阅读说明：本技术 一种在超导腔内部对锡源进行局部加热的双电极直流结构 (Double-electrode direct current structure for locally heating tin source in superconducting cavity ) 是由 杨自钦 何源 吴安东 李雪峰 李世珍 谢斌 初青伟 皇世春 谭腾 张生虎 于 2021-09-16 设计创作，主要内容包括：本发明提供一种在超导腔内部对锡源进行局部加热的双电极直流结构。包括：具有若干加速单元的超导腔,所述超导腔为Nb-(3)Sn薄膜生长的衬底结构；两根加热电极,一根作为正电极,另一根作为负电极,所述两根加热电极贯通所述超导腔,在所述超导腔内部对锡源进行加热；若干薄壁锡源坩埚,所述超导腔的每一个加速单元内均放置有一个薄壁锡源坩埚,所述若干薄壁锡源坩埚均横跨在所述两根加热电极上与所述两根加热电极组成直流回路；温度热偶,用于测量所述超导腔内锡源的温度。本发明能够对位于多加速单元超导腔内部的多个锡源进行局部加热,在每个加速单元内均实现超导腔与锡源的单独控温,使每一个加速单元均拥有相同的“超导腔-锡源”温度组合。(The invention provides a dual-electrode direct current structure for locally heating a tin source in a superconducting cavity. The method comprises the following steps: a superconducting cavity with several accelerating elements, the superconducting cavity being Nb 3 A substrate structure for Sn film growth; two heating electrodes, one of which is used as a positive electrode and the other is used as a negative electrode, the two heating electrodes penetrate through the superconducting cavity, and a tin source is heated in the superconducting cavity; the thin-wall tin source crucibles are placed in each accelerating unit of the superconducting cavity, and all the thin-wall tin source crucibles cross over the two heating electrodes to form a direct current loop with the two heating electrodes; and the temperature thermocouple is used for measuring the temperature of the tin source in the superconducting cavity. The invention can locally heat a plurality of tin sources positioned in the superconducting cavity of the multiple accelerating units, and realizes the independent temperature control of the superconducting cavity and the tin sources in each accelerating unit, so that each accelerating unit has the same temperature combination of the superconducting cavity and the tin sources.)

1. A dual electrode dc structure for locally heating a tin source within a superconducting cavity, comprising:

a superconducting cavity with multiple accelerating units, the superconducting cavity is Nb₃A substrate structure for Sn film growth;

two heating electrodes, one as a positive electrode and the other as a negative electrode, which are respectively connected with an external heating power supply, wherein the two heating electrodes penetrate through the superconducting cavity and heat the tin source in the superconducting cavity;

each acceleration unit of the superconducting cavity is internally provided with a thin-wall tin source crucible, the thin-wall tin source crucibles are containers for containing tin metal particles, and the thin-wall tin source crucibles all cross over the two heating electrodes to form a direct current loop with the two heating electrodes;

and the temperature thermocouple is used for measuring the temperature of the tin source in the superconducting cavity.

2. The bipolar direct current structure of claim 1, wherein: the two heating electrodes are positioned at the axial position of the superconducting cavity;

the temperature thermocouple is located at the axial position of the superconducting cavity.

3. The bipolar direct current structure of claim 1 or 2, wherein: the superconducting cavity main body is processed by niobium metal;

the residual resistivity of the metal niobium is more than or equal to 40;

the working frequency and the number of the accelerating units of the superconducting cavity are determined by application requirements.

4. The bipolar direct current structure of any one of claims 1-3, wherein: the heating electrodes are two metal straight rods with rectangular cross sections;

the heating electrode is processed by pure niobium metal with the residual resistivity more than or equal to 40 or high-purity tungsten metal with the purity of 99.95 percent;

the length of the heating electrode is determined according to the shape of the superconducting cavity.

5. The bipolar direct current structure of any one of claims 1-4, wherein: the thin-wall tin source crucible is processed by pure metal niobium with the residual resistivity more than or equal to 40 or high-purity metal tungsten with the purity reaching 99.95 percent;

the number of the thin-wall tin source crucibles is the same as that of the accelerating units of the superconducting cavity;

the thickness of the crucible wall of the thin-wall tin source is 0.2-0.5mm,

the crucible wall of the thin-wall tin source and the two heating electrodes are fixed by pure tungsten or pure niobium fastening screws and ensure electrical contact;

the fixed positions of the thin-wall tin source crucible on the two heating electrodes are positioned in the center of each accelerating unit.

6. The bipolar direct current structure of any one of claims 1-5, wherein: the temperature thermocouple can measure the high temperature of 1200-1500 ℃, and can be a tungsten-rhenium thermocouple with a molybdenum protection tube.

