JPH0690267B2 - Digital squid - Google Patents
Digital squidInfo
- Publication number
- JPH0690267B2 JPH0690267B2 JP62177509A JP17750987A JPH0690267B2 JP H0690267 B2 JPH0690267 B2 JP H0690267B2 JP 62177509 A JP62177509 A JP 62177509A JP 17750987 A JP17750987 A JP 17750987A JP H0690267 B2 JPH0690267 B2 JP H0690267B2
- Authority
- JP
- Japan
- Prior art keywords
- squid
- current
- output
- digital
- positive
- 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.)
- Expired - Fee Related
Links
Landscapes
- Superconductor Devices And Manufacturing Methods Thereof (AREA)
- Measuring Magnetic Variables (AREA)
- Measurement Of Current Or Voltage (AREA)
Description
【発明の詳細な説明】 〔概要〕 微小な磁束や電流の測定に用いられるディジタル・スク
ィドに関し, ディジタル・スクィドの出力パルスが正と負が略交互に
現れるようにして,アップダウンカウンタのビット数を
低減し,実装上有利で高感度の測定装置の実現を目的と
し, 超伝導インダクタンスと2個以上のジョセフソン接合を
含む超伝導ループよりなるスクィドと,被測定電流を流
し,かつ該スクィドに磁界結合する線と,該スクィドに
振幅変調波形のバイアス電流を与える振幅変調波形発生
器とを有し,該スクィドの少なくとも1組の注入端子に
振幅変調波を加え,かつ出力をパルス列で取り出すよう
に構成する。DETAILED DESCRIPTION OF THE INVENTION [Outline] Regarding a digital squid used for measuring a minute magnetic flux or current, the number of bits of an up / down counter is set so that positive and negative output pulses of the digital squid appear almost alternately. For the purpose of realizing a highly sensitive and highly sensitive measuring device in terms of mounting, a squid consisting of a superconducting loop including a superconducting inductance and two or more Josephson junctions, and a current to be measured is passed through the squid. A magnetic field coupling line and an amplitude modulation waveform generator for applying a bias current of an amplitude modulation waveform to the squid, the amplitude modulation wave is applied to at least one injection terminal of the squid, and the output is extracted as a pulse train. To configure.
本発明は高感度の磁束や電流の測定に用いられるディジ
タル・スクィドに関する。The present invention relates to a digital squid used for highly sensitive magnetic flux and current measurement.
2個以上のジョセフソン接合と超伝導インダクタンスを
含む超伝導ループを狭義にスクィド(SQUID,Supercondu
cting Quantum Interference Device,量子干渉素子)と
呼び,ジョセフソン接合が2個の場合は2接合量子干渉
計とも呼ばれている。これは現在では最高感度で磁束
(電流)を検出できる素子であり,これに対して表題で
いうスクィドとは広義に検知系,フィードバック系等の
回路を含めた磁束計としての機能をもつ全体の系をい
う。In the narrow sense, a superconducting loop including two or more Josephson junctions and a superconducting inductance is squeezed (SQUID, Supercondu
cting Quantum Interference Device), and it is also called a two-junction quantum interferometer when it has two Josephson junctions. At present, this is an element that can detect magnetic flux (current) with the highest sensitivity. On the other hand, squid in the title is a general term that has a function as a magnetometer including circuits such as detection system and feedback system. The system.
従って,ここでは狭義のスクィドをSQUIDと表示する。Therefore, the squid in the narrow sense is indicated as SQUID here.
既に,市販されているアナログ・スクィドは,例えば身
体の神経系に流れる微小電流により発生する磁束を検出
して心磁図や脳磁図等を得る医療機器に使用さている。The analog squid, which is commercially available, has already been used in a medical device for obtaining a magnetocardiogram, a magnetoencephalogram, etc. by detecting a magnetic flux generated by a minute electric current flowing in the nervous system of the body.
