JP4465457B2 - Radiation detector and neutron detector with radiation type discrimination function - Google Patents
Radiation detector and neutron detector with radiation type discrimination function Download PDFInfo
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- JP4465457B2 JP4465457B2 JP2004004560A JP2004004560A JP4465457B2 JP 4465457 B2 JP4465457 B2 JP 4465457B2 JP 2004004560 A JP2004004560 A JP 2004004560A JP 2004004560 A JP2004004560 A JP 2004004560A JP 4465457 B2 JP4465457 B2 JP 4465457B2
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- 230000005855 radiation Effects 0.000 title claims description 35
- 239000013078 crystal Substances 0.000 claims description 18
- 239000000758 substrate Substances 0.000 claims description 13
- 238000010894 electron beam technology Methods 0.000 claims description 12
- 239000002245 particle Substances 0.000 claims description 12
- 238000010521 absorption reaction Methods 0.000 claims description 8
- ZOXJGFHDIHLPTG-BJUDXGSMSA-N Boron-10 Chemical compound [10B] ZOXJGFHDIHLPTG-BJUDXGSMSA-N 0.000 claims description 4
- WHXSMMKQMYFTQS-BJUDXGSMSA-N (6Li)Lithium Chemical compound [6Li] WHXSMMKQMYFTQS-BJUDXGSMSA-N 0.000 claims description 3
- 239000000470 constituent Substances 0.000 claims 1
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 4
- 239000012212 insulator Substances 0.000 description 4
- 239000004065 semiconductor Substances 0.000 description 4
- 238000001514 detection method Methods 0.000 description 3
- 238000010586 diagram Methods 0.000 description 3
- 230000005251 gamma ray Effects 0.000 description 3
- 238000006243 chemical reaction Methods 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 230000005260 alpha ray Effects 0.000 description 1
- LBDSXVIYZYSRII-IGMARMGPSA-N alpha-particle Chemical compound [4He+2] LBDSXVIYZYSRII-IGMARMGPSA-N 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 239000002887 superconductor Substances 0.000 description 1
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Description
本発明は、単結晶基盤上に製作された超伝導トンネル接合素子により放射線吸収により基盤で発生したフォノンを検出する放射線検出器において、ガンマ線またはＸ線または電子線と、粒子線（アルファ線、中性子など）との線種弁別機能を持った放射線検出器に関するものである。 The present invention relates to a radiation detector for detecting phonons generated on a substrate by radiation absorption by a superconducting tunnel junction device manufactured on a single crystal substrate, and includes a gamma ray, an X-ray or an electron beam, and a particle beam (alpha ray, neutron). Etc.) related to a radiation detector having a line type discrimination function.
特に、本発明は、超伝導トンネル接合素子の電荷パルス信号の立ち上がり時間が放射線種により異なることを利用することを特徴としている。また、ボロン10（10B）やリチウム６（6Li）などの中性子捕獲断面積の大きな元素を含む単結晶基盤を用いて検出器を構成した場合、中性子検出が可能となり、バックグランドとなるガンマ線、Ｘ線、電子線との弁別が可能となる。このため、各放射線種が混在するような放射線場においても中性子対バックグランド比に優れた中性子検出が可能となり、中性子ビームを用いた実験や分析などの検出器として用いることができる。 In particular, the present invention is characterized by utilizing the fact that the rise time of the charge pulse signal of the superconducting tunnel junction element varies depending on the radiation type. Also, in the case of constituting the detector using a single crystal base containing a large element of neutron capture cross section such as boron 10 (10 B) and lithium 6 (6 Li), it is possible to neutron detection, gamma rays as a background , X-ray and electron beam can be discriminated. This makes it possible to detect neutrons with excellent neutron-to-background ratio even in a radiation field in which various radiation types coexist, and can be used as a detector for experiments and analyzes using neutron beams.
従来より、半導体検出器あるいはシンチレーション検出器においては、放射線の線種によりパルス信号の立ち上がり時間が異なることを利用して、放射線の弁別を行う放射線検出器あるいは中性子検出器が開発され使用されてきた（例えば、非特許文献１参照 ）。また、図４に示すようにＧeなどの半導体検出素子上にフォノンセンサを形成した放射線検出器においては、Ｇｅ半導体素子による電離信号とフォノンセンサからのフォノン信号の相関をとることで、中性子とガンマ線の弁別が行われている(例えば、非特許文献２参照)。 Conventionally, in semiconductor detectors or scintillation detectors, radiation detectors or neutron detectors that discriminate radiation have been developed and used by utilizing the fact that the rise time of the pulse signal differs depending on the radiation line type. (For example, refer nonpatent literature 1). Further, in a radiation detector in which a phonon sensor is formed on a semiconductor detection element such as Ge as shown in FIG. 4, neutrons and gamma rays are obtained by correlating the ionization signal from the Ge semiconductor element and the phonon signal from the phonon sensor. Is discriminated (see, for example, Non-Patent Document 2).
