JP5760290B2 - Field emission X-ray generator for static elimination - Google Patents

Field emission X-ray generator for static elimination Download PDF

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JP5760290B2
JP5760290B2 JP2010293652A JP2010293652A JP5760290B2 JP 5760290 B2 JP5760290 B2 JP 5760290B2 JP 2010293652 A JP2010293652 A JP 2010293652A JP 2010293652 A JP2010293652 A JP 2010293652A JP 5760290 B2 JP5760290 B2 JP 5760290B2
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electron
field emission
current control
emitting device
control resistor
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JP2012142171A (en
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稲葉　仁
仁 稲葉
好弘 鬼塚
好弘 鬼塚
智宣 中村
智宣 中村
淳生 定塚
淳生 定塚
高寿 小池
高寿 小池
康成 福田
康成 福田
光明 熊野
光明 熊野
芳浩 野口
芳浩 野口
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Takasago Thermal Engineering Co Ltd
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Takasago Thermal Engineering Co Ltd
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Priority to KR1020110142240A priority patent/KR20120075396A/en
Priority to TW100148905A priority patent/TW201237915A/en
Priority to CN2011104620635A priority patent/CN102665370A/en
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    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05G—X-RAY TECHNIQUE
    • H05G1/00—X-ray apparatus involving X-ray tubes; Circuits therefor
    • H05G1/08—Electrical details
    • H05G1/26—Measuring, controlling or protecting
    • H05G1/30—Controlling
    • H05G1/32—Supply voltage of the X-ray apparatus or tube
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J1/00—Details of electrodes, of magnetic control means, of screens, or of the mounting or spacing thereof, common to two or more basic types of discharge tubes or lamps
    • H01J1/02—Main electrodes
    • H01J1/30—Cold cathodes, e.g. field-emissive cathode
    • H01J1/304—Field-emissive cathodes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J35/00—X-ray tubes
    • H01J35/02—Details
    • H01J35/04—Electrodes ; Mutual position thereof; Constructional adaptations therefor
    • H01J35/06—Cathodes
    • H01J35/065—Field emission, photo emission or secondary emission cathodes

Description

本発明は、除電用の電界放出型Ｘ線発生装置に関するものである。 The present invention relates to a field emission X-ray generator for static elimination .

近年、たとえばフラットパネルディスプレイの製造工程では、軟Ｘ線（微弱Ｘ線）を照射してイオンを生成し、これを利用して除電する技術が使われている。軟Ｘ線を発生させる装置としては、これまでフィラメント方式のＸ線発生装置が使用されてきたが、このフィラメント方式のＸ線発生装置では、消費電力が大きいという問題があった。   In recent years, for example, in a manufacturing process of a flat panel display, a technique of generating ions by irradiating with soft X-rays (weak X-rays) and removing electricity using the ions is used. As an apparatus for generating soft X-rays, a filament-type X-ray generation apparatus has been used so far. However, this filament-type X-ray generation apparatus has a problem of high power consumption.

そこで最近では、電界放出型電子源を用いたＸ線管（電界放出型Ｘ線管）が、常温での電子放出が可能なことから消費電力を低く抑えることができるため、従来のフィラメント方式のＸ線管に代わる方式として期待されている。しかしながら、数ｋＶ〜数十ｋＶの高圧電圧を電界放出型Ｘ線管に印加すると、点灯時間の経過とともに電子放出特性が劣化するという問題がある。そのため数千時間以上の寿命が最低限要求される用途、すなわち除電用では、電界放出型Ｘ線管を用いた装置は実用化されていないのが実情である。 Therefore, recently, an X-ray tube (field emission X-ray tube) using a field emission electron source can emit electrons at room temperature, so that power consumption can be kept low. It is expected as an alternative to X-ray tubes. However, when a high voltage of several kV to several tens of kV is applied to the field emission X-ray tube, there is a problem that the electron emission characteristics deteriorate as the lighting time elapses. For this reason, it is the actual situation that an apparatus using a field emission X-ray tube has not been put to practical use in applications requiring a minimum life of several thousand hours, that is, for static elimination .

