CN102023268A - Device and method for measuring quench propagation velocity of superconducting coil - Google Patents

Abstract

The device for measuring the quench propagation velocity of a superconducting coil of the present invention realizes a certain background magnetic field through a back-field superconducting magnet (4), and uses a refrigerator (2) and a low-temperature liquid to provide two low-temperature working environments. The superconducting coil (5) to be tested is installed in the cryogenic container (8). The tested superconducting coil (5) includes the tested superconducting coil sparsely wound part (15) and the tested superconducting coil densely wound part (16), which are respectively used to measure the measured superconducting coil (5) along the wire direction. The quench propagation velocity and the quench propagation velocity in the radial direction. The device can realize the measurement of the quench propagation speed of the superconducting coil in the two-dimensional direction, and the measurement is accurate.

Description

Device for Measuring Quench Propagation Velocity of Superconducting Coil and Its Measuring Method

technical field

The invention relates to a device for measuring the quench propagation speed of a superconductor and a measuring method thereof, in particular to a device for measuring the quench propagation speed of a superconducting coil and a measuring method thereof.

Background technique

The continuous development of superconducting materials and low-temperature technology has made superconducting magnets more and more widely used in electric power, medicine, industrial processing, scientific exploration and military fields. The demand for modernization has greatly improved the performance and precision of various equipment.

During the design and manufacture of superconducting magnets, various stabilization methods are usually adopted to improve the stability of the magnet operation. However, due to the influence of factors such as magnetic flux jump, coil vibration, wire movement, epoxy impregnation cracking, thermal interference, power output voltage ripple, etc., the local temperature of the superconductor may rise and a normal state region appears, that is, a quench occurs. Phenomenon. After the superconductor is partially quenched, the normal state region may shrink and gradually return to the superconducting state, or may continue to expand to cause quench propagation, which is closely related to the trigger energy, working conditions and cooling environment. The current of a superconducting magnet is very large. If the superconducting magnet is quenched, it will be accompanied by a series of problems such as overvoltage and heat generation, which may cause breakdown of the magnet insulation material. Severe local temperature rise will cause wire insulation and coil The joints are melted, causing the magnets to malfunction or even burn out. Therefore, the electrical and thermal properties of quench (normal region) propagation are an important issue that must be considered in the application of superconducting magnets. Quench propagation characteristics mainly include quench propagation velocity and minimum quench energy, etc., which are very important parameters for judging the stability of superconductors. Accurate testing of quench propagation characteristics provides important parameters for the design of superconducting magnets and quench protection control in accordance with.

In general, the quench propagation velocity of high-temperature superconductors is on the order of cm/s, which is two to three orders of magnitude slower than that of low-temperature superconductors. This is mainly due to the fact that high-temperature superconductors have high heat capacity and high critical temperature, and to some extent the stability of high-temperature superconductors is better than that of low-temperature superconductors. But on the other hand, if the propagation in the normal region is too slow, hot spots will form locally in the superconductor, and the heat will only spread in a small range. If the quench protection is not handled properly, the magnet will burn out due to the heat not being released quickly, resulting in permanent damage. Therefore, no matter what kind of superconducting material is used, it is necessary to measure the quench propagation velocity of the superconducting material, that is, the propagation velocity of Joule heat in the local normal region along the line (strip) material. Only by having a sufficient understanding of the quench behavior of the superconducting materials used and mastering the quench propagation characteristics of superconductors can we lay a solid guarantee for the stability design, quench detection and protection of superconducting magnets, and improve the operation stability of superconducting magnets and security.

