JPS631251Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a magnetic flux detector, and more specifically, the present invention relates to a magnetic flux detector. The present invention relates to a magnetic flux detector.

Figure 1 is a diagram explaining the principle of a conventional magnetic flux detector, Figure 2
The figure is an equivalent circuit diagram of Figure 1, in which 1 is a pickup coil, 2 is a superconducting wire, 3a, 3b, 3
c is a trimming coil, 4 is an input coil,
5 is Squid. In addition, pick-up coil 1, superconducting wire 2, trimming coils 3a, 3b,
3c, input coil 4, and squid 5
is placed in a dewar filled with liquid helium to maintain its superconducting state. In FIG. 1, when a magnetic flux Φx coming from the outside tries to enter the pick-up coil 1, a shielding current i flows through the pick-up coil 1, and the pick-up coil 1 and the magnetic flux transformer pass through the superconducting wire 2 and trimming coils 3a, 3b, and 3c. The shielding current i flows through the input coil 4 constituting the input coil 4 to generate a magnetic flux Φs, which is transmitted to the SQUID 5 as a signal. The pick-up coil 1 is differentially connected to cancel magnetic noise from a distance and detect magnetic signals from a short distance with high sensitivity. It is not limited to a secondary gradient type magnetic flux coil, and various modifications are possible within the range of the configuration that can cancel external magnetic noise. For example, a secondary gradient type magnetic flux coil having four partial coils is possible. It may be. By the way, the ability of the pick-up coil 1 to cancel out external magnetic noise is affected by the dimensional accuracy during manufacturing and the magnetic field near the coil, but it is extremely difficult to eliminate the above-mentioned dimensional errors and distortion of the magnetic field. Therefore, a method of compensating for the above-mentioned dimensional errors and distortion of the magnetic field has been adopted using trimming coils 3a, 3b, and 3c as shown in FIG.

However, the trimming coils 3a, 3b, 3c
Even if the above-mentioned dimensional error and magnetic field distortion can be compensated for by using the trimming coils 3a, 3b, 3c,
There has been an inconvenience in that the ability to cancel the magnetic noise is adversely affected by dimensional errors in manufacturing. In addition, trimming coils 3a, 3b,
The trimming coils 3c often lose their balance during manufacture, and there is also the inconvenience that it is necessary to spend a lot of time adjusting the trimming coils 3a, 3b, and 3c when manufacturing the magnetic flux detector. That is, while considering the external magnetic noise that changes over time, the trimming coils 3a, 3b, and 3c are adjusted to balance points in the horizontal axis direction (x direction), vertical axis direction (y direction), and vertical axis direction (z direction), respectively. It was necessary to spend a lot of time and make adjustments through trial and error in order to find the correct value.

The present invention has been devised in view of these drawbacks, and its purpose is to provide a magnetic flux detector that allows accurate and rapid adjustment of the main body of the device even in the presence of external magnetic noise that changes over time.

A feature of the present invention is that a remotely controllable superconducting switch is provided between the pick-up coil that detects external magnetic flux in the magnetic flux detector and the trimming coil that compensates for errors in the detection signal of the pick-up coil. The trimming coils are connected in series or each independently to a pickup coil and an input coil constituting a magnetic flux transformer via superconducting wires.

Hereinafter, the present invention will be explained in detail using figures. FIG. 3 is an explanatory diagram of the principle represented by an equivalent circuit showing one embodiment of the present invention. In the figure, 6 is a superconducting switch, and A, B, C, and D are terminals of the superconducting switch. . Further, in FIG. 3, the same symbols as in FIG. 2 are used with the same meanings, and the explanations here will be omitted. The superconducting switch 6 is a commercially available general switch made of superconducting metal (for example, Nb,
The wire plated with Ta, Pd, etc.) is used, but various modifications are possible as long as the circuit connection in the superconducting state can be done remotely. For example, when superconducting wires are connected and compared to an adapter made of soft superconducting metal (e.g. white metal)
A superconducting wire that has a switch function by inserting and removing a plug made of Nb, or a superconducting wire that has a coil-shaped heater wound around a superconducting wire with a temperature-dependent resistance value and turns the heater on and off. It is also possible to provide a switch function by applying a change in resistance value based on a thermal change. In addition, a superconducting switch here refers to a switch that can connect a circuit in a superconducting state, and has zero electrical resistance when switched on and a finite value when switched off. In the invention, the dewar is configured to be remotely controllable from outside via a lead wire or the like.

