JP3020172B1 - Superconducting magnetic field generator and superconducting detector - Google Patents

Abstract

Abstract: A small initial current is applied from the outside to generate a large magnetic field inside, and finally, a magnetic field is generated without electric power in a state separated from the outside by a superconducting permanent current. SOLUTION: The superconducting tunnel junction element 5 is, for example,
A radiation detector with a microstrip coil,
It is arranged in a cryogenic environment 8. A DC current is applied from the DC power supply 1 to the primary coil 21 of the superconducting transformer 2 so that the first
Current flows through the superconducting loop 6 of the first superconducting gate 3
, A circulating current is set in the first and second superconducting loop circuits 6 and 7 to reduce the DC current of the primary coil 21 of the superconducting transformer 2 to provide a second superconducting loop circuit. To generate a superconducting 7-permanent permanent current. Furthermore, the second
When the superconducting permanent circulating current flows through the superconducting loop circuit 7, the first and second superconducting gates 3 and 4 are simultaneously switched to cut off the superconducting permanent circulating current.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a superconducting magnetic field generator and a superconducting detector, and more particularly to a superconducting tunnel junction (hereinafter simply referred to as "STJ") element for a sensor, and a light, X-ray. The present invention relates to a superconducting magnetic field generator and a superconducting detector for detecting radiation such as rays and high-energy particles.

[0002]

2. Description of the Related Art FIG. 19 is an explanatory view of the principle of a radiation detector using an STJ element. Conventionally, a detector shown in FIG. 19A is known as a radiation detector. Reference numeral 81 denotes an STJ element having a size of several hundred microns square, which is the heart of the radiation detector. The superconducting electrode material used in the element is cooled to a temperature about one-tenth of the superconducting transition temperature (Tc). A cooling device is provided. In the STJ element, an insulating film serving as a tunnel barrier layer of about 1 nm is usually formed on a lower electrode superconducting thin film having a thickness of several hundred nanometers.
It has a sandwich-type configuration in which an upper electrode superconducting thin film having the same thickness as the lower electrode superconducting thin film is formed thereon. 82 is an upper electrode superconducting thin film of the STJ element, 83 is a lower electrode superconducting thin film, and 84 is a tunnel barrier insulating layer, for example, an Al2Ox insulator layer. Reference numerals 85 and 86 denote a bias current I to the STJ element electrode by a constant current source not shown.
, And 87 is a measured voltage V between the upper and lower electrodes. Numeral 88 denotes radiation applied to the inside of the upper electrode 82. The upper electrode 82 and the lower electrode 83 function as a radiation sensor surface of the radiation detector.

FIG. 19B shows current-voltage characteristics of a radiation detector. When the X-ray 88 as the radiation is not irradiated on the upper electrode 82 and the lower electrode 83 on the sensor surface, the current-voltage characteristic is the line 89 and the voltage between the junction electrodes is V0. When radiation is applied to the electrodes, the superconductors are excited, quasiparticles are generated, the current-voltage characteristics fluctuate from line 89 to line 90, and the measured voltage between the junction electrodes drops from V0 to V1.
Radiation is detected based on the voltage change ΔV = V0−V1. Since the energy gap of an STJ element is about 1/1000 that of a semiconductor, the statistical fluctuation is known to be several tenths of that of a semiconductor, and the energy resolution is improved accordingly. Already, we have succeeded in measuring X-rays having an input energy of 5.9 KeV with a sensitivity of 70 eV using an STJ element using niobium superconducting metal. This far exceeds the theoretical limit of semiconductor detectors of 120 eV. Thus, the SJT element detector is expected to be used for ultra-precision measurement such as physical property analysis and medical diagnosis. The semiconductor detector measures at the sensitivity of the theoretical limit, but the SJT element detector has a theoretical limit of 4 eV, so it is expected that the resolution is improved by one digit or more.