しかし、放射線吸収により単結晶基盤で発生したフォノンを、単結晶上に製作した超伝導トンネル接合素子により検出し、放射線あるいは中性子を検出する検出器においては、放射線種によりその信号の立ち上がり時間特性が異なることが知られていなかったため、立ち上がり時間の差を利用して放射線種弁別を行った例はない。
単結晶基盤で発生したフォノンを超伝導トンネル接合素子で検出する放射線検出器おいて、従来技術では放射線のエネルギー情報を必要とし、また複数のセンサーからの信号相関を取る必要があるため検出器の構造、信号処理回路等が複雑になるという問題があった。この欠点を改善し、入射する放射線のエネルギーに関係なく、ガンマ線またはＸ線または電子線と、粒子線とを明確に分離することが解決すべき課題である。 In radiation detectors that detect phonons generated on a single crystal substrate with a superconducting tunnel junction element, the conventional technology requires energy information of radiation, and it is necessary to correlate signals from multiple sensors. There is a problem that the structure, the signal processing circuit, and the like are complicated. The problem to be solved is to remedy this drawback and to clearly separate gamma rays or X-rays or electron beams from particle beams regardless of the energy of the incident radiation.
単結晶基盤上に製作された超伝導トンネル接合素子による放射線吸収により基盤で発生したフォノンを検出する放射線検出器において、超伝導トンネル接合型素子の電荷パルス信号の立ち上がり時間が、Ｘ線またはガンマ線または電子線吸収による場合と、粒子線吸収による場合とにおいて異なることを利用して放射線種弁別を可能とする。 In a radiation detector for detecting phonons generated in a substrate by radiation absorption by a superconducting tunnel junction device fabricated on a single crystal substrate, the rise time of the charge pulse signal of the superconducting tunnel junction device is X-ray or gamma ray or The radiation type discrimination is made possible by utilizing the difference between the case of electron beam absorption and the case of particle beam absorption.
本発明の検出器により、入射する放射線のエネルギーに関係なく、ガンマ線またはＸ線または電子線と、粒子線とを明確に分離することができる。 With the detector of the present invention, gamma rays, X-rays, electron beams, and particle beams can be clearly separated regardless of the energy of incident radiation.
（実施例１）
実施例１として、本発明による検出器について、図１、図２を参照して述べる。本実施例では図１に示すような単結晶上に超伝導（Ｓ）／絶縁体（Ｉ）／超伝導（Ｓ）構造（ＳＩＳ構造）のＮｂ／Ａｌ／Ａｌ2Ｏ3／Ａｌ／Ｎｂ構造を用いた超伝導トンネル接合素子を形成し、放射線吸収により基盤で発生したフォノンを検出する放射線検出器を製作する。実施例では単結晶体としてはＬＢＯ（Ｌｉ2Ｂ4Ｏ7）を用いた。超伝導トンネル接合素子からの信号は電荷アンプにより増幅して読み出す。図２は、Ｘ線(55Fe線源、エネルギー 5.9 keV)、ガンマ線(60Co線源、1.17MeV、1.33MeV、電子線と等価)及び熱中性子 (241Am/Li線源、α粒子と7Ｌｉとに対応)を入射した場合における超伝導トンネル素子からの電荷パルス信号の立ち上がり時間分布が示している。この実験結果より、Ｘ線またはガンマ線（電子線）と、α粒子と7Ｌｉ（中性子との核反応により発生）とにおいて電荷パルス信号の立ち上がり時間が異なることがわかる。
Example 1
As a first embodiment, a detector according to the present invention will be described with reference to FIGS. In this example, a Nb / Al / Al 2 O 3 / Al / Nb structure of superconducting (S) / insulator (I) / superconducting (S) structure (SIS structure) on a single crystal as shown in FIG. A superconducting tunnel junction device is formed, and a radiation detector that detects phonons generated on the substrate by radiation absorption is manufactured. In the examples, LBO (Li 2 B 4 O 7 ) was used as the single crystal. A signal from the superconducting tunnel junction element is amplified and read by a charge amplifier. Figure 2 shows X-rays ( 55 Fe source, energy 5.9 keV), gamma rays ( 60 Co source, 1.17 MeV, 1.33 MeV, equivalent to electron beam) and thermal neutrons ( 241 Am / Li source, α particles and 7 The rise time distribution of the charge pulse signal from the superconducting tunnel element in the case of incidence on Li) is shown. From this experimental result, it can be seen that the rise time of the charge pulse signal differs between X-rays or gamma rays (electron beams) and α particles and 7 Li (generated by a nuclear reaction between neutrons).
この電荷パルス信号を電荷アンプの後に接続されたライズタイム・パルス波高変換回路により立ち上がり時間をパルス波高値に変換し、その後に設けられた波高弁別器により、図２の立ち上がり時間分布情報に基づいて放射線線種毎のパルス波高を選別する。選別した信号は、Ｘ線またはガンマ線用と粒子用の２つの計数回路により計数される。このように、超伝導トンネル接合素子の電荷パルス信号の立ち上がり時間を利用することで、ガンマ線またはＸ線または電子線と、粒子線との線種弁別を可能とする放射線検出器を構成できる。 The charge pulse signal is converted into a pulse peak value by a rise time pulse height converter circuit connected after the charge amplifier, and the pulse height discriminator provided thereafter is used based on the rise time distribution information of FIG. Select the pulse height for each radiation type. The selected signal is counted by two counting circuits for X-rays or gamma rays and particles. In this way, by using the rise time of the charge pulse signal of the superconducting tunnel junction device, a radiation detector that enables line type discrimination between gamma rays, X-rays, electron beams, and particle beams can be configured.
（実施例２）
実施例２として、本発明による検出器について、図３を参照して述べる。本実施例では、単結晶基盤として10Ｂを９６％まで濃縮したＬＢＯ（ＬｉＢ3Ｏ5あるいはＬｉ2Ｂ4Ｏ7）単結晶を用い、その上に超伝導（Ｓ）／絶縁体（Ｉ）／超伝導（Ｓ）構造（ＳＩＳ構造）のＮｂ／Ａｌ／Ａｌ2Ｏ3／Ａｌ／Ｎｂ構造を用いた超伝導トンネル接合素子を製作し検出器とする。10Ｂを９６％まで濃縮することにより自然のＬＢＯ単結晶（10Ｂ含有率２０％）の約５倍の中性子捕獲率を持つ検出器を構成することができる。ＬＢＯ単結晶基盤に入射した中性子はＬＢＯ単結晶中の10Ｂと核反応し、α粒子と6Ｌｉを生成する。このため、実施例１で述べたように、Ｘ線またはガンマ線（電子線）または中性子（α粒子及び7Ｌｉに対応）とにおいて立ち上がり時間が異なる。
(Example 2)
As Example 2, a detector according to the present invention will be described with reference to FIG. In this example, an LBO (LiB 3 O 5 or Li 2 B 4 O 7 ) single crystal enriched with 10 B up to 96% is used as a single crystal substrate, and a superconductor (S) / insulator (I) is formed thereon. A superconducting tunnel junction element using an Nb / Al / Al 2 O 3 / Al / Nb structure having a / superconducting (S) structure (SIS structure) is fabricated and used as a detector. By concentrating 10 B to 96%, a detector having a neutron capture rate about 5 times that of a natural LBO single crystal ( 10 B content 20%) can be constructed. Neutrons incident on the LBO single crystal substrate undergo a nuclear reaction with 10 B in the LBO single crystal to generate α particles and 6 Li. For this reason, as described in Example 1, the rise time is different for X-rays, gamma rays (electron beams), or neutrons (corresponding to α particles and 7 Li).
実施例１と同様に、この電荷バルス信号を電荷アンプの後に接続されたライズタイム・パルス波高変換回路により立ち上がり時間をパルス波高値に変換し、その後に設けられた波高弁別器により、図２の立ち上がり時間分布情報に基づいて放射線線種毎のパルス波高を選別する。選別した信号は、Ｘ線またはガンマ線用と、中性子用の２つの計数回路により計数される。このように、超伝導トンネル接合素子の電荷パルス信号の立ち上がり時間を利用することで、ガンマ線またはＸ線または電子線と、中性子との線種弁別を可能とする中性子検出器を構成できる。 As in the first embodiment, the rise time is converted into a pulse peak value by a rise time pulse height converter circuit connected after the charge amplifier, and the pulse discriminator provided thereafter converts the charge pulse signal into the pulse peak value shown in FIG. Based on the rise time distribution information, the pulse wave height for each radiation ray type is selected. The selected signals are counted by two counting circuits for X-rays or gamma rays and for neutrons. In this way, by using the rise time of the charge pulse signal of the superconducting tunnel junction device, a neutron detector that enables line type discrimination between gamma rays, X-rays, electron beams, and neutrons can be configured.
Claims (2)
In the first aspect, neutron detectors comprising boron 10 (10 B) or lithium 6 (6 Li) as a constituent element of the single crystal base.
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| JP7418659B2 (en) * | 2021-04-15 | 2024-01-19 | 三菱電機株式会社 | radiation analyzer |
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