A chip signal coupling system for a metal magnetic calorimeter

Abstract

The application relates to a chip signal coupling system for a metal magnetic calorimeter, belonging to the technical field of nuclear radiation detection, which comprises an MMC detector chip and a SQUID amplifier chip, and signal coupling is realized between the MMC detector chip and the SQUID amplifier chip through a superconducting transformer structure; the MMC detector chip comprises two series-connected pickup coils, each pickup coil is covered with a flat plate type paramagnetic temperature sensor, an absorber is arranged on each paramagnetic temperature sensor, and the MMC detector chip adopts a differential connection mode to read the magnetic communication signal generated by the paramagnetic temperature sensor; the SQUID amplifier chip comprises a primary SQUID amplifier, the primary SQUID amplifier comprises a SQUID signal input coil and a SQUID superconducting ring, and the pickup coil of the MMC detector chip is superconductively connected with the SQUID signal input coil. The coupling system provided by the application can realize the transmission of the output signal of the magnetic calorimeter between different chips, so that the processing is convenient, and the transmission process is accurate and reliable.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of nuclear radiation detection, and particularly relates to a chip signal coupling system for a metallic magnetic calorimeter. BACKGROUND

[0002] Precise measurement of nuclear attribution in nuclear materials, homeland security, environmental protection, nuclear medicine and nuclear non-proliferation relies on the differentiation of energy similar gamma ray analysis, wherein it is difficult to achieve high accuracy and high resolution measurement of low-energy gamma nuclides with characteristic energy on the Compton platform using existing traditional detection technology, and it is difficult to detect the weak difference between isotope composition. The low-energy gamma ray detection technology based on a superconducting quantum interference device (SQUID) can solve the problem and expand the lower limit of detection and improve the low-energy gamma nuclide radioactivity measurement capability.

[0003] The pickup coil in the MMC detector chip has the functions of providing a magnetic field and picking up an induced current, and the current generated in the pickup coil is amplified by the SQUID amplifier chip and finally converted into a voltage-level output voltage. However, during the connection between the detector chip and the SQUID amplifier chip, it will be affected by various factors, thereby affecting the readout accuracy. SUMMARY

[0004] To solve the defects in the prior art, the purpose of the present application is to provide a chip signal coupling system for a metallic magnetic calorimeter, which can transmit the output signal of the magnetic calorimeter between different chips, and ensure the accuracy and reliability of the transmission process while facilitating processing.

[0005] To achieve the above purpose, a technical solution adopted by the present application is as follows:

[0006] A chip signal coupling system for a metallic magnetic calorimeter, comprising an MMC detector chip and a SQUID amplifier chip, wherein:

[0007] The MMC detector chip comprises two multiplexed pickup coils connected in series, and each pickup coil is covered with a flat panel paramagnetic temperature sensor, and each paramagnetic temperature sensor is provided with an absorber, which is used to convert the energy of incident particles into heat energy, and the heat energy causes the temperature rise of the paramagnetic temperature sensor to change the magnetization state of the paramagnetic temperature sensor, thereby generating a magnetic communication signal; the MMC detector chip reads the magnetic communication signal in a differential connection mode between the two pickup coils;

[0008] The SQUID amplifier chip comprises a primary SQUID amplifier, the primary SQUID amplifier comprises a SQUID signal input coil and a SQUID superconducting ring, and the pickup coil of the MMC detector chip is connected with the SQUID signal input coil;

[0009] The signal coupling between the MMC detector chip and the SQUID amplifier chip is realized through a superconducting transformer structure, the primary coil of the superconducting transformer structure is the pickup coil of the MMC detector chip, and the secondary coil is the SQUID signal input coil.

[0010] Further, the chip signal coupling system for the metal magnetic calorimeter as described above, the primary SQUID amplifier is used to convert the magnetic communication signal transmitted by the pickup coil into a voltage signal of the order of 100 microvolts to millivolts.

[0011] Further, the chip signal coupling system for the metal magnetic calorimeter as described above, the pickup coil of the MMC detector chip is connected with the SQUID signal input coil through a superconducting aluminum wire.

[0012] Further, the chip signal coupling system for the metal magnetic calorimeter as described above, the SQUID amplifier chip further comprises a secondary SQUID series array amplifier, the primary SQUID amplifier and the secondary SQUID series array amplifier together constitute a two-stage SQUID amplification circuit, and the secondary SQUID series array amplifier is used to further amplify the voltage signal transmitted by the primary SQUID amplifier into a signal of the order of hundreds of millivolts to volts, and then deliver it to the room temperature electronics module.