この点に関し、電界放出型のＸ線発生装置の長寿命を確保する技術して、エミッタとゲート電極間を所定の抵抗をもった配線で短絡する技術が提案されている（特許文献１）。   In this regard, as a technique for ensuring a long life of a field emission type X-ray generator, a technique for short-circuiting between an emitter and a gate electrode with a wiring having a predetermined resistance has been proposed (Patent Document 1).

特開２００８−５３２４１号公報JP 2008-53241 A

しかしながら、特許文献１に記載の技術は、静電気帯電起因の電位発生による放電破壊防止を目的にしており、後述のように高圧ケーブルによって、電源と電界放出型Ｘ線管を結ぶ装置として構成した場合には、高圧ケーブルに発生する過電流や特に点灯開始時に発生しやすい突発的な異常電流の対策には十分ではない。   However, the technique described in Patent Document 1 is intended to prevent discharge breakdown due to potential generation due to electrostatic charging, and is configured as a device that connects a power source and a field emission X-ray tube with a high-voltage cable as described later. Therefore, it is not sufficient for the countermeasure against the overcurrent generated in the high-voltage cable and the sudden abnormal current that is likely to occur at the start of lighting.

本発明はかかる点に鑑みてなされたものであり、長寿命の除電用の電界放出型Ｘ線発生装置を提供して、上記した問題の解決を図ることを目的としている。 The present invention has been made in view of such points, and an object of the present invention is to provide a field emission type X-ray generator for static elimination with a long lifetime, and to solve the above problems.

発明者らが鋭意研究したところ、数ｋＶ〜数十ｋＶの高圧電圧をＸ線管に印加した場合に、電子放出特性が劣化する大きな原因は、電界放出型Ｘ線管特有の電子放出源の電流の変動に誘発される過電流の発生であることが判った。   As a result of extensive research by the inventors, when a high voltage of several kV to several tens of kV is applied to the X-ray tube, the major cause of the deterioration of the electron emission characteristics is the electron emission source specific to the field emission X-ray tube. It was found that this was the occurrence of overcurrent induced by current fluctuation.

これを図に基づいて説明すると、図２に示したように、たとえば除電用の装置として構成する場合、電界放出型Ｘ線管１０１に対しては、高圧ケーブル１０２を介して直流電源１０３から電界放出型Ｘ線管１０１内の電子放出素子に対して電圧を印加する構成となる。この高圧ケーブル１０２には、ケーブル長さに由来して寄生するいわゆる寄生インダクタンスＬとキャパシタンスＣが存在する。また高圧ケーブル１０２における直流電源１０３近傍の箇所には、過電流防止のための過電流防止抵抗１０４が設けることが通常考えられる。   This will be described with reference to the drawings. As shown in FIG. 2, for example, when configured as a device for static elimination, the electric field emission X-ray tube 101 is electrically connected to the electric field from the DC power supply 103 via the high-voltage cable 102. A voltage is applied to the electron-emitting devices in the emission X-ray tube 101. The high-voltage cable 102 has a so-called parasitic inductance L and capacitance C that are parasitic due to the cable length. Further, it is generally considered that an overcurrent prevention resistor 104 for preventing overcurrent is provided at a location near the DC power supply 103 in the high voltage cable 102.

この状態で電界放出型Ｘ線管１０１が点灯すると、電界放出型Ｘ線管１０１はフィラメント方式のＸ線管よりも電子放出量の変動が大きく、この変動に起因して前記した寄生インダクタンスＬとキャパシタンスＣによって、高電圧がいわば二次的に高圧ケーブル１０２に発生することが判った。この二次的に発生した電圧は、過電流防止抵抗１０４を経由せず、その結果、図２に示した装置構成は、結局、図３に示した回路と等価となる。そのため、過電流防止抵抗１０４による過電流防止機能が働かず、電子源の電子放出量がさらに増大し、異常放電によるエミッタ（電子放出素子）の劣化を引き起こしてしまう。   When the field emission X-ray tube 101 is lit in this state, the field emission X-ray tube 101 has a larger variation in the amount of electron emission than the filament type X-ray tube. It has been found that a high voltage is generated in the high-voltage cable 102 secondarily by the capacitance C. This secondarily generated voltage does not pass through the overcurrent prevention resistor 104, and as a result, the device configuration shown in FIG. 2 is eventually equivalent to the circuit shown in FIG. Therefore, the overcurrent prevention function by the overcurrent prevention resistor 104 does not work, the amount of electron emission from the electron source further increases, and the emitter (electron-emitting device) is deteriorated due to abnormal discharge.