7. The bipolar direct current structure of any one of claims 1-6, wherein: the accelerating units at the head end and the tail end are connected with a tool flange through superconducting cavity beam pipeline flanges;

the number of the tool flanges is two,

and the two tool flanges are in through-wall butt joint with the two heating electrodes and the temperature thermocouple to provide a supporting structure.

8. The bipolar direct current structure of claim 7, wherein: the tool flange is butted with the superconducting cavity beam pipeline flange through a pure tungsten or pure niobium fastening screw;

the tool flange and the two heating electrodes are insulated through a ceramic sleeve, and the ceramic sleeve is made of high-purity ceramic with the purity of 99%.

9. The bipolar direct current structure of claim 7 or 8, wherein: the superconducting cavity beam pipeline flange is processed by adopting a pure metal niobium or niobium-titanium alloy material with the residual resistivity more than or equal to 40.

10. The bipolar direct current structure of any one of claims 7-9, wherein: the tooling flange is formed by processing high-purity niobium metal with the residual resistivity more than or equal to 40 or high-purity tungsten metal or niobium-titanium alloy with the purity of 99.95 percent;

the size of the tool flange is determined by the superconducting cavity beam pipeline flange.

Technical Field

The invention relates to a double-electrode direct current structure for locally heating a tin source in a superconducting cavity, and belongs to the technical field of superconduction.

Background

Nb₃The Sn film superconducting cavity is the next generation radio frequency superconducting key technology, and the engineering application thereof will cause the technical revolution in the field of radio frequency superconducting. In the tin vapor diffusion method, at a high temperature of above 9300C, Sn atoms reach the inner surface of the superconducting cavity in a vapor mode and react with Nb atoms in situ to generate a pure and high-quality Nb3Sn film. The temperature of the tin source determines the magnitude of the saturated vapor pressure of tin and the rate at which Sn molecules reach the inner surface of the superconducting cavity. The temperature of the superconducting cavity determines the diffusion of Sn molecules to the inner surface of the superconducting cavity to generate Nb₃The rate of Sn film. The best quality Nb can be produced only if the rate of Sn molecules reaching the superconducting cavity is matched with the rate of Sn molecules diffusing to the inner surface of the superconducting cavity₃And a Sn film. Therefore, Nb is developed by tin vapor diffusion₃In the process of the Sn film superconducting cavity, the high-performance Nb is obtained by independently controlling the temperature of the superconducting cavity and the tin source₃The key of the Sn thin film superconducting cavity.

However, current separate temperature control of the superconducting cavity from the tin source is achieved by placing the tin source outside the superconducting cavity and locally heating it. For engineering practical superconducting cavity containing multiple accelerating units (the accelerating units contain electromagnetic field to accelerate and energize charged particles, and the multiple accelerating units can keep the phase of the charged particles and the electromagnetic field synchronous and obtain continuous acceleration and energization in a superconducting cavity)If the tin source continues to be placed outside the superconducting cavity for localized heating, limited by its longer dimension, the tin vapor partial pressure will decrease rapidly with increasing distance from the tin source, resulting in a "superconducting cavity-tin source" temperature combination that is suitable for acceleration units closer to the tin source and not suitable for acceleration units further from the tin source. The tin source is placed outside the superconducting cavity to carry out local heating and grinding on the high-performance multi-acceleration-unit engineering practical Nb₃The Sn thin film superconducting cavity can not overcome the difficulty.

Disclosure of Invention

In view of the above, it is an object of the present invention to provide a dual electrode dc structure for locally heating a tin source inside a superconducting cavity. According to the structure, the tin source is placed in each accelerating unit, and the tin source in each accelerating unit is locally heated through a temperature control program, so that each accelerating unit has a proper temperature combination of a superconducting cavity and the tin source, and the problem that the superconducting cavities of multiple accelerating units cannot adopt a superconducting cavity and tin source independent temperature control technical route to develop high-performance Nb is solved₃The difficulty of the Sn film superconducting cavity.

In order to achieve the purpose, the invention adopts the following technical scheme:

a dual electrode dc structure for locally heating a tin source within a superconducting cavity, comprising:

a superconducting cavity with multiple accelerating units, the superconducting cavity is Nb₃A substrate structure for Sn film growth;

two heating electrodes, one as a positive electrode and the other as a negative electrode, which are respectively connected with an external heating power supply, wherein the two heating electrodes penetrate through the superconducting cavity and heat the tin source in the superconducting cavity;

each acceleration unit of the superconducting cavity is internally provided with a thin-wall tin source crucible, the thin-wall tin source crucibles are containers for containing tin metal particles, and the thin-wall tin source crucibles all cross over the two heating electrodes to form a direct current loop with the two heating electrodes;

and the temperature thermocouple is used for measuring the temperature of the tin source in the superconducting cavity.