The current-voltage characteristics shown in FIG. 19 (b) have been described with reference to the characteristics of zero bias current and zero voltage between junction electrodes.
Actually, due to the direct current Josephson effect, no voltage V is generated between the electrodes even if a bias current I equal to or less than the Josephson current (critical current) Ic is applied to the junction. In order to use the SJT element as a radiation detector, the Josephson current must be suppressed, especially in a state where almost no current flows. Conventionally, in this type of radiation detector, it was considered that a large magnetic field generator was installed around the cryostat for cooling the STJ element, and an external magnetic field Φ was applied in parallel to the SJT plane to suppress Josephson current. . The Josephson current is periodically attenuated and changed in accordance with the external magnetic field Φ, so that almost no current flows.

[0005]

SUMMARY OF THE INVENTION A superconducting tunnel junction (ST)
The radiation detector using J) is one time smaller than the conventional semiconductor.
Since it has an energy resolution improvement of 0 times or more and has excellent radiation resistance, it has a long life, excellent high-speed response, and features that can be integrated. Then, S as a radiation detector
In order to operate the TJ element at a very low temperature (up to 1K), it was necessary to suppress the Josephson current of the junction. Conventionally, for this purpose, an external magnetic field is generated by sandwiching a large magnet or electromagnet from the outside of the cryostat storing the STJ element, and a magnetic field parallel to the tunnel barrier of the STJ element has been given.

The main purpose of this external magnetic field Φ is to suppress the Josephson current of the STJ element.
It was found that a current step (Fiske step) due to resonance occurred in J. Therefore, the bias current of the radiation detector needs to be set to a value that is not affected by this current step. However, the external magnetic field and ST
It has been confirmed that even if the relative position with respect to J fluctuates, the current step itself also fluctuates. When the radiation detector is cooled by the cryostat, a slight vibration is generated in the STJ due to the boiling of the liquid helium and the vibration of the pump.
The current step also varies. This is considered to be a major factor that hinders improvement in energy resolution. Therefore, it is important to stabilize the external magnetic field itself and to stabilize the relative position between the STJ element and the external magnetic field.

However, in this method, the external magnetic field is
A magnetic field exists not only in the STJ element but also in the periphery thereof.
Therefore, a superconducting quantum interference device (SQUID, Superconducting Quantum Int) for detecting a weak pulse signal generated when X-rays or other radiation enters the STJ device.
It is difficult to integrate peripheral circuits using STJ elements that require Josephson current on the same chip, such as ERference Devices). Until now, strict magnetic shields have been provided at locations away from the STJ. The circuit was housed in. Therefore, the present inventors have filed Japanese Patent Application No. 10-250655.
By using an element having a structure in which a superconducting coil of a microstrip line is directly coupled to an STJ element on a substrate provided with a ground plane as disclosed in the above, the magnetic field is locally confined to only the STJ element part. A magnetic field application method that applies a magnetic field and does not affect the others can be said to be an effective means for coexisting the signal processing by the STJ element and the Josephson logic circuit on the same chip.
Further, when the STJs are arranged in an array to capture an image image such as an X-ray, the present invention in which a signal processing circuit can be provided in the vicinity of the STJ element brings about a dramatic improvement in processing speed. It is considered something.

In view of the above, the present invention relates to a radiation detector having a high speed and a high energy resolution using a superconducting tunnel junction, and in particular, by applying a current to a superconducting strip wire coupled to the superconducting tunnel junction itself. Regarding the method of suppressing Josephson current, a large initial magnetic field can be generated by applying a small initial current from the outside, and at the same time, a magnetic field can be generated with no power while being separated from the outside by a superconducting persistent current Thus, an object of the present invention is to provide a superconducting magnetic field generator and a superconducting detector that generate a magnetic field without loss using this superconducting permanent current. The present invention suppresses the Josephson current of the STJ by using a permanent current flowing in a superconducting closed loop circuit formed on the same chip, and is excellent in reproducibility, stability, low power consumption, low noise, and array compatibility. It is an object to provide a superconducting magnetic field generator and a superconducting detector provided with a Josephson current suppression circuit. In addition, the present invention provides a superconducting magnetic field generator that generates an external magnetic field applied to the sensor STJ element by using a microfabrication technology so as to confine the magnetic field on the same chip as the sensor STJ element. An object of the present invention is to provide a superconducting magnetic field generator and a superconducting detector radiation detector capable of realizing, on the same chip, an STJ element for a sensor, a superconducting magnetic generator, a Josephson logic element for performing digital processing, and the like.

