JPH05211052A - Pulse electron gun - Google Patents

Abstract

PURPOSE:To provide a pulse electron gun which has high repeatability, allow the width of electron beam to be easily increased or decreased to efficiently generate electron beam. CONSTITUTION:An insulator 20 is disposed between the wall of an ionization chamber 12 and the wall of a device 4 and a bias voltage source (not shown) for providing electric potential difference is connected between the wall of the ionization chamber 12 and the wall of the device 4. The bias voltage source allows the electric potetial of the ionization chamber to stay higher than that of the device.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-power pulse electron gun, and more particularly, to a pulse electron improved so that the pulse repetition rate of the electron beam or the electron beam width can be changed efficiently and easily. It's about guns.

[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 and welding, and a pulse electron gun has been used as a source of this electron beam. FIG. 4 shows an example of a conventional pulse electron gun. That is, the pulsed electron gun has an ionization chamber 3 in which an anode wire 1 is penetrated through an insulator 2,
It is composed of a high voltage chamber 5 communicating with the ionization chamber 3 via a conductive extraction grid 11 described later. In the ionization chamber 3, on the side opposite to the high voltage chamber 5,
An exit window 9 that is transparent to electrons is formed, and a conductive extraction grid 10 having a voltage substantially equal to the voltage of the exit window 9 is formed at the connection portion with the high voltage chamber 5.

On the other hand, a cathode 6 having a high negative bias voltage is accommodated in the high voltage chamber 5 supported by an insulator 7, and a voltage introducing terminal 8 is provided from the cathode 6 to the outside of the high voltage chamber 5.
Has been withdrawn. Further, the high voltage chamber 5 is provided with an exhaust port 11 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. The wall 12 of the ionization chamber 3 and the wall 4 of the device are both at ground potential. Further, when performing ionization, a pulse voltage of 10 to 20 kilovolts is applied to the anode wire 1 to perform wire discharge.

On the other hand, the cathode 6 is a high voltage supply source (not shown).
A negative bias voltage (e.g., -150 kilovolts) is constantly maintained through a voltage introduction terminal 8 connected to. The exit window 9 is also composed 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, in many applications, especially those related to the processing of materials by irradiation,
The window width exceeds 1 cm.

In the conventional pulse electron gun having such a structure, pulsed electrons which serve as a pulse 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, the wall 1 of the ionization chamber at ground potential is applied.
A discharge is generated between the two and plasma is generated in the ionization chamber 3.

On the other hand, the cathode 6 arranged in the high voltage chamber 5
Draws positive ions from the plasma that has diffused from the ionization chamber 3 toward the conductive extraction grid 10. The cations enter the high voltage chamber 5 through the conductive extraction grid 10 arranged between the ionization chamber 3 and the high voltage chamber 5, and hit the cathode 6. Then, on the surface of the cathode 6, 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 10, and further pass through the ionization chamber 3 to reach the exit window 9 and are pulsed electrons. Supplied as a beam source.

Here, ignoring the initial energy of the cations in the vicinity of the conductive extraction grid 10 and letting the negative bias voltage at the cathode 6 be VHT and the charge amount of the cations be e, the cations are (single It can be considered that the cathode 6 reaches the cathode 6 with energy equal to e · VHT. Further, on the surface of the cathode 6, the electrons secondary-emitted by the impact of the cations extracted from the extraction grid are accelerated toward the conductive extraction grid 10, where the electrons are e.
Reach the energy of VHT. Under these conditions, one cation and an electron emitted by this cation have substantially overlapping orbits corresponding to the same electric field line.

In the pulse electron gun as described above, the pulse electron gun is mainly replaced by a gas laser or magnet hydrodynamic generator by electronic excitation, and the exit window 9 is replaced by a target for X-ray generation. It is applicable to a pulse X-ray generator.

By the way, the pulse repetition rate required for the pulsed electron beam generated by the pulsed electron gun is extremely dependent on the object of application (for example, a gas laser by electronic excitation). Therefore, conventionally, as a measure against the above pulse repetition rate, a pulse voltage according to the pulse repetition rate is applied to the anode wire 1 penetratingly arranged in the ionization chamber 3, and plasma is generated in the ionization chamber 3 to generate the pulse repetition rate. Was used to control the.