Wherein the two heating electrodes are positioned at the axial position of the superconducting cavity;

the temperature thermocouple is positioned at the axial position of the superconducting cavity;

the superconducting cavity main body is processed by niobium metal;

the residual resistivity of the metal niobium is more than or equal to 40;

the working frequency and the number of the accelerating units of the superconducting cavity are determined by application requirements;

the heating electrodes are two metal straight rods with rectangular cross sections;

the heating electrode is processed by pure niobium metal with the residual resistivity more than or equal to 40 or high-purity tungsten metal with the purity of 99.95 percent;

the length of the heating electrode is determined according to the shape of the superconducting cavity.

The thin-wall tin source crucible is processed by pure metal niobium with the residual resistivity more than or equal to 40 or high-purity metal tungsten with the purity reaching 99.95 percent;

the number of the thin-wall tin source crucibles is the same as that of the accelerating units of the superconducting cavity;

the thickness of the thin-wall tin source crucible is 0.2-0.5mm, specifically 0.2mm,

the thin-wall tin source crucible and the two heating electrodes are fixed through pure tungsten or pure niobium fastening screws and good electric contact is ensured;

the fixed positions of the thin-wall tin source crucible on the two heating electrodes are positioned in the center of each accelerating unit;

the temperature thermocouple can measure 12000-15000C high temperature, and can be a tungsten-rhenium thermocouple with a tungsten protection tube;

the accelerating units at the head end and the tail end are connected with a tool flange through superconducting cavity beam pipeline flanges;

the number of the tool flanges is two,

the two tool flanges are in through-wall butt joint with the two heating electrodes and the temperature thermocouple to provide a supporting structure;

the tool flange is butted with the superconducting cavity beam pipeline flange through a pure tungsten or pure niobium fastening screw;

the tool flange and the two heating electrodes are insulated through a ceramic sleeve, and the ceramic sleeve is made of high-purity ceramic with the purity of 99 percent;

the superconducting cavity beam pipeline flange is processed by adopting a pure metal niobium or niobium-titanium alloy material with the residual resistivity more than or equal to 40;

the tool flange is processed by adopting pure metal niobium with the residual resistivity more than or equal to 40 or pure metal tungsten or niobium-titanium alloy with the purity of 99.95 percent;

the size of the tool flange is determined by the superconducting cavity beam pipeline flange;

in a word, two leads of a heating power supply are respectively connected to two heating electrodes, one heating electrode is used as a positive electrode, the other heating electrode is used as a negative electrode, and a parallel loop is formed by each thin-wall tin source crucible. The thin-wall tin source crucible has very thin wall and much higher resistance than the straight rod electrode part, so that in each loop of the straight rod electrode and the tin source crucible, the voltage of each tin source crucible is basically the same, most of heat productivity in the loop is concentrated on the thin-wall tin source crucible, and the local heating of the thin-wall tin source crucible is realized.

Because the thin-wall tin source crucibles are in parallel connection, the local heating conditions of the thin-wall tin source crucibles at different positions are the same, and the temperature probe of the temperature thermocouple is close to the first thin-wall tin source crucible through the measuring position of the tool flange. The heating power supply takes the actual measured temperature of the temperature thermocouple as feedback, and the specified temperature control heating of the thin-wall tin source crucible is realized.

Compared with the existing tin vapor diffusion method which only can place a tin source outside the superconducting cavity to realize local heating and independent temperature control, the method has the following beneficial effects: the invention can locally heat a plurality of tin sources in the superconducting cavity of the multiple accelerating units, and realizes the independent temperature control of the superconducting cavity and the tin sources in each accelerating unit, so that each accelerating unit has the same temperature combination of the superconducting cavity and the tin sources, and the technical route of the independent temperature control of the superconducting cavity and the tin sources can also be applied toHigh performance multiple acceleration unit Nb₃Development of superconducting cavity of Sn film, for Nb₃The engineering application of the Sn film superconducting cavity has important significance.

Drawings

FIG. 1 is a schematic diagram of a dual-electrode DC configuration for localized heating of a tin source within a superconducting cavity in accordance with the present invention. Wherein 1 is a superconducting cavity, 2 is a heating electrode 1, 3 is a heating electrode 2, 4 is a thin-wall tin source crucible, 5 is a temperature thermocouple, 6 is a tooling flange 1,7 is a tooling flange 2, charged particles enter the superconducting cavity from a port 6 in the figure, and leave the superconducting cavity from a port 7 after being accelerated.

