Output adjustment mechanism, field emission device, and output control method for field emission device

Abstract

Provided are an output adjustment mechanism capable of arbitrarily controlling the output characteristics of a field emission device by a single high-voltage power supply, a field emission device, and a control method therefor. 【Solution means】The field emission device 1 includes an emitter unit 3 that supports an emitter 31 in a vacuum vessel 2, a guard electrode 4 provided on the outer periphery of the emitter 31 so as to be separable from and contactable with the emitter 31 in the vacuum vessel 2, a target unit 5 including a target 51 facing the emitter 31 in the vacuum vessel 2, a grid electrode 7 disposed between the emitter unit 3 and the target 51, a grid electrode support 8 that extends from the electrode main body portion 71 of the grid electrode 7 in the direction of the emitter unit 3 and supports the grid electrode 7 so as to be reciprocally movable in the axial direction, and a support holder 10 that holds the grid electrode support 8 so as to be reciprocally movable in the axial direction.

Description

Technical Field

[0001] The present invention relates to a field emission device and an electromagnetic shielding structure applicable to various devices such as an X-ray apparatus, an electron tube, and a lighting device.

Background Art

[0002] As an example of a field emission device applicable to various devices such as an X-ray apparatus, an electron tube, and a lighting device, a voltage is applied between an emitter and a target located in opposite directions in a vacuum chamber of a vacuum vessel, and an electron beam emitted from the emitter is made to collide with the target to exhibit a desired function (for example, X-ray fluoroscopic resolution in the case of an X-ray apparatus).

[0003] For example, the field emission device 1 of Patent Document 1 shown in FIG. 4 includes a vacuum vessel 2 that forms a vacuum chamber 20 with one end and the other end of a cylindrical insulator 21 sealed by an emitter unit 3 and a target unit 5, respectively. A grid electrode 7 extending in the radial direction of the vacuum chamber 20 is provided between the emitter unit 3 and the target unit 5. A high-voltage power supply 11a is connected to the emitter unit 3 and the target unit 5. A high-voltage power supply 11b is connected to the grid electrode 7 and the target unit 5.

[0004] The emitter unit 3 includes an emitter 31 having an electron generation part 30 facing the target unit 5, and an emitter support part 33 that supports the emitter 31 in the vacuum chamber 20 and seals one end of the insulator 21.

[0005] A guard electrode 4 is provided on the outer peripheral side of the electron generation part 30 of the emitter 31. The guard electrode 4 is provided on the outer peripheral side of the emitter 31 so as to be separable from the emitter 31 and forms a cylindrical shape extending in both end directions of the vacuum chamber 20. And this guard electrode 4 is supported by a guard electrode support part 41 so as to be movable in the axial direction of the vacuum vessel 2 on one end side of the insulator 21.

[0006] In the field emission device 1, for the modification process such as the guard electrode 4 to suppress the flashover phenomenon, the guard electrode support portion 41 is operated to move the guard electrode 4 toward the grid electrode 7 side to suppress the field emission of the emitter 31, and a voltage is applied to the guard electrode 4 to cause repeated discharges. Thereby, the guard electrode 4 and the like can be modified while suppressing the field emission of the emitter 31, and the characteristics of the field emission device can be improved.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0008] Since the field emission device 1 has three electrodes, namely, an emitter unit 3, a target unit 5, and a grid electrode 7, two high-voltage power supplies are required. Generally, the higher the tube voltage, the larger the high-voltage power supply becomes, and the entire system combining the field emission device 1 and the high-voltage power supply becomes larger. Here, if voltage division is performed by a plurality of resistors R1 shown in FIG. 5, a voltage can be applied to the field emission device 1 from a single high-voltage power supply 11.

[0009] However, since the voltage on the resistor R1 side is uniquely determined by the voltage of the high-voltage power supply 11a, the output characteristics (for example, tube current) of the field emission device 1 cannot be arbitrarily controlled. A method of controlling the output characteristics by moving the emitter 31 together with the guard electrode 4 is also conceivable, but the movable structure and its control become complicated.

[0010] The present invention has been made in view of the above circumstances, and an object thereof is to provide an output adjustment mechanism capable of arbitrarily controlling the output characteristics of a field emission device with a single high-voltage power supply, a field emission device, and a control method thereof.