[0013] Further, the chip signal coupling system for the metal magnetic calorimeter as described above, the secondary SQUID series array amplifier comprises a plurality of SQUID amplifiers connected in series, the coupling of the superconducting ring of each SQUID amplifier with its input coil, the coupling of the superconducting ring with its feedback coil, and the critical current are consistent, so that the magnetic flux-voltage characteristic of the secondary SQUID series array amplifier is similar to that of a single SQUID amplifier.

[0014] Further, the chip signal coupling system for the metal magnetic calorimeter as described above, the multiplexed pickup coil is a flat plate type multiplexed pickup coil, and the material is niobium.

[0015] Further, the chip signal coupling system for the metal magnetic calorimeter as described above, the primary SQUID amplifier and the secondary SQUID series array amplifier are prepared on the same chip.

[0016] The chip signal coupling method for the metal magnetic calorimeter has the following remarkable technical effects:

[0017] 1. The MMC detector chip adopts two multiplex pickup coils in series, and a differential connection mode is adopted to pick up signals from the two, so that the excitation current does not pass through the SQUID coil, and saturation of the SQUID caused by the excitation current is avoided.

[0018] 2. The pickup coil of the detector chip and the signal input coil of the SQUID amplifier are coupled through a superconducting transformer structure, and a two-stage SQUID amplifier circuit is constructed by using a SQUID series array amplifier, which has the advantages of simple structure, high system reliability, low readout noise and large signal bandwidth. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 A structural schematic diagram of a chip signal coupling system for a metal magnetic calorimeter provided in an embodiment of the present application;

[0020] Figure 2 An equivalent circuit model of the two series multiplex pickup coils of the MMC detector chip;

[0021] Figure 3 A superconducting transformer coupling principle diagram between the MMC detector chip and the SQUID amplifier chip;

[0022] Figure 4 A two-stage SQUID amplifier circuit diagram of the SQUID amplifier. DETAILED DESCRIPTION

[0023] The present application will be further described below in combination with specific embodiments and the accompanying drawings of the specification.

[0024] In view of the problem that the metal magnetic calorimeter mentioned in the background art is affected by various factors during the connection process of the detector chip and the SQUID amplifier chip, thereby affecting the readout precision, the present application provides a chip signal coupling system for a metal magnetic calorimeter, which has the advantages of simple structure, high system reliability and low readout noise.

[0025] Figure 1 A structural schematic diagram of a chip signal coupling system for a metal magnetic calorimeter provided in an embodiment of the present application, the coupling system comprising an MMC detector chip 100 and a SQUID amplifier chip 200, the MMC detector chip 100 and the SQUID amplifier chip 200 being coupled through a superconducting transformer structure, and a magnetic communication signal output by the MMC detector chip 100 being measured by the SQUID amplifier chip 200.

[0026] The MMC detector chip 100 comprises two multiplexed pick-up coils 110 connected in series, each of which is covered with a flat plate type paramagnetic temperature sensor, and each of the paramagnetic temperature sensors is provided with an absorber, which maintains good thermal contact with the paramagnetic temperature sensor. The materials and structures of the absorbers are different for different detection objects, but the main function is to convert the energy of the incident particles into heat energy; the heat energy causes the temperature rise of the paramagnetic temperature sensor, which changes the magnetization state of the paramagnetic temperature sensor, thereby generating a magnetic communication signal; and the magnetic communication signal is read by adopting a differential connection mode between the two pick-up coils 110, and a stable magnetic field is generated. Figure 2 An equivalent circuit model of the two multiplexed pick-up coils 110 connected in series is shown, L1 and L2 represent the inductance of the two multiplexed pick-up coils 110, TP_S1 and TP_S2 are two output points for picking up the magnetic communication signal, and TP_I1 and TP_I2 are two input points for superconducting current. In the stable working state, the superconducting current flows through L1-L2-L_Nb_Bypass to form a closed superconducting loop, and since the loop is completely in the superconducting state, the superconducting excitation current remains constant. The electromagnetic field of L1 and L2 is coupled with the paramagnetic temperature sensor located on the upper part thereof, and the magnetic force lines generated by the multiplexed pick-up coil 110 pass through the sensitive area of the paramagnetic temperature sensor and are coupled therewith. This structure has many advantages, such as the complete coincidence of the pick-up coil magnetic field and the excitation coil electromagnetic field, and the necessary bias magnetic field of the paramagnetic temperature sensor is generated by the continuous current in the two snakelike loops, so that an external excitation coil is not needed; the stable excitation current does not pass through the SQUID coil, avoiding the saturation of the SQUID caused by the excitation current.