[0009]

SUMMARY OF THE INVENTION In order to solve the above-mentioned conventional problems, in the present invention, a current flowing through a superconducting coil coupled to an STJ on a ground plane disclosed in Japanese Patent Application No. 10-250655 is disclosed. A small DC current is given to the superconducting transformer from the outside to amplify the current and supply it as a permanent current. One of the features of the present invention is that a superconducting transformer capable of forming a large current flowing through a superconducting coil integrated with an STJ on the same chip, a strip line forming a superconducting loop connected thereto, and a superconducting transformer. By injecting a small current through a wire introduced from the room temperature system into a permanent current generator consisting of a Josephson gate for adjusting the permanent current flowing in the loop, the Josephson current of the STJ can be suppressed, so wiring In addition, it is possible to minimize the heat inflow to the cryogenic temperature, to supply a large current for generating a large magnetic field to a large number of STJs in an array at the same time, and to extremely reduce the leakage magnetic field associated therewith.

According to a first solution of the present invention, there is provided a superconducting strip line coupled to a superconducting detecting element, a first superconducting loop circuit connecting a first superconducting gate, and the superconducting strip. A second superconducting loop circuit in which a wire and a second superconducting gate are connected in series, a primary coil connected to an external power supply, and a secondary coil in which the first and second loop circuits are connected in parallel And a superconducting transformer having the following.

According to a second solution of the present invention, a superconducting tunnel junction element for detecting radiation, a superconducting stripline coupled to the superconducting detecting element, and a first superconducting gate connected to the first superconducting gate. A superconducting loop circuit, a second superconducting loop circuit in which the superconducting strip line and the second superconducting gate are connected in series, a primary coil connected to an external power supply, and the first and second superconducting loop circuits. And a superconducting transformer having a secondary coil connected in parallel with the loop circuit.

[0012]

FIG. 1 is a block diagram of a superconducting detector according to the present invention. This superconducting detector is, for example,
DC power supply 1, superconducting transformer 2, superconducting gates 3, 4,
It comprises superconducting tunnel junction elements 5, which are arranged in a cryogenic environment 8.

The superconducting tunnel junction element 5 is, for example, a radiation detector with a microstrip coil (coupled to the microstrip coil) for X-rays, light, high energy particles and the like. As a specific configuration, for example, a configuration described later can be used. When radiation such as X-rays is applied, a radiation detection signal is output from a connected bias line. The DC power supply 1 is placed in a room temperature system and supplies a DC current to the superconducting tunnel junction element 5 from outside. The superconducting transformer 2 includes a primary-side superconducting coil 21 and a secondary-side superconducting coil 22.
When a direct current is supplied to the superconducting loop circuits 6 and 7 through the secondary superconducting coil 22 when a direct current is supplied from the current source 1 to the outside, the direct current is supplied. Superconducting transformer 2
When a loop circuit using a superconducting wire is connected to the secondary coil 22 of the above, when a DC current flows through the primary coil 21, a DC current is induced in the secondary coil 22 and a circulating current flows through the loop circuit . The DC current flowing to the primary side can be amplified by the ratio (n1 / n2) of the number of primary windings (n1) and the number of secondary windings (n2).

A superconducting loop circuit 6 including a superconducting gate 3, a superconducting tunnel junction element 5 with a microstrip coil, and a superconducting gate 4 are connected in series to a secondary coil 22 of the superconducting transformer 2. Superconducting loop circuits 7 are connected in parallel. The superconducting gate 3 is controlled so as to switch when a signal is input through the control signal input line 31 to cut off the current flowing through the superconducting gate 3. The superconducting gate 4 is controlled so as to switch when a signal is input through the control signal input line 41 to cut off the current flowing through the superconducting gate 4. As the superconducting gates 3 and 4, for example, the following various gates using a conventionally developed Josephson device can be used. That is, as an example, a quantum interference type gate (two junction type, three junction type, etc.), an in-line type gate, a current injection type gate (4
JL type, MVTL type, RCL type, RCJL type, JAWS type, CIL type, DCL type, etc.). It is also possible to arrange a plurality of superconducting tunnel junction elements 5 for sensors two-dimensionally in an array to obtain information on detection positions.