In the embodiment of the present invention having the above configuration, when the terminal A of the superconducting switch 6 is first connected to the terminal D, the pick-up coil 1 is short-circuited and only the signals from the trimming coils 3a, 3b, and 3c are superconducting. The signal is transmitted to the SQUID 5 via the input coil 4. In this state, an adjustment signal that is sufficiently large compared to the magnetic fields of the trimming coils 3a, 3b, and 3c and provides a uniform magnetic field to the trimming coils (for example, a signal such as an artificial magnetic field generated by a simple hand-wound coil) ), a sine wave magnetic signal is supplied independently in each of the x direction, y direction, and z direction, and each trimming coil is sequentially adjusted so that the sine wave output from the trimming coil is minimized. .

Next, when the terminal C in the superconducting switch 6 is connected to the terminal D, the trimming coils 3a, 3
b and 3c are short-circuited, and only the signal from the pickup coil 1 is transmitted to the SQUID 5 via the superconducting wire 2 and the input coil 4. In this state, the pick-up coil 1 is checked for dimensional errors in manufacturing and distortion of the magnetic field near the coil, and necessary measures are taken (for example, if it is possible to remove anything that is distorting the magnetic field near the coil, remove it, etc.) .

Thereafter, terminal B of superconducting switch 6 is connected to terminal D. In this state, the pick-up coil 1 is connected to the superconducting wire 2 and the trimming coil 3.
It is connected to the input coil 4 via a, 3b, and 3c, and the amount that cannot be adjusted by adjusting the pickup coil 1 and the trimming coils 3a, 3b, and 3c alone is checked. Since the unadjusted amount is often very small, the final adjustment can then be easily made in a short time by readjusting the trimming coils 3a, 3b, and 3c.

According to the embodiment of the present invention as described in detail above, it is no longer necessary to adjust the magnetic flux detector, which took a long time to eliminate the influence of external magnetic noise on the pickup coil 1 in the conventional example. , trimming coils 3a, 3 using signals such as an artificial magnetic field generated from a simple hand-wound coil, etc.
There is an advantage that the adjustment of b and 3c can be easily performed even individually, and as a result, the magnetic flux detector can be adjusted easily and in a short time. Further, according to the embodiment of the present invention, unlike the conventional example, the pick-up coil 1 and the trimming coils 3a, 3b, and 3c can each be adjusted independently, making it easier to determine the adjustment range and increasing the speed of each adjustment process. There is also the advantage of being able to do so. Furthermore, since the magnetic flux detector can be easily adjusted and the adjustment time is shortened, there is also the advantage that the amount of liquid helium consumed in the dewar in which the pickup coil 1 and the like are housed can be reduced.

[Brief explanation of the drawing]

Figure 1 is a diagram explaining the principle of a conventional magnetic flux detector, Figure 2
This figure is an equivalent circuit diagram of FIG. 1, and FIG. 3 is an equivalent circuit diagram showing an embodiment of the present invention. 1...Pick-up coil, 2...Superconducting wire,
3a, 3b, 3c...trimming coil, 4...
Input coil, 5...SQUID, 6...Superconducting switch.

Claims (1)

[Claims for Utility Model Registration] 1. In a magnetic flux detector that detects magnetic flux by utilizing the fact that a superconductor including a Josefson junction shows a response to external magnetic flux changes using magnetic flux quanta as a unit of operation, a pickup coil for detecting the magnetic flux of the pickup coil; an input coil that constitutes a magnetic flux transformer via the pickup coil and a superconducting wire; and an input coil for detecting the magnetic flux of the pickup coil and a trimming coil connected in series with the input coil to compensate for errors in the detection signal of the pickup coil; and a superconducting switch that is remotely controllable and connects either or both of the pickup coil and the trimming coil to the input coil. A magnetic flux detector comprising: 2. The superconducting switch has two states: the pick-up coil and the trimming coil are connected in series and connected to the input coil, and the pick-up coil and the trimming coil are individually connected to the input coil. Utility model registration claim No. (1) that is configured to alternately switch between
Magnetic flux detector described in section.