[0027] In a specific embodiment of the present application, the multiplexed pick-up coil 110 is a flat plate type snakelike multiplexed pick-up coil 110, and the material is niobium.

[0028] The SQUID amplifier chip 200 adopts a two-stage SQUID amplification circuit comprising a primary SQUID amplifier 210 and a secondary SQUID series array amplifier 220, and the primary SQUID amplifier 210 is connected with the MMC detector chip 100. Figure 4 A schematic diagram of the two-stage SQUID amplification circuit of the SQUID amplifier chip 200 is shown, the primary SQUID amplifier 210 serves as a very sensitive magnetic flux-voltage converter, which is responsible for converting the magnetic communication signal transmitted by the multiplexed pick-up coil 110 into a voltage signal of the order of hundreds of microvolts to millivolts; and the secondary SQUID series array amplifier 220 is responsible for further amplifying the voltage signal transmitted by the primary SQUID amplifier 210 into a signal of the order of hundreds of millivolts to volts, and then delivering it to the room temperature electronics module.

[0029] The primary SQUID amplifier 210 comprises a SQUID signal input coil 211 and a SQUID superconducting ring 212, and the multiplexed pickup coil 110 of the MMC detector chip 100 is connected in parallel with the SQUID signal input coil 211. As shown in Figure 3 Fig. 1, the MMC detector chip 100 and the SQUID amplifier chip 200 are connected through a superconducting transformer structure, the primary coil of the superconducting transformer structure is the multiplexed pickup coil 110 of the MMC detector chip, the secondary coil is the SQUID signal input coil 211 of the primary SQUID amplifier, and the two are connected through a superconducting aluminum wire, thereby forming a superconducting transformer, and Ls represents the inductance of the SQUID signal input coil. The magnetic communication signal δΦ generated by the MMC detector chip is transmitted to the SQUID signal input coil 211 of the primary SQUID amplifier through the multiplexed pickup coil 110, and then coupled into the SQUID superconducting ring 212 through the coupling inductance M is between the SQUID signal input coil 211 and the SQUID superconducting ring 212, to generate a corresponding output voltage signal δU. In order to optimize the signal amplitude, L1 = L2 = Ls should be satisfied.

[0030] Since the output voltage of a single SQUID device is very low, generally only a few tens of microvolts, and its impedance is only a few ohms, it is difficult to match the impedance with a commonly used semiconductor voltage amplifier. In order to solve this problem, the present application uses a SQUID series array as a secondary amplifier in a two-stage SQUID amplification circuit. The secondary SQUID series array amplifier is composed of a plurality of SQUID devices, and through optimized design, the coupling between the superconducting ring and the input coil of each SQUID amplifier in the array, the coupling between the superconducting ring and the feedback coil thereof, and the critical current are all consistent, so that the magnetic flux-voltage characteristic of the entire secondary SQUID series array amplifier is similar to that of a single SQUID amplifier. The advantage of the SQUID series array lies in that its output voltage can reach the order of hundreds of microvolts or even millivolts, and its output impedance can reach the order of hundreds of ohms, so it is easy to match with a room-temperature semiconductor amplifier; at the same time, due to its excellent noise characteristic, the signal bandwidth of the entire SQUID amplifier chip can reach the level of megahertz, which is much higher than the bandwidth of the feedback control circuit constructed by using a phase-locked amplifier in the past.

[0031] As to why not directly using SQUID array amplifier to read the signal of MMC probe, it is because the power consumption of SQUID array amplifier is generally much larger than that of single primary SQUID device. If the SQUID array is directly coupled with the MMC probe chip, the heat and electromagnetic radiation generated during operation (typical power consumption of SQUID array is about 10nW order of magnitude) will have a greater adverse effect on the operation of the MMC probe. Therefore, the application uses a low-power (100pW level), low-noise primary SQUID amplifier to couple with the MMC probe chip, and uses a SQUID series array amplifier to construct a two-stage SQUID amplification circuit.