FIGS. 2 to 5 are explanatory diagrams (1) to (4) showing the circuit operation of the superconducting detector according to the present invention.

(1) Application of DC Current (FIG. 2) In FIG. 2, when a DC current is supplied from the current source 1 to the primary superconducting coil 21 of the superconducting transformer 2, the secondary superconducting coil 22 The induced DC current is applied to the superconducting gate 3
And two superconducting loop circuits 6 through the superconducting gate 4,
Divide to 7 At this time, since the superconducting loop circuit 7 to which the microstrip coil is connected has an inductance component Lms due to the coil of the loop circuit 7, most of the current flows through the superconducting gate 3 having a small inductance component.
Flow through The current flowing through each of the superconducting loop circuits 6 and 7 through the superconducting gate 3 and the superconducting gate 4 is respectively
Assuming Ig3 and Ig4, the superconducting loop circuit 7 supplied to the microstrip coil of the superconducting tunnel junction device 5
Is equal to Ig4. Assuming that the current flowing through the secondary coil L2 of the superconducting transformer is IL2, this current becomes Ig3 ≒ IL2 Ig4 ≒ 0.

(2) Setting of the circulating current (FIG. 3) In the state of FIG. 2, when the control signal Ic3 is given to the superconducting gate 3, the superconducting gate 3 switches as shown in FIG. , Commutate to the superconducting loop circuit 7 through the superconducting gate 4. As a result, each current is as follows. Ig3 ≒ 0 Ig4 ≒ IL2

(3) Generation of Superconducting Permanent Circular Current (FIG. 4) As the current of DC power supply 1 is reduced from the state of FIG.
As shown in FIG. 4, only Ig3 decreases, and Ig4 is hardly affected. This is because when the superconducting gate 3 is switched in FIG. 2, a counterclockwise superconducting circulating current is generated in the superconducting loop circuit 6, and a clockwise superconducting circulating current is generated in the superconducting loop circuit 7. It is considered that these currents are cancelled in the superconducting gate 3. Therefore, when the DC power supply I is reduced, only the superconducting circulating current flowing in the superconducting loop circuit 6 decreases, and the superconducting circulating current of the superconducting loop circuit 7 can continue to flow without being affected. .

The value of the superconducting circulating current flowing through the superconducting loop circuit 7 necessary for the microstrip coil of the superconducting tunnel junction device with the microstrip coil is adjusted to a desired value by adjusting the current supplied from the DC power supply 1. Can be obtained. Since the circulating permanent current flowing in the superconducting loop circuit 7 is determined by the magnetic flux quantum Φo held in the loop, only discrete values of the current value are allowed. The minimum unit current ΔI is Φo / L when simplified except for the effect of the junction.
ms. By the way, Φo = 2.07 × 10 ^-15 [Wb], Lms =
If 1 × 10 ⁻⁹ [H], it becomes 2 microamps,
It can be seen that the current can be controlled precisely for a circulating current of more than a milliamp. Since the superconducting circulating current flowing in the superconducting loop circuit 7 is a permanent current, the magnetic field generated by this current does not fluctuate. In the superconducting tunnel junction element 11 with a microstrip coil,
The microstrip coil for generating a magnetic field is integrated so as to be integrated with the superconducting tunnel junction. For this reason, it is possible to eliminate a change in the geometrical arrangement between the magnetic field and the junction, and it is expected that the temporal and spatial stability of the magnetic field can be significantly improved.