Means for Solving the Problems

[0011] Therefore, one aspect of the present invention is an output adjustment mechanism having an emitter unit that supports an emitter in a vacuum vessel, a target unit having a target facing the emitter in the vacuum vessel, a guard electrode provided on the outer periphery of the emitter so as to be detachably contacted with the emitter in the vacuum vessel, a grid electrode disposed between the emitter unit and the target, a grid electrode support body that extends from the electrode main body portion of the grid electrode in the direction of the emitter unit and supports the grid electrode so as to be reciprocally movable in the axial direction of the vacuum vessel, and a support body holding portion that holds the grid electrode support body so as to be reciprocally movable in the axial direction.

[0012] One aspect of the present invention is that, in the output adjustment mechanism, the grid electrode further has a grid electrode flange that is electrically connected to the grid electrode through a bellows through which the grid electrode support body is inserted and seals one end side of the vacuum vessel, and the grid electrode flange is formed with an insertion hole into which the guard electrode is inserted and sealed, and an insertion hole through which the grid electrode support body is inserted.

[0013] One aspect of the present invention is that, in the output adjustment mechanism, the grid electrode support body further includes a shielding portion that shields the outer peripheral surface of one end side of the bellows.

[0014] One aspect of the present invention is that, in the output adjustment mechanism, the support body holding portion operates the grid electrode support body such that the distance between the grid electrode and the guard electrode decreases when increasing the tube current of the field emission device, and the distance increases when decreasing the tube current.

[0015] One aspect of the present invention is that, in the output adjustment mechanism, the output adjustment mechanism further includes a single power source connected between the emitter unit and the target unit, and resistors connected between the emitter unit and the grid electrode and between the target unit and the grid electrode.

[0016] One aspect of the present invention further includes an emitter unit support that supports the emitter unit so as to be reciprocally movable in the axial direction in the output adjustment mechanism.

[0017] One aspect of the present invention is a field emission device including the output adjustment mechanism.

[0018] One aspect of the present invention is a method for controlling the output of a field emission device including the output adjustment mechanism, wherein the support holding portion controls the tube current of the field emission device by adjusting the distance between the grid electrode and the guard electrode by operating the grid electrode support.

Advantages of the Invention

[0019] According to the present invention as described above, it is possible to provide an output adjustment mechanism capable of arbitrarily controlling the output characteristics of a field emission device with a single high-voltage power supply, a field emission device, and a control method thereof.

Brief Description of the Drawings

[0020]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Embodiments for Carrying Out the Invention

[0021] Embodiments of the present invention will be described below with reference to the drawings.

[0022] The control system of the field emission device 1 to which the output adjustment mechanism, which is one aspect of the present invention shown in FIG. 1, is applied includes a vacuum vessel 2, an emitter unit 3, a guard electrode 4, a target unit 5, an emitter unit support 6, a grid electrode 7, a grid electrode support 8, a grid electrode flange 9, a support holder 10, a high-voltage power supply 11, a resistor R1, an insulating coupling 12, a drive conversion mechanism 13, and a motor 14.

[0023] The vacuum vessel 2 forms a vacuum chamber 20 by sealing both ends of a cylindrical insulator 21.

[0024] The emitter unit 3 includes an emitter 31 having an electron generation part 30 that emits an electron beam L1 and is supported coaxially with the vacuum vessel 2 inside the vacuum chamber 20 on one end side of the vacuum vessel 2, and an emitter support part 32 that supports the emitter 31.

[0025] The guard electrode 4 is provided on the outer peripheral side of the emitter 31 so as to be separable from and contactable with the emitter 31 inside the vacuum chamber 20 on one end side of the vacuum vessel 2, forms a cylindrical shape extending in both end directions of the vacuum chamber 20, and is supported coaxially with the vacuum vessel 2 on the other end side of the vacuum chamber 20.

[0026] The target unit 5 is supported coaxially with the vacuum vessel 2 inside the vacuum chamber 20 on the other end side of the vacuum vessel 2, and includes a target 51 that faces the emitter 31 and receives the electron beam L1 from the electron generation part 30 of the emitter 31 and emits X-rays L2 and the like to the outside of the vacuum vessel 2.

[0027] The emitter unit support 6 is inserted into a bellows 61 interposed between the inner surface of one end of the guard electrode 4 and the emitter support part 32, and supports the emitter support part 32 so as to be movable in the axial direction of the vacuum vessel 2.

[0028] The grid electrode 7 is disposed between the emitter unit 3 and the target 51 inside the vacuum chamber 20, and includes an electrode main body part 71 in which holes 70 through which an electron beam emitted from the emitter 31 passes to the target 51 are formed.