[0032] In the application, the primary SQUID amplifier 210 and the secondary SQUID series array amplifier 220 are prepared on the same chip, thereby improving the integration of the system and being more conducive to the electromagnetic shielding design of the MMC probe chip and the SQUID amplifier chip periphery, thereby reducing the influence of environmental electromagnetic radiation on the performance of the probe.

[0033] The application provides a chip signal coupling system for a metal magnetic calorimeter, adopts two multiplex pickup coils in series, and takes a differential connection between the two to pick up signals, so that the excitation current does not pass through the SQUID coil, avoiding the excitation current from saturating the SQUID; the pickup coil of the magnetic calorimeter probe chip and the signal input coil of the SQUID amplifier chip are coupled through a superconducting transformer structure, and a two-stage SQUID amplification circuit is constructed by using a SQUID series array amplifier, which has the advantages of simple structure, high system reliability, low readout noise, and large signal bandwidth.

[0034] The above embodiments are only illustrative of the application, and the application can be implemented in other specific ways or other specific forms without departing from the spirit or essential characteristics of the application. Therefore, the described embodiments should be considered illustrative rather than limiting in any aspect. The scope of the application should be illustrated by the appended claims, and any changes equivalent to the intent and scope of the claims should be included in the scope of the application.

Claims

1. A chip signal coupling system for a metal magnetic calorimeter, characterized by, The system comprises an MMC detector chip (100) and a SQUID amplifier chip (200), wherein: The MMC detector chip (100) comprises two multiplexed pick-up coils (110) connected in series, each of which is covered with a planar paramagnetic temperature sensor, and each of the paramagnetic temperature sensors is provided with an absorber for converting the energy of incident particles into heat energy, which causes the paramagnetic temperature sensor to be magnetized and the temperature of the paramagnetic temperature sensor to rise, thereby generating a magnetic communication signal; the MMC detector chip reads the magnetic communication signal in a differential connection mode between the two multiplexed pick-up coils (110). The SQUID amplifier chip (200) comprises a primary SQUID amplifier (210), which comprises a SQUID signal input coil (211) and a SQUID superconducting ring (212), and the multiplexed pick-up coil (110) of the MMC detector chip (100) is connected to the SQUID signal input coil (211). The MMC detector chip (100) and the SQUID amplifier chip (200) are coupled through a superconducting transformer structure, the primary coil of the superconducting transformer structure being the multiplexed pick-up coil (110) of the MMC detector chip, and the secondary coil being the SQUID signal input coil (211).

2. The chip signal coupling system for a metal magnetic calorimeter according to claim 1, characterized in that, The primary SQUID amplifier (210) is used to convert the magnetic communication signal transmitted by the multiplexed pick-up coil (110) into a voltage signal of the order of 100 microvolts to millivolts.

3. The chip signal coupling system for a metallic magnetic calorimeter according to claim 1 or 2, characterized in that, The multiplexed pick-up coil (110) of the MMC detector chip (100) is connected to the SQUID signal input coil (211) through a superconducting aluminum wire.

4. The chip signal coupling system for a metal magnetic calorimeter according to claim 3, characterized in that, The SQUID amplifier chip (200) further comprises a secondary SQUID series array amplifier (220), and the primary SQUID amplifier (210) and the secondary SQUID series array amplifier (220) together constitute a two-stage SQUID amplification circuit, and the secondary SQUID series array amplifier (220) is used to further amplify the voltage signal transmitted by the primary SQUID amplifier (210) into a signal of the order of hundreds of millivolts to volts, and then deliver it to a room-temperature electronics module.

5. The chip signal coupling system for a metal magnetic calorimeter according to claim 4, wherein, The secondary SQUID series array amplifier (220) comprises a plurality of SQUID amplifiers connected in series, and the coupling of the superconducting ring of each SQUID amplifier to its input coil, the coupling of the superconducting ring to its feedback coil, and the critical current are all consistent, so that the flux-voltage characteristic of the secondary SQUID series array amplifier is similar to that of a single SQUID amplifier.

6. The chip signal coupling system for a metal magnetic calorimeter according to claim 5, wherein, The multiplexed pick-up coil (110) is a planar serpentine multiplexed pick-up coil made of niobium.

7. The chip signal coupling system for a metal magnetic calorimeter according to any one of claims 4-6, characterized in that, The primary SQUID amplifier (210) and the secondary SQUID series array amplifier (220) are prepared on the same chip.

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