(4) Interruption of circulating current (FIG. 5) When a superconducting permanent circulating current flows in the superconducting loop circuit 7, when a control signal Ic4 is applied to the superconducting gate 4 as shown in FIG. The circulating current is cut off. At this time, in order to cut off all the superconducting current, the superconducting gates 3 and 4 are simultaneously switched.

Next, FIG. 6 is a diagram for explaining the current control to the superconducting microstrip coil. FIG.
Is a trace of an example of an operation waveform obtained as a result of performing a computer simulation on the superconducting detector of FIG. In the circuit of FIG. 1, first, at time T in FIG.
In FIG. 1, when a current is input to the superconducting transformer 2 by the DC power supply 1 (e), this current flows to the superconducting loop circuit 6 through the superconducting gate 3 (b). Thereafter, at time T2, when an input signal is applied to the superconducting gate 3 (d), T2
It can be seen that the current flowing in the superconducting gate 3 at the time of (1) decreases and the current flowing in the superconducting microstrip coil through the superconducting gate 4 increases (a). Here, the superconducting gate 3 is switched by the switch of the superconducting gate 3.
The current flowing through the superconducting gate 3
Is switched, and when the current flowing therethrough decreases, the superconducting gate 3 is reset from the voltage state to the superconducting state. This characteristic depends on the level of the input signal, the type of superconducting gate used, the damping resistance inserted in parallel with the superconducting gate, etc., so it is necessary to select an appropriate superconducting gate in consideration of the usage environment .

Next, in item T3, when the current of the DC power supply 1 is reduced, the current flowing through the superconducting gate 3 is further reduced to a negative value. This is because the circulating current flowing in the superconducting loop circuit 6 is reduced, so that there is no longer a canceling effect with the current of the superconducting loop circuit 7. At this time, the current circulating in the superconducting loop circuit 7 becomes a permanent current, and a stable current is supplied to the superconducting microstrip coil. At time T4, in order to cut off this current, a signal is input to the superconducting gates 3 and 4 to switch them. It can be seen that the current is reduced by the switches of both superconducting gates 3 and 4 (b, c).

Hereinafter, each component will be described in detail. FIG. 7 shows a schematic configuration diagram of a superconducting tunnel junction device 5 with a microstrip coil. Superconducting tunnel junction device 5
Are the superconducting ground plane 101 and the superconducting lower electrode 1
02, tunnel barrier 103, superconducting lower electrode 104,
A superconducting microstrip coil 105, a contact hole 106, and a superconducting wiring 107 are provided. A superconducting tunnel junction (102, 103, 104) is formed on a superconducting ground plane 101 via an insulating layer, and a superconducting microstrip coil 105 is formed thereon via an insulating layer. In this figure, a plurality (four) of superconducting microstrip coils are formed, but a single coil may be used. In the case of multiple superconducting microstrip coils, by connecting each coil in series and passing current,
Assuming that the number of coils is n, an n-fold magnetic field can be generated.

FIGS. 8 and 9 are sectional views (1) and (2) of the tunnel junction device 5 with a superconducting microstrip coil. 8 and 9 are cross-sectional views in parallel and perpendicular directions to the microstrip coil of FIG. 7, respectively. A superconducting lower electrode 102 and a tunnel barrier 103 are formed on a superconducting ground plane 101 via an insulating layer 108.
A superconducting tunnel junction composed of a superconducting upper electrode 104 is formed, and a microstrip coil 105 is disposed thereon with an insulating layer 109 interposed therebetween. The electric wiring of the superconducting upper electrode 104 is connected to the superconducting wiring 107 by providing a hole 106 in the insulating layer.

FIGS. 10 and 11 are explanatory diagrams (1) and (2) of a superconducting detector (Japanese Patent Application No. 10-250655).
No.). Numeral 31 denotes an inductance line disposed above the STJ element 1 via an insulating layer and magnetically coupled to the upper electrode 2, and 32 denotes a superconducting ground disposed above the substrate 5 via the insulating layer. It is plain. FIG. 3B is a view seen from above, and FIG. 10A is a cross-sectional view taken along line AA ′ of FIG. 10B.

