JP5380258B2 - Photocathode manufacturing method - Google Patents
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この発明は、光電子増倍管等で用いられるフォトカソードの製造方法に関するものである。 The present invention relates to a method for producing a photocathode used in a photomultiplier tube or the like.
フォトカソードの光電面は、ＧａＮ等の半導体結晶上にアルカリ金属やその酸化物などを被膜することで形成される。これは、表面準位を下げて光電子放出を容易にするため（活性化するため）であり、したがって、この被覆層がフォトカソードの感度を決定する１つの大きな要因となる。 The photocathode of the photocathode is formed by coating an alkali metal or oxide thereof on a semiconductor crystal such as GaN. This is to lower the surface level to facilitate (activate) photoemission, and this coating layer is therefore one major factor in determining the photocathode sensitivity.
このような被覆層を形成する際は、感度を最大にすべく、特許文献１の段落００４１に記載されているように、例えば水銀ランプからの紫外光をフォトカソードに照射して光電流を測定しながら、その光電流値に基づいて被覆層材料の供給量をコントロールしている。より具体的に言えば、アルカリ金属の酸化物で被覆層を形成する場合、アルカリ金属と酸素とを交互に繰り返し供給するが、その各供給サイクルでの光電流値のピーク値を測定しておき、そのピーク値の増加幅がサチュレートした時点で、材料供給を停止する。 When such a coating layer is formed, the photocurrent is measured by irradiating the photocathode with, for example, ultraviolet light from a mercury lamp, as described in paragraph 0041 of Patent Document 1, in order to maximize sensitivity. However, the supply amount of the coating layer material is controlled based on the photocurrent value. More specifically, when the coating layer is formed of an alkali metal oxide, alkali metal and oxygen are repeatedly supplied alternately, and the peak value of the photocurrent value in each supply cycle is measured. When the increase of the peak value is saturated, the material supply is stopped.
もちろん、供給時間や圧力、温度など、その他の多くのパラメータも調整することも高品質なフォトカソードを製造するためには欠かせない。 Of course, adjustment of many other parameters such as supply time, pressure, and temperature is also essential for producing a high-quality photocathode.
ところが、水銀ランプの光は、比較的広波長帯域の光である。一方、前記感度はフォトカソードに照射される光の波長に依存する。したがって、前述の方法のように、被覆層の形成過程において、水銀ランプを照射して光電流を測定するのでは、その波長帯域全体の積算あるいは平均化された感度しか把握することができない。 However, the light from the mercury lamp is light in a relatively wide wavelength band. On the other hand, the sensitivity depends on the wavelength of light applied to the photocathode. Therefore, when the photocurrent is measured by irradiating the mercury lamp in the process of forming the coating layer as in the above-described method, only the integrated or averaged sensitivity of the entire wavelength band can be grasped.
つまり、前述した方法は、製造中にフォトカソードの感度特性を測定でき、品質管理面で大きく貢献するものではあるが、その結果保証される感度特性は、言わば大雑把なものであり、例えば、波長毎の感度特性を把握したり、非常に狭い波長域の光に対する感度特性を保証したりするには、結局、製造後の検査を待たなければならない。 In other words, the above-described method can measure the photocathode sensitivity characteristic during manufacturing and greatly contributes to quality control. However, the sensitivity characteristic guaranteed as a result is roughly, for example, wavelength. In order to ascertain the sensitivity characteristics of each, or to guarantee the sensitivity characteristics with respect to light in a very narrow wavelength range, it is necessary to wait for inspection after manufacturing.
そのため、生産リードタイムが延びるだけでなく、所望の単波長光に対して一定感度を有したフォトカソードを製造するには、製造後のセレクトに頼らざるを得ず、これでは生産効率を向上させることは難しい。また、被覆層形成パラメータのうちどれが各波長光に対する感度に寄与しているのか、といった、より細やかな生産条件を特定できないため、開発や研究にも支障がある。 Therefore, not only the production lead time is extended, but in order to produce a photocathode having a constant sensitivity with respect to a desired single wavelength light, it is necessary to rely on a selection after the production, which improves the production efficiency. It ’s difficult. Further, since it is not possible to specify more detailed production conditions such as which of the coating layer formation parameters contributes to the sensitivity to each wavelength light, there is a problem in development and research.