The operation stability of a high-field superconducting magnet is an important and indispensable engineering index for the use of superconducting scientific instruments, and the quench propagation speed of a superconductor is one of the important factors determining the stability of a superconducting magnet. Therefore, it is necessary to accurately measure the quench propagation velocity and the minimum quench energy of superconductors through specific test equipment. Most of the currently disclosed devices and methods for measuring the quench propagation velocity measure a section of superconducting wire (ribbon) material sample, and only measure the one-dimensional quench propagation velocity along the direction of the wire. In practical application, the superconducting wire (tape) material should be wound into a superconducting coil to form a superconducting magnet, and the quench propagation not only propagates along the wire direction of the superconducting wire (tape) material, but also along the diameter of the wire (tape) material ( Horizontal) propagates in the same direction. Therefore, the quench propagation characteristics of superconducting magnets can be more accurately analyzed only by simulating the actual superconducting coil under the back field to measure the quench propagation velocity in two-dimensional or even three-dimensional directions.

Contents of the invention

The purpose of the present invention is to overcome the shortcoming that the existing measuring devices mostly measure short samples of a section of superconducting wire or strip under zero field, and can only measure the one-dimensional quench propagation velocity along the direction of the wire, and provide a quench propagation velocity The measurement device, which is equipped with a refrigerator, can measure the quench propagation velocity of the superconducting coil in the two-dimensional direction under the background magnetic field. The device can not only meet the requirements of measuring the quench propagation velocity of various superconducting coils under the background magnetic field, but also realize two low-temperature working environments of direct conduction cooling and low-temperature liquid immersion cooling, and the measurement of quench propagation velocity is more accurate.

The device for measuring the quench propagation velocity of superconducting coils of the present invention includes a Dewar container, a refrigerator, a back field superconducting magnet, a superconducting coil to be tested, a cryogenic container, a heating wire, a current lead, a measuring lead, a cooling belt, and an infusion tube , air return pipe and epoxy rod.

The back-field superconducting magnet is installed in the Dewar container of the present invention, and the back-field superconducting magnet is a high-temperature superconducting magnet. The cold shield of the container reduces the fabrication and installation of the cold shield of the measuring device. A refrigerator is installed at the center of the upper end of the Dewar container, and the top of the back field superconducting magnet is connected to the upper end of the Dewar container through an epoxy tie rod, and the back field superconducting magnet is powered to generate the required energy through the current lead of the back field superconducting magnet. The background magnetic field, the magnetic field strength can reach 1-5T.

The low-temperature container of the present invention is connected to the lower end of the secondary cold head of the refrigerator, and the superconducting coil to be tested is installed inside the low-temperature container. If the superconducting coil to be tested is in a vacuum environment when it is working, it can be refrigerated by a refrigerator to make the cryogenic container reach the required low temperature. If the superconducting coil to be tested is immersed in a low-temperature liquid environment during operation, the low-temperature liquid can be fed into the low-temperature container through the infusion tube. If the superconducting coil under test is a high-temperature superconducting coil, liquid nitrogen is input into the cryogenic container; if the superconducting coil under test is a low-temperature superconducting coil, liquid helium is input into the cryogenic container, and the liquid vapor is discharged through the gas return pipe. The infusion pipe and air return pipe are symmetrically arranged on the upper end of the cryogenic container and connected with the upper cover plate of the cryogenic container. The upper cover plate of the cryogenic container is also connected with a current lead wire of the superconducting coil under test and a measurement lead wire of the superconducting coil under test.

The tested superconducting coil of the present invention includes a tested superconducting coil sparsely wound part and a tested superconducting coil densely wound part, and is wound on the wire between the tested superconducting coil sparsely wound part and the tested superconducting coil densely wound part Heating wire. The heating wire is a manganin wire with a resistance of 10-50 ohms. The heating wire is powered by a pulsed current source. The superconducting coil under test is connected with a pair of current leads of the superconducting coil under test, and is powered by a DC power supply. A pair of sparsely wound part measurement lead wires 1 and a pair of sparsely wound part measurement lead wires 2 are welded on the wires of the sparsely wound part of the superconducting coil to be tested; Lead one and a pair of tightly wound part measurement leads two. The distance between the first measurement lead wire of the sparsely wound part and the second measurement lead wire of the sparsely wound part along the wire direction is L ₁ , and the distance between the two leads of each pair of sparsely wound part measurement leads along the direction of the wire is _L2 . The distance between the measurement lead wire 1 of the densely wound part and the measurement lead wire 2 of the densely wound part along the wire direction is S. The distance between the two leads of each pair of sparsely wound part measuring leads along the wire direction is d. The wire diameter or width of the superconducting coil to be tested is d. Measure the quench propagation velocity along the length direction of the wire through two pairs of sparsely wound measuring leads of the tested superconducting coil, and measure the quench along the radial direction of the wire through two pairs of closely wound measuring leads of the tested superconducting coil transmission speed.

In order to more accurately measure the quench propagation velocity along the wire radial direction, the diameter of the superconducting coil to be tested is 40-60 times larger than the diameter of the wire of the superconducting coil to be tested. The tested superconducting coil is wrapped with low-temperature epoxy glue to maintain the heat insulation effect of the superconducting coil. The thickness of the low-temperature epoxy glue is 5-10mm.

In the present invention, two pairs of sparsely wound part measuring leads and two pairs of densely wound part measuring leads are connected to a multi-channel data acquisition instrument, and the voltage of each pair of measuring leads at each moment is measured by the multi-channel data acquisition instrument. The difference between the time of 0.5 times the maximum voltage generated by a pair of sparsely wound measuring leads adjacent to the heating wire and the time of 0.5 times the maximum voltage generated by the other pair of sparsely wound measuring leads is recorded as t1. The difference between the time of 0.5 times the maximum voltage generated by a pair of closely wound measuring leads adjacent to the heating wire and the time of 0.5 times the maximum voltage generated by another pair of closely wound measuring leads is recorded as t2.

The measuring method step sequence of the present invention is:

1. First, energize the background superconducting magnet to form a background magnetic field of a certain size, and energize the measured superconducting coil under the background magnetic field, and the current size is equal to 0.8-0.95 times the critical current value of the superconducting wire (tape) material;

2. The heating wire is energized, and when a certain amount of heat is generated, the quenching of the superconducting coil under test is triggered;

3. Use the multi-channel data acquisition instrument to measure the voltage, record the time of 0.5 times the maximum voltage generated by the measurement lead 1 of the sparse winding part and the measurement lead 2 of the sparse winding part respectively, and record the difference between the two times as t1. In addition, record the time of 0.5 times the maximum voltage generated by the two pairs of closely wound measuring leads respectively, and record the difference between the two times as t2;

4. The quench propagation velocity of the superconducting coil under test along the direction of the wire is measured as (L1+L2)/t1 through the measurement lead wire 1 of the sparsely wound part and the measurement lead wire 2 of the sparsely wound part, and the measurement lead wire 1 and The second measuring lead wire of the densely wound part measures and obtains that the quench propagation velocity of the superconducting coil (5) under test along the radial direction of the wire is (2d+S)/t2.

The measuring device is equipped with a refrigerator for cooling, which can realize a background magnetic field of a certain size, and can also measure high-temperature superconducting coils or low-temperature superconducting coils in a vacuum low-temperature environment and a low-temperature liquid immersion environment. It can not only measure the quench propagation velocity in the wire direction, but also measure the quench propagation speed in the radial direction of the wire, and the measurement is more accurate.