FIG. 11 explains that the generated magnetic field is localized parallel to the STJ junction surface. When a current flows through the superconductor, the current concentrates on the superconductor surface due to the Meissner effect. In addition, when another superconductor (2) comes close to the superconductor (1) in which a current is flowing, the superconductor (1)
Superconductor (2) to cancel the magnetic field induced by the electric current
Current flows due to the mirror (mirror image) effect. First, Figure 1
As shown in the sectional view of FIG. 1B, when the current I1 flows through the inductance line 31 in the direction of the arrow, the current flows intensively on the lower surface of the inductance line 31 by the Meissner effect and the Miller effect. Therefore, a mirror current I2 opposite to the current I1 flows on the upper surface of the upper electrode 2 of the STJ. This mirror current returns to the lower surface of the STJ as a current I3 in the opposite direction.
Here, since the currents I1 and I2 flow in opposite directions and oppose each other, the same effect as when a coil is formed is obtained. As a result, the magnetic field due to the current I1 is generated between the inductance wire and the upper electrode of the STJ. Enclosed in the insulating layer (1), a magnetic field Φ1 is generated from the front to the rear of the drawing.

Similarly, the current I3 induces the current I4 through the tunnel barrier insulator 4 of the STJ1, and finally the current I6 is generated in the ground plane through the reverse current I5. Due to the currents I5 and I6, the magnetic field concentrates on the insulating layer (2) between the lower electrode and the ground plane, and a magnetic field Φ2 is generated from the front to the rear of the drawing. Further, a magnetic field Φ · 10 is generated in the tunnel barrier insulator between the upper electrode 2 and the lower electrode 3 in the direction from the rear to the front in the drawing by the currents I3 and I4. The presence of the ground plane reduces the inductance of the inductance line. Since the magnetic field is localized in the insulating layers (1) and (2) and the tunnel barrier insulator, it does not adversely affect other STJ elements. In the configurations shown in FIGS. 10 and 11, the magnetic field generated by the inductance line is increased by causing the inductance line 31 to return a plurality of times on the STJ element. When a ground plane is used, the inductance of the STJ magnetically coupled to the inductance line becomes small.

FIG. 12 is a sectional view of a ground plane hole type superconducting tunnel junction device with a microstrip coil. 10 and 11 (Japanese Patent Application No. 10-25065)
In the structure disclosed in No. 5), radiation such as X-rays is incident through a superconducting microstrip coil, but the energy of the radiation is reduced and the light level (1 ke) is obtained.
V or less), the coil cannot pass through, and the detection sensitivity decreases. As a method for preventing this, as shown in FIG. 16, a structure in which a ground plane is formed on the uppermost layer of a circuit, holes are formed in the ground plane, and radiation is incident on the ground plane is effective.

Next, FIG. 13 shows an equivalent circuit diagram of the superconducting gates 3 and 4. Here, a two-junction quantum interference gate is given as an example of a switching gate that can be used as a superconducting gate for turning on and off a superconducting current. This gate consists of two Josephson junctions (201,
202) and two inductances (203, 204) are connected in series to form a superconducting loop, and when the two inductances (205, 206) coupled to these inductances have a signal input Ic, a gate Is switched off and Ig is cut off. The dimensions are usually
For example, it is several tens of microns square.

FIG. 14 shows the superconducting gates 3 and 4 of FIG.
FIG. 4 shows a threshold characteristic diagram of a (two-junction type quantum interference gate).
The vertical axis indicates the controlled current Ig of the gate, and the horizontal axis indicates the control signal input current Ic. In the region below the curve in the figure, the superconducting gate is in a superconducting state and does not switch. Beyond this curve, the superconducting gate will switch off the superconducting current.

FIG. 15 is an explanatory view of a modification of the superconducting gate. Such a damping resistor inserted in parallel with the superconducting gate stabilizes the characteristics of the superconducting gate after switching to improve reproducibility, and determines the reset characteristic from the voltage state to the superconducting state. As the damping resistance is reduced, the switching speed generally becomes slower, the waveform becomes dull, and the stability increases, but the cutoff of the current is reduced and the remaining current is generated. When a magnetic coupling type gate such as a SQUID type or an in-line type is used as the superconducting gate, the subgap resistance changes depending on the input signal level, so that the residual current can be controlled.