これらは,電圧を検出する今までの心電図等に代わっ
て,磁束の検出により同様の,あるいはより微細な身体
の情報を得るものである。In place of the electrocardiogram etc. which have been used to detect voltage, these obtain similar or finer body information by detecting magnetic flux.
また,SQUIDは,未だ検出に成功していないが,重力波の
検出に応用されている。Moreover, SQUID has not been successfully detected yet, but it has been applied to the detection of gravitational waves.
アナログ・スクィドは,SQUIDにdcバイアスをかけ,入力
信号に比例する電圧,または電流で出力が得られる。こ
れに対し,本発明者の提起したディジタル・スクィドは
バイアス電流をacにして,入力信号に比例し,かつバイ
アスのacと同じ周期をもつパルス数で出力できるように
したものである。The analog squid applies a dc bias to the SQUID and obtains an output at a voltage or current proportional to the input signal. On the other hand, the digital squid proposed by the present inventor is such that the bias current is set to ac so that it can be output with the number of pulses that is proportional to the input signal and has the same period as the bias ac.
第3図(1)〜(3)はそれぞれ従来例によるディジタ
ル・スクィドの回路図,動作説明図と出力パルスを示す
図である。3 (1) to 3 (3) are a circuit diagram, an operation explanatory diagram, and an output pulse diagram of a digital squid according to a conventional example, respectively.
このディジタル・スクィドは,本発明者により提起され
たもので,正の出力パルスの数と負の出力パルスの数の
差に比例する電流Ifをフィードバックすることにより被
測定磁束Φcを求めるようにしたものである。This digital squeeze is proposed by the present inventor, and seeks the measured magnetic flux Φ c by feeding back a current I f proportional to the difference between the number of positive output pulses and the number of negative output pulses. It is the one.
被測定磁束Φcは, Φc=(L1+L2)×Ic. で表される。ここにIcは被測定電流,L1はピックアップ
コイルとなる,L2はSQUIDに磁界結合する,いずれも被
測定超伝導ループを構成する超伝導インダクタンスであ
る。The measured magnetic flux Φ c is Φ c = (L 1 + L 2 ) × I c . It is represented by. Where I c is the current to be measured, L 1 is the pickup coil, and L 2 is the magnetic coupling to the SQUID, and both are superconducting inductances that form the superconducting loop to be measured.
より一般的には,ピックアップコイルL1を用いないで,
被測定電流Icを直接超伝導インダクタンスL2に流せば電
流計として用いることができる。More generally, without using the pickup coil L 1 ,
It can be used as an ammeter if the measured current I c is directly applied to the superconducting inductance L 2 .
この方式では,フィードバックする量は正と負のパルス
数の差であって,各々の絶対値は必要でない。In this method, the amount of feedback is the difference between the positive and negative pulse numbers, and the absolute value of each is not necessary.
つぎに,このディジタル・スクィドの動作について説明
する。Next, the operation of this digital squeeze will be described.
図において,2個のジョセフソン接合J1,J2と,超伝導イ
ンダクタンスLを含む超伝導ループは2接合SQUIDと呼
ばれる。In the figure, a superconducting loop including two Josephson junctions J 1 and J 2 and a superconducting inductance L is called a two-junction SQUID.
超伝導インダクタンスL1をもつピックアップコイルに,
被測定磁束Φcが叉交するとこの磁束を打ち消すように
被測定電流Icが被測定超伝導ループに流れ,これが2接
合SQUIDに磁界をつくり,2接合SQUIDの特性を変化させ
て,その変化より磁束を求める。For a pickup coil with superconducting inductance L 1 ,
When the measured magnetic flux Φ c crosses over, the measured current I c flows in the measured superconducting loop so as to cancel this magnetic flux, and this creates a magnetic field in the two-junction SQUID, changing the characteristics of the two-junction SQUID and changing it. Find more magnetic flux.
2接合SQUIDの注入(バイアス)端子に第1の交流波形
発生器1より第1のac電流を注入する。A first ac waveform generator 1 injects a first ac current into the injection (bias) terminal of the two-junction SQUID.