Description of drawings

Figure 1 Schematic diagram of the measuring device, in the figure: 1 Dewar container, 2 refrigerator, 3 epoxy rod, 4 back field superconducting magnet, 5 tested superconducting coil, 6 conductive cold belt, 7 back field superconducting magnet current lead , 8 low-temperature container, 9 low-temperature epoxy glue, 10 heating wire, 11 infusion tube, 12 air return tube, 13 current lead of the superconducting coil under test, 14 measurement lead of the superconducting coil under test;

Fig. 2 Schematic diagram of the superconducting coil to be tested, in the figure: 15 the sparsely wound part of the tested superconducting coil, 16 the densely wound part of the tested superconducting coil, 17 the measurement lead wire 1 of the sparsely wound part, 18 the measurement lead wire 2 of the sparsely wound part, 19 densely wound part The first winding part of the measurement lead wire, the 20 densely wound part of the measurement lead wire two, the 21 tested superconducting coil power supply, and the 22 multi-channel data acquisition instrument.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

As shown in Figure 1, the upper cover of the Dewar vessel 1 is equipped with a refrigerator 2, the back field superconducting magnet 4 is connected to the upper cover through an epoxy tie rod 3, and the back field superconducting magnet 4 is connected to the refrigerator through a cold conducting belt 6. 2 primary cold head connections. The cryogenic container 8 is connected to the lower end of the refrigerant 2, and the tested superconducting coil 5 is installed in the cryogenic container 8, and the surface of the tested superconducting coil 5 is coated with low-temperature epoxy glue 9 with a thickness of 5-10 mm. If the superconducting coil 5 to be tested is in a vacuum environment when it works, it can be refrigerated by the refrigerator 2 to make the cryogenic container 8 reach the required low temperature. If the superconducting coil 5 under test is immersed in a low-temperature liquid environment during operation, the low-temperature liquid can be fed into the low-temperature container through the infusion tube 11 . If the superconducting coil 5 under test is a high-temperature superconducting coil, liquid nitrogen is input into the cryogenic container; The infusion tube 11 and the air return tube 12 are arranged symmetrically on the upper end of the cryogenic container 8 and connected with the upper cover of the cryogenic container 8 . The superconducting coil current lead 13 under test and the superconducting coil measuring lead 14 under test are connected on the upper cover plate of the cryogenic container. After the Dewar vessel 1 is evacuated, the refrigerator 2 is turned on, and when the required working temperature is reached, the back field superconducting magnet 4 is energized through the back field superconducting magnet current lead 7 to provide the required background magnetic field, and then passed The current lead wire 13 of the superconducting coil under test energizes the superconducting coil 5 under test, and passes a pulse current through the pulse current source to the heating wire 10 to generate a certain amount of heat to trigger the quenching of the superconducting coil 5 under test. The data transmitted back by the lead wire 14 can measure the quench propagation velocity of the tested superconducting coil 5 under the background magnetic field of 1-5T.

As shown in Fig. 2, the tested superconducting coil 5 includes the tested superconducting coil sparsely wound part 15 and the tested superconducting coil densely wound part 16, and the tested superconducting coil sparsely wound part 15 and the tested superconducting coil densely wound part 15 The heating wire 10 is wound around the wire between the winding portions 16 . The heating wire 10 is a manganin wire with a resistance of 10-50 ohms. The heating wire 10 is powered by a pulse current source. The tested superconducting coil 5 is connected with the tested superconducting coil current lead 13 and is powered by the tested superconducting coil power supply 21 . On the wire of the sparsely wound part 15 of the tested superconducting coil, the distance along the direction of the wire is _L1. Weld two pairs of sparsely wound part measuring leads, respectively the sparsely wound part measuring lead 17 and the sparsely wound part measuring lead 2 18, each pair The distance of the sparsely wound part of the measuring lead along the wire direction is L ₂ . Weld the measuring leads of the closely wound part on the closely wound part 16 of the superconducting coil to be tested along the two adjacent turns of the wire. Lead wire two 20, the distance between the two pairs of closely wound parts measuring the lead wire along the wire direction is S. The wire diameter or width of the superconducting coil 5 to be tested is d. Measure the quench propagation velocity along the length direction of the wire through the two pairs of sparsely wound measurement leads of the superconducting coil 5 under test, and measure the quench propagation velocity along the radial direction of the wire through the two pairs of closely wound measurement leads of the superconducting coil 5 under test. Quench propagation velocity.