The electron beam width required for the pulsed electron beam generated by the pulsed electron gun also remarkably depends on the object of application (for example, a gas laser by electron excitation). Therefore, conventionally, as a countermeasure against the electron beam width, a method of changing the size of the exit window 9 to control the electron beam width has been used.

[0013]

However, the conventional pulse electron gun as described above has the following problems to be solved. That is, in order to increase the pulse repetition rate, it is sufficient to apply a pulse voltage according to the required pulse repetition rate to the anode wire, but when the repetition rate becomes high repetition (KHz class), the wire discharge Since the time interval becomes short, charged particles (especially electrons) generated by the wire discharge remain until the next wire discharge, and the next wire discharge cannot be stably ignited.

In addition, the method of changing the size of the exit window 9 to change the width of the electron beam has a drawback that the electron beam cannot be efficiently taken out because an unnecessary electron beam is forced to be generated. It was

The present invention was proposed in order to solve the above-mentioned drawbacks of the prior art, and its first object is to provide a pulse electron gun capable of higher repetition rate, A second object is to provide a pulse electron gun capable of easily increasing and decreasing the electron beam width and efficiently extracting the electron beam.

[0016]

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 pulsed electron gun including the high voltage chamber, an insulator is provided between the wall of the ionization chamber and the wall of the electron gun device, and between the wall of the ionization chamber and the device wall, and between them. It is characterized in that a bias voltage source for making a potential difference is connected.

Further, the invention according to claim 2 is the same pulse electron gun, wherein the high voltage chamber is divided into a plurality of parts, and different cathodes are provided in the respective high voltage chambers. It is what

[0018]

According to the pulse electron gun of the first aspect, a pulsed positive bias voltage is applied between the wall of the ionization chamber and the wall of the apparatus immediately after the wire discharge is completed, and the pulsed electron gun By making the electric potential higher than the electric potential of the wall of the device, it becomes possible to collect the residual charged particles generated by the wire discharge in a short time. As a result, even during high repetition operation,
Since the wire discharge can be ignited in a stable state, it is possible to obtain a pulse electron gun capable of higher repetition rate.

According to the pulse electron gun of claim 2,
By dividing the high voltage chamber into a plurality of parts, it is possible to apply the high voltage only to the cathodes in the high voltage chambers of a number that can secure the required electron beam width. As a result, even when an electron beam having the same width as that of the conventional one is obtained, the power supply capacity applied to the cathode is required to be the minimum necessary, and an efficient pulse electron gun can be obtained.

[0020]

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 FIG. 4 are designated by the same reference numerals, and the description thereof will be omitted.

(A) First Embodiment In this embodiment, as shown in FIG. 1, an insulator 20 is provided between the wall 12 of the ionization chamber and the wall 4 of the apparatus, and the ionization chamber is also provided. A bias pulse power supply for establishing a potential difference between the wall 12 and the device wall 4 is connected. The bias voltage source is configured to allow the wall potential of the ionization chamber to be higher than the wall potential of the device. Other configurations are the same as those of the conventional type shown in FIG.

In the pulse electron gun of this embodiment having such a configuration, the pulse repetition rate of the pulse electron beam 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 3 and the wall 12 of the ionization chamber 3, the number of pulse repetitions is increased by the pulse wire discharge, as shown in FIG. 2 (A). The wire discharge corresponding to is ignited, and the wire discharge current flows.

At this time, the charged particles (particularly electrons) in the plasma generated by the pulse wire discharge are
Since it diffuses and disappears into the wall 12 of the ionization chamber, the ionization chamber is generated from the pulse power supply for bias according to the trigger signal from the pulse power supply for wire discharge at the time timing as shown in FIG. 2B. By applying a positive bias voltage in a pulsed manner to the wall 12 of the electrode 12, residual charged particles (particularly electrons) generated by the wire discharge can be recovered in a short time. As a result, the next pulse wire discharge can be stably ignited, and the pulse repetition rate of the electron beam can be greatly increased.

