, 1
The individual cations and the electrons emitted by the cations 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 magnet hydrodynamic generator by electronic excitation, and by replacing the exit window 11 with an X-ray generating target. It is applicable to a generator.

By the way, the intensity of the electron beam generated by the electron gun remarkably depends on the object of application (for example, a gas or laser by electron excitation). So, conventionally,
As a measure for the above beam intensity, the plasma density (discharge current density) in the entire ionization chamber 2 is changed by changing the pulse voltage applied to the anode wire 1 shown in FIG.
A method of controlling the electron beam intensity by changing the number of positive ions extracted into the high voltage chamber 6 to change the number of electrons emitted by the positive ions has been used.

[0012]

However, the conventional electron gun as described above has the following problems to be solved. That is, in order to increase the electron beam intensity, it is sufficient to increase the number of cations as described above. Conventionally, this means is used to increase the plasma density (discharge current density) in the ionization chamber. That is, it is necessary to increase the pulse voltage applied to the anode wire. Therefore, in order to increase the electron beam intensity, it is necessary to increase the pulse power supply capacity in order to increase the pulse voltage, which is very inefficient.

The present invention has been proposed in order to solve the above-mentioned drawbacks of the prior art, and an object thereof is to provide a highly efficient electron gun capable of easily adjusting the electron beam intensity. To provide.

[0014]

SUMMARY OF THE INVENTION The present invention comprises an exit window permeable to electrons and a conductive extraction grid on the opposite side thereof, and a gas to be ionized at low pressure, A high voltage chamber, which is connected to an ionization chamber equipped with an anode wire for ionizing this gas to generate cations and the ionization chamber via the conductive extraction grid, and a cathode is housed at a position facing the conductive extraction grid. In the electron gun consisting of, a heater for heating the conductive extraction grid is provided.

[0015]

According to the electron gun of the present invention, by heating the conductive extraction grid by the heater, the discharge current density of the wire discharge in the conductive extraction grid direction can be locally increased, and the conductive extraction grid can be extracted. More positive ions can be extracted through the grid. As a result, the electron beam intensity can be easily increased.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be specifically described below with reference to FIG. The same members as those of the conventional type shown in FIG. 2 are designated by the same reference numerals, and the description thereof will be omitted.

In this embodiment, as shown in FIG.
A heater 20 for heating the conductive extraction grid 4 is provided in the vicinity of the conductive extraction grid 4. This heater 20 has an insulator 21 attached to the wall 3 of the ionization chamber.
And the electric current is supplied to the heater 20 from the outside. The other structure is the same as that of the conventional type shown in FIG.

In the electron gun of this embodiment having such a structure, the electron beam intensity can be easily increased as described below. That is, when a pulse voltage is applied between the anode wire 1 arranged in the ionization chamber 2 and the wall 3 of the ionization chamber, wire discharge is generated between the anode wire and the wall of the ionization chamber, and plasma is generated. It The positive ions in the plasma thus generated pass through the conductive extraction grid 4, are accelerated toward the cathode 5 in the high voltage chamber 6, and collide with the cathode 5.

In the electron gun of this embodiment, since the conductive extraction grid 4 is heated by the heater 20 at this time, the discharge current density of the wire discharge in the conductive extraction grid direction locally increases. There is. Therefore, the number of cations existing in the direction of the conductive extraction grid is increased compared to the case without heating, and as a result, 2
The number of electrons emitted next is increased, and the electron beam intensity is increased.

Therefore, when it is necessary to significantly increase the electron beam intensity, the conductive extraction grid 4 is kept until the required electron beam intensity is obtained even when the pulsed voltage applied to the anode wire is low. By heating with the heater 20, a desired electron beam intensity can be easily obtained.

Further, since the pulse voltage applied to the anode wire can be reduced, it is not necessary to increase the pulse power source capacity, and it is easy to extend the life of the pulse power source and increase the pulse repetition rate. Further, even when the same electron beam intensity as in the conventional case is obtained, the conductive extraction grid 4 is connected to the heater 20.
Since the electron beam intensity can be increased with high efficiency by heating at, the pulse voltage applied to the anode wire can be reduced.

It should be noted that the present invention is not limited to the above-mentioned embodiment, the heater may be arranged in the vicinity of the conductive extraction grid, and is supported by an insulator attached to the wall 7 of the high voltage chamber. May be.

[0023]

As described above, according to the present invention, the discharge current density of the wire discharge in the direction of the conductive extraction grid is made possible by the simple structure of arranging the heater for heating the conductive extraction grid. By locally increasing the number of positive ions through the conductive extraction grid, the electron beam intensity can be easily adjusted.
A highly efficient electron gun can be provided.

[Brief description of drawings]

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

FIG. 2 is a sectional view showing an example of a conventional electron gun.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Anode wire 2 ... Ionization chamber 3 ... Ionization chamber wall 4 ... Conductive extraction grid 5 ... Cathode 6 ... High-voltage chamber 7 ... High-voltage chamber wall 8 ... Insulator 9 ... High-voltage introduction terminal 10 ... Exhaust port 11 … Exit window 20… Heater 21… Insulator

Claims (1)

[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 an anode wire for generating an electric field, and an electron gun connected to the ionization chamber through the conductive extraction grid and having a cathode housed at a position facing the conductive extraction grid. An electron gun comprising a heater for heating the sex extraction grid.