これに対し、レーザ等の単波長光を照射しながら被覆層を制御形成する方法も考えられるが、複数波長に対する感度特性を知ることはできない。 On the other hand, a method of controlling and forming the coating layer while irradiating a single wavelength light such as a laser is also conceivable, but the sensitivity characteristic with respect to a plurality of wavelengths cannot be known.
さらに、いずれの方法においても、例えば、所定の波長域にだけ、あるいは所定の波長以上の帯域にだけ、一定の感度を有し、その他の波長域では感度が低いといったシャープな波長感度特性を有するフォトカソードを開発したり、生産したりするときに、限界がある。 Furthermore, in any method, for example, it has a sharp wavelength sensitivity characteristic that has a certain sensitivity only in a predetermined wavelength range or only in a band of a predetermined wavelength or more and low sensitivity in other wavelength ranges. There are limitations when developing and producing photocathodes.
本発明はかかる問題を一挙に解決すべく図ったものであり、波長毎の感度特性を製造過程で把握でき、その結果として、生産効率を向上できたり、所望の波長帯域に良好な感度特性を有するフォトカソードを確実に生産できたり、あるいは種々の被覆層形成パラメータのより細やかな最適化を図ることができたりするフォトカソードの製造方法を提供することを主たる目的とするものである。 The present invention is intended to solve such problems all at once, so that the sensitivity characteristic for each wavelength can be grasped in the manufacturing process, and as a result, the production efficiency can be improved, and a good sensitivity characteristic can be obtained in a desired wavelength band. The main object of the present invention is to provide a method for producing a photocathode that can reliably produce a photocathode having the above-described properties, or can finely optimize various coating layer forming parameters.
すなわち本発明は、半導体結晶からなる光吸収層上に、アルカリ金属又はこれらの酸化物などからなる被覆層を形成してなるフォトカソードの製造方法に係るものであって、前記被覆層の形成中に、ピーク波長が互いに異なる複数の単波長光を順次照射し、各単波長光の照射による放出電流をそれぞれ測定するとともに、前記各放出電流にそれぞれ基づいて、前記被覆層の形成態様を制御し、前記単波長光が、感度を切り替えたい所望の境界波長を境にして感度が要求される側の波長帯域にピーク波長がある第１単波長光と、感度が不要な側の波長帯域にピーク波長がある第２単波長光とを少なくとも含み、前記第１波長光からの光照射による放出電流から算出される感度が、前記第２波長光からの光照射による放出電流から算出される感度を所定以上上回ることを特徴とするものである。 That is, the present invention relates to a method for producing a photocathode in which a coating layer made of an alkali metal or an oxide thereof is formed on a light absorption layer made of a semiconductor crystal, wherein the coating layer is being formed. In addition, a plurality of single-wavelength lights having different peak wavelengths are sequentially irradiated, emission currents due to irradiation of each single-wavelength light are respectively measured , and the formation mode of the coating layer is controlled based on each of the emission currents. The single-wavelength light is peaked in the first single-wavelength light having a peak wavelength in the wavelength band on the side where sensitivity is required with the desired boundary wavelength to be switched in sensitivity, and in the wavelength band on the side where sensitivity is not required. And a sensitivity calculated from an emission current generated by light irradiation from the first wavelength light, and a sensitivity calculated from an emission current generated by light irradiation from the second wavelength light. Is characterized in that the above predetermined value or more.
このようなものであれば、各光の波長を適宜設定することによって、広狭に拘らず所望の波長帯域での感度特性を確認しながら、フォトカソードを製造することができる。 If it is such, it can manufacture a photocathode, confirming the sensitivity characteristic in a desired wavelength band, regardless of wideness by setting the wavelength of each light suitably.
前記各放出電流に基づいて、前記被覆層の形成態様を制御するようにしたものであれば、所望の波長帯域に良好な感度特性を有するフォトカソードを確実に生産できる。 A photocathode having good sensitivity characteristics in a desired wavelength band can be reliably produced as long as the formation mode of the coating layer is controlled based on each emission current.