Since the quench propagation velocity along the conductor direction is much greater than the quench propagation velocity along the conductor radial direction, in order to more accurately measure the quench propagation velocity along the conductor radial direction, the diameter of the superconducting coil 5 to be tested is larger than the diameter of the measured superconducting coil 5 Measure 40-60 times of the wire diameter of superconducting coil 5.

The measuring lead wire 1 17 of the sparsely wound part and the measuring lead wire 2 18 of the sparsely wound part, the measuring lead wire 1 19 of the densely wound part and the measuring lead wire 2 20 of the densely wound part are all connected to the multi-channel data acquisition instrument 22, and the multi-channel data acquisition instrument 22 can be keithley2182 The voltmeter or the data acquisition card of NI Company measures the voltage of each pair of measuring leads at each moment through the multi-channel data acquisition instrument 22 . The difference between the time of 0.5 times the maximum voltage generated by a pair of sparsely wound measuring leads 18 adjacent to the heating wire 10 and the time of 0.5 times the maximum voltage generated by another pair of sparsely wound measuring leads 17 is recorded as t1. The difference between the time of 0.5 times the maximum voltage generated by the first pair of closely wound measuring leads 19 adjacent to the heating wire 10 and the time of 0.5 times the maximum voltage generated by the second pair of closely wound measuring leads 20 is recorded as t2. Then the quench propagation velocity of the tested superconducting coil 5 along the wire direction is (L ₁ +L ₂ )/t1, and the quench propagation velocity of the tested superconducting coil 5 along the wire radial direction is (2d+ S)/t2.

The measuring method of the present invention is firstly to energize the tested superconducting coil 5 under the background magnetic field, and the magnitude of the current is equal to 0.8-0.95 times the critical current value of the superconducting wire (tape) material. Pass a pulse current to the heating wire 10, and when a certain amount of heat is generated, the quenching of the superconducting coil 5 under test is triggered, and the voltage is measured by the multi-channel data acquisition instrument 22, and the measurement lead 17 of the sparsely wound part and the measurement lead 2 of the sparsely wound part are recorded. 18 respectively generate 0.5 times the maximum voltage time, and record the two time differences as t1. In addition, record the time of 0.5 times the maximum voltage generated by the first 19 of the tightly wound measuring lead and the second 20 of the tightly wound measuring lead, and record the difference between the two times as t2. Then the measured quench propagation velocity of the tested superconducting coil along the wire direction is (L ₁ +L ₂ )/t1, and the quench propagation velocity of the tested superconducting coil along the wire radial direction is (2d +S)/t2.

Claims (8)

1. a device of measuring superconducting coil quench propagation speed is characterized in that described device comprises Dewar type container (1), refrigeration machine (2), epoxy pull bar (3), a back of the body superconducting magnet (4), tested superconducting coil (5), conduction cooling band (6), low-temperature (low temperature) vessel (8), woven hose (11) and muffler (12); A back of the body superconducting magnet (4) is installed in Dewar type container (1), a back of the body superconducting magnet (4) is by the one-level cold head conduction refrigeration of conduction cooling band (6) by refrigeration machine (2), refrigeration machine (2) is installed in the center, upper surface of Dewar type container (1), and back of the body superconducting magnet (a 4) top is connected with the upper surface of Dewar type container (1) by epoxy pull bar (3); Low-temperature (low temperature) vessel (8) is connected the lower end of refrigeration machine (2) secondary cold head; Tested superconducting coil (5) is installed in low-temperature (low temperature) vessel (8) inside; Woven hose (11) and muffler (12) are connected with low-temperature (low temperature) vessel (8) upper cover plate in low-temperature (low temperature) vessel (8) upper end symmetric arrangement.Be connected to tested superconducting coil current lead-in wire (13) and tested superconducting coil measuring lead wire (14) on the upper cover plate of low-temperature (low temperature) vessel (8).

