JPH04204279A - Multi-channel squid magnetic flux meter - Google Patents

Multi-channel squid magnetic flux meter

Info

Publication number
JPH04204279A
JPH04204279A JP2337130A JP33713090A JPH04204279A JP H04204279 A JPH04204279 A JP H04204279A JP 2337130 A JP2337130 A JP 2337130A JP 33713090 A JP33713090 A JP 33713090A JP H04204279 A JPH04204279 A JP H04204279A
Authority
JP
Japan
Prior art keywords
squid
channel
current
current bias
magnetometer
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
JP2337130A
Other languages
Japanese (ja)
Other versions
JP3058681B2 (en
Inventor
Keiko Makie
牧絵　恵子
Masao Hotta
正生 堀田
Matsuo Yamazaki
山崎　松夫
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Hitachi Ltd
Original Assignee
Hitachi Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Hitachi Ltd filed Critical Hitachi Ltd
Priority to JP2337130A priority Critical patent/JP3058681B2/en
Priority to DE19914139212 priority patent/DE4139212C2/en
Publication of JPH04204279A publication Critical patent/JPH04204279A/en
Application granted granted Critical
Publication of JP3058681B2 publication Critical patent/JP3058681B2/en
Anticipated expiration legal-status Critical
Expired - Fee Related legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G01R33/02—Measuring direction or magnitude of magnetic fields or magnetic flux
    • G01R33/035—Measuring direction or magnitude of magnetic fields or magnetic flux using superconductive devices
    • G01R33/0354—SQUIDS
    • G01R33/0356—SQUIDS with flux feedback

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  • Physics & Mathematics (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • General Physics & Mathematics (AREA)
  • Measuring Magnetic Variables (AREA)
  • Measurement And Recording Of Electrical Phenomena And Electrical Characteristics Of The Living Body (AREA)

Abstract

PURPOSE:To prevent the increase of signal lines and reduce the scattering among many SQUID elements by connecting resistances in series in a cooling medium for current bias or SQUID elements driving SQUID and driving many SQUID magnetic flux meter with the use of the same current bias with the average value of the bias current of SQUID. CONSTITUTION:When a current bias 9 is set at a certain value, the output of a preamplifier 4 becomes a value indicating the sensitivity of a SQUID magnetic flux meter. Next channel changing-over is performed by a multiplexer 10 and a microcomputer 12 holds the output voltage of each channel and a current bias value with the use of an A/D convertor 11 to successively measure SQUID sensitivity as the current bias is changed so as to obtain a specified sensitivity curve. And the current value representing the optimum sensitivity each channel is calculated from the data of the output voltage and the bias by the use of the microcomputer 12 to find the average value of the current bias so as to set the output current of a current source 9 through a D/A convertor 13.

Description

【発明の詳細な説明】[Detailed description of the invention]

