CN103035354B - A kind of naked superconducting magnet - Google Patents

Abstract

The invention belongs to the field of superconducting technology, and in particular relates to a non-insulated superconducting magnet. The non-insulated superconducting magnet of the present invention includes a bobbin and a superconducting wire wound on the bobbin. The surface of the superconducting wire has no insulating layer or the wrapped insulating layer is incomplete, and the inter-turns of the superconducting wire are filled with conductive A mixture of materials, thermally conductive materials, cured materials and wetted materials, the inter-turn resistance is between 0.1 ohm-100 kohm; the volume percentage of each part of the material is: conductive material 0.01-99.9%, thermal conductive material 0-99.99%, Cured material 0‑99%, 0‑5% wetted material. The non-insulated superconducting magnet of the present invention is filled with conductive components between each turn of the superconducting coil, so that the inter-turn maintains a high resistance, which not only exerts the characteristics of no insulation between the turns, but also facilitates the charging and excitation of the superconducting magnet. Quench protection.

Description

A non-insulated superconducting magnet

technical field

The invention belongs to the field of superconducting technology, and in particular relates to a non-insulated superconducting magnet.

Background technique

Superconducting magnets are one of the most important aspects of the application of superconducting technology. According to different working forms, they can be divided into low-temperature superconducting magnets and high-temperature superconducting magnets. Low-temperature superconducting magnets usually refer to superconducting magnets that work at the temperature of liquid helium (4.2K), while high-temperature superconducting magnets usually work above the temperature of liquid helium, and the general working temperature is 10-100K. Superconducting magnets are generally made of NbTi, Nb ₃ Sn, Bi-based, MgB ₂ , YBCO and other superconducting wires or strips. Most of the superconducting wires and tapes used in superconducting magnets must be wrapped and insulated. Materials, usually Kapton tape and insulating varnish, etc., superconducting magnets that are wound with superconducting wires wrapped in insulating layers, generally have to be filled with wax or epoxy resin to fill the gaps inside the superconducting magnets. Filling materials should have the characteristics of low temperature resistance and good thermal conductivity. The main purpose of insulation and filling is to make superconducting magnet turns well insulated. The magnetic field of a superconducting magnet is generally 0.5T-20T. Another purpose of filling the magnet is to ensure that the superconducting wire inside the superconducting magnet is firmly fixed, avoiding displacement under the action of a strong magnetic field force, and reducing the occurrence of superconductors. Risk of overshooting.

Generally, low-temperature superconducting magnets are immersed in liquid helium when they work. High temperature superconducting magnets can be immersed in liquid nitrogen or in liquid helium during operation. Due to immersion in liquid helium, liquid nitrogen and other cooling liquids with large cooling capacity, the temperature of superconducting magnets is usually cooled to the boiling point of cryogenic liquids. A slight temperature rise in the superconducting magnet will evaporate a large amount of cryogenic liquid to take away the heat to keep the temperature constant. With the development of cryogenic technology, cryogenic refrigerators with operating temperatures of 4.2K or 20K have appeared in recent years. The superconducting magnet is connected to the refrigerator with a cold-conducting material, and the superconducting magnet is lowered to the working temperature. This working method is called conduction cooling. Whether it is a low-temperature superconducting magnet or a high-temperature superconducting magnet, due to the limited thermal conductivity, the disadvantage of conduction cooling is that the temperature is not uniform everywhere on the superconducting magnet. Because of poor heat conduction, when thermal, electrical, and magnetic disturbances occur inside the superconducting magnet, it is easy to cause local overheating, and the risk of quench propagation is relatively serious.

Generally, the diameter of a superconducting wire is about 1 mm, the thickness of a superconducting strip is generally about 0.5 mm, and the width is about 5 mm. There are usually multiple strands of superconducting filaments inside the superconducting wire and strip, and the number of filaments is several to tens of thousands. Varying, superconducting filaments (occasionally wrapped in barrier metal) are embedded in a thermally conductive metal matrix such as copper or silver as a temperature stabilizer. Under stable working conditions, the internal current of the superconducting magnet only flows in the superconducting filament as the superconducting material, and does not flow in the temperature stable body such as copper and silver wrapped in the superconducting material. , The insulating material wrapped outside the superconducting wire and strip is completely useless, and the insulating material only plays a role when the magnet is magnetized and demagnetized. In addition, when the superconducting magnet fails, it is necessary to take protective measures for the superconducting magnet. The insulating material will restrict the current and have an adverse effect on the superconducting magnet.