この劣化は、電子放出性能を次第に劣化させるため、電界放出型Ｘ線管１０１の寿命が短くなる。さらにまた、前記した寄生インダクタンスＬとキャパシタンスＣによって、とりわけ点灯開始時に極めて短時間に高電圧が高圧ケーブル１０２に発生することも判った。発明者らの知見では、最大で電界放出型Ｘ線管１０１の定格の１１０％の電圧が印加される可能性がある。   Since this deterioration gradually deteriorates the electron emission performance, the life of the field emission X-ray tube 101 is shortened. Furthermore, it has been found that the high voltage is generated in the high-voltage cable 102 in a very short time by the above-described parasitic inductance L and capacitance C, particularly at the start of lighting. According to the knowledge of the inventors, a voltage of 110% of the rated value of the field emission X-ray tube 101 may be applied at the maximum.

そこでこのような問題に鑑み、本発明の除電用電界放出型Ｘ線発生装置は、電子を放出する電子放出素子と、前記電子放出素子から放出された電子の照射によってＸ線を発生するターゲットと、前記ターゲットで発生したＸ線を外部に放出する窓部を有するＸ線管と、このＸ線管に対して高圧ケーブルを介して電圧を印加する電源部とを備え、前記電源部近傍には、当該電源部から前記高圧ケーブルを流れる電流を制限する第１の電流制御抵抗が設けられ、前記電子放出素子近傍には、前記高圧ケーブルから電子放出素子に流れる電流を制限する第２の電流制御抵抗が設けられ、前記第２の電流制御抵抗の抵抗値は、前記電子放出素子固有の抵抗値と前記電子放出素子−前記ターゲット間の抵抗値との合計抵抗値よりも小さく、かつ前記第２の電流制御抵抗の抵抗値は、１０ ３ 〜１０ ７ Ωであることを特徴としている。 In view of such a problem, the field emission X-ray generator for static elimination of the present invention includes an electron-emitting device that emits electrons, a target that generates X-rays by irradiation of electrons emitted from the electron-emitting devices, and An X-ray tube having a window for emitting X-rays generated at the target to the outside, and a power supply unit for applying a voltage to the X-ray tube via a high-voltage cable, and in the vicinity of the power supply unit A first current control resistor for limiting a current flowing from the power source to the high-voltage cable is provided, and a second current control for limiting a current flowing from the high-voltage cable to the electron-emitting device is provided in the vicinity of the electron-emitting device. resistance is provided, said second resistance value of the current control resistor, the electron emission device-specific resistance value and the electron-emitting devices - rather smaller than the total resistance value of the resistance value between the target and the second 2 Resistance value of the current control resistor is characterized in that a 10 3 ~10 7 Ω.

本発明によれば、前記した電源近傍に設けられる過電流防止用の第１の電流制御抵抗の他に、電子放出素子近傍に、前記高圧ケーブルから電子放出素子に流れる電流を制限する第２の電流制御抵抗が設けられているので、前記したような、寄生インダクタンスとキャパシタンスによって極めて短時間に高電圧が高圧ケーブルに発生しても、この第２の電流制御抵抗によって、電子放出素子からの電子放出量を抑制し、当該放出素子の保護を図って長寿命を実現することが可能である。   According to the present invention, in addition to the first current control resistor for preventing overcurrent provided in the vicinity of the power source, the second current for limiting the current flowing from the high-voltage cable to the electron emitting element in the vicinity of the electron emitting element. Since the current control resistor is provided, even if a high voltage is generated in the high-voltage cable in a very short time due to the parasitic inductance and capacitance as described above, the second current control resistor allows the electrons from the electron-emitting device to be generated. It is possible to realize a long life by suppressing the amount of emission and protecting the emission element.

また前記第２の電流制御抵抗は、前記電子放出素子と高圧ケーブル間において、前記電子放出素子から２ｍ以内に設けられ、前記第２の電流制御抵抗と前記電子放出素子との間の高圧ケーブルに寄生するインダクタンスは２μＨ以下、かつキャパシタンスは２００ｐＦ以下であることが好ましい。   The second current control resistor is provided within 2 m from the electron emission device between the electron emission device and the high voltage cable, and is provided on the high voltage cable between the second current control resistor and the electron emission device. It is preferable that the parasitic inductance is 2 μH or less and the capacitance is 200 pF or less.