2接合SQUIDに磁界結合する超伝導インダクタンスL
3に,第2の交流波形発生器2より第1のac電流より周
波数の低い第2のac電流を供給する。Superconducting inductance L magnetically coupled to a two-junction SQUID
A second ac current having a frequency lower than that of the first ac current is supplied to the third AC waveform generator 2.
第3図(2)は2接合SQUIDのしきい値特性を示す図
で,縦軸はバイアス電流IGを,横軸は被測定電流Icを表
す。FIG. 3 (2) is a diagram showing the threshold characteristics of the two-junction SQUID, in which the vertical axis represents the bias current I G and the horizontal axis represents the measured current I c .
動作点が曲線内にあるときはSQUIDの電圧は0,曲線外に
有る時はジョセフソン接合は電圧状態となり,SQUIDの電
圧は有限の電圧となる。When the operating point is inside the curve, the voltage of the SQUID is 0, and when it is outside the curve, the Josephson junction is in the voltage state, and the voltage of the SQUID is a finite voltage.
いま,第2のac電流の波形を図示のように三角波とし,
その正方向の半周期をt1〜t2,負方向の半周期をt2〜t3
とする。Now, make the waveform of the second ac current a triangular wave as shown in the figure,
Its positive half-cycle is t 1 to t 2 , and its negative half-cycle is t 2 to t 3.
And
まず,t1近傍ではIcはA点(OAは被測定磁束Φcを変換
した電流とフィードバック電流Ifの差に相当する)付近
にあり,ここでバイアスIGが入っても動作点はしきい値
を越えることなく,SQUIDはスィッチしない。First, in the vicinity of t 1 , I c is in the vicinity of point A (OA corresponds to the difference between the current obtained by converting the measured magnetic flux Φ c and the feedback current I f ), and even if the bias I G is entered here, the operating point is SQUID does not switch without exceeding the threshold.
t1より時間が経過してIcが増加してゆくと,ある点よ
り,バイアスIGが入ったときに動作点はしきい値を越
え,SQUIDはスィッチして電圧出力が出る。バイアスIGが
落ちるとその出力電圧は0となる。すなわちバイアスパ
ルス1個に対して出力パルス1個が出る。As time passes from t 1, I c increases, and from a certain point, the operating point exceeds the threshold value when bias I G enters, and SQUID switches to output a voltage. When the bias I G drops, its output voltage becomes zero. That is, one output pulse is output for each bias pulse.
しきい値特性は左右非対称であるので,Icが正側にある
ときは,出力は正側にスィッチし,負側にスィッチしな
い。The threshold characteristic is a left-right asymmetry, when I c is in the positive, the output is switch to the positive side, it does not switch on the negative side.
反対に,t1〜t3の半周期では出力は負側にスィッチし,
正側にはスィッチしない。On the contrary, in the half cycle of t 1 to t 3 , the output switches to the negative side,
Do not switch to the positive side.
三角波の中心が原点にありIc=0の場合はしきい値特性
が原点対称であるので,出力は正側にスィッチする数と
負側にとスィッチする数が等しくなる。ところがIc≠0
の場合は,しきい値特性は左右アンバランスになり,Ic
が正の場合は正の出力パルスが多く,Icが負の場合は負
の出力パルスが多くなる。When the center of the triangular wave is at the origin and I c = 0, the threshold characteristic is symmetrical with respect to the origin, so that the number of outputs that are switched to the positive side is equal to the number that is switched to the negative side. However, I c ≠ 0
In the case of, the threshold characteristic is left-right unbalanced and I c
When is positive, there are many positive output pulses, and when I c is negative, there are many negative output pulses.
従って,正負の出力パルス数の差が入力電流Icを表す。Thus, the difference between the positive and negative of the output pulse is representative of the input current I c.