In 2011, a new non-insulated superconducting magnet technology was developed abroad, that is, when winding a superconducting magnet, no insulating material is used between the superconducting wire and the strip, or stainless steel strip or Hastelloy strip (Hastelloy strip) is used directly. ) and other conductive metal strips are used as the spacer material between superconducting wires and strips. Each turn of superconducting wires and strips inside the winding are conductive and short-circuited. The contact resistance between turns is usually less than 0.01 ohms, which is for superconducting magnets The charging excitation caused more serious difficulties. For non-insulated superconducting magnets, during the working process of superconducting magnets, once the superconductor undergoes partial quenching, the superconducting wire and a certain section of the belt appear resistance, and the current will be shunted to the adjacent superconducting wires, which is more beneficial to the protection of superconducting magnets. Quenched superconducting wires and strips will not be continuously heated by large operating currents, which can avoid damage to superconducting magnets. However, once a quench occurs in a magnet wrapped with insulating materials and inter-turn insulation, a protective circuit needs to be activated immediately. The superconducting magnet current is reduced to a harmless level within a fraction of a second or a few seconds, so the non-insulated superconducting magnet technology can greatly reduce the risk of damaging the superconducting magnet. The so-called non-insulation in this latest non-insulation technology is essentially a complete conductive contact. The inter-turn resistance of the coil is extremely small, which is not conducive to the normal charging and excitation of the magnet.

Compared with traditional filling techniques such as wax dipping or epoxy resin dipping, the thermal conductivity of superconducting magnets using non-insulation technology is better, which is conducive to the internal temperature balance of superconducting magnets and avoids the occurrence of local over-temperature areas inside the magnets. Hazardous work of superconducting magnets. It has more important significance for the conduction cooling magnets of refrigerators, which are currently receiving much attention. According to the latest literature reports, foreign research on non-insulated superconducting magnet technology has just started, and it is still limited to a simple non-insulated state with a direct transition from high insulation to a few milliohms between turns.

At present, the non-insulated superconducting magnets developed abroad do not insulate directly between the superconducting wires or strips, or simply use metal as the spacer material. hardly. This completely gets rid of the barrier effect of the original insulating layer, which is very unfavorable for the charging and excitation of the superconducting magnet. For a large non-insulated superconducting magnet with an extremely low resistance close to micro-ohms inside the magnet and an inductance of Henry’s order of magnitude, the charging and excitation time needs to be More than ten days is unacceptable in the actual application process.

Contents of the invention

Aiming at the deficiencies in the prior art, the present invention provides a non-insulated superconducting magnet, the purpose of which is to enhance the internal thermal conductivity of the superconducting magnet and at the same time focus on controlling the turn-to-turn resistance inside the superconducting magnet so that the thermal conductivity and Non-insulated superconducting magnet with high temperature stability and high turn-to-turn resistance ratio.

The non-insulated superconducting magnet of the present invention includes a bobbin and a superconducting wire wound on the bobbin. The surface of the superconducting wire has no insulating layer or the wrapped insulating layer is incomplete, and the inter-turns of the superconducting wire are filled with conductive Materials, thermally conductive materials, cured materials and wetted materials, the inter-turn resistance is between 0.1 ohm and 100 kohm; the volume percentage of each part of the material is: conductive material 0.01-100%, thermal conductive material 0-99.99%, cured material 0-99%, 0-5% wetted material.

The heat conducting material is aluminum nitride, boron nitride, aluminum oxide, beryllium oxide, zinc oxide, silicon oxide, magnesium oxide, aluminum chloride, silicon carbide or aluminum carbide; silicon, germanium, phosphorus, sulfur, selenium, arsenic , boron or carbon, or compounds formed by the combination of the above semiconductors; tin, lead, zinc, aluminum, copper, gallium, indium, cadmium, antimony, bismuth, magnesium, calcium, barium, lithium, sodium, potassium, mercury, titanium, zirconium , vanadium, niobium, manganese, iron, cobalt, nickel or copper, and their alloys, oxides, sulfides, nitrides, fluorides, chlorides, carbides.

The conductive material mentioned therein is tin, lead, zinc, aluminum, copper, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, gallium, indium, cadmium, antimony, bismuth, magnesium, calcium, barium, lithium, sodium , potassium or mercury, or alloys formed by combining the above metals; or carbon, silicon, germanium, phosphorus, sulfur, selenium or arsenic, or compounds formed by combining the above semiconductors; or compounds of the above alloys and the above semiconductors.