(B) Second Embodiment In this embodiment, as shown in FIG. 3, at a position facing the ionization chamber 3 with the conductive extraction grid 10 interposed therebetween,
A plurality of high voltage chambers 22a, 22b, 22c are provided. Cathodes 6a to 6c are arranged in the high voltage chambers 22a to 22c, respectively, and a high voltage can be independently applied to each cathode by switches 23a to 23c provided outside the pulse electron gun. Is configured. Other configurations are the same as those of the conventional type shown in FIG.

In the pulse electron gun of this embodiment having such a structure, the electron beam width can be efficiently controlled as described below. That is, the high voltage is applied only to the cathodes in the high voltage chambers of a number sufficient to secure the electron beam width required for the application target (in FIG. 3,
The cathodes 6b and 6c are switched on), and no high voltage is applied to the other cathodes in the high voltage chamber (in FIG. 3, only the cathode 6a is switched off).

Next, a pulse voltage is applied between the anode wire 1 arranged in the ionization chamber 3 and the wall 12 of the ionization chamber, and plasma is generated in the ionization chamber 3 by pulse wire discharge. At this time, the cations in the plasma generated by the pulse wire discharge diffuse in the direction of the conductive extraction grid and pass through the conductive extraction grid 10. Then, among the plurality of high voltage chambers, the cations that have entered the high voltage chambers 6b and 6c in which the high voltage is applied to the cathode thereof are accelerated in the direction of the cathode and collide with the cathode so that electrons are secondarily emitted. And generate an electron beam. On the other hand, the cations that have entered the high voltage chamber 6a where the high voltage is not applied to the cathode are not accelerated and do not collide with the cathode, so that no electron beam is generated.

Therefore, when it is necessary to greatly increase the electron beam width, it is sufficient to apply a high voltage to the cathodes in all the high voltage chambers, and conversely, when the required electron beam width is small. For, it suffices to appropriately select a cathode to which a high voltage is applied and switch on only that cathode. as a result,
Even if an electron beam having the same width as the conventional one is obtained, a useless electron beam is not generated, so that the capacity of the high voltage power source applied to the cathode can be significantly reduced, and an efficient pulse electron gun can be obtained. it can.

[0028]

As described above, according to the present invention, an insulator is provided between the wall of the ionization chamber and the wall of the electron gun device,
Further, by connecting a bias voltage source for providing a potential difference between the wall of the ionization chamber and the wall of the apparatus, it is possible to provide a pulse electron gun capable of higher repetition rate. Further, by dividing the high voltage chamber into a plurality of parts and disposing different cathodes in each high voltage chamber, the electron beam width can be easily increased or decreased, and the electron beam can be extracted efficiently. An electron gun can be provided.

[Brief description of drawings]

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

2A is a diagram showing a wire discharge current generated in an ionization chamber, and FIG. 2B is a diagram showing a timing of a bias voltage applied to a wall of the ionization chamber.

FIG. 3 is a sectional view showing a second embodiment of the pulse electron gun of the present invention.

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

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Anode wire 2 ... Insulator 3 ... Ionization chamber 4 ... Device wall 5 ... High-voltage chamber 6, 6a-6c ... Cathode 7 ... Insulator 8 ... Voltage introduction terminal 9 ... Exit window 10 ... Conductive extraction grid 12 ... Wall of ionization chamber 20 ... Insulators 22a-22c ... High-voltage chamber 23a-23c ... Switch

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. In a pulsed electron gun including a high voltage chamber that is connected to the ionization chamber through the conductive extraction grid and that houses a cathode at a position facing the conductive extraction grid. An insulator is arranged between the wall of the chamber and the wall of the electron gun device, and a bias voltage source for establishing a potential difference between the wall of the ionization chamber and the wall of the device is connected. A pulsed electron gun characterized by. 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. In a pulsed electron gun comprising a high voltage chamber that is connected to the ionization chamber through the conductive extraction grid and that contains a cathode at a position facing the conductive extraction grid. A pulse electron gun characterized in that the voltage chamber is divided into a plurality of parts, and different cathodes are provided in the respective high voltage chambers.