FIG. 15A shows a superconducting gate having no damping resistance and its current-voltage characteristics. In this example, when the current is increased from the state of the center point of the current 0, a superconducting current due to the Josephson effect flows to the gate. When the current exceeds the Josephson critical current Ij, the gate switches and the state changes to a finite voltage Vg. When the current is further reduced, the current returns to the zero point in the resistance state. This process exhibits a hysteresis characteristic. Critical current when input signal Ic is input
It switches when Ij falls and becomes smaller than the bias current Ig. In the switch at this time, the switching operation is fast, but therefore, the waveform after the switch oscillates and may cause unstable operation. FIG. 15 (B)
When the damping resistor Rd is inserted in parallel with the superconducting gate as shown in the above, the current characteristic in a voltage state smaller than Vg is expanded, and the reset operation returning from the voltage state to the superconducting state becomes remarkable. As shown in FIG. 15C, the reset current value has a dependency that the reset current value decreases as the input signal Ic increases. Therefore, the residual current can be changed by changing the level of the input signal Ic. FIG.
The current-voltage characteristics of FIG. 3C show that the input signal Ic reduces the Ic and the reset current.

FIG. 16 shows a schematic configuration diagram of the superconducting transformer 2. In this example, a hole 304 is formed in the superconducting ground plane 303, a secondary coil 302 is formed therein, and a primary coil is formed thereon via an insulating layer. In the figure, as an example, a four-turn primary coil is formed. The hole in the ground plane is
This is to increase the inductance of the secondary coil so that a large induced voltage can be obtained.

FIG. 17 is a sectional view of the superconducting transformer 2. This figure shows a cross-sectional structure along the line AA ′ of the superconducting transformer 2 shown in FIG. Next, application examples of the present invention will be described.

FIG. 18 is an explanatory diagram of an application example of the present invention to a two-dimensional radiation detection circuit chip. Here, superconducting X
A superconducting tunnel junction device 302 having a 4-turn superconducting microstrip coil is attached to the line detecting chip 308.
Here is an example of the arrangement. Each superconducting tunnel junction element 302
Are connected in series in a spiral loop, and form a superconducting loop circuit with the superconducting gates 304 and 305 and the superconducting transformer 303. The output signal of each superconducting tunnel junction element 302 is subjected to data processing such as signal amplification, analog / digital conversion, and digital filtering by a Josephson signal processing circuit 306 integrated on a ground plane 307 on the same chip 308. Done. The superconducting ground plane acts as (1) good electromagnetic shielding, (2) superconducting mirror effect, and (3) ground point.

[0036]

According to the present invention, as described above, a radiation detector using a superconducting tunnel junction having a high speed and high energy resolution is provided, and in particular, a current is supplied to a superconducting strip line coupled to the superconducting tunnel junction itself. With regard to the method of suppressing Josephson current by flowing, a small initial current is given from the outside and a large magnetic field is generated inside,
Finally, a superconducting magnetic field generator and a superconducting detector that can generate a magnetic field without loss by using this superconducting permanent current can generate a magnetic field without loss in a state of being separated from the outside by the superconducting persistent current. Vessels can be provided.

According to the present invention, the Josephson current of the STJ is suppressed by the permanent current flowing in the superconducting closed loop circuit formed on the same chip, so that reproducibility and stability are excellent, low power consumption, and low noise. It is possible to provide a superconducting magnetic field generator and a superconducting detector provided with an array-compatible Josephson current suppression circuit. Also, according to the present invention,
By forming a superconducting magnetic field generator that generates an external magnetic field applied to the sensor STJ element using microfabrication technology on the same chip as the sensor STJ element so that the magnetic field is confined, the sensor STJ element It is possible to provide a superconducting magnetic field generator and a superconducting detector radiation detector capable of realizing, on the same chip, a conductive magnetism generator and a Josephson logic element for performing digital processing and the like.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a superconducting detector according to the present invention.