測定系は実際には第3図(1)のようにフィードバック
回路を付加して,ヌルメソッドが採用されている。The measurement system actually uses a null method with a feedback circuit added as shown in FIG.
2接合SQUIDの注入端子Bから出力を取り出すが,ここ
には第3図(3)に示される出力パルスが出てくる。The output is taken out from the injection terminal B of the two-junction SQUID, and the output pulse shown in Fig. 3 (3) appears here.
これをアップダウンカウンタ3に入れ,積分器4で積分
し,D/A変換器5でアナログ量であるフィードバック電流
Ifに変換し,2接合SQUIDに磁界結合する超伝導インダク
タンスLfに戻す。This is put in the up / down counter 3, integrated by the integrator 4, and fed back by the D / A converter 5 which is an analog amount of feedback current
It is converted to I f and returned to the superconducting inductance L f that is magnetically coupled to the two-junction SQUID.
戻し方の符号は正の出力パルスが多いときはIc軸で負方
向に電流が流れる向きにする。反対の場合は逆向きにす
る。When there are many positive output pulses, the sign of return is such that the current flows in the negative direction on the I c axis. If the opposite is the case, reverse.
出力はIfをとるか,あるいはフィードバック回路の途中
からIcに相当するディジタルのパルス数をとってもよ
い。The output may take I f , or may take the digital pulse number corresponding to I c from the middle of the feedback circuit.
正と負のパルス数の差はアップダウンカウンタにより得
られるが,カウンタには,例えば正のパルスが続いて現
れ,それが終わってから負のパルスが出てくる。これら
の数は例えば104(13〜14ビット)といった大きな数に
なるが,被測定磁束のダイナミックレンジが極端に大き
くない場合はこの差は通常これよりはるかに小さい数と
なる。例えば0〜102程度の小さな数であるが,カウン
タは一時的に104程度のパルス数をカウントしなければ
ならない。The difference between the number of positive and negative pulses is obtained by the up / down counter, but, for example, a positive pulse appears in succession in the counter, and a negative pulse comes out after that. These numbers are large numbers such as 10 4 (13 to 14 bits), but when the dynamic range of the measured magnetic flux is not extremely large, this difference is usually a much smaller number. For example, a small number such as 0 to 10 2 , but the counter must temporarily count the number of pulses of about 10 4 .
このため,アップダウンカウンタのビット数を必要以上
に多くしていた。また次段のD/A変換器もビット数が増
え,フィードバック回路に負担を強いることになってい
た。Therefore, the number of bits of the up / down counter has been increased more than necessary. In addition, the D / A converter in the next stage also had an increased number of bits, which placed a burden on the feedback circuit.
上記問題点の解決は,超伝導インダクタンスと2個以上
のジョセフソン接合を含む超伝導ループからなるスクィ
ドと,被測定電流を流し,かつ該スクィドに磁界結合す
るループと,該スクィドにバイアス電流として交流波を
注入し,該スクィドの出力をパルス列で取り出す手段
と,該パルス列の正の出力パルスと負の出力パルスの差
を計数する手段とを有するディジタル・スクィドであっ
て,該スクィドに注入するバイアス電流として振幅変調
波を与える振幅変調波形発生器を有し,該スクィドは,
バイアス電流を与える注入端子が該スクィドの非対称の
位置に設けられているか,あるいは各々のジョセフソン
接合が異なった臨界電流値を有するディジタル・スクィ
ドにより達成される。To solve the above problems, a squid consisting of a superconducting loop including a superconducting inductance and two or more Josephson junctions, a loop for passing a measured current and magnetically coupling to the squid, and a bias current for the squid are used. A digital squid having means for injecting an AC wave and extracting the output of the squid as a pulse train, and means for counting the difference between the positive output pulse and the negative output pulse of the pulse train, which is injected into the squid It has an amplitude modulation waveform generator that gives an amplitude modulation wave as a bias current.
Injection terminals providing bias current are provided at asymmetrical locations on the squid, or each Josephson junction is achieved by a digital squid having different critical current values.
本発明は2接合以上のSQUIDの注入端子を非対称の位置
におくか,または各々のジョセフソン接合が異なった臨
界電流を有するように構成して,しきい値特性を変形
し,SQUIDに振幅変調波を与えることにより,出力パルス
列を正負交互に出るようにして,一時的にカウント数が
膨大になることがないようにしたものである。According to the present invention, the injection terminals of two or more SQUIDs are placed at asymmetrical positions, or each Josephson junction is configured to have different critical currents, the threshold characteristics are modified, and the SQUIDs are amplitude-modulated. By applying a wave, the output pulse train alternates between positive and negative, so that the number of counts does not temporarily increase.
第1図(1)〜(5)は本発明の原理を説明するディジ
タル・スクィドの回路図,動作説明図と出力パルスを示
す図である。1 (1) to (5) are a circuit diagram of a digital squeeze for explaining the principle of the present invention, an operation explanatory diagram and an output pulse.
図において,装置は,2個のジョセフソン接合J1,J2と,
超伝導インダクタンスLで形成される超伝導ループより
なる2接合SQUIDと,これに磁界結合し,かつ被測定電
流Icを流す超伝導インダクタンスL2を有し,出力端子を
兼ねる注入端子Bは2接合SQUIDの非対称の位置に設
け,ここに振幅変調波形発生器1Aより振幅変調されたバ
イアス電流IGを注入する。In the figure, the device is composed of two Josephson junctions J 1 and J 2 .
A two-junction SQUID composed of a superconducting loop formed of a superconducting inductance L, and a superconducting inductance L 2 that is magnetically coupled to the superconducting loop and allows a current I c to be measured to flow therethrough. The junction SQUID is provided at an asymmetric position, and the amplitude-modulated waveform generator 1A injects the amplitude-modulated bias current I G.
第1図(2),(4)は2接合SQUIDのしきい値特性を
示す図で,縦軸はバイアス電流IG,横軸は被測定電流Ic
を表す。FIGS. 1 (2) and 1 (4) are diagrams showing threshold characteristics of a two-junction SQUID, where the vertical axis represents the bias current I G and the horizontal axis represents the measured current I c.
Represents
しきい値特性は注入端子を非対称の位置に設けることに
より,対称の位置に設けた従来例に比しIG軸方向のピー
ク値は左右にずれる。Threshold characteristics by providing the injection terminal positioned asymmetrically, the peak value of I G axis direction compared with the conventional example in which the position of symmetry is shifted to the left and right.
第1図(2)は磁界結合電流(被測定電流)Ic=0の場
合を示し,動作点はしきい値特性図の縦軸上を動く。こ
の場合正負のしきい値はそれぞれ+I0,−I0であり,絶
対値は等しい。バイアスIGがしきい値を越すと,すなわ
ち+I0以上,あるいは−I0以下になると,SQUIDはスィッ
チして,各々正のパルスあるいは負のパルスを生ずる。
この出力パルス列は第1図(3)に示すように正負が交
互に出力される。FIG. 1 (2) shows the case where the magnetic field coupling current (current to be measured) I c = 0, and the operating point moves on the vertical axis of the threshold characteristic diagram. In this case, the positive and negative threshold values are + I 0 and −I 0 , respectively, and their absolute values are equal. When the bias I G exceeds the threshold value, that is, when it becomes + I 0 or more or −I 0 or less, the SQUID switches to generate a positive pulse or a negative pulse, respectively.
This output pulse train alternately outputs positive and negative as shown in FIG.
従って,Ic=0ならば正と負の出力パルス数は等しく,
その差は0である。Therefore, if I c = 0, the number of positive and negative output pulses is equal,
The difference is 0.
第1図(4)はIc≠0,例えばIc>0の場合を示し,正の
しきい値I1はI0より小さく(I1<I0),また,負のしき
い値−I2は−I0より小さい(I2>I0)。FIG. 1 (4) shows the case where I c ≠ 0, for example I c > 0, the positive threshold I 1 is smaller than I 0 (I 1 <I 0 ), and the negative threshold − I 2 is smaller than −I 0 (I 2 > I 0 ).
従って第1図(5)に示すように出力パルス列は正のパ
ルス数が負のパルス数より多くなる。Therefore, as shown in FIG. 1 (5), the output pulse train has more positive pulses than negative pulses.
例えば,振幅変調波形のバイアス電流IGの包絡線(変調
波)を三角波とし,波形の最大,最小値をIg2,Ig1と
し,また変調三角波の1周期の中にM周期の交流波形
(例えば正弦波)があると,正および負の出力パルス数
の差は 〔(I2−I1)/(Ig2−Ig1)〕×M. で表される。しきい値特性がわかっていれば,I1−I1か
らIcを求めることができる。For example, the envelope (modulation wave) of the bias current I G of the amplitude modulation waveform is a triangular wave, the maximum and minimum values of the waveform are I g2 and I g1, and the AC waveform of M cycles in one cycle of the modulation triangular wave ( For example, if there is a sine wave, the difference between the number of positive and negative output pulses is represented by [(I 2 −I 1 ) / (I g2 −I g1 )] × M. Knowing the threshold characteristics can be obtained I c from I 1 -I 1.
実際には,フィードバックをかけて,パルス数の差が0
になるように,すなわちI2=I1=I0になるようにフィー
ドバック電流Ifを流すようにしているので,しきい値特
性の形を知る必要はなく,Ifより被測定電流が求められ
る。In practice, feedback is applied and the difference in the number of pulses is 0.
Since the feedback current I f is made to flow so that I 2 = I 1 = I 0 , it is not necessary to know the shape of the threshold characteristic, and the measured current can be obtained from I f. To be
第2図は本発明の一実施例を説明するディジタル・スク
ィドの回路図である。FIG. 2 is a circuit diagram of a digital squeeze for explaining an embodiment of the present invention.
2接合SQUIDの注入端子Bから出力を取り出し,アップ
ダウンカウンタ3に入れ,出力パルス数の差を得て,積
分器4で積分し,D/A変換器5でフィードバック電流Ifに
変換し,超伝導インダクタンスLfに戻し,2接合SQUIDに
磁界結合される。The output is taken out from the injection terminal B of the two-junction SQUID, put into the up / down counter 3, the difference in the number of output pulses is obtained, integrated by the integrator 4, and converted into the feedback current If by the D / A converter 5, It returns to the superconducting inductance L f and is magnetically coupled to the two-junction SQUID.
出力は積分されたパルス数として得られる。The output is obtained as the number of integrated pulses.
実際の回路は,通常のフィードバック回路において行わ
れる応答制御回路や,またD/A変換器の過渡動作により
異常なフィードバック電流が流れないようにするための
ラッチ回路等を付加している。The actual circuit has a response control circuit that is used in a normal feedback circuit, and a latch circuit that prevents abnormal feedback current from flowing due to the transient operation of the D / A converter.
また実施例において,2接合SQUIDは注入端子の位置を変
えてもよく,また2つのジョセフソン接合の臨界電流の
比を変えてもよい。In the embodiment, the two-junction SQUID may change the position of the injection terminal, and may change the ratio of the critical currents of the two Josephson junctions.
さらに,振幅変調波形を注入端子と磁界結合線とに分流
して加えてもよい。Furthermore, the amplitude modulation waveform may be shunted and added to the injection terminal and the magnetic field coupling line.
また,変調波形は三角波でなく,その他の波形,例えば
正弦波であってもよいし,変調される波形もその他の波
形,例えば矩形波あるいはJJパルサ(2個のジョセフソ
ン接合を利用したパルス発生器)から発生する半値幅の
短いパルス等であってもよい。Also, the modulating waveform may be other waveforms such as a sine wave instead of a triangular wave, and the waveform to be modulated is also another waveform, such as a rectangular wave or a JJ pulser (pulse generation using two Josephson junctions. Pulse) having a short half-value width or the like.