さらにまた本発明で使用される前記電子放出素子は、グラファイトを基材とした冷陰極であることが好ましい。   Furthermore, the electron-emitting device used in the present invention is preferably a cold cathode based on graphite.

本発明によれば、特殊な電子放出素子を用いることなく、長寿命の除電用電界放出型Ｘ線発生装置を得ることができる。 According to the present invention, a long-life field emission X-ray generator for static elimination can be obtained without using a special electron-emitting device.

実施の形態にかかる除電用電界放出型Ｘ線発生装置の構成を模式的に示した説明図である。It is explanatory drawing which showed typically the structure of the field emission type X-ray generator for static elimination concerning embodiment. 従来技術の下で構成した除電用の電界放出型Ｘ線発生装置の構成を模式的に示した説明図である。It is explanatory drawing which showed typically the structure of the field emission type | mold X-ray generator for static elimination comprised under the prior art. 図２の除電用の電界放出型Ｘ線発生装置の使用時の等価回路を示す説明図である。It is explanatory drawing which shows the equivalent circuit at the time of use of the field emission type | mold X-ray generator for static elimination of FIG.

以下、本発明の実施の形態について説明すると、図１は実施の形態にかかる除電用電界放出型Ｘ線発生装置１の全体の構成を模式的に示しており、電界放出型Ｘ線管１０は、真空容器としての筐体１１、電子放出素子としての冷陰極１２、ターゲット１３、及び筐体１１内で発生したＸ線を外部に放出させる窓１４を有している。 Hereinafter, an embodiment of the present invention will be described. FIG. 1 schematically shows the entire configuration of a field emission X-ray generator 1 for static elimination according to the embodiment. A field emission X-ray tube 10 is shown in FIG. A housing 11 as a vacuum container, a cold cathode 12 as an electron-emitting device, a target 13, and a window 14 for emitting X-rays generated in the housing 11 to the outside.

筐体１１は、内部を気密に維持できる絶縁性のある材質で構成されている。たとえばガラス材と絶縁材とで構成される。筐体１１内部には、冷陰極１２とターゲット１３とが対向している。   The casing 11 is made of an insulating material that can keep the inside airtight. For example, it is composed of a glass material and an insulating material. Inside the housing 11, the cold cathode 12 and the target 13 are opposed to each other.

電子放出素子となる冷陰極１２は、導電性の薄板で構成しても良いが、グラファイトによって構成してもよい。本実施の形態では、グラファイトを基材とした電子材料（グラファイトナノスパインズ）を使用した。その他、炭素を主材料とする素材、たとえばカーボンナノチューブを用いることもできる。   The cold cathode 12 serving as an electron-emitting device may be composed of a conductive thin plate, but may be composed of graphite. In the present embodiment, an electronic material (graphite nanospines) based on graphite is used. In addition, a material mainly composed of carbon, for example, a carbon nanotube can be used.

ターゲット１３は窓１４を介して接地され、ターゲット１３及び窓１４は接地電位である。ターゲット１３の材質は、たとえばタングステン、銅など、導電性の良好な金属材料によって構成されている。窓１４は、ターゲット１３で発生したＸ線を外部に放出する機能を持った材料が使用され、たとえばＸ線の透過性にすぐれたベリリウムによって構成されている。   The target 13 is grounded through the window 14, and the target 13 and the window 14 are at ground potential. The material of the target 13 is made of a metal material having good conductivity, such as tungsten or copper. The window 14 is made of a material having a function of emitting X-rays generated from the target 13 to the outside, and is made of beryllium having excellent X-ray transmission, for example.

冷陰極１２は、直流電源２１と高圧ケーブル２２によって電気的に接続されている。直流電源２１は、正極側が接地されており、冷陰極１２に対して、高圧の負電圧、たとえば−９ｋＶ〜−１６ｋＶを印加することが可能になっている。   The cold cathode 12 is electrically connected by a direct current power source 21 and a high voltage cable 22. The DC power supply 21 is grounded on the positive electrode side, and can apply a high voltage negative voltage, for example, −9 kV to −16 kV, to the cold cathode 12.