前記各単波長光に加えて多波長光を順次照射するとともに、前記多波長光の照射による放出電流を測定し、前記単波長光の照射による各放出電流に加えて、前記多波長光の照射による各放出電流に基づいて、前記被覆層の形成態様を制御するものであってもよい。
ここで、多波長光とは、複数の波長成分からなる光であり、例えば、水銀ランプ、ハロゲンランプ等から射出される光が挙げられる。このようなものであれば、波長帯域全体の積算あるいは平均化された感度特性を確認しながら、所望の波長帯域に良好な感度特性を有するフォトカソードを確実に生産できる。
Irradiation of multi-wavelength light in addition to each single-wavelength light, and measurement of an emission current due to irradiation of the multi-wavelength light, and irradiation of the multi-wavelength light in addition to each emission current due to irradiation of the single-wavelength light The formation mode of the coating layer may be controlled based on each emission current.
Here, the multi-wavelength light is light composed of a plurality of wavelength components, for example, light emitted from a mercury lamp, a halogen lamp, or the like. With such a configuration, it is possible to reliably produce a photocathode having good sensitivity characteristics in a desired wavelength band while checking the integrated or averaged sensitivity characteristics of the entire wavelength band.
より具体的には、前記被覆層の形成過程では前記多波長光の照射による放出電流の時間変化に基づいて被覆層材料を供給し、前記形成過程の終了時には前記単波長光の照射による各放出電流に基づいて前記被覆層材料の供給を終了するようにしたものが挙げられる。 More specifically, in the formation process of the coating layer, the coating layer material is supplied based on the time change of the emission current due to the irradiation of the multi-wavelength light, and at the end of the formation process, each emission by the irradiation of the single wavelength light. Examples thereof include those in which the supply of the coating layer material is terminated based on an electric current.
前記被覆層の形成過程では前記単波長光のうちいずれか１つの照射による放出電流の時間変化に基づいて被覆層材料を供給し、前記形成過程の終了時には前記単波長光の照射による各放出電流に基づいて前記被覆層材料の供給を終了するようにしたものであってもよい。 In the formation process of the coating layer, a coating layer material is supplied based on the time change of the emission current caused by the irradiation of any one of the single wavelength light, and at the end of the formation process, each emission current caused by the irradiation of the single wavelength light. The supply of the coating layer material may be terminated based on the above.
前記被覆層材料であるアルカリ金属及び酸素を交互に光吸収層上に導入するサイクルを複数回繰り返すことによってアルカリ金属の酸化物からなる前記被覆層を形成するものであって、各サイクルでのアルカリ金属の導入期間及び酸素の導入期間を各サイクルでの放出電流に基づいて設定することで前記被覆層の形成態様を制御するようにしたものでもよい。 The coating layer made of an oxide of an alkali metal is formed by repeating a cycle of alternately introducing alkali metal and oxygen as the coating layer material onto the light absorption layer, and the alkali in each cycle. The formation mode of the coating layer may be controlled by setting the metal introduction period and the oxygen introduction period based on the emission current in each cycle.
所望の波長域にだけ、あるいは所定の波長以上の帯域にだけ、一定の感度を有し、その他の波長域では感度が低いといった波長感度特性を有するフォトカソードを確実に生産するには、次のようなものであればよい。
すなわち、前記単波長光が、感度を切り替えたい所望の境界波長を境にして感度が要求される側の波長帯域にピーク波長がある第１単波長光と、感度が不要な側の波長帯域にピーク波長がある第２単波長光とを少なくとも含み、前記第１波長光からの光照射による放出電流から算出される感度が、前記第２波長光からの光照射による放出電流から算出される感度を所定以上上回るように前記被覆層の形成態様を制御するものである。
In order to reliably produce photocathodes having wavelength sensitivity characteristics that have a constant sensitivity only in a desired wavelength range or only in a band of a predetermined wavelength or more and low sensitivity in other wavelength ranges, the following is required. Anything is acceptable.
That is, the single-wavelength light is divided into a first single-wavelength light having a peak wavelength in a wavelength band on the side where sensitivity is required with a desired boundary wavelength for which sensitivity is to be switched, and a wavelength band on the side where sensitivity is not required. And a sensitivity calculated from an emission current generated by light irradiation from the first wavelength light, and a sensitivity calculated from the emission current generated by light irradiation from the second wavelength light. The formation mode of the coating layer is controlled so as to exceed a predetermined value.
かかる構成のものであれば、フォトカソードの波長毎の感度特性を被覆層の形成中に知ることができるので、所望の感度特性を有するフォトカソードを確実に生産でき、かつ、所望の感度特性を有するフォトカソードの製造条件を特定しやすくなり、生産効率を向上させるとともに研究開発にも寄与できる。 With such a configuration, the sensitivity characteristic for each wavelength of the photocathode can be known during the formation of the coating layer, so that a photocathode having the desired sensitivity characteristic can be reliably produced and the desired sensitivity characteristic can be obtained. This makes it easier to specify the manufacturing conditions of the photocathode, which can improve production efficiency and contribute to research and development.
以下、本発明の一実施形態について図面を参照して説明する。 Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
本実施形態に係るフォトカソード１０は、光電子増倍管４０等（図４に示す）で用いられるものであり、図１に示すように、例えばガラスからなる基板上１１にＩｎＮ、ＡｌＮ、ＧａＮ等の半導体結晶からなる光吸収層１２を成長させた後、例えばＣｓ、Ｋ、Ｎａ、Ｓｂ等のアルカリ金属又はこれらの酸化物などからなる被覆層１３を形成させることで製造される。
しかしてこの実施形態では、特に被覆層１３の形成方法に特徴があることから、この被覆層１３形成方法について以下に詳述する。
The photocathode 10 according to the present embodiment is used in a photomultiplier tube 40 or the like (shown in FIG. 4). As shown in FIG. 1, an InN, AlN, GaN or the like is formed on a substrate 11 made of glass, for example. After the light absorption layer 12 made of a semiconductor crystal is grown, for example, a coating layer 13 made of an alkali metal such as Cs, K, Na, or Sb or an oxide thereof is formed.
In this embodiment, since the method for forming the coating layer 13 is particularly characteristic, the method for forming the coating layer 13 will be described in detail below.
被覆層１３は、基板１１に光Ｐ１〜Ｐ４を照射して、そのときに放出される光電子Ｅ−を測定しながら、被覆層１３の形成材料（以下、被覆層材料とも言う）を供給し、光吸収層１２に付着させることで形成するが、まずその形成方法を説明するに先立って、前記光Ｐ１〜Ｐ４を照射する照射部２０及び前記光電子Ｅ−を測定するための測定部３０について説明する。 The coating layer 13 irradiates the substrate 11 with light P1 to P4 and supplies the material for forming the coating layer 13 (hereinafter also referred to as coating layer material) while measuring the photoelectrons E − emitted at that time. Although it formed by attaching the light absorption layer 12, first, before a description of the forming method, the irradiation unit 20 and the photoelectron E irradiating the light P1 to P4 - measurement unit 30 for measuring the description To do.
照射部２０は、図１に示すように、複数の光源、すなわち、それぞれ２８５ｎｍ、３７５ｎｍ及び４７５ｎｍがピーク波長である単波長光Ｐ１〜Ｐ３を射出するＬＥＤ２１ａ、２１ｂ、２１ｃと、多波長光Ｐ４を射出する水銀ランプ２２とを有するものである。そして、これら各光源２１ａ、２１ｂ、２１ｃ、２２から光Ｐ１、Ｐ２、Ｐ３、Ｐ４が順次基板１１に照射されるように構成してある。
なお、単波長光Ｐ１〜Ｐ３は、例えばＬＥＤ、レーザー等から射出される光が挙げられるが、ここでは、感度を切り替えたい所望の境界波長を境にして、感度が要求される側の波長帯域にピーク波長がある単波長光と、感度が不要な側の波長帯域にピーク波長がある単波長光とを少なくとも含んでいるものであればよい。多波長光Ｐ４とは、複数の波長成分からなる光であり、前記水銀ランプ２２の他に、ハロゲンランプ等から射出される光が挙げられる。
As shown in FIG. 1, the irradiation unit 20 includes a plurality of light sources, that is, LEDs 21a, 21b, and 21c that emit single-wavelength light P1 to P3 whose peak wavelengths are 285 nm, 375 nm, and 475 nm, respectively, and multiwavelength light P4. And a mercury lamp 22 for injection. The light sources P1, P2, P3, and P4 are sequentially irradiated from the light sources 21a, 21b, 21c, and 22 to the substrate 11.