【産業上の利用分野１ 本発明は、生体磁場などの微小磁場の測定を多点で行う
多チャンネルＳＱＵＩＤｉｉ束計に関する。 【従来の技ｔｌｆｌ ＳＱＵＩＤ磁束計は少なくとも１つのジョセフソン接合
を持ツＳ　Ｑ　Ｕ　Ｉ　Ｄ　（Ｓｕｐｅｒｃｏｎｄｕｃ
ｔｉｎｇ　ＱＵａｎｔｕｍ　Ｉｎｔｅｒｆｅｒｅｎｃｅ
　Ｄｅｖｉｃｅ）とインプットコイル、フィードバック
コイル、磁場を検出するピックアップコイル及び、電子
回路系などにより構成される。ＳＱＵＩＤ磁束計は、磁
束を電圧に変換する働きを持ち、通常磁束計の動作点を
固定するためにＦ　Ｌ　Ｌ　（Ｆｌｕｘ−Ｌｏｃｋｅｄ
　Ｌｏｏｐ）とよばれる帰還回路の構成をなし、微弱磁
場の計測に用いられている９直流型ＳＱＵＩＤにおける
磁束計の感度は、ＳＱＵＩＤに与える電流バイアスを磁
束検出感度が最大になるように設定する。従来の多チャ
ンネルＳＱＵＩＤ磁束計は、■チャネルＳＱＵＩＤ磁束
計を多数配列して構成されている。その例はジャパニー
ズ・ジャーナル・オブ・アプライド・フィジックス（Ｊ
ａｐａｎｅｓｅ　Ｊｏｕｒｎａｌ　ｏｆ　Ａｐｐｌｉｅ
ｄ　Ｐｈｙｓｉｃｓ）Ｖｏｌ、２８．　Ｎｏ、３．１９
８９．　ｐｐＬ４５６−Ｌ４５８に記載される。 【発明が解決しようとする課題】 １チャンネルＳＱＵＩＤ磁束計を多数配列して多チャン
ネルＳＱＵＩＤ磁束計を構成した場合、個々のＳＱＵＩ
Ｄの磁束検出感度を最良の状態にするためにはチャネル
数と同数のバイアスを供給する電流源が必要となる。し
かしながら、この場合には信号線数が増加するため電子
回路系の構成が複雑となり、さらに冷却媒体への入力信
号線数も多くなり冷却媒体の蒸発を早めるという問題が
あった。 また、多チャンネルＳＱＵＩＤ磁束計を同一電流バイア
スで駆動する場合、ＳＱＵＩＤ素子の特性のバラツキに
関して考慮がなされていないため。 正常に動作する素子から磁場検出に必・要な検出感度を
得ることのできないという問題があった。[Industrial Application Field 1] The present invention relates to a multi-channel SQUIDii fluxmeter that measures micromagnetic fields such as biomagnetic fields at multiple points. [Conventional technology tlfl SQUID magnetometers have at least one Josephson junction.
ting QUantum Interference
It consists of an input coil, a feedback coil, a pickup coil that detects a magnetic field, and an electronic circuit system. A SQUID magnetometer has the function of converting magnetic flux into voltage, and usually uses FLL (Flux-Locked) to fix the operating point of the magnetometer.
The sensitivity of the magnetometer in the 9 DC type SQUID, which forms a feedback circuit called a loop) and is used to measure weak magnetic fields, is set so that the current bias applied to the SQUID is set to maximize the magnetic flux detection sensitivity. A conventional multi-channel SQUID magnetometer is constructed by arranging a large number of channel SQUID magnetometers. An example is the Japanese Journal of Applied Physics (J
apanese Journal of Applie
d Physics) Vol, 28. No, 3.19
89. It is described in ppL456-L458. [Problems to be Solved by the Invention] When a multi-channel SQUID magnetometer is constructed by arranging a large number of 1-channel SQUID magnetometers, each SQUID magnetometer is
In order to achieve the best magnetic flux detection sensitivity of D, current sources supplying the same number of biases as the number of channels are required. However, in this case, the number of signal lines increases, which complicates the configuration of the electronic circuit system.Furthermore, the number of input signal lines to the cooling medium also increases, causing the problem of hastening the evaporation of the cooling medium. Furthermore, when driving a multi-channel SQUID magnetometer with the same current bias, no consideration is given to variations in the characteristics of the SQUID elements. There has been a problem in that it is not possible to obtain the detection sensitivity required for magnetic field detection from elements that operate normally.

【課題を解決するための手段ｌ このような問題点を解決するため１本発明では、ＳＱＵ
ＩＤを駆動する電流バイアスおよび５ＱｔＪ１０素子に
対して直列に抵抗を冷却媒体内で接続し、それらのＳＱ
ＵＩＤ素子を並列接続して、さらに各ＳＱＵＩＤの電流
バイアスの平均値により、多数のＳＱＵＩＤ磁束計を同
一電流バイアスで駆動する。 【作用】　・ 冷却媒体内で電流バイアスとＳＱＵＩＤ素子に抵抗を直
列接続し、各ＳＱＵＩＤの電流バイアスの平均値を用い
て多数の５ＱｔＪ４Ｄ磁束計を同一電流バイアスで駆動
することにより、多チャンネル化に伴う信号線の増加を
防ぎ、さらに多数のＳＱＵＩＤ素子間のバラツキを低減
し、高感度で駆動することができる。[Means for Solving the Problems] In order to solve these problems, the present invention uses SQU
Connect a resistor in series with the current bias driving the ID and the 5QtJ10 element in the cooling medium, and set their SQ
UID elements are connected in parallel, and a large number of SQUID magnetometers are driven with the same current bias based on the average value of the current bias of each SQUID. [Function] - By connecting a resistor in series to the current bias and the SQUID element in the cooling medium, and driving a large number of 5QtJ4D magnetometers with the same current bias using the average value of the current bias of each SQUID, it is possible to increase the number of channels. It is possible to prevent the accompanying increase in signal lines, further reduce variations among a large number of SQUID elements, and drive with high sensitivity.