直流電源２１は、制御装置２３によってその電圧、電流が制御される。かかる制御は、高圧ケーブル２２に流れる電流、または電界放出型Ｘ線管１０に印加される電圧値を検出するモニタ２４からの検出信号に基づいて、当該電圧や電流を一定値に制御するフィードバック制御によってなされる。   The voltage and current of the DC power source 21 are controlled by the control device 23. Such control is based on feedback control for controlling the voltage or current to a constant value based on a detection signal from a monitor 24 that detects a current flowing through the high-voltage cable 22 or a voltage value applied to the field emission X-ray tube 10. Made by.

そして高圧ケーブル２２における直流電源２１の近傍には、第１の電流制御抵抗３１が高圧ケーブル２２に対して直列に設けられている。この第１の電流制御抵抗３１の抵抗値は、本実施の形態では、たとえば１００ｋΩである。   A first current control resistor 31 is provided in series with the high voltage cable 22 in the vicinity of the DC power supply 21 in the high voltage cable 22. In the present embodiment, the resistance value of the first current control resistor 31 is, for example, 100 kΩ.

また高圧ケーブル２２における直流電源２１の近傍には、第２の電流制御抵抗４１が高圧ケーブル２２に対して直列に設けられている。この第２の電流制御抵抗４１の抵抗値は、電界放出型Ｘ線管１０に印加される電圧の絶対値をＶｏ［Ｖ］としたとき、０．１×Ｖｏ〜１０００×Ｖｏ［Ω］である。   Further, a second current control resistor 41 is provided in series with the high voltage cable 22 in the vicinity of the DC power source 21 in the high voltage cable 22. The resistance value of the second current control resistor 41 is 0.1 × Vo to 1000 × Vo [Ω] when the absolute value of the voltage applied to the field emission X-ray tube 10 is Vo [V]. is there.

発明者の知見によれば、既述した過電流を信頼性高く防止するためには、第２の電流制御抵抗４１の抵抗値は０．１Ω以上、好ましくは１０Ω以上あればよく、これより高くすればするほど、より異常放電防止機能は向上する。すなわち、既述したように、電界放出型Ｘ線管１０での電流変動に伴う寄生インダクタンス起因の電圧が発生した場合、第２の電流制御抵抗４１の抵抗値が高いほど、より多くの電圧が第２の電流制御抵抗４１に付加され、その分電界放出型Ｘ線管１０への負過電圧は少なくなり、過電流を発生させるリスクが小さくなる。   According to the inventor's knowledge, in order to reliably prevent the above-described overcurrent, the resistance value of the second current control resistor 41 may be 0.1Ω or more, preferably 10Ω or more, and higher. The more it is done, the more abnormal discharge prevention function is improved. That is, as described above, when a voltage due to the parasitic inductance associated with the current fluctuation in the field emission X-ray tube 10 is generated, the higher the resistance value of the second current control resistor 41, the more voltage is generated. Added to the second current control resistor 41, the negative overvoltage to the field emission X-ray tube 10 is reduced accordingly, and the risk of generating an overcurrent is reduced.

一方、第２の電流制御抵抗３４を直列に接続することは、電界放出型Ｘ線管１０の定常点灯時、たとえば５００μＡで点灯中、第２の電流制御抵抗４１には、この第２の電流制御抵抗４１の抵抗値×０．０００５Ａの電圧がかかる。そうすると、たとえば第２の電流制御抵抗４１の抵抗値が１００ｋΩの場合には、５０ｖの電圧がかかるので、その結果、第２の電流制御抵抗４１では、５０［ｖ］×０．０００５［Ａ］＝０．０２５［Ｗ］の電力が消費されることになる。   On the other hand, connecting the second current control resistor 34 in series means that when the field emission X-ray tube 10 is steadily lit, for example, at 500 μA, the second current control resistor 41 is connected to the second current control resistor 41. A voltage of resistance value of control resistor 41 × 0.0005A is applied. Then, for example, when the resistance value of the second current control resistor 41 is 100 kΩ, a voltage of 50 v is applied. As a result, in the second current control resistor 41, 50 [v] × 0.0005 [A]. = 0.025 [W] of power is consumed.

このように０．０２５Ｗ程度のレベルだと問題はないが、第２の電流制御抵抗４１で消費される電力が数Ｗ以上になると、電界放出型Ｘ線管１０を用いることで従来のフィラメント型Ｘ線管よりも少ない電力で所定のＸ線を発生させられるという、電界放出型Ｘ線管のメリットは減じられ、優位性がなくなってしまう。   Thus, there is no problem if the level is about 0.025 W, but when the power consumed by the second current control resistor 41 becomes several W or more, the conventional filament type can be obtained by using the field emission X-ray tube 10. The merit of the field emission X-ray tube, in which predetermined X-rays can be generated with less power than that of the X-ray tube, is reduced and the advantage is lost.

そこで、前記したように、第２の電流制御抵抗４１の抵抗値の上限は、１０００×Ｖｏ［Ω］とした。なお発明者の知見では、より好適で実用的な範囲は、電界放出型Ｘ線管１０に印加される電圧の絶対値をＶｏ［Ｖ］としたとき、数Ｖｏ〜数百Ｖｏ［Ω］である。   Therefore, as described above, the upper limit of the resistance value of the second current control resistor 41 is set to 1000 × Vo [Ω]. According to the inventor's knowledge, a more suitable and practical range is several Vo to several hundred Vo [Ω] when the absolute value of the voltage applied to the field emission X-ray tube 10 is Vo [V]. is there.

この例では、第２の電流制御抵抗４１の抵抗値は、１０５Ωとした。これは冷陰極１２の抵抗（エミッタ抵抗：冷陰極１２を構成する素子固有の抵抗値と当該素子−ターゲット１３間の抵抗値との合計抵抗値）よりも小さいものである。すなわち本実施の形態では、冷陰極１２の抵抗が、２×１０７Ω（１０ｋＶ印加で０．５ｍＡが測定されることから算出）であるとき、好ましい第２の電流制御抵抗４１の抵抗値の範囲は、０．１×１０４〜１０００×１０４Ω、すなわち、１０３〜１０７Ωである。これは、冷陰極１２の抵抗（エミッタ抵抗）よりも小さいものである。 In this example, the resistance value of the second current control resistor 41 is set to 10 5 Ω. This is smaller than the resistance of the cold cathode 12 (emitter resistance: the total resistance value of the resistance value unique to the element constituting the cold cathode 12 and the resistance value between the element and the target 13). That is, in the present embodiment, when the resistance of the cold cathode 12 is 2 × 10 7 Ω (calculated from 0.5 mA measured at 10 kV applied), the resistance value of the preferred second current control resistor 41 is The range is 0.1 × 10 4 to 1000 × 10 4 Ω, that is, 10 3 to 10 7 Ω. This is smaller than the resistance (emitter resistance) of the cold cathode 12.

また第２の電流制御抵抗４１を電界放出型Ｘ線管１０の近傍に直列に設ける位置については、冷陰極１２から２ｍ以内が好ましい。これは、冷陰極１２から離れれば離れるほど、高圧ケーブル２２に寄生するインダクタンスとキャパシタンスが大きくなり、その分これらを原因とする過電流によるリスクが増大する。一方発明者が実験で確かめたところ、冷陰極１２から２ｍ以内であれば、本発明の所期の効果が得られることが確認できた。また前記リスクを考慮すれば、第２の電流制御抵抗４１は、冷陰極１２と直接接続してもよいが、そうすると、冷陰極１２自体の構造を改変する必要がある。したがって、実用上は、冷陰極１２から１〜１０ｃｍ以内が好ましい。これによって、高圧ケーブル２２の材質にもよるが、一般的なこの種の用途に使用されるシリコーンゴム等で絶縁された銅線の数十ｋＶ用の高圧ケーブルに寄生するインダクタンスを２μＨ以下、かつキャパシタンスは２００ｐＦ以下に抑えることができる。   The position where the second current control resistor 41 is provided in series in the vicinity of the field emission X-ray tube 10 is preferably within 2 m from the cold cathode 12. As the distance from the cold cathode 12 increases, the inductance and capacitance parasitic on the high-voltage cable 22 increase, and the risk of overcurrent caused by these increases accordingly. On the other hand, as a result of experiments, the inventors have confirmed that the desired effect of the present invention can be obtained within 2 m from the cold cathode 12. Considering the risk, the second current control resistor 41 may be directly connected to the cold cathode 12, but in that case, the structure of the cold cathode 12 itself needs to be modified. Therefore, practically, it is preferably within 1 to 10 cm from the cold cathode 12. Accordingly, although depending on the material of the high-voltage cable 22, the inductance parasitic to the high-voltage cable for several tens kV of copper wire insulated with silicone rubber or the like used in this general application is 2 μH or less, and The capacitance can be suppressed to 200 pF or less.

本実施の形態は、以上の構成を有しているので、直流電源２１から高圧ケーブル２２を介して電界放出型Ｘ線管１０の電界放出素子である冷陰極１２に対して、絶対値が数十ｋＶの電圧を印加した際、図１に示したように、高圧ケーブル２２に寄生するインダクタンスＬやキャパシタンスＣに起因する起電力によって過電流が発生しても、第２の電流制御抵抗４１によって、当該過電流がそのまま冷陰極１２に流れることを防止できる。したがって、冷陰極１２すなわち、電界放出型Ｘ線管１０の寿命を従来よりもはるかに延ばすことができ、たとえば除電用途に必要な数千時間以上の寿命を確保できる。   Since the present embodiment has the above-described configuration, the absolute value is several times that of the cold cathode 12 which is the field emission element of the field emission X-ray tube 10 from the DC power source 21 via the high voltage cable 22. When a voltage of 10 kV is applied, even if an overcurrent occurs due to an electromotive force caused by an inductance L or a capacitance C parasitic on the high-voltage cable 22 as shown in FIG. The overcurrent can be prevented from flowing to the cold cathode 12 as it is. Therefore, the lifetime of the cold cathode 12, that is, the field emission X-ray tube 10 can be extended much more than before, and for example, the lifetime of several thousand hours or more necessary for static elimination applications can be secured.

また点灯開始時に、電流のゆらぎ（変動）と前記した寄生インダクタンスＬおよびキャパシタンスＣの相互作用により発生する起電力による電圧が防止されるので、点灯開始時において、極めて短時間に流れるたとえばパルス的な電圧印加も防止できる。   In addition, since the voltage due to the electromotive force generated by the interaction between the current fluctuation (fluctuation) and the parasitic inductance L and the capacitance C is prevented at the start of lighting, for example, a pulse-like current that flows in a very short time at the start of lighting. Voltage application can also be prevented.

図１に示した除電用電界放出型Ｘ線発生装置１を用いて発明者が実験したところ、次のような結果が得られた。すなわち、電界放出型Ｘ線管１０に印加される電圧が−１４ｋＶ、第２の電流制御抵抗４１の抵抗値が１００ｋΩ、高圧ケーブル２２の長さが１５ｍの場合、点灯初期と１０００時間経過後の冷陰極１２に流れる電流を測定したところ、いずれも５００μＡで安定していた。 When the inventor conducted an experiment using the field emission X-ray generator 1 for static elimination shown in FIG. 1, the following results were obtained. That is, when the voltage applied to the field emission X-ray tube 10 is −14 kV, the resistance value of the second current control resistor 41 is 100 kΩ, and the length of the high-voltage cable 22 is 15 m, the initial lighting and after 1000 hours have elapsed. When the current flowing through the cold cathode 12 was measured, all were stable at 500 μA.

これに対し、第２の電流制御抵抗４１を持たない図２に示した装置で、同じ条件で調べたところ、点灯初期は、冷陰極１２に流れる電流は５００μＡであったが、２４時間経過後には、既に２００μＡまで低下しており、２４時間後には既に冷陰極１２が所期の機能を発揮しえなくなっていることが確認できた。   On the other hand, when the device shown in FIG. 2 without the second current control resistor 41 was examined under the same conditions, the current flowing through the cold cathode 12 was 500 μA at the beginning of lighting, but after 24 hours had elapsed. Has already decreased to 200 μA, and it has been confirmed that the cold cathode 12 can no longer perform its intended function after 24 hours.

なお本実施の形態では、電子放出素子となる冷陰極１２に、グラファイトを基材とした電子材料（グラファイトナノスパインズ）を使用したが、そのようなグラファイトを利用した電子材料を用いなくとも、本発明の所期の効果である、フィラメント方式よりもエネルギー効率がよく、かつ長寿命の除電用の電界放出型Ｘ線発生装置を実現できる。 In the present embodiment, an electronic material based on graphite (graphite nanospines) is used for the cold cathode 12 serving as an electron-emitting device, but the present invention can be used without using such an electronic material using graphite. It is possible to realize a field emission X-ray generator for static elimination that is energy efficient and has a longer life than the filament system, which is an expected effect of the invention.

本発明は、長時間連続して使用する除電用の電界放出型Ｘ線発生装置に有用である。 The present invention is useful for field emission X-ray generator for neutralization to be used continuously for a long time.

１ 除電用電界放出型Ｘ線発生装置
１０ 電界放出型Ｘ線管
１１ 筐体
１２ 冷陰極
１３ ターゲット
１４ 窓
２１ 直流電源
２２ 高圧ケーブル
２３ 制御装置
２４ モニタ
３１ 第１の電流制御抵抗
４１ 第２の電流制御抵抗 DESCRIPTION OF SYMBOLS 1 Field emission X-ray generator for static elimination 10 Field emission X-ray tube 11 Case 12 Cold cathode 13 Target 14 Window 21 DC power supply 22 High voltage cable 23 Controller 24 Monitor 31 1st current control resistance 41 2nd electric current Control resistance

Claims (3)

除電用の電界放出型Ｘ線発生装置であって、
電子を放出する電子放出素子と、前記電子放出素子から放出された電子の照射によってＸ線を発生するターゲットと、前記ターゲットで発生したＸ線を外部に放出する窓部を有するＸ線管と、
このＸ線管に対して高圧ケーブルを介して電圧を印加する電源部とを備え、
前記電源部近傍には、当該電源部から前記高圧ケーブルを流れる電流を制限する第１の電流制御抵抗が設けられ、
前記電子放出素子近傍には、前記高圧ケーブルから電子放出素子に流れる電流を制限する第２の電流制御抵抗が設けられ、
前記第２の電流制御抵抗の抵抗値は、前記電子放出素子固有の抵抗値と前記電子放出素子−前記ターゲット間の抵抗値との合計抵抗値よりも小さく、
かつ前記第２の電流制御抵抗の抵抗値は、１０ ３ 〜１０ ７ Ωであることを特徴とする、除電用電界放出型Ｘ線発生装置。 A field emission X-ray generator for static elimination,
An electron-emitting device that emits electrons, a target that generates X-rays by irradiation of electrons emitted from the electron-emitting device, an X-ray tube having a window that emits X-rays generated from the target to the outside,
A power supply unit that applies a voltage to the X-ray tube via a high-voltage cable;
In the vicinity of the power supply unit, a first current control resistor for limiting a current flowing from the power supply unit through the high-voltage cable is provided,
In the vicinity of the electron-emitting device, a second current control resistor for limiting a current flowing from the high-voltage cable to the electron-emitting device is provided,
Said second resistance value of the current control resistor, the electron emission device-specific resistance value and the electron-emitting devices - rather smaller than the total resistance value of the resistance value between the target,
And the resistance value of said 2nd current control resistance is 10 < 3 > -10 < 7 > (omega | ohm), The field emission type X-ray generator for static elimination characterized by the above-mentioned. 前記第２の電流制御抵抗は、前記電子放出素子と高圧ケーブル間において、前記電子放出素子から２ｍ以内に設けられ、
前記第２の電流制御抵抗と前記電子放出素子との間の高圧ケーブルに寄生するインダクタンスは２μＨ以下、かつキャパシタンスは２００ｐＦ以下であることを特徴とする、請求項１に記載の除電用電界放出型Ｘ線発生装置。 The second current control resistor is provided within 2 m from the electron-emitting device between the electron-emitting device and the high-voltage cable,
2. The field emission type for static elimination according to claim 1, wherein an inductance parasitic to a high-voltage cable between the second current control resistor and the electron-emitting device is 2 μH or less and a capacitance is 200 pF or less. X-ray generator. 前記電子放出素子は、グラファイトを基材とした冷陰極素子であることを特徴とする、請求項１または２のいずれか一項に記載の除電用電界放出型Ｘ線発生装置。 The field emission type X-ray generator for static elimination according to claim 1, wherein the electron-emitting device is a cold cathode device using graphite as a base material.
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