[0029] The grid electrode support 8 extends, for example, from the electrode body 71 of the grid electrode 7 in the direction of the emitter unit 3, is inserted into the bellows 81, and supports the grid electrode 7 so as to be movable in the axial direction of the vacuum vessel 2. Further, the grid electrode support 8 includes a shielding portion 82 that shields the bellows 81, thereby suppressing the electric field concentration on the protruding portion of the bellows 81 on the outer peripheral surface. The form of the grid electrode support 8 is not particularly limited as long as it can support the grid electrode 7 in the radial direction of the vacuum vessel 2. For example, a pair of rod-shaped or plate-shaped cross-sectional arcs symmetrically arranged about the axis of the vacuum vessel 2 can be mentioned.

[0030] The grid electrode flange 9 is electrically connected to the grid electrode 7 via the bellows 81 and seals one end side of the vacuum vessel 2. As illustrated in FIG. 3, the grid electrode flange 9 is formed with an insertion hole 91 into which the guard electrode 4 is inserted and sealed by the insulator 21, and an arc-shaped insertion hole 92 through which the grid electrode support 8 is inserted.

[0031] The shape of the insertion hole 92 is not limited to an arc shape as long as the grid electrode support 8 can be inserted therethrough. For example, when the grid electrode support 8 is rod-shaped, the insertion hole 92 is set to a diameter slightly larger than the outer diameter of the grid electrode support 8, and a pair is formed symmetrically about the axis of the vacuum vessel 2 according to the arrangement of the pair of grid electrode supports 8. The grid electrode supports 8 inserted into the pair of insertion holes 92 are individually surrounded by the bellows 81. Further, when the insertion hole 92 is formed in an arc shape as shown in FIG. 3, an example of the form of the bellows 81 is a double bellows structure including an inner peripheral side bellows that surrounds the outer periphery of the guard electrode 4 and an outer peripheral side bellows that surrounds the inner peripheral side bellows with the insertion hole 92 therebetween. The insertion hole 92 is not limited to a pair and can be set according to the number of grid electrode supports 8.

[0032] The support body holding part 10 is connected to the insulating coupling 12 and holds the grid electrode support 8 so as to be reciprocally movable by the drive conversion mechanism 13. In particular, the support body holding part 10 operates the grid electrode support 8 such that the axial distance between the grid electrode 7 and the guard electrode 4 is reduced when increasing the tube current of the field emission device 1, and the distance is enlarged when decreasing the tube current.

[0033] The high-voltage power supply 11 is grounded and connected between the emitter unit 3 and the target unit 5 to supply voltage to the field emission device 1.

[0034] The resistors R1 are connected between the emitter unit 3 and the grid electrode 7 and between the target unit 5 and the grid electrode 7 to divide the voltage of the high-voltage power supply 11.

[0035] The insulating coupling 12 connects the support body holding part 10 and the drive conversion mechanism 13.

[0036] The drive conversion mechanism 13 converts the rotation of the motor 14 into a linear reciprocating motion along the axial direction of the vacuum vessel 2 and transmits it to the insulating coupling 12. As the drive conversion mechanism 13, well-known ball screw drive or piston drive methods are applied.

[0037] The conventional field emission device 1 in FIG. 4 operates the guard electrode 4 to control the output characteristics, while the field emission device 1 of the present embodiment in FIG. 1 operates the grid electrode 7 using a single high-voltage power supply 11 to control the output characteristics.

[0038] In the field emission device 1 of the present embodiment, since the high-voltage power supply 11 is single, the voltages between the target 51 and the grid electrode 7 and between the grid electrode 7 and the emitter 31 cannot be individually controlled. However, by moving the grid electrode 7 to change the axial distance gap between the grid electrode 7 and the emitter 31, the tube current can be arbitrarily increased or decreased. Specifically, when increasing the tube current, the distance gap between the grid electrode 7 and the emitter 31 is reduced, and when decreasing the tube current, the distance gap is enlarged.

[0039] The effect of increasing or decreasing the tube current by changing the distance gap between the grid electrode 7 and the emitter 31 can be obtained even when the guard electrode 4 or the emitter 31 is operated. However, in this case, since the electric field on the surface of the emitter 31 changes with a minute change, fine adjustment is not effective. To confirm this, the electric field and electron trajectories were analyzed using the analysis model shown in FIG. 2.

[0040] Table 1 shows a comparison of the surface electric field of the emitter 31 and the focus dimension due to the electron trajectory when the axial distance A between the grid electrode 7 and the guard electrode 4 and the axial distance B between the guard electrode 4 and the emitter 31 are each changed with respect to the distance gap between the grid electrode 7 and the emitter 31.

[0041]

Table 1

[0042] No. 2 in which only the distance A is changed and No. 4 in which only the distance B is changed have the same gap. However, No. 4 has a significantly lower surface electric field of the emitter 31 and no electron emission can be obtained compared to No. 1 in which the distances A and B are not changed, so there is no electron trajectory and no focus dimension can be obtained. This result indicates that in No. 4 where only the guard electrode 4 or the emitter 31 is operated, the surface electric field of the emitter 31 changes drastically and fine adjustment of the tube current is difficult. On the other hand, in No. 2 and No. 3 where only the grid electrode 7 of the present embodiment is operated, a desired electric field can be obtained on the surface of the emitter 31 compared to No. 4, and fine adjustment of the tube current becomes possible.

[0043] As described above, according to the field emission device 1 of the present embodiment, by operating the grid electrode 7, the output characteristics of the field emission device 1 can be arbitrarily controlled by a single high-voltage power supply 11. Incidentally, when the emitter 31 is simultaneously movable together with the guard electrode 4, it is considered that the same effect as when only the grid electrode 7 is operated can be obtained, but the movable structure becomes complicated. On the other hand, according to the field emission device 1, only the grid electrode 7 can be reciprocally operated by the grid electrode support 8 inserted into the insertion hole 92 of the grid electrode flange 9 in FIG. 3, and the movable structure of the grid electrode 7 becomes simple.

Explanation of Signs

[0044] 1…Field emission device 2…Vacuum vessel, 20…Vacuum chamber, 21…Insulator 3…Emitter unit, 30…Electron generation part, 31…Emitter, 32…Emitter support part 4…Guard electrode 5…Target unit, 51…Target 6…Emitter unit support, 61…Bellows 7…Grid electrode, 70…Hole, 71…Electrode main body part 8…Grid electrode support, 81…Bellows, 82…Shielding part 9…Grid electrode flange, 91…Insertion hole, 92…Insertion through hole 10…Support holding part 11…High-voltage power supply R1…Resistor 12…Insulating coupling 13…Drive conversion mechanism 14…Motor

Claims

1. an emitter unit supporting an emitter in a vacuum vessel; a target unit including a target facing the emitter in the vacuum vessel; a guard electrode provided around the outer periphery of the emitter in the vacuum vessel so as to be detachable from the emitter; a grid electrode disposed between the emitter unit and the target; a grid electrode support extending from an electrode body of the grid electrode toward the emitter unit and supporting the grid electrode so as to be reciprocable in the axial direction of the vacuum vessel; a support holding portion that holds the grid electrode support so as to be reciprocatable in the axial direction; An output adjustment mechanism comprising:

2. a grid electrode flange electrically connected to the grid electrode via a bellows through which the grid electrode support is inserted and sealing one end of the vacuum vessel; the grid electrode flange has an insertion hole into which the guard electrode is inserted and sealed; An insertion hole through which the grid electrode support is inserted is formed. The output adjustment mechanism according to claim 1 .

3. 3. The output adjustment mechanism according to claim 2, wherein the grid electrode support further comprises a shielding portion that shields an outer circumferential surface of one end side of the bellows.

4. 2. The output adjustment mechanism according to claim 1, wherein the support holding unit operates the grid electrode support so that a distance between the grid electrode and the guard electrode decreases when a tube current is increased, and so that the distance increases when the tube current is decreased.

5. a single power supply connected between the emitter unit and the target unit; resistors connected between the emitter unit and the grid electrode and between the target unit and the grid electrode; The output adjustment mechanism according to claim 1, further comprising:

6. 2. The output adjustment mechanism according to claim 1, further comprising an emitter unit support that supports the emitter unit so that the emitter unit can reciprocate in the axial direction.

7. 2. A field emission device comprising the output adjustment mechanism according to claim 1.

8. 2. A method for controlling output of a field emission device equipped with the output adjustment mechanism according to claim 1, characterized in that the support holding unit adjusts the distance between the grid electrode and the guard electrode by operating the grid electrode support to control a tube current.

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