【実施例】【Example】

以下、本発明の実施例を図面により説明する。 第２図は、電流バイアスに対する磁束検出感度の変化を
模擬的に表したものである。ＳＱＵＩＤ素子により最適
感度及び最適感度をとる電流バイアス値が異なっている
ため、各チャネルの利得を等しくするためには、磁束検
出感度が等しくなるようにＳＱＵＩＤ素子ごとに電流バ
イアスを設定しなければならない。しかしながら、ＳＱ
ＵＩＤ磁束計は通常ＦＬＬと呼ばれる帰還ループ構成で
動作させるため、多少の感度バラツキによる□系の利得
の変動誤差はあまり問題とはならない。このため、各Ｓ
　Ｑ’Ｕ　Ｉ　Ｄの最適感度をとる電流バイアス値工、
〜工、の平均値をもって、同一の電流バイアス値に設定
することが可能となる。このときの同一の電流バイアス
値を工、とすると、１、＝（１，＋・・・＋１１＋・・
・＋Ｉｎ）／ｎで表せる。ここでｎはチャネル数である
。 第１図に本発明の第１の実施例を示す。 まず、ＳＱＵＩＤ磁束計の動作について説明する。ＳＱ
ＵＩＤ素子１は、インプットコイル２からの外部磁束と
フィードバックコイル３からの変調磁束及び帰還磁束の
磁束の差を電圧に変換する。 この電圧はプリアンプ４で増幅されたのち、電子回路７
により変調信号との同期検波などの処理が行われて出力
される。また、出力電圧は電圧電流変換器６で電流に変
換された後、変調信号とともにフィードバックコイルへ
入力される。 本発明の特徴は複数のＳＱＵＩＤ素子の電流バイアスを
同一の電流源で設定できることである。 各ＳＱＵＩＤ素子１の持つ抵抗値は素子製作上バラツキ
があるため、ＳＱＵＩＤ素子の持つ抵抗値に比べて大き
なほぼ等しい抵抗値Ｒをもつ複数の抵抗８をＳＱＵＩＤ
素子１にそれぞれ直列に接続したのち、各チャネルを並
列に接続し、各チャネルに共通な電流バイアス用の電流
源９に接続する。 この結果、各ＳＱＵＩＤ素子の電流バイアス値がほぼ等
しくなるように設定することができる。また、この際、
各ＳＱＵＩＤ素子に直列に接続する抵抗８を冷却媒体内
に設置することにより、冷却媒体内から取り出す電流バ
イアス線を１本とすることができるため、冷却媒体の蒸
発量を低減することができる。第１図において、冷却媒
体内ｔこ設置される部分破線内にて示した。 電流バイアスの設定は第３図に示すようなフローチャー
トに従って行う。まず、電流バイアス９をある値に設定
する。この時のプリアンプの出力は、ＳＱＵＩＤ磁束計
の感度を示す値である。マルチプレクサ１０によりチャ
ネル切替えを行い、各チャネルの出力電圧をＡ／Ｄ変換
器１１によりマイクロコンピュータ１２に取り込む。マ
イクロコンピュータでは、各チャネルの出力電圧値及び
電流バイアス値を保持する。電流バイアスを変化させな
からＳＱＵＩＤ感度を順次測定することにより、第２図
と同様な感度曲線を得ることができる。次に、各チャネ
ルの最適感度を示す電流値を出力電圧及び電流バイアス
のデータからマイクロコンピュータにより計算し、電流
バイアスの平均値を求めて、Ｄ／Ａ変換器１３を介して
電流源９の出力電流を設定する。本方法により、同一電
流バイアスで多数のＳＱＵＩＤを駆動することが可能と
なる。 しかしながら、正常に動作しないＳＱＵＩＤ素子が存在
する場合、その素子からは出力電圧が得られないため、
電流バイアス設定時に誤差が生じる。 この問題を解決するための実施例を第４図のフローチャ
ートにより説明する。チャネルの感度レベルがあるしき
い値に達しているか否かをマイクロコンピュータにより
判断する。しきい値に達しないＳＱＵＩＤ素子は使用し
ないと判定し、電流バイアス設定時の対象から外す。こ
の結果、電流バイアスをより正確に設定することが可能
となる。 本発明の第１及び第２の実施例では、各チャネルごとに
磁束検出感度が高くなる電流バイアスを求めた後に多チ
ャンネルの電流バイアス値を設定する。このためにはマ
イクロコンピュータを介すことが必要となり、電流の設
定が複雑で時間がかかるという問題がある。 この問題を解決し、電流バイアス設定を短時間に行うた
めの実施例を第５図に示す。先に述べたようにＳＱＵＩ
Ｄ磁束計はＦＬＬ状態で動作させるため、多少の感度バ
ラツキによる系の利得の変動誤差はあまり問題とはなら
ない。そこで、素子特性に大きなバラツキがない場合に
は、各チャネルの電流バイアスの平均値を求めることは
各チャネルの磁束検出感度の和が最大になるように電流
バイアス値を設定することと等価になる。 磁束検出感度をあられすプリアンプ４の出力電圧を加算
器１４で加算する。加算後の信号が最大となるように電
流バイアス調整器１５は調整出力を発して電流源９の出
力電流を調整する。このような電流バイアスの調整は、
インプットコイルに擬似信号を入力したときのプリアン
プの出力レベルが最大になるように最適電流バイアス値
を設定する方法や、電流バイアスを変化させたときの変
調信号の倍周波数成分をとらえる方法などにより容易に
行うことができる。本実施例により、電流バイアス設定
に要する時間を大幅に短縮することができ、さらに故障
したＳＱＵＩＤ素子が存在した場合にも正確に電流バイ
アスの設定を行うことができる。 上記の実施例はＳＱＵＩＤ素子のバラツキ度合いがほぼ
等しく、小さいとの仮定のもとで考えられている。しか
、しながら、作成されたチップごとにＳＱＵＩＤ素子の
特性が異なる可能性がある。 このため、上記の電流バイアスの設定方法を同一チップ
上のＳＱＵＩＤ素子に関して適用し、チップごとに電流
バイアスを設定することが有効であると考えられる。本
方法に関する実施例を第６図に示す、複数の超伝導回路
チップ１６には、それぞれ特性の等しい２つ以上のＳＱ
ＵＩＤ素子が配列され、各チップごとに第１の実施例で
述べたような回路構成を持っている。つまり同一チップ
上のＳＱＵＩＤ素子に対して共通の電流ｉ！９を有し、
それぞれ抵抗を介して電流バイアスが与えられる。 図のようにｍ枚のチップがある場合にはｍ個の電流バイ
アスで駆動する。この結果、全てのＳＱＵＩＤを同一電
流バイアスを用いて駆動する場合に比べて、素子感のバ
ラツキの影響を低減できるため、磁束検出感度を向上し
高精度で磁場の検出を行うことが可能となる。なお、二
のときの電流バイアス値の設定は本発明の第１、第２あ
るいは第３の実施例を用いることで実現可能である。 上記の実施例では、同一電流バイアスを用いた場合にＳ
ＱＵＩＤの感度がほぼ等しくなると仮定している。しか
しながら、各チャネルの感度を正確に知ることは磁場強
度を測定する上で重要であり、各チャネルの磁束検出感
度を記録することが有効である。このための実施例を示
すフローチャートを第７図により説明する。本発明の第
１の実施例において述べたように、電流バイアス設定時
のプリアンプの出力は磁束検出感度を表す。そこで、第
３図のフローチャートで示す同一電流バイアスの設定後
、プリアンプの出力を各チャネルごとにＡ／Ｄ変換器を
介してマイクロコンピュータ−に取り込む、このように
各チャネルの磁束検出感度のデータを記録しておくこと
により、各チャネルの感度バラツキを防ぐことができる
。また、この方法は５本発明の第２及び第３の実施例に
おいてもプリアンプ出力をＡ／Ｄ変換器を介してマイク
ロコンピュータに取り込むことにより、実現可能である
。Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 is a simulated representation of changes in magnetic flux detection sensitivity with respect to current bias. Since the optimum sensitivity and the current bias value for achieving the optimum sensitivity differ depending on the SQUID element, in order to equalize the gain of each channel, the current bias must be set for each SQUID element so that the magnetic flux detection sensitivity is equal. . However, SQ
Since the UID magnetometer is normally operated with a feedback loop configuration called FLL, fluctuation errors in the gain of the □ system due to slight variations in sensitivity do not pose much of a problem. For this reason, each S
Current bias value engineer to obtain optimal sensitivity of Q'UID,
It becomes possible to set the same current bias value by using the average value of . Letting the same current bias value at this time be 1, = (1, +...+11+...
・It can be expressed as +In)/n. Here n is the number of channels. FIG. 1 shows a first embodiment of the present invention. First, the operation of the SQUID magnetometer will be explained. SQ
The UID element 1 converts the difference between the external magnetic flux from the input coil 2 and the modulated magnetic flux and feedback magnetic flux from the feedback coil 3 into a voltage. After this voltage is amplified by the preamplifier 4, the electronic circuit 7
Processing such as synchronous detection with the modulated signal is performed and output. Further, the output voltage is converted into a current by the voltage-current converter 6, and then input to the feedback coil together with the modulation signal. A feature of the present invention is that the current biases of a plurality of SQUID elements can be set using the same current source. Since the resistance value of each SQUID element 1 varies due to element manufacturing, a plurality of resistors 8 having approximately equal resistance value R, which is larger than the resistance value of the SQUID element, is connected to the SQUID element.
After each channel is connected in series to the element 1, each channel is connected in parallel and connected to a current source 9 for current bias common to each channel. As a result, the current bias values of each SQUID element can be set to be approximately equal. Also, at this time,
By installing the resistor 8 connected in series to each SQUID element in the coolant, only one current bias line can be taken out from the coolant, thereby reducing the amount of evaporation of the coolant. In FIG. 1, the portion of the cooling medium installed within the cooling medium is shown within the broken line. Setting of the current bias is performed according to a flowchart as shown in FIG. First, the current bias 9 is set to a certain value. The output of the preamplifier at this time is a value indicating the sensitivity of the SQUID magnetometer. A multiplexer 10 performs channel switching, and an A/D converter 11 inputs the output voltage of each channel into a microcomputer 12. The microcomputer holds the output voltage value and current bias value of each channel. By sequentially measuring the SQUID sensitivity without changing the current bias, a sensitivity curve similar to that shown in FIG. 2 can be obtained. Next, a current value indicating the optimum sensitivity of each channel is calculated by a microcomputer from the output voltage and current bias data, an average value of the current bias is calculated, and the current value is outputted from the current source 9 via the D/A converter 13. Set the current. This method makes it possible to drive multiple SQUIDs with the same current bias. However, if there is a SQUID element that does not operate normally, no output voltage can be obtained from that element.
An error occurs when setting the current bias. An embodiment for solving this problem will be explained with reference to the flowchart of FIG. A microcomputer determines whether the sensitivity level of the channel has reached a certain threshold. A SQUID element that does not reach the threshold value is determined not to be used, and is excluded from the target when setting the current bias. As a result, it becomes possible to set the current bias more accurately. In the first and second embodiments of the present invention, the current bias values for multiple channels are set after determining the current bias that increases the magnetic flux detection sensitivity for each channel. For this purpose, it is necessary to use a microcomputer, and there is a problem that setting the current is complicated and takes time. An embodiment for solving this problem and setting the current bias in a short time is shown in FIG. As mentioned earlier, SQUI
Since the D magnetometer is operated in the FLL state, fluctuation errors in the system gain due to slight variations in sensitivity do not pose much of a problem. Therefore, if there are no large variations in the element characteristics, finding the average value of the current bias for each channel is equivalent to setting the current bias value so that the sum of the magnetic flux detection sensitivities of each channel is maximized. . The output voltage of the preamplifier 4, which determines the magnetic flux detection sensitivity, is added by an adder 14. The current bias regulator 15 outputs an adjustment output to adjust the output current of the current source 9 so that the signal after the addition becomes the maximum. This adjustment of current bias is
This can be easily done by setting the optimal current bias value so that the preamplifier's output level is maximized when a pseudo signal is input to the input coil, or by capturing the double frequency component of the modulation signal when changing the current bias. can be done. According to this embodiment, the time required to set the current bias can be significantly shortened, and even if a faulty SQUID element exists, the current bias can be set accurately. The above embodiments have been considered on the assumption that the degree of variation in the SQUID elements is approximately equal and small. However, the characteristics of the SQUID element may differ depending on the chip produced. Therefore, it is considered effective to apply the above-described current bias setting method to SQUID elements on the same chip and set the current bias for each chip. An embodiment of this method is shown in FIG. 6. A plurality of superconducting circuit chips 16 each include two or more SQ
UID elements are arranged, and each chip has a circuit configuration as described in the first embodiment. In other words, a common current i! for SQUID elements on the same chip! has 9;
A current bias is applied to each through a resistor. If there are m chips as shown in the figure, they are driven with m current biases. As a result, compared to driving all SQUIDs using the same current bias, the influence of variations in element sensitivity can be reduced, improving magnetic flux detection sensitivity and making it possible to detect magnetic fields with high precision. . Note that setting of the current bias value in the second case can be realized by using the first, second, or third embodiment of the present invention. In the above embodiment, when using the same current bias, S
It is assumed that the QUID sensitivities are approximately equal. However, accurately knowing the sensitivity of each channel is important in measuring magnetic field strength, and it is effective to record the magnetic flux detection sensitivity of each channel. A flowchart showing an embodiment for this purpose will be explained with reference to FIG. As described in the first embodiment of the present invention, the output of the preamplifier when the current bias is set represents the magnetic flux detection sensitivity. Therefore, after setting the same current bias as shown in the flowchart in Figure 3, the output of the preamplifier is input to the microcomputer via the A/D converter for each channel, and the magnetic flux detection sensitivity data of each channel is By recording the information, it is possible to prevent variations in the sensitivity of each channel. Furthermore, this method can also be implemented in the second and third embodiments of the present invention by taking in the preamplifier output into the microcomputer via an A/D converter.

【発明の効果】【Effect of the invention】

多チャンネルＳＱＵＩＤ磁束計において、ＳＱＵＩＤを
駆動する電流バイアスおよびＳＱＵＩＤ素子に対して直
列に抵抗を冷却媒体内で接続し。 それらのＳＱＵＩＤ素子を並列接続して、さらに各ＳＱ
ＵＩＤの電流バイアスの平均値により、多数のＳＱＵＩ
Ｄ磁束計を同一電流バイアスで駆動することにより、多
チャンネル化に伴う信号線の増加を防ぎ、多数のＳＱＵ
ＩＤをほぼ等しい高感度で駆動することができる。In a multi-channel SQUID magnetometer, a resistor is connected within the cooling medium in series with the current bias driving the SQUID and the SQUID element. These SQUID elements are connected in parallel, and each SQUID element is further connected in parallel.
Due to the average value of the UID current bias, a large number of SQUI
By driving the D magnetometer with the same current bias, it is possible to prevent an increase in the number of signal lines due to multichannelization, and to reduce the number of SQUs.
The ID can be driven with almost the same high sensitivity.

【図面の簡単な説明】[Brief explanation of the drawing]

第１図は本発明の第１の実施例を示す図、第２図は電流
バイアス値に対する磁束検出感度を模擬的に表した図、
第３図は本発明の第１の実施例を明の第３の実施例を示
す図、第６図は本発明の第４の実施例を示す図、第７図
は本発明の第５０実施例を説明するフローチャートであ
る。 符号の説明 １・・・ＳＱＵＩＤ素子、２インプツトコイル、３・・
フィードバックコイル、４・・・プリアンプ、５・・１
チャンネルＳＱＵＩＤ磁束計、６・・・電圧電流変換器
、７・・・電子回路、８・・抵抗、９電流バイアス、１
０・・・マルチプレクサ、１１・・・Ａ／Ｄ変換器、１
２・・・マイクロコンピュータ、１３・・・Ｄ／Ａ変換
器、１４・・・加算器、１５・・・電流バイアス調整器
、１６・・１チツプ上のＳＱＵＩＤ磁束計代理人弁理士
　小　川　勝　男・パ ＼−ノ′ Ｖ、　・　・　・Ｖ、　・　・・へFIG. 1 is a diagram showing a first embodiment of the present invention, FIG. 2 is a diagram simulating magnetic flux detection sensitivity with respect to current bias value,
FIG. 3 is a diagram showing a third embodiment of the invention, FIG. 6 is a diagram showing a fourth embodiment of the invention, and FIG. 7 is a diagram showing a fiftieth embodiment of the invention. 3 is a flowchart illustrating an example. Explanation of symbols 1...SQUID element, 2 input coils, 3...
Feedback coil, 4...Preamplifier, 5...1
Channel SQUID magnetometer, 6...voltage-current converter, 7...electronic circuit, 8...resistance, 9 current bias, 1
0... Multiplexer, 11... A/D converter, 1
2...Microcomputer, 13...D/A converter, 14...Adder, 15...Current bias regulator, 16...SQUID magnetometer on one chip Masaru Ogawa, patent attorney Man/Pa＼－ノ' V、 ・ ・ ・V、 ・ ・・・to

Claims (1)

【特許請求の範囲】 １、少なくとも１つのジョセフソン接合を持ち、冷却媒
体内に配置されるＳＱＵＩＤ素子を用いる磁束計におい
て、前記ＳＱＵＩＤ素子を駆動する電流バイアス源と前
記ＳＱＵＩＤ素子の間が前記冷却媒体内に配置される抵
抗で直列に接続されることを特徴とするＳＱＵＩＤ磁束
計。 ２、第１請求項に記載のＳＱＵＩＤ磁束計を少なくとも
２つ以上有する多チャンネルＳＱＵＩＤ磁束計において
、抵抗を直列接続したＳＱＵＩＤ素子を並列に接続し、
同一電流バイアスで駆動することを特徴とする多チャン
ネルＳＱＵＩＤ磁束計。 ３、少なくとも１つのジョセフソン接合を有し、冷却媒
体内に配置されるＳＱＵＩＤ素子と、該ＳＱＵＩＤ素子
に検出すべき入力磁束を伝達する入力系と、該ＳＱＵＩ
Ｄ素子の出力に対応する磁束と変調磁束とを帰還する帰
還系とを有する磁束検出回路を複数チャンネル有すると
ともに各チャンネルのＳＱＵＩＤ素子に電流バイアスを
与えるための各チャンネル共通の電流源を有し、各チャ
ンネルのＳＱＵＩＤ素子にそれぞれ直列に接続された抵
抗を介して前記電流バイアスが各ＳＱＵＩＤ素子に供給
されることを特徴とする多チャンネルＳＱＵＩＤ磁束計
。 ４、前記抵抗は各チャンネル間でほぼ等しい抵抗値を有
することを特徴とする請求項３に記載の多チャンネルＳ
ＱＵＩＤ磁束計。 ５、前記抵抗は前記ＳＱＵＩＤ素子よりも大きな抵抗値
を有することを特徴とする請求項３に記載の多チャンネ
ルＳＱＵＩＤ磁束計。 ６、前記抵抗は前記冷却媒体内に配置され、かつ前記冷
却媒体内で共通に接続されてその共通接続点と前記電流
源とが接続されることを特徴とする請求項３に記載の多
チャンネルＳＱＵＩＤ磁束計。 ７、前記電流源の出力電流は複数のＳＱＵＩＤ素子の電
流バイアスの最適値の平均値に対応して設定されること
を特徴とする請求項３に記載の多チャンネルＳＱＵＩＤ
磁束計。 ８、請求項３に記載の多チャンネルＳＱＵＩＤ磁束計に
おいて、複数チャンネルのＳＱＵＩＤ素子の磁束検出感
度が最大となる電流バイアス値をそれぞれ検出し、各チ
ャネルの電流バイアスがその平均値となるよう前記電流
源の出力電流を設定する手段を更に有することを特徴と
する多チャンネルＳＱＵＩＤ磁束計。 ９、請求項３に記載の多チャンネルＳＱＵＩＤ磁束計に
おいて、複数チャンネルのＳＱＵＩＤ素子の磁束検出感
度の和が最大になるように前記電流源の出力電流を設定
する手段を更に有することを特徴とする多チャンネルＳ
ＱＵＩＤ磁束計。 １０、前記出力電流設定手段は、正常動作しないＳＱＵ
ＩＤ素子を除いて電流バイアス値を設定することを特徴
とする請求項８もしくは９に記載の多チャンネルＳＱＵ
ＩＤ磁束計。 １１、複数の超伝導回路チップの各々にそれぞれ複数の
ＳＱＵＩＤ磁束計を備え、同一チップ上のＳＱＵＩＤ素
子を同一電流バイアスで駆動し、各チップごとに電流バ
イアスを調整する手段を有することを特徴とする多チャ
ンネルＳＱＵＩＤ磁束計。[Claims] 1. In a magnetometer using a SQUID element having at least one Josephson junction and disposed in a cooling medium, the cooling is provided between a current bias source that drives the SQUID element and the SQUID element. A SQUID magnetometer characterized in that it is connected in series with a resistor placed in a medium. 2. In a multi-channel SQUID magnetometer having at least two or more SQUID magnetometers according to the first claim, SQUID elements having resistors connected in series are connected in parallel,
A multi-channel SQUID magnetometer characterized by being driven with the same current bias. 3. a SQUID element having at least one Josephson junction and disposed in a cooling medium; an input system for transmitting input magnetic flux to be detected to the SQUID element;
It has a plurality of channels of magnetic flux detection circuits each having a feedback system that returns the magnetic flux corresponding to the output of the D element and the modulated magnetic flux, and has a current source common to each channel for applying a current bias to the SQUID element of each channel, A multi-channel SQUID magnetometer, characterized in that the current bias is supplied to each SQUID element through a resistor connected in series to each SQUID element of each channel. 4. The multi-channel S according to claim 3, wherein the resistor has a substantially equal resistance value between each channel.
QUID magnetometer. 5. The multi-channel SQUID magnetometer according to claim 3, wherein the resistor has a larger resistance value than the SQUID element. 6. The multi-channel device according to claim 3, wherein the resistors are disposed within the cooling medium and are commonly connected within the cooling medium so that the common connection point is connected to the current source. SQUID magnetometer. 7. The multi-channel SQUID according to claim 3, wherein the output current of the current source is set corresponding to an average value of optimal values of current biases of a plurality of SQUID elements.
Magnetic flux meter. 8. In the multi-channel SQUID magnetometer according to claim 3, the current bias value at which the magnetic flux detection sensitivity of the SQUID elements of the plural channels is maximized is detected, and the current bias value of each channel is adjusted so that the current bias of each channel becomes the average value. A multi-channel SQUID magnetometer, further comprising means for setting the output current of the source. 9. The multi-channel SQUID magnetometer according to claim 3, further comprising means for setting the output current of the current source so that the sum of magnetic flux detection sensitivities of the SQUID elements of the plurality of channels is maximized. Multi-channel S
QUID magnetometer. 10. The output current setting means is used for SQU that does not operate normally.
The multi-channel SQU according to claim 8 or 9, wherein the current bias value is set excluding the ID element.
ID flux meter. 11. Each of the plurality of superconducting circuit chips is provided with a plurality of SQUID magnetometers, the SQUID elements on the same chip are driven with the same current bias, and the current bias is adjusted for each chip. Multi-channel SQUID magnetometer.
JP2337130A 1990-11-30 1990-11-30 Multi-channel SQUID magnetometer Expired - Fee Related JP3058681B2 (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
JP2337130A JP3058681B2 (en) 1990-11-30 1990-11-30 Multi-channel SQUID magnetometer
DE19914139212 DE4139212C2 (en) 1990-11-30 1991-11-28 Multi-channel SQID magnetometer

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP2337130A JP3058681B2 (en) 1990-11-30 1990-11-30 Multi-channel SQUID magnetometer

Publications (2)

Publication Number Publication Date
JPH04204279A true JPH04204279A (en) 1992-07-24
JP3058681B2 JP3058681B2 (en) 2000-07-04

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR100313910B1 (en) * 1999-02-25 2001-11-15 구자홍 Apparatus and Method for Multichannel Measuring of Magnetic field

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CA2303677A1 (en) 1999-04-09 2000-10-09 Hideo Itozaki Device and method for easily adjusting working point of squid
ES2213620T3 (en) 1999-10-04 2004-09-01 Qest Quantenelektronische Systeme Tubingen Gmbh Sitz Boblingen DEVICE FOR MEASURING HIGH RESOLUTION OF MAGNETIC FIELDS.

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4906930A (en) * 1987-02-27 1990-03-06 Hitachi, Ltd. Magnetometer using a Josephson device and superconducting phototransistor
JPH02257076A (en) * 1989-03-30 1990-10-17 Fujitsu Ltd System for controlling digital squid
JPH07104402B2 (en) * 1990-09-07 1995-11-13 ダイキン工業株式会社 Magnetic flux lock method and device

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR100313910B1 (en) * 1999-02-25 2001-11-15 구자홍 Apparatus and Method for Multichannel Measuring of Magnetic field

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DE4139212A1 (en) 1992-06-11
DE4139212C2 (en) 1994-02-03

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