FIG. 2 is an explanatory diagram (1) of a circuit operation of the superconducting detector according to the present invention.

FIG. 3 is an explanatory diagram (2) of the circuit operation of the superconducting detector according to the present invention.

FIG. 4 is an explanatory view (3) of the circuit operation of the superconducting detector according to the present invention.

FIG. 5 is an explanatory diagram (4) of the circuit operation of the superconducting detector according to the present invention.

FIG. 6 is a diagram illustrating current control for a superconducting microstrip coil.

FIG. 7 is a schematic configuration diagram of a superconducting tunnel junction device 5 with a microstrip coil.

FIG. 8 is a sectional view (1) of a tunnel junction element 5 with a superconducting microstrip coil.

FIG. 9 is a sectional view (2) of the tunnel junction element 5 with a superconducting microstrip coil.

FIG. 10 is an explanatory view (1) of a superconducting detector.

FIG. 11 is an explanatory view (2) of a superconducting detector.

FIG. 12 is a cross-sectional view of a ground plane hole type superconducting tunnel junction device with a microstrip coil.

FIG. 13 is an equivalent circuit diagram of superconducting gates 3 and 4.

FIG. 14 is a threshold characteristic diagram of the superconducting gates 3 and 4 (two-junction quantum interference gate) of FIG.

FIG. 15 is an explanatory diagram of a modified example of a superconducting gate.

FIG. 16 is a schematic configuration diagram of a superconducting transformer 2.

FIG. 17 is a sectional view of a superconducting transformer 2;

FIG. 18 is an explanatory diagram of an application example of the present invention to a two-dimensional radiation detection circuit chip.

FIG. 19 is an explanatory diagram of the principle of a radiation detector using an STJ element.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 DC power supply 2 Superconducting transformer 3, 4 Superconducting gate 5 Superconducting tunnel junction element

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-61-41223 (JP, A) JP-A-61-263310 (JP, A) JP-A-59-28669 (JP, A) JP-A 57-263 167691 (JP, A) JP-A-7-273378 (JP, A) JP-A-60-15895 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01T 1/24 G01T 1 / 00 ZAA H01L 39/22 ZAA

Claims (5)

(57) [Claims] 1. A superconducting strip line coupled to a superconducting detection element, a first superconducting loop circuit connecting a first superconducting gate, and the superconducting strip line and a second superconducting gate. A second superconducting loop circuit connected in series; a primary coil connected to an external power supply;
And a superconducting transformer having a secondary coil connected in parallel with the loop circuit. 2. A superconducting tunnel junction element for detecting radiation, a superconducting strip line coupled to the superconducting detecting element, a first superconducting loop circuit connecting a first superconducting gate, and A second superconducting loop circuit in which a conductive strip line and a second superconducting gate are connected in series; a primary coil connected to an external power supply;
And a superconducting transformer having a secondary coil connected in parallel with the loop circuit. 3. A superconducting tunnel junction device comprising a plurality of superconducting tunnel junction elements, wherein said second superconducting loop circuit connects a plurality of said superconducting strip lines coupled to a plurality of superconducting tunnel junction elements in series. The superconducting magnetic field generator according to claim 1 or the superconducting detector according to claim 2. 4. Applying a direct current to a primary coil of the superconducting transformer, causing a current to flow through the first superconducting loop, and providing a control signal to a first superconducting gate to provide the first and second superconducting gates with a control signal. And setting a circulating current in the second superconducting loop circuit, reducing a direct current of the primary coil of the superconducting transformer, and generating a superconducting permanent circulating current in the second superconducting loop circuit. The superconducting magnetic field generator or the superconducting detector according to claim 1. 5. A superconducting permanent circulating current is cut off by simultaneously switching the first and second superconducting gates when a superconducting circulating current flows in the second superconducting loop circuit. The superconducting magnetic field generator or superconducting detector according to claim 4, characterized in that: