JP5290087B2 - Electron beam emitter - Google Patents

Description

The present invention relates to an apparatus that focuses an electron beam generated from an electron emitter (emitter), shields the generation of X-rays inside, and emits the same as it is.

X-rays are generated when an electron beam collides with a metal such as tungsten. The electron beam has a property as a particle beam, and the X-ray has a property as light. The X-rays are used in non-destructive inspection equipment or X-ray CT equipment, etc., while the electron beam acts on molecules in the substance to select reactive species such as ionic species and radical species. Therefore, in addition to radical reaction, graft polymerization reaction, and resist film modification, it is also used for sterilization.

As the above-mentioned electron beam emission device, the one disclosed in Patent Document 1 is known. In this electron beam emission device, an electron emission layer is formed on a cathode electrode (cathode), and a gate electrode for extracting electrons from the electron emission layer is disposed between the cathode electrode and an anode electrode (anode) opposite to the cathode electrode. In addition, the voltage applied between the gate electrode and the cathode electrode and the voltage applied between the anode electrode and the cathode electrode are individually managed.

As an electron emitter, a pointed carbon film in which carbon nanotubes shown in Patent Document 2 and graphene sheets shown in Patent Document 3 are stacked in multiple layers is known.

JP 2002-093307 A JP 2006-290691 A JP 2008-150253 A

FIG. 6 is a diagram showing a relationship between a conventional electron emitter (emitter) and an anode. A window portion is formed on an anode made of stainless steel or the like, and this window portion is formed of beryllium foil, which is a light element, between the atmosphere and vacuum. Is sealed. In recent low-voltage / ultra-low-voltage electron tubes, an acceleration voltage of 100 kV or less is applied between the electron emitter and the anode. When a voltage is applied, electrons are emitted from the electron emitter toward the anode. However, since electrons are emitted with a certain extent, some of them hit the anode. Since the anode is made of stainless steel, X-rays are generated when electrons collide.

When an electron beam is converted into an X-ray, the X-ray is not preferable for the troublesomeness caused by radiating to the outside, the sterilization of food, and the like. Therefore, in Patent Document 1, a gate electrode is provided, an electron beam transmitted through the gate electrode is narrowed, and the electron beam is irradiated only to the window portion of the anode.

However, even in Patent Document 1, the voltage applied between the gate electrode and the electron emitter is about 40 kV, and if the distance between the gate electrode and the electron emitter is 4 mm, an electric field of 10 kV / mm is applied to the emitter. It will be. On the other hand, the electric field characteristic of a normal emitter has a threshold value of 1 to 1.5 kV / mm. When the threshold is exceeded, a current flows rapidly, and a current of several tens to several hundreds of mA flows in an electric field of 10 kV / mm. . When such a large current flows, the window, that is, the anode loss increases, exceeding the cooling capacity of the window, and finally the window is damaged.

Further, even if the carbon films disclosed in Patent Documents 2 and 3 are formed on the electron emission surface, the electric field strength acting on the electron emission surface is not lowered, but a preferable current value (0.1 to 1 mA / cm ² ) cannot be adjusted.

In order to solve the above-described problems, an electron beam emission apparatus according to the present invention includes a metal plate (anode) in which a power supply unit (cathode) is formed on a power supply body (cathode) connected to the cathode side of a DC power supply and connected to the anode side of the DC power supply. ) Is formed with a window portion closed by a thin metal foil through which an electron beam is transmitted, and an electron emission tip (emitter) is detachably attached to the power supply portion, and the electron emission tip is made of a conductive material. A chip body is provided, and the chip body is provided with a coupling portion to the power supply body, and the tip portion of the chip body is an annular guard electrode, and is retracted from the guard electrode at an inner portion surrounded by the guard electrode. The structure is such that an electron emission surface on which a carbon film is formed is provided at the position.

A grid electrode is disposed between the electron emission tip and a metal plate serving as an anode and at a position close to the electron emission tip, and a voltage applied between the electron emission tip and the grid electrode is set between the electron emission tip and the anode. The effective electric field can be further reduced by making it smaller than the voltage applied between the two.

  According to the electron beam emission apparatus of the present invention, since the coupling portion to the power supply body (cathode) is provided as the structure of the electron emission chip incorporated inside, the replacement is easy, and a large number of electron emission chips are connected to the power supply body (cathode). ) Is advantageous when attached to.

  The electric field strength between the electron emission tip and the anode is determined by the distance between the tip of the electron emission tip and the anode. In the present invention, the tip of the electron emission tip is the tip of the guard electrode. Since the surface is retracted from the tip of the guard electrode, the electric field intensity at the electron emission surface is weakened and a large current can be prevented from flowing.

Configuration diagram of an electron beam emission apparatus according to the present invention Front view of the feeder connected to the cathode side Sectional view of the electron emission tip coupled to the feeder Enlarged view of the tip of the electron emission tip (A) thru | or (c) is a figure which shows another Example of an electron emission chip | tip. A diagram explaining a conventional problem

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. As shown in FIG. 1, the electron beam emission apparatus includes a power supply body (cathode) 1 connected to the cathode side of the DC power source in the vacuum vessel, a metal plate (anode) 2 connected to the anode side of the DC power source, A grid electrode 3 is provided between the power feeder 1 and the metal plate 2.

A plurality of female screw holes 4 as power supply parts are formed in the power supply body 1, and male screw parts 6 of electron emission chips (emitters) 5 are screwed into the female screw holes 4.

The electron emission chip 5 includes a chip body 7 made of a conductive material such as stainless steel. The tip of the chip body 7 is a guard electrode 8 having an annular shape, and a substrate 9 is formed on the inner side surrounded by the guard electrode 8. The surface of the substrate 9 is embedded as a concave surface 10.

This concave surface 10 has a constant radius of curvature R0, and there is a focal point F that converges assuming that parallel rays are incident. For example, the focal point F is set so as to be at the position of the metal plate (anode) 2.

On the surface of the concave surface 10, a carbon film 11 for electron emission is formed with a thickness of several μm to several tens of μm. The carbon film 11 is constituted by a number of protrusions developed in a planar shape, and the protrusions further include a raised portion formed on the surface of the concave surface 10 and a needle-like portion extending from the raised portion.

The guard electrode 8 protrudes from the carbon film 11. That is, the carbon film 11 which is an electron emission surface is in a position retracted from the tip of the guard electrode 8.

Here, the curvature radius R1 on the outer peripheral side of the guard electrode 8 is set to be equal to or larger than the curvature radius R2 on the carbon film 2 side. Thus, by setting the shape of the guard electrode 3 to R1 ≧ R2, it is possible to suppress local electric field concentration on the surface of the carbon film 2 and to prevent current deterioration and discharge phenomenon due to thermal deterioration from occurring. . Further, the radius of curvature R0 of the concave surface 10 satisfies R0 ≧ R1. By setting R0 ≧ R1, electric field concentration on the electron-emitting chip is limited, and electric field application between the chips is averaged. Thus, there is an effect that the electron emitter can be controlled to a necessary current at an actual applied voltage.

The metal plate (anode) 2 is made of, for example, stainless steel, and window portions 12 are formed at locations corresponding to the respective electron emission chips 5, and these window portions 12 are closed with a beryllium foil 13.

  In the above, a DC voltage of 50 kV is applied between the power supply body (cathode) 1 and the metal plate (anode) 2, and a DC voltage of 1 kV is applied between the power supply body (cathode) 1 and the grid electrode 3.

  Then, electrons are drawn out by the voltage applied between the power feeder (cathode) 1 and the grid electrode 3, and the electrons constricted by the grid electrode 3 are between the power feeder (cathode) 1 and the metal plate (anode) 2. Is accelerated by the voltage applied to the light and transmitted through the beryllium foil 13 of the window portion 12 and released to the outside.

  Here, it is also possible to adopt a bipolar structure in which the grid electrode 3 is not provided. In this case, as shown in FIG. 4, when the distance between the metal plate (anode) 2 and the guard electrode 8 is d and the applied voltage is V, the electric field strength E is E = V / d. By retracting the concave surface 10 (carbon film 11), which is an electron emission surface, from the tip of the guard electrode 8, the electric field applied to the concave surface 10 (carbon film 11) is reduced. Since an electron beam does not require a high voltage, the concave surface 10 (carbon film 11) is retracted (h) from the tip of the guard electrode 8 so that a current of about 0.1 to 1 mA flows. The retraction amount is preferably 0.5 to 2.0 mm.

  In the case of the three-pole structure shown in the figure, the applied voltage can be reduced to about 1 kV between the power feeder (cathode) 1 and the grid electrode 3, so there is no possibility that a large current flows. By retracting the (carbon film 11) from the tip of the guard electrode 8, electrons can be stably generated.

  5 (a) to 5 (c) show another embodiment of the electron emission tip 5. The electron emission tip 5 shown in FIG. 5 (a) has a male screw portion 14 that is screwed into the female screw hole 4 of the power supply body 1. It is provided on the back side.

The electron-emitting chip 5 shown in FIG. 5B is formed with a female screw portion 15, and the power feeding body 1 is provided with a male screw portion into which the female screw portion 15 is screwed.

The electron emission chip 5 shown in FIG. 5C has a long shape, and a guard electrode 8 is provided on the entire periphery. In this embodiment, a convex portion 16 is formed along the length direction to be slid and engaged with the power supply body 1, and the power supply body 1 has a groove (a dovetail groove) with which the convex portion 16 is engaged. ).

  The electron-emitting device according to the present invention can be applied to the promotion of chemical reaction and sterilization.

DESCRIPTION OF SYMBOLS 1 ... Power feeding body (cathode), 2 ... Metal plate (anode), 3 ... Grid electrode, 4 ... Female screw hole, 5 ... Electron emission chip | tip (emitter), 6 ... Male screw part, 7 ... Chip body, 8 ... Guard Electrode, 9 ... substrate, 10 ... concave surface, 11 ... carbon film, 12 ... window portion, 13 ... beryllium foil, 14 ... male screw portion, 15 ... female screw portion, 16 ... convex portion, R0 ... radius of curvature of concave surface, R1 ... curvature radius on the outer peripheral side of the guard electrode, R2 ... radius of curvature on the inner peripheral side of the guard electrode.

Claims (2)

A power feeding part is formed on the power feeding body connected to the cathode side of the DC power source, and a metal plate connected to the anode side of the DC power source is formed with a window part closed with a thin metal foil through which an electron beam passes, An electron-emitting chip is detachably attached to the power supply section, and the electron-emitting chip includes a chip body made of a conductive material. The chip body is provided with a coupling section for the power supply body. The electron beam emitting device is characterized in that the part is an annular guard electrode, and an electron emission surface in which a carbon film is formed is provided at a position retracted from the guard electrode in an inner part surrounded by the guard electrode. 2. The electron beam emitting device according to claim 1, wherein a grid electrode is disposed between the electron emission tip and a metal plate serving as an anode and close to the electron emission tip, and between the electron emission tip and the grid electrode. The electron beam emitting device is characterized in that a voltage applied to the electrode is made smaller than a voltage applied between the electron emission tip and the anode.