2. according to the device of the described measurement superconducting coil of claim 1 quench propagation speed, it is characterized in that described tested superconducting coil (5) comprises that tested superconducting coil is thin close around part (16) around part (15) and tested superconducting coil, dredges around part (15) and tested superconducting coil close around partly twining heater strip (10) on the lead between (16) at tested superconducting coil.

3. according to the device of the described measurement superconducting coil of claim 2 quench propagation speed, it is characterized in that described heater strip (10) is a manganese-copper filament, the resistance of heater strip (10) is 10-50 ohm.

4. according to the device of the described measurement superconducting coil of claim 1 quench propagation speed, it is 5-10mm low temperature epoxy glue (9) that the appearance that it is characterized in that described tested superconducting coil (5) scribbles thickness.

5. according to the device of the described measurement superconducting coil of claim 1 quench propagation speed, it is characterized in that the diameter of described tested superconducting coil (5) is greater than 40-60 times of the diameter of wire of tested superconducting coil (5).

6. according to the device of the described measurement superconducting coil of claim 1 quench propagation speed, it is characterized in that, when tested superconducting coil (5) is worked, be in the vacuum environment, directly freeze, make in the low-temperature (low temperature) vessel (8) to reach needed low temperature by refrigeration machine (2) secondary cold head; When tested superconducting coil (5) is worked, be immersed in the cryogenic liquid environment, in low-temperature (low temperature) vessel (8), import cryogenic liquid by woven hose (11); If tested superconducting coil (5) is a then input liquid nitrogen in low-temperature (low temperature) vessel (8) of high temperature superconductor coil, if tested superconducting coil (5) is the low-temperature superconducting coil then imports liquid helium that in low-temperature (low temperature) vessel (8) liquid vapour is discharged by muffler (12).

7. according to the device of the described measurement superconducting coil of claim 1 quench propagation speed, it is characterized in that, dredge at tested superconducting coil and on the lead of part (15), be welded with a pair of dredging around part measuring lead wire one (17) and a pair of dredging around part measuring lead wire two (18); Tested superconducting coil close around the part (16) lead on be welded with a pair of close around part measuring lead wire one (19) and a pair of close around part measuring lead wire two (20); Dredge around part measuring lead wire one (17) and thin be L around part measuring lead wire two (18) along the spacing of lead direction ₁, every pair of two lead-in wires dredging around the part measuring lead wire are L along the distance on the lead direction ₂Close around part measuring lead wire one (19) and close be S around part measuring lead wire two (20) along the spacing on the lead direction; Every pair of two lead-in wires dredging around the part measuring lead wire are d along the distance on the lead direction; The diameter of wire of tested superconducting coil or width are d.

8. according to the method for the described measurement superconducting coil of claim 1 quench propagation speed, it is characterized in that the sequence of steps of measuring method is:

1. at first give tested superconducting coil (5) energising under background magnetic field, size of current equals the critical electric current value of 0.8～0.95 times of superconducting wire or band;

Promote blood circulation towards electric current 2. for heater strip (10), after producing certain heat, trigger tested superconducting coil (5) quench;

3. carry out voltage measurement by multi-channel data acquisition instrument (22), note and dredge, two mistimings are remembered t1 around part measuring lead wire one (17) and time of dredging the 0.5 times of maximum voltage that produces respectively around part measuring lead wire two (18); Note close time in addition, two mistimings are designated as t2 around part measuring lead wire one (19) and the close 0.5 times of maximum voltage that produces respectively around part measuring lead wire two (20);

4. be (L by dredging around part measuring lead wire one (17) and thin measuring along the quench propagation speed of the tested superconducting coil (5) on the lead direction around part measuring lead wire two (18) ₁+ L ₂)/t1 is (2d+S)/t2 by close around part measuring lead wire one (19) and close measuring along the quench propagation speed of lead tested superconducting coil (5) in the radial direction around part measuring lead wire two (20).

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