The single-wavelength light P1 to P3 is, for example, light emitted from an LED, a laser, or the like. Here, the wavelength band on the side where sensitivity is required with a desired boundary wavelength to be switched as a boundary. In other words, it is sufficient to include at least single-wavelength light having a peak wavelength and single-wavelength light having a peak wavelength in the wavelength band on the sensitivity unnecessary side. The multi-wavelength light P4 is light composed of a plurality of wavelength components, and includes light emitted from a halogen lamp or the like in addition to the mercury lamp 22.
測定部３０は、例えば、図４に示される光電子Ｅ−を増倍する複数のダイノード４４ａからなる増倍部４４と、増倍された光電子Ｅ−を収集して電流として出力する陽極４５とを具備するものである。これら増倍部４４や陽極４５は、このフォトカソード１０が最終的に組み込まれる光電子倍増管４０を構成するものであり、フォトカソード１０及び光電子増倍管４０が同時に製造でき、かつ、光電子増倍管４０に取り付けられた状態でのフォトカソード１０の感度特性を知ることができるという効果を得られる。
なお、光電子増倍管４０は、例えば図４にその完成状態を示すように、両端に開口部を有する筒状の容器４１と、一端の開口部を封止し基板１１側を容器４１外部へ向けたフォトカソード１０と、他端の開口部を封止し電極ピン４２ａが設けられた電極部材４２とを備えており、容器４１内部には、フォトカソード１０の被覆層１３側から放出された光電子Ｅ−を増倍部４４へ導く集束電極４３と、光電子Ｅ−を増倍する複数のダイノード４４ａからなる増倍部４４と、増倍された光電子Ｅ−を収集する陽極４５とを備えている。集束電極４３と増倍部４４と陽極４５とは、電極ピン４２ａに電気的に接続されている。
The measurement unit 30 includes, for example, a multiplication unit 44 composed of a plurality of dynodes 44a for multiplying the photoelectrons E − shown in FIG. 4 and an anode 45 that collects the multiplied photoelectrons E − and outputs them as a current. It has. The multiplier 44 and the anode 45 constitute a photomultiplier tube 40 in which the photocathode 10 is finally incorporated. The photocathode 10 and the photomultiplier tube 40 can be manufactured at the same time, and the photomultiplier The effect that the sensitivity characteristic of the photocathode 10 in the state attached to the tube 40 can be known can be obtained.
The photomultiplier tube 40 has a cylindrical container 41 having openings at both ends and a substrate 11 side outside the container 41, for example, as shown in FIG. The photocathode 10 is directed to an electrode member 42 which is sealed at the other end and provided with an electrode pin 42a. The inside of the container 41 is discharged from the coating layer 13 side of the photocathode 10. A focusing electrode 43 that guides the photoelectrons E− to the multiplication unit 44, a multiplication unit 44 composed of a plurality of dynodes 44a that multiply the photoelectrons E−, and an anode 45 that collects the multiplied photoelectrons E− are provided. Yes. The focusing electrode 43, the multiplication unit 44, and the anode 45 are electrically connected to the electrode pin 42a.