The curing material is shellac, lacquer, wax, epoxy resin, pitch, oil, water, glass powder, glass fiber or asbestos.

The wetting material is indium oxide, tin oxide, tin chloride, palladium chloride, boric acid or sodium stearate.

The characteristics of the present invention are: it has a structure different from any traditional magnet, fully utilizes the characteristics of superconducting materials to conduct electricity and transmit current, eliminates highly insulating or completely conductive contact forms between coil turns, and replaces them with resistance contact. This gives full play to the characteristics of superconducting technology and is a substantial improvement over the traditional magnet structure.

In the non-insulated superconducting magnet of the present invention, conductive materials are added between the turns of the superconducting magnet to maintain a uniform low-resistance non-insulated state between turns, and by adjusting the proportion of conductive materials, the inter-turn resistance is much higher than that between conductors. Contact resistance to help reduce the difficulty of magnet charging and excitation; at the same time, a large number of high thermal conductivity materials can help the temperature of the magnet to be uniform and improve temperature stability. Increasing the amount of material used can help increase the overall heat capacity and improve the low temperature stability of the magnet; Curing and wetting materials help to improve the microcosmic bonding performance of conductive materials and thermally conductive materials, and increase the overall thermal conductivity and mechanical properties of the magnet.

Compared with the traditional superconducting magnet, the non-insulated superconducting magnet of the present invention does not use an insulating layer or uses an incomplete insulating layer on the surface of the superconducting wire, thereby improving the overall electrical performance of the superconducting magnet. By filling each turn of the superconducting coil with a thermally conductive material with excellent thermal conductivity at low temperature, the comprehensive thermal conductivity and heat capacity of the superconducting magnet are improved, and the purpose of improving the low-temperature temperature stability of the magnet is achieved. The non-insulated superconductor of the present invention The magnet is filled with conductive components between each turn of the superconducting coil to maintain a high resistance between the turns, which not only exerts the characteristics of no insulation between the turns, but also facilitates the charging excitation and quench protection of the superconducting magnet.

The specific advantages of the non-insulated superconducting magnet of the present invention include the following aspects:

(1) Maintain a certain turn-to-turn resistance to reduce the risk of high temperature rise, high temperature gradient and thermal stress damage during magnet quenching;

(2) Maintain a high turn-to-turn resistance, which is conducive to the rapid charging and excitation of superconducting magnets with large inductance;

(3) Improve the internal thermal conductivity of superconducting magnets and improve temperature stability;

(4) Improve the overall heat capacity of superconducting magnets, so that the ability of superconducting magnets to withstand heat and electromagnetic disturbances is improved;

(5) The technology is mature and easy to manufacture.

Description of drawings

Fig. 1 is a schematic diagram of a typical superconducting magnet winding structure in the prior art;

Fig. 2 is a partial enlarged view of part A in Fig. 1;

Fig. 3 is a schematic structural view of a typical superconducting magnet in the prior art after being filled and solidified;

Fig. 4 is a partially enlarged view of part B in Fig. 3;

Fig. 5 is the schematic diagram of the microstructure of the non-insulated superconducting magnet of the embodiment 1-3 according to the present invention;

Fig. 6 is a schematic structural diagram of a non-insulated superconducting magnet in Embodiment 4 of the present invention;

7 is a schematic diagram of an equivalent circuit corresponding to the microstructure of the non-insulated superconducting magnet of the present invention;

Fig. 8 is a schematic diagram of the equivalent circuit structure of the superconducting magnet of the present invention;

Fig. 9 is an equivalent circuit diagram of the superconducting magnet of the present invention;

Fig. 10 is the equivalent circuit data of the superconducting magnet of the present invention: the trend curve of total resistance changing with the number of coil layers;

In the figure: 1: coil bobbin; 2: superconducting wire; 3: insulating layer; 4: superconducting filament; 5: metal temperature stabilizer; 6: thermally conductive curing material; 7: thermally conductive material; 8: curing material; 9: Conductive material; 10: incomplete insulating layer; 11: total equivalent resistance of the coil; 12: total resistance data point of the coil with an odd number of total layers; 13: data point of the total resistance of a coil with an even number of total layers.

detailed description

The technical solution of the present invention will be further described below in conjunction with the accompanying drawings and embodiments of the specification.