また実施例においては,2接合SQUIDを用いたが,3接合以
上のSQUIDを用いてもよい。Further, in the embodiment, the two-junction SQUID is used, but the three-junction or more SQUID may be used.
以上詳細に説明したように本発明によれば,ディジタル
・スクィドの出力パルスが正と負が略交互に現れるの
で,アップダウンカウンタのビット数を必要以上に多く
しないですむ。As described above in detail, according to the present invention, the positive and negative output pulses of the digital squid appear alternately, so that the number of bits of the up / down counter need not be increased more than necessary.
かつ,従来例では周波数が大きく異なる2つの交流波形
を加える必要があったが,この方式では振幅変調波1つ
を加えるだけでよく,装置の実装上有利である。Moreover, in the conventional example, it was necessary to add two alternating-current waveforms having greatly different frequencies, but in this method, only one amplitude-modulated wave needs to be added, which is advantageous in mounting the apparatus.
さらに,この測定は微小測定であるので,外よりの誘導
とか,まわり込み等があると誤動作の原因となる。従っ
て,従来例のように2つの波形を入れると相互のまわり
込み等の原因となり,入力する波形が少ない本発明の方
式の方が高感度測定に適している。Furthermore, since this measurement is a minute measurement, it may cause malfunction if there is guidance from the outside or wraparound. Therefore, when two waveforms are inserted as in the conventional example, they cause mutual wraparound and the like, and the method of the present invention with less input waveforms is more suitable for high sensitivity measurement.
第1図(1)〜(5)は本発明の原理を説明するディジ
タル・スクィドの回路図,動作説明図と出力パルスを示
す図, 第2図は本発明の一実施例を説明するディジタル・スク
ィドの回路図, 第3図(1)〜(3)はそれぞれ従来例によるディジタ
ル・スクィドの回路図,動作説明図と出力パルスを示す
図である。 図において, J1,J2はジョセフソン接合, Lは超伝導インダクタンス, Icは被測定電流, Φcは被測定磁束, L1はピックアップコイルで超伝導インダクタンス, L2は被測定超伝導ループの超伝導インダクタンス, Lfはフィードバック用超伝導インダクタンス, Bは注入端子, IGはバイアス電流, Ifはフィードバック電流, 1Aは振幅変調波形発生器, 3はアップダウンカウンタ, 4は積分器, 5はD/A変換器 である。1 (1) to (5) are circuit diagrams of a digital squeeze for explaining the principle of the present invention, operation explanatory diagrams and output pulse diagrams, and FIG. 2 is a digital squeeze for explaining an embodiment of the present invention. A circuit diagram of the squid, and FIGS. 3 (1) to 3 (3) are a circuit diagram, an operation explanatory diagram and an output pulse diagram of a digital squid according to a conventional example, respectively. In the figure, J 1 and J 2 are Josephson junctions, L is the superconducting inductance, I c is the measured current, Φ c is the measured magnetic flux, L 1 is the pickup coil superconducting inductance, and L 2 is the measured superconducting. Loop superconducting inductance, L f is feedback superconducting inductance, B is injection terminal, I G is bias current, I f is feedback current, 1A is amplitude modulation waveform generator, 3 is up-down counter, 4 is integrator , 5 are D / A converters.
Claims (1)
フソン接合を含む超伝導ループからなるスクィドと, 被測定電流を流し,かつ該スクィドに磁界結合するルー
プと, 該スクィドにバイアス電流として交流波を注入し,該ス
クィドの出力をパルス列で取り出す手段と, 該パルス列の正の出力パルスと負の出力パルスの差を計
数する手段とを有するディジタル・スクィドであって, 該スクィドに注入するバイアス電流として振幅変調波を
与える振幅変調波形発生器を有し, 該スクィドは,バイアス電流を与える注入端子が該スク
ィドの非対称の位置に設けられているか,あるいは各々
のジョセフソン接合が異なった臨界電流値を有すること
を特徴とするディジタル・スクィド。1. A squid consisting of a superconducting loop including a superconducting inductance and two or more Josephson junctions, a loop for passing a current to be measured and magnetically coupling to the squid, and an AC wave as a bias current for the squid. A bias current to be injected into the squeeze, the digital squeeze having a means for injecting the squid and extracting the output of the squid as a pulse train and a means for counting the difference between the positive output pulse and the negative output pulse of the pulse train As the squid, an injection terminal for applying a bias current is provided at an asymmetrical position of the squid, or each of the Josephson junctions has a different critical current value. A digital squid characterized by having.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP62177509A JPH0690267B2 (en) | 1987-07-16 | 1987-07-16 | Digital squid |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP62177509A JPH0690267B2 (en) | 1987-07-16 | 1987-07-16 | Digital squid |
Publications (2)
Publication Number | Publication Date |
---|---|
JPS6421378A JPS6421378A (en) | 1989-01-24 |
JPH0690267B2 true JPH0690267B2 (en) | 1994-11-14 |
Family
ID=16032149
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
JP62177509A Expired - Fee Related JPH0690267B2 (en) | 1987-07-16 | 1987-07-16 | Digital squid |
Country Status (1)
Country | Link |
---|---|
JP (1) | JPH0690267B2 (en) |
Families Citing this family (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2677658B2 (en) * | 1989-03-03 | 1997-11-17 | 日本電信電話株式会社 | Metal core identification device |
US5272479A (en) * | 1992-07-22 | 1993-12-21 | Trw Inc. | High sensitivity superconductive digitizer |
Family Cites Families (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS62125469A (en) * | 1985-11-27 | 1987-06-06 | Hitachi Ltd | Request system for inspection item |
-
1987
- 1987-07-16 JP JP62177509A patent/JPH0690267B2/en not_active Expired - Fee Related
Non-Patent Citations (1)
Title |
---|
「ジョセフソン効果基礎と応用」PP.148−150電気学会昭和53年5月20日発行 |
Also Published As
Publication number | Publication date |
---|---|
JPS6421378A (en) | 1989-01-24 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
US4893027A (en) | Proximity switch insensitive to interference fields | |
US5045788A (en) | Digital SQUID control system for measuring a weak magnetic flux | |
JP3081902B2 (en) | Magnetic field detection circuit | |
JPH0690267B2 (en) | Digital squid | |
EP0446923A2 (en) | High-sensitive magnetometer | |
EP0505250B1 (en) | Superconducting circuit having a rectifier for converting a bipolar signal to a unipolar signal | |
JPH0640124B2 (en) | Digital squid | |
JPH0785104B2 (en) | Superconducting quantum interference device | |
JPH04357482A (en) | Squid driving circuit | |
JPH0588433B2 (en) | ||
JP3525145B2 (en) | Multi-phase high frequency flux driven superconducting quantum interference device | |
JP2955356B2 (en) | Multi-input magnetic field detector | |
JPS61284679A (en) | Superconductive quantum interference device | |
JP3133830B2 (en) | SQUID magnetometer | |
JP2871772B2 (en) | Superconducting circuit | |
JPH04208885A (en) | Multi-input magnetic field detector | |
JPH05240933A (en) | Magnetic flux transformer for squid fluxmeter | |
JPH0933625A (en) | Squid element | |
JP2807519B2 (en) | Superconducting device | |
JP2902007B2 (en) | Magnetic flux detector | |
JPH04332886A (en) | Method for detecting drive of digital-type squid | |
JP2613559B2 (en) | SQUID magnetometer | |
JP2782900B2 (en) | Squid magnetometer | |
JPH0933626A (en) | Squid element | |
JPH01291180A (en) | Magnetism detecting device |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
LAPS | Cancellation because of no payment of annual fees |