かかる構成の下、被覆層１３を形成するには、まず被覆層材料の１つであるＣｓ蒸気をほぼ一定流量で光吸収層１２上に供給する。このことによって光吸収層１２上にＣｓが付着しはじめる。
また、その一方で、ＬＥＤ２１ａ〜２１ｃ及び水銀ランプ２２を順次切り替えて所定時間点灯し、それぞれの光Ｐ１〜Ｐ４の照射による放出電流の値を経時的に測定して記録しておく。
そして、例えば、図２に示すように、Ｃｓ蒸気の供給開始後（図２の点Ａ）、水銀ランプ２２の照射による放出電流の時間変化がピークとなると、Ｃｓ蒸気の供給を中断する（点Ｂ）。
次に、所定時間経過後、被覆層材料として酸素を供給し（点Ｃ）、光吸収層１２上に形成されたＣｓ層を酸化して、Ｃｓ２Ｏ層を形成する。水銀ランプ２２の照射による放出電流の時間変化がピークとなると、酸素の供給を中断し（点Ｄ）、所定時間経過後、Ｃｓ蒸気の供給を再開する（点Ｅ）。このＣｓ蒸気と酸素とを交互に光吸収層１２上に供給するサイクルを複数回繰り返し、サイクルごとに水銀ランプ２２の照射による放出電流のピーク値を取り出して、そのピーク値の増加幅がサチュレートしたか否かを判定し、サチュレートした場合は次の段階へと進む。
続いて、２８５ｎｍ及び３７５ｎｍがピーク波長である単波長光Ｐ１、Ｐ２を射出する２つのＬＥＤ２１ａ、２１ｂの照射による各放出電流の値が、４７５ｎｍがピーク波長である単波長光Ｐ３を射出するＬＥＤ２１ｃの照射による放出電流の値を、それぞれ所定値以上上回った時に、被覆層材料の供給を終了し（点Ｆ、点Ｇ、点Ｈ）、被覆層１３の形成が完了する。
In order to form the coating layer 13 under such a configuration, first, Cs vapor, which is one of the coating layer materials, is supplied onto the light absorption layer 12 at a substantially constant flow rate. As a result, Cs begins to adhere on the light absorption layer 12.
On the other hand, the LEDs 21a to 21c and the mercury lamp 22 are sequentially switched and turned on for a predetermined time, and the values of the emission current due to the irradiation of the respective lights P1 to P4 are measured and recorded over time.
Then, for example, as shown in FIG. 2, after the start of the supply of Cs vapor (point A in FIG. 2), when the time change of the emission current due to the irradiation of the mercury lamp 22 reaches a peak, the supply of Cs vapor is interrupted (point B).
Next, after a predetermined time has elapsed, oxygen is supplied as a coating layer material (point C), and the Cs layer formed on the light absorption layer 12 is oxidized to form a Cs 2 O layer. When the time variation of the emission current due to the irradiation of the mercury lamp 22 reaches a peak, the supply of oxygen is interrupted (point D), and the supply of Cs vapor is restarted after a predetermined time (point E). The cycle in which Cs vapor and oxygen are alternately supplied onto the light absorption layer 12 is repeated a plurality of times, and the peak value of the emission current due to the irradiation of the mercury lamp 22 is extracted for each cycle, and the increase in the peak value is saturated. If it is saturated, the process proceeds to the next stage.
Subsequently, the value of each emission current by irradiation of the two LEDs 21a and 21b that emit the single wavelength light P1 and P2 whose peak wavelengths are 285 nm and 375 nm is the value of the LED 21c that emits the single wavelength light P3 whose peak wavelength is 475 nm. When the value of the emission current due to irradiation exceeds a predetermined value, supply of the coating layer material is finished (point F, point G, point H), and the formation of the coating layer 13 is completed.
このようなフォトカソード１０の製造方法によれば、図３に示すように、境界波長よりも短波長帯域での感度が、境界波長よりも長波長帯域での感度よりも所定以上上回るような感度特性を有するフォトカソード１０を確実に製作することができ、また、所望の感度特性を有するフォトカソード１０の製造条件を特定しやすくなる。
また、図２に示すように、２回目の酸素供給前では、２８５ｎｍ及び３７５ｎｍがピーク波長である単波長光Ｐ１、Ｐ２の照射による放出電流の値は高く、４７５ｎｍがピーク波長である単波長光Ｐ３の照射による放出電流の値は低くなっており、すなわち、境界波長が３７５ｎｍ〜４７５ｎｍとなっている（図２のプロセスＰ３）。そして、２回目の酸素供給によって、３７５ｎｍがピーク波長である単波長光Ｐ２の照射による放出電流の値が低くなり、すなわち、境界波長が２８５ｎｍ〜３７５ｎｍとなる（プロセスＰ４）。このように、酸素の供給期間を長くする（供給量を増やす）ことで、境界波長を短くすることができる。より具体的には、放出電流の時間変化がピークとなった後も酸素を供給しつづけることで、境界波長を短くすることができる。
According to such a manufacturing method of the photocathode 10, as shown in FIG. 3, the sensitivity in which the sensitivity in the shorter wavelength band than the boundary wavelength exceeds the sensitivity in the longer wavelength band than the boundary wavelength by a predetermined value or more. The photocathode 10 having the characteristics can be reliably manufactured, and the manufacturing conditions of the photocathode 10 having the desired sensitivity characteristics can be easily specified.