The structure of superconducting magnets in the prior art is shown in Figures 1-4, and also includes a coil frame (1) and a superconducting wire (2), wherein the superconducting wire (2) is stabilized by superconducting filaments (4) and metal temperature Body (5), and a complete insulating layer (3) is coated on the outside of the superconducting wire to achieve the purpose of insulation between coil turns. In order to fix the superconducting wire, epoxy resin curing agent is usually filled between the coil turns. Powder particles with good thermal conductivity such as alumina or aluminum nitride are usually mixed in the curing agent to increase the thermal conductivity of the cured material, as shown in Figure 4 for the thermally conductive cured material (6).

The non-insulated superconducting magnet of the present invention also includes a bobbin (1) and a superconducting wire (2), wherein the superconducting wire (2) is composed of a superconducting filament (4) and a metal temperature stabilizer (5), the difference is that The exterior of the superconducting wire is covered with an incomplete insulating layer (10) as shown in Figure 6, or without an insulating layer, as shown in Figure 5, and the turns of the superconducting wire (2) are filled with thermally conductive materials (7), conductive For the mixture of material (9) and curing material (8), it is often necessary to use a wetting material to improve the surface activity of the powder and superconducting wire during the coil filling and curing process, so as to reduce the voids during the curing process and improve the uniformity of the curing components. As shown in Figure 5 and Figure 6, its structure is to wrap a thin layer of metal conductive material (9) on the outer surface of particles of thermally conductive materials (7) such as alumina, so that the originally non-conductive insulating particles become To form conductive particles, a large number of conductive particles are mixed into conductive or epoxy resin-based non-conductive cured materials (8), so that the conductivity of the material can be varied in a wide range, and the turns can be easily adjusted by changing the conductive properties and dosage of conductive particles. The inter-turn resistance can form various forms of non-insulated magnet structures including incomplete insulation. The turns of the superconducting coil are in non-insulated contact. By adjusting the volume percentage of each component material, the inter-turn resistance can be purposefully changed to make it Reach 0.1 ohms - 100 kilo ohms.

The range of change calculated by volume ratio: 0.01-99.99% for thermally conductive materials, 0.01-99.9% for conductive materials, 0-99% for cured materials, and 0-5% for wetted materials.

The internal turn-to-turn structure of the superconducting wire of the non-insulated superconducting magnet of the present invention can be decomposed into the circuit structure shown in Figure 7, each turn of the superconducting wire can be expressed by a small inductance, and the resistance between each turn is the non-insulation technology The inter-turn resistance in the superconducting coil, the internal circuit structure of the superconducting coil can be described by the inductance and resistance network shown in Figure 8. The circuit parameters of the complex network are difficult to calculate. Factors such as being an even number will greatly affect the overall resistance. If the circuit shown in Figure 9 is used to describe the overall circuit characteristics of the non-insulated magnet coil, it is obviously different from the conventional superconducting magnet in that there is a small resistance in parallel with the magnet inductance Using the resistance network shown in Figure 8, the total resistance in parallel with the inductance of the non-insulated magnet coil can be obtained according to the change law of the number of layers of the coil. As shown in Figure 10, the inter-turn resistance of the coil and the parallel total resistance of the coil There is a clear computational relationship.

The appearance shape of the bobbin of the present invention includes not only the cylindrical shape shown in the accompanying drawings, but also various existing bobbin shapes such as saddle shape and racetrack type. The spiral form also includes the existing double-cake form, single-cake form, track type, saddle type and other winding methods.

The manufacturing process of the non-insulated superconducting magnet of the present invention is similar to the traditional method, and will be described in detail below.

Example 1

Wind the superconducting wire on the coil frame, and at the same time spread the surface-activated micron or nano-sized alumina powder in the form of dry powder or wet powder between the turns of the coil, and wind the superconducting wire in a vacuum chamber of 1-100Pa The completed superconducting coil is immersed in the metal tin liquid at 150-300°C, then remove the vacuum, rely on atmospheric pressure, or apply a pressure of 0.1-10MPa at the same time, so that the metal tin liquid is immersed in the inter-turn of the superconducting coil, and the metal is cooled. The non-insulated superconducting magnet with the structure shown in Figure 5 is obtained. According to the volume percentage, the superconducting magnet is filled with 1%-99% alumina-based heat-conducting material, and 0.1%-99% is filled with a solidified and conductive material. For metal tin-based materials, the dosage of pure inorganic curing materials is 0%.