In addition, as shown in FIG. 2, before the second oxygen supply, the value of the emission current due to the irradiation of the single wavelength light P1 and P2 whose peak wavelengths are 285 nm and 375 nm is high, and the single wavelength light whose peak wavelength is 475 nm. The value of the emission current due to the irradiation of P3 is low, that is, the boundary wavelength is 375 nm to 475 nm (process P3 in FIG. 2). Then, by the second oxygen supply, the value of the emission current due to the irradiation with the single wavelength light P2 whose peak wavelength is 375 nm is lowered, that is, the boundary wavelength is 285 nm to 375 nm (process P4). Thus, the boundary wavelength can be shortened by lengthening the oxygen supply period (increasing the supply amount). More specifically, the boundary wavelength can be shortened by continuing to supply oxygen even after the time variation of the emission current peaks.
なお、本発明は前記実施形態に限られるものではない。例えば、本実施形態においては、被覆層材料の導入期間を設定することで被覆層の形成様態を制御するものとしたが、被覆層の導入量や濃度等、又は、容器内部の温度や圧力等を設定するようにしてもよい。 The present invention is not limited to the above embodiment. For example, in this embodiment, the formation mode of the coating layer is controlled by setting the introduction period of the coating layer material. However, the amount and concentration of the coating layer, or the temperature and pressure inside the container, etc. May be set.
被覆層の形成様態の制御は、単波長光の照射による放出電流にそれぞれ基づくとしてもよい。例えば、被覆層の形成過程では単波長光のうちいずれか１つの照射による放出電流の時間変化に基づいて被覆層材料を供給し、形成過程の終了時には単波長光の照射による各放出電流に基づいて被覆層材料の供給を終了するものとしてもよい。
また、単波長光及び多波長光の照射による放出電流の両方あるいはこれらの組み合わせに同時に基づくとしてもよいし、交互に基づくとしてもよい。
Control of the formation mode of the coating layer may be based on the emission current caused by the irradiation with the single wavelength light. For example, in the formation process of the coating layer, the coating layer material is supplied based on the temporal change of the emission current caused by irradiation of any one of the single wavelength light, and based on each emission current caused by the irradiation of the single wavelength light at the end of the formation process. Thus, the supply of the coating layer material may be terminated.
Further, it may be based on both of the emission currents due to irradiation with single wavelength light and multi-wavelength light, or a combination thereof, or may be based alternately.
また、被覆層の形成様態の制御のタイミング、例えば被覆層材料の供給の開始、中断、再開、終了といったタイミングは、放出電流の値またはその時間変化が、所定値となった時点、ピークとなった時点、ピークの前後の時点、所定値以上又は以下の値を所定時間保った時点、ピーク値の増加幅がサチュレートした時点等としてもよいし、各放出電流の値またはそれらの時間変化をそれぞれ比較して所定の状態となった時点（例えば、各放出電流の値の比率が所定値となった時点）としてもよいし、さらには、被覆層材料の導入量及び濃度等、容器内部の温度等が所定の状態になった時点としてもよい。 In addition, the timing of controlling the formation mode of the coating layer, for example, the timing of starting, interrupting, resuming, or ending the supply of the coating layer material, peaks when the value of the emission current or its change over time reaches a predetermined value. The time point before and after the peak, the time point when the value above or below the predetermined value is kept for a predetermined time, the time point when the increase width of the peak value is saturated, etc. It may be a point in time when compared to a predetermined state (for example, a point when the ratio of each emission current value reaches a predetermined value), and further, the temperature inside the container, such as the amount and concentration of the coating layer material introduced It is good also as the time when etc. became a predetermined state.
さらに、供給制御部を設けてもよい。これは、放出電流の値やその時間変化に所定の演算処理を施して被覆層の形成様態を制御するものである。このようなものであれば、フォトカソードの製造を自動化することができ、生産効率を向上させることができる。 Further, a supply control unit may be provided. In this method, a predetermined calculation process is performed on the value of the emission current and its change over time to control the formation mode of the coating layer. If it is such, manufacture of a photocathode can be automated and production efficiency can be improved.
加えて言えば、本実施形態は受光面と光電面が別である透過型フォトカソードに係るものであるが、受光面と光電面が同一である反射型フォトカソードにも適用できることは言うまでもない。 In addition, the present embodiment relates to a transmissive photocathode in which the light receiving surface and the photocathode are separate, but it goes without saying that the present embodiment can also be applied to a reflective photocathode in which the light receiving surface and the photocathode are the same.
その他、本発明はその趣旨を逸脱しない範囲で種々変形が可能である。 In addition, the present invention can be variously modified without departing from the spirit of the present invention.
１０・・・フォトカソード
１１・・・基板
１２・・・光吸収層
１３・・・被覆層
２０・・・照射部
２１ａ、２１ｂ、２１ｃ・・・ＬＥＤ
２２・・・水銀ランプ
３０・・・測定部
４０・・・光電子増倍管
４１・・・容器
４２・・・電極部材
４２ａ・・・電極ピン
４３・・・集束電極
４４・・・増倍部
４４ａ・・・ダイノード
４５・・・陽極
Ｐ１、Ｐ２、Ｐ３・・・単波長光
Ｐ４・・・多波長光
Ｅ−・・・光電子
DESCRIPTION OF SYMBOLS 10 ... Photocathode 11 ... Board | substrate 12 ... Light absorption layer 13 ... Cover layer 20 ... Irradiation part 21a, 21b, 21c ... LED
22 ... mercury lamp 30 ... measuring unit 40 ... photomultiplier tube 41 ... container 42 ... electrode member 42a ... electrode pin 43 ... focusing electrode 44 ... multiplication unit 44a ... dynode 45 ... anode P1, P2, P3 ... single-wavelength light P4 ... multi-wavelength light E - ... photoelectron
Claims (5)
前記被覆層の形成中に、ピーク波長が互いに異なる複数の単波長光を順次照射し、各単波長光の照射による放出電流をそれぞれ測定するとともに、前記各放出電流にそれぞれ基づいて、前記被覆層の形成態様を制御し、
前記単波長光が、感度を切り替えたい所望の境界波長を境にして感度が要求される側の波長帯域にピーク波長がある第１単波長光と、感度が不要な側の波長帯域にピーク波長がある第２単波長光とを少なくとも含み、
前記第１波長光からの光照射による放出電流から算出される感度が、前記第２波長光からの光照射による放出電流から算出される感度を所定以上上回ることを特徴とするフォトカソードの製造方法。 A method for producing a photocathode, wherein a coating layer made of an alkali metal or an oxide thereof is formed on a light absorption layer,
During the formation of the coating layer, a plurality of single-wavelength lights having different peak wavelengths are sequentially irradiated, emission currents due to the irradiation of each single-wavelength light are respectively measured , and the coating layer is based on each of the emission currents. Control the formation of
The single wavelength light includes a first single wavelength light having a peak wavelength in a wavelength band on the side where sensitivity is required at a desired boundary wavelength for which sensitivity is to be switched, and a peak wavelength in a wavelength band on the side where sensitivity is not required. And at least a second single wavelength light,
A sensitivity calculated from an emission current generated by light irradiation from the first wavelength light exceeds a sensitivity calculated from an emission current generated by light irradiation from the second wavelength light by a predetermined value or more. .
各サイクルでのアルカリ金属の導入期間及び酸素の導入期間を各サイクルでの放出電流に基づいて設定することで前記被覆層の形成態様を制御することを特徴とする請求項３又は４記載のフォトカソードの製造方法。
The coating layer made of an oxide of an alkali metal is formed by repeating a cycle of alternately introducing alkali metal and oxygen, which are the coating layer materials, onto the light absorption layer,
5. The photo according to claim 3 , wherein the formation mode of the coating layer is controlled by setting the introduction period of the alkali metal and the introduction period of oxygen in each cycle based on the emission current in each cycle. Manufacturing method of cathode.
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