The surface-activated micron or nano-scale alumina powder refers to the use of physical or chemical methods in the prior art to wrap metal on the surface of alumina powder particles, or directly use tin chloride or palladium chloride solution to moisten the surface of the alumina powder. Wet the surface of the powder particles, or use sodium stearate or boric acid to make the surface of the alumina powder particles and the metal as a conductive material wet well; The volume ratio of the internal alumina powder reduces the amount of tiny voids inside the magnet so that the volume of metal tin immersed in the magnet reaches 2%-10%, so that the average resistivity between turns can reach more than ten times the resistivity of pure metal tin. The inter-turn resistance is more than ten times higher than the direct contact resistance between metals. For magnets with large coil diameters and small turn-to-turn spacing ratios, the inter-turn resistance can reach 0.1 ohms; for magnets with small coil diameters and large turn-to-turn spacing, the inter-turn resistance Can reach more than 1 ohm.

You can also directly choose metal lead, zinc, or metal tin, lead, zinc, etc. and aluminum, copper, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, gallium, indium, cadmium, antimony, bismuth, magnesium, calcium, An alloy made of barium, lithium, sodium, potassium or mercury replaces pure metal tin and fills the inter-turns of superconducting wires as a conductive material, which can also form different inter-turn resistances. Among them, constantan alloys with high resistivity are used for filling, which can The inter-turn resistance is further increased to 1 ohm to 10 ohm.

Among them, when adding lead to the metal tin to reduce the cost, it is necessary to increase the working temperature when vacuum impregnating the metal, and increasing the amount of metals such as aluminum, copper, titanium, vanadium, chromium, manganese, iron, cobalt, and nickel in the immersion alloy can reduce the cost. Greatly change the resistivity of the impregnated metal, and greatly increase the turn-to-turn resistance compared with pure metal tin; increase the amount of gallium, indium, cadmium, antimony, bismuth, magnesium, calcium, barium, lithium, sodium, potassium or mercury in the impregnated alloy , can reduce the working temperature when the magnet is immersed in the alloy; the use of Wood alloy type low-melting point metals containing different proportions of lead, tin, bismuth, cadmium, and indium can reduce the working temperature of the magnet when immersed in the alloy to 47°C-200°C.

While satisfying the electrical conductivity, it is necessary to enhance the heat conduction and heat storage performance of the magnet under low temperature conditions. Aluminum nitride, beryllium oxide, boron nitride, silicon carbide, silicon oxide, magnesium oxide and other inorganic materials with good low temperature heat conduction can also be used. Instead of alumina to have a similar thermal conductivity, zinc oxide, aluminum chloride or aluminum carbide, or silicon, germanium, phosphorus, sulfur, selenium, arsenic, boron, carbon semiconductors and their compounds; or tin, lead, zinc, aluminum, Copper, gallium, indium, cadmium, antimony, bismuth, magnesium, calcium, barium, lithium, sodium, potassium, mercury, titanium, zirconium, vanadium, niobium, manganese, iron, cobalt, nickel, copper oxides, sulfides, Nitride, fluoride, chloride, and carbide can all be used as thermal conductivity materials to replace alumina, although the low-temperature thermal conductivity of these materials is not as good as alumina, aluminum nitride, beryllium oxide, boron nitride, silicon carbide and other materials, but in Under relatively high temperature conditions above 100K, it can still be used as a material with relatively good comprehensive performance of heat conduction and heat storage.

Since the particle size of alumina powder is very small, it can also be mixed into the liquid metal conductive material and filled into the magnet at one time by vacuum or pressure method in order to simplify the magnet manufacturing process. In this filling method, the volume of the conductive metal in the final magnet is relatively large, and the proportion of the non-conductive heat-conducting material is relatively small, which is not easy to form a high inter-turn resistance. It is suitable for magnets with low inter-turn resistance, and the heat-conducting material accounts for the proportion The volume ratio can be reduced to 1%-30%, and the volume ratio of conductive materials can reach 70%-99%.

Extensive use of metals, alloys or alumina and other high-heat-capacity, thermal-conductive heat-conducting materials can increase the overall heat capacity of the magnet and help increase low-temperature stability. A large amount of beryllium oxide, aluminum nitride, boron nitride, Silicon carbide, zinc oxide, silicon oxide, magnesium oxide, aluminum chloride or aluminum carbide and other materials replace the aluminum oxide in the above-mentioned magnets, and the best low-temperature heat capacity and thermal conductivity can be adjusted to adapt to the corresponding superconducting working temperature. In order to improve the heat conduction and cold storage performance of the magnet, a large amount of heat conduction material is used around the superconducting wire of the magnet, which can make the volume ratio of heat conduction material used in the magnet as high as 99%.

Example 2

First, micron or nanometer aluminum nitride powder is wetted in tin chloride liquid and air-dried to make a powder with surface activity. The surface of the powder particles is coated with a thin metallic silver conductive layer by electrochemical method to form a conductive layer. The volume ratio of the conductive fine powder is 1%-50%. Since the conductive metal material is only attached to a thin layer on the outer surface of the aluminum nitride powder particle, the larger the aluminum nitride powder particle is, the smaller the relative volumetric gravity of the surface metal is. , the volume ratio of the conductive material in the filling material between turns of the final coil is 0.1%-1%, and the rest is epoxy resin curing material, accounting for about 50%-99% by volume.

While winding the superconducting coil on the coil frame, apply conductive micropowder between the superconducting coils, put the wound magnet into a vacuum container, control the vacuum degree of 1 Pa -100Pa, and remove the air between the turns of the magnet , Immerse the superconducting coil in the epoxy resin liquid, then remove the vacuum, rely on atmospheric pressure, or apply a pressure of 0.1-10MPa at the same time, so that the epoxy resin liquid penetrates into all the inter-turn gaps, cool to room temperature, and the epoxy resin solidifies Afterwards, the non-insulated superconducting magnet with the structure shown in Figure 5 is obtained. Because there are a large number of surface conductive aluminum nitride powder particles, the cured epoxy resin has obvious conductivity, which can form a large inter-turn resistance, adjust The amount and volume specific gravity of the conductive aluminum nitride powder particles, the inter-turn resistance is between 1 ohm and 100 kohm.

Copper, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, gallium, and indium oxide can also be used as conductive materials to replace silver-wrapped aluminum nitride powder particles and reduce raw material costs; aluminum oxide, beryllium oxide, and nitride can be used Boron, silicon carbide, silicon oxide, magnesium oxide and other inorganic materials with good low-temperature heat conduction can replace aluminum nitride to achieve the same heat conduction effect, or choose zinc oxide, aluminum chloride or aluminum carbide, silicon, germanium, phosphorus, sulfur, selenium , arsenic, boron, carbon semiconductors and their compounds, tin, lead, zinc, aluminum, copper, gallium, indium, cadmium, antimony, bismuth, magnesium, calcium, barium, lithium, sodium, potassium, mercury, titanium, zirconium, vanadium , niobium, manganese, iron, cobalt, nickel, copper oxides, sulfides, nitrides, fluorides, chlorides and carbides as thermal conductive materials to replace aluminum nitride. Metal powder or semiconductor powder with conductive properties can not be wrapped with metal, and has both electrical and thermal conductivity.

Directly mix carbon powder or metal or alloy powder of tin, lead, zinc, aluminum, copper, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, gallium, indium in liquid epoxy resin; or silicon, germanium, phosphorus , sulfur, selenium, arsenic semiconductors or other conductive powders such as their compounds can also achieve the purpose of making the cured epoxy resin conductive.

Shellac, lacquer, wax, asphalt, oil, water can also be selected for use to condense into the material of harder solid at low temperature to replace epoxy resin.

For this type of magnet superconducting magnet, when the magnetic field is small and the stress intensity is low, less or no curing material can be used. In the case of no curing material, the volume ratio of aluminum nitride powder particles can reach 99.99% %, the volume proportion of the metal on the surface of aluminum nitride powder particles can reach 0.01%, and the inter-turn resistance can reach 100 ohms-100 kohms. By treating the magnet at high temperature, the metals on the surface of the aluminum nitride powder particles can be fused together to achieve a certain curing effect, and at the same time increase the conductivity, so that the inter-turn resistance can be greatly reduced to 10 ohms-1 kohms.

Example 3

Mix silicon carbide powder with water or shellac into a paste, soak the glass fiber braided paste with silicon carbide thermal conductivity and metal lead conductive powder, wind the glass fiber flat tape with powder attached and the superconductive flat tape side by side to make Superconducting single-cake or double-cake coils, put the wound magnet into a vacuum container, control the vacuum degree at 1-10Pa, use high temperature heating to melt the metal lead of the glass fiber braid, and fuse with the silicon carbide heat-conducting powder Together, inter-turn interlayers with high electrical resistance are formed, resulting in non-insulated superconducting magnets.

Only a small amount of conductive and thermally conductive materials are impregnated in the thin glass fiber braid, which helps to form a lower turn-to-turn resistance. Usually, the thickness of the glass fiber conductive tape is smaller than that of the superconducting tape. Glass fiber is an attachment of conductive and thermally conductive materials. The inter-turn resistance can be controlled by adjusting the thickness of the fiber braid and the amount of impregnated conductive components. Silicon carbide with a volume ratio of 10%-50% and lead with a volume ratio of 10%-50% can be used. The inter-turn resistance of the prepared coil can be controlled between 1 ohm and 100 kohm by mixing and immersing the glass fiber braided tape whose volume ratio accounts for 40%-80%.

Non-woven glass fibers and asbestos can also be used to replace glass fiber braids; conductive materials and thermally conductive materials as described in Examples 1 and 2 can be selected to be mixed to make electrical conductivity under low temperature conditions, and mixed powder with good thermal conductivity; use 5%-10% shellac helps the conductive and heat-conducting powder to better adhere to the glass fiber tape, and reducing the amount of shellac helps to improve the electrical and thermal conductivity of non-insulated magnets. Different effects can be obtained by replacing shellac with adhesives such as lacquer, wax, epoxy, asphalt, oil, etc.

The single-cake, double-cake or racetrack-shaped coils wound with formed conductive tape and superconducting tape can also be immersed in conductive metal and further solidified with metal. The final turn-to-turn resistance is low and can be controlled between 0.1 ohm and 100 ohm. between. Add glass powder and other low-melting point materials to the formed conductive strip, and heat the glass powder to melt through the heating furnace, so that the magnet can be sintered into a whole body solidified with glass, which helps to improve the strength of the magnet.

Example 4

First, the outer surface of the wire, that is, the surface of the metal temperature stabilizer, is oxidized to form a non-conductive thin metal oxide layer, and the surface resistance of the superconducting wire is very large. With the thickening of the surface oxide layer, the surface resistance can approach the semi-insulating state. Then attach an inert conductive protective layer such as indium oxide on the surface of the superconducting wire. A superconducting magnet is made by winding a surface-treated superconducting coil. Put the finished coil into a vacuum container, control the vacuum degree 1-100Pa, remove the air between the turns, immerse it in the metal lead liquid at 250-500 ℃, and finally remove the vacuum, rely on atmospheric pressure, or apply 0.1- The air pressure of 10MPa pressure makes the metal liquid immerse between the turns to obtain a non-insulated superconducting magnet. The inter-turn resistance can be adjusted by controlling the thickness of the surface resistance layer of the superconductor, and the inter-turn resistance can reach 1 ohm-1 megohm. Except for a small amount of indium oxide, the volume ratio of the inter-turn conductive metal material can reach 99.9%.

This method uses a large amount of metal as the inter-turn filling material, and the non-insulated magnet has relatively good overall electrical and thermal conductivity, and its stress resistance is also high. This approach differs from other approaches in that the key to controlling the turn-to-turn resistance in an uninsulated magnet is concentrated on the surface of the superconducting wire. The manufacturing process requirements are relatively high, and the film layer is easily scratched during the process of winding the magnet, which affects the uniformity of the inter-turn resistance. In addition, when the resistance layer on the surface of the superconducting wire is relatively thick, it will have a great adverse effect on the thermal conductivity of the magnet.

The resistance layer on the surface of the superconducting wire can be obtained by using a thin layer of metal oxide, or a thin layer of incompletely insulating sulfide, nitride, fluoride, chloride, carbide, or by coating a semiconductor resistor The coating is obtained as long as the surface resistive state can be achieved. It is also possible to wrap the surface of the superconducting wire with a traditional insulating layer first, and then peel off part of the insulating layer on the surface in the form of a regular pattern such as a spiral to expose the conductive surface of the superconducting wire in a certain proportion, see Figure 6. Adjusting the exposed area of the conductive surface is used to form different average surface resistances, thereby forming a non-insulated structure with different conductivity between turns. The surface non-insulation effect of the superconducting wire can also be achieved by wrapping the superconducting wire with a traditional insulating material mixed with conductive metal powder particles.

In this non-insulated superconducting magnet structure, tin, lead, zinc, aluminum, copper, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, gallium, indium, cadmium, antimony, bismuth, magnesium, calcium, Barium, lithium, sodium, potassium, or mercury, or alloys formed by combining the above metals; or carbon, silicon, germanium, phosphorus, sulfur, selenium, or arsenic, or compounds formed by semiconductorization and formation of the above; or compounds of the above alloys and the above semiconductors As a conductive material, replace metal lead for curing filling.

In this non-insulated superconducting magnet structure, aluminum oxide, aluminum nitride, beryllium oxide, boron nitride, silicon carbide, zinc oxide, aluminum chloride or aluminum carbide, or silicon, Germanium, phosphorus, sulfur, selenium, arsenic, boron, carbon semiconductors and their compounds; or tin, lead, zinc, aluminum, copper, gallium, indium, cadmium, antimony, bismuth, magnesium, calcium, barium, lithium, sodium, potassium , Mercury, titanium, zirconium, vanadium, niobium, manganese, iron, cobalt, nickel, copper oxides, sulfides, nitrides, fluorides, chlorides and carbides as thermal conductive materials. Thermally conductive materials are usually added in the form of fine powder particles. Before use, the outer surface of the powder particles needs to be metallized and alloyed to increase the wettability with the metal. In the final turn-to-turn material, the volume proportion of thermally conductive materials reaches 1%-70%, the volume proportion of conductive materials reaches 30%-99%, and the inter-turn resistance is controlled between 1 ohm and 100 kohm.

Claims (4)

1. A non-insulated superconducting magnet, comprising a bobbin and a superconducting wire wound on the bobbin, the superconducting wire is made up of a superconducting filament and a metal temperature stabilizer, and is characterized in that the insulating surface of the superconducting wire is wrapped The layer is incomplete or not wrapped with an insulating layer, and the turns of the superconducting wire are filled with thermally conductive materials, conductive materials, cured materials and wetting materials, and the resistance between each turn is between 0.1 ohms and 100 kiloohms; each part of the The volume percentage of materials is: conductive material 0.01-99.9%, thermal conductive material 0.01-99.99%, cured material 0-99%, and the volume fraction of cured material is not 0%, 0-5% wetted material, the sum of the four is 100%; said conductive material is tin, lead, zinc, aluminum, copper, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, gallium, indium, cadmium, antimony, bismuth, magnesium, calcium, barium, lithium, Sodium, potassium, or mercury, or alloys formed by combining the above metals; or carbon, silicon, germanium, phosphorus, sulfur, selenium, or arsenic, or compounds formed by a combination reaction between carbon, silicon, germanium, phosphorus, sulfur, selenium, or arsenic ; or the compounds of the above alloys and carbon, silicon, germanium, phosphorus, sulfur, selenium or arsenic; the specific filling method is to wrap a thin layer of metal conductive material on the outer surface of the thermally conductive material particles to form conductive particles, when the volume fraction of the cured material is not At 0%, a large number of conductive particles are mixed into the conductive or non-conductive cured material, so that the conductivity of the material changes in a wide range. The resistance between each turn is adjusted by changing the conductive properties and dosage of the conductive particles. By adjusting the composition of the materials The volume percentage changes the resistance between each turn of the superconducting coil to 0.1 ohm-100 kohm. 2. A non-insulated superconducting magnet according to claim 1, characterized in that said thermally conductive material is aluminum nitride, boron nitride, aluminum oxide, beryllium oxide, zinc oxide, silicon oxide, magnesium oxide, chlorine Aluminum oxide, silicon carbide or aluminum carbide; silicon, germanium, phosphorus, sulfur, selenium, arsenic, boron or carbon, or compounds formed by combining silicon, germanium, phosphorus, sulfur, selenium, arsenic, boron or carbon; tin, Lead, zinc, aluminum, copper, gallium, indium, cadmium, antimony, bismuth, magnesium, calcium, barium, lithium, sodium, potassium, mercury, titanium, zirconium, vanadium, niobium, manganese, iron, cobalt, nickel or copper, And its alloys, oxides, sulfides, nitrides, fluorides, chlorides, carbides. 3. A non-insulated superconducting magnet according to claim 1, characterized in that said solidified material is shellac, lacquer, wax, epoxy resin, asphalt, oil, water, glass powder, glass fiber or asbestos . 4. A non-insulated superconducting magnet according to claim 1, characterized in that said wetting material is indium oxide, tin oxide, tin chloride, palladium chloride, boric acid or sodium stearate.