Detailed Description

The experimental procedures used in the following examples are all conventional procedures unless otherwise specified.

Materials, reagents and the like used in the following examples are commercially available unless otherwise specified.

The structure of the present invention is schematically shown in fig. 1, and the following describes in detail the dual-electrode dc structure for locally heating the tin source inside the superconducting cavity.

The superconducting cavity 1 in the figure is a 650MHz ellipsoid superconducting cavity with 6 accelerating units, the cavity body is processed by adopting high-purity metal niobium with residual resistivity larger than 300, the beam pipeline flange is processed by adopting niobium-titanium alloy, and the mass percent of the niobium is 45%.

The two heating electrodes 2 and 3 are processed by high-purity metal tungsten with the purity not lower than 99.95 percent, and the high-purity metal tungsten is adopted because the melting point of the tungsten is as high as 34100 ℃, the saturated vapor pressure is extremely low at the high temperature of 12000-15000 ℃, and no pollution element is introduced; the length of the heating electrodes 2 and 3 is determined by the shape and the size of the superconducting cavity 1, and the length of the heating electrodes 2 and 3 in the figure is 1340 mm; in order that the thin-walled tin source crucible 4 does not roll inside the superconducting chamber 1, the heating electrodes 2,3 in the present illustration are rectangular with a cross section of 10mmx20 mm; the two heating electrodes 2 and 3 need to be processed with straight-through holes at the same positions, so that the thin-wall tin source crucible 4 and the heating electrodes 2 and 3 can be conveniently fastened and assembled through screws; the number of the through holes is the same as that of the accelerating units of the superconducting cavity 1, and 6 through holes are processed on the heating electrodes 2 and 3; the specific position of the through hole needs to ensure that the assembled thin-wall tin source crucible 4 is positioned at the center of each accelerating unit; the diameter of the through hole in this example is 6.6 mm.

The thin-wall tin source crucible 4 is processed by high-purity metal niobium with residual resistivity of more than 300 and wall thickness of 0.2mm, and the reason for processing the metal niobium is that the metal niobium has good ductility and can not introduce pollution elements, thereby being beneficial to ensuring good electric contact between the thin-wall tin source crucible 4 and the heating electrodes 2 and 3 under the fastening connection of screws; the number of the thin-wall tin source crucibles 4 is 6, and 1-3g of high-purity metallic tin particles with the purity not lower than 99.9995 percent are put into each thin-wall tin source crucible 4; the thin-wall tin source crucible 4 needs to be provided with a through hole which is fastened and assembled with the heating electrodes 2 and 3 through screws, the diameter of the through hole is the same as that of the through hole of the heating electrodes, the distance between the through holes is determined by the assembly distance between the two heating electrodes 2 and 3, the diameter of the through hole of the thin-wall tin source crucible 4 in the embodiment is 6.6mm, and the distance between the two through holes is 42.3 mm; the thin-wall tin source crucible is fastened and connected with the two heating electrodes 2 and 3 through M6 pure tungsten fastening screws, so that the thin-wall tin source crucible 4 is kept in good electric contact with the heating electrodes 2 and 3.

The temperature thermocouple 5 is used for measuring the local temperature of the locally heated thin-wall tin source crucible 4 in the superconducting cavity 1 in real time, the temperature thermocouple 5 in the embodiment adopts a tungsten-rhenium thermocouple, and a tungsten tube with the diameter of 6mm is sheathed and protected by a tungsten-rhenium thermocouple wire, so that the influence of tin vapor adsorbed to the tungsten-rhenium thermocouple wire on the measurement accuracy is prevented; the tip of the tungsten-rhenium thermocouple was placed against the first thin-walled tin source crucible 4.

The two tool flanges 6 and 7 are formed by processing high-purity metal tungsten with the purity not lower than 99.95 percent, and the specific size of the flanges is determined by beam pipeline flanges of the superconducting cavity; in the embodiment, through holes required for butt joint with beam pipeline flanges are processed on the tool flange, the number of the through holes is 20, the through holes are uniformly distributed along the circumference, the diameter of each through hole is 8.8mm, and the tool flange 6,7 and the superconducting cavity beam pipeline flange are assembled through pure tungsten fastening screws of M8; wall through holes needed by butt joint of the two heating electrodes 2 and 3 and the temperature thermocouple 4 are processed on the tool flanges 6 and 7; the distance between the wall through holes of the two heating electrodes 2 and 3 on the tool flanges 6 and 7 determines the distance between the two heating electrodes 2 and 3 after assembly, and the shape of the wall through hole is determined by the section sizes of the heating electrodes 2 and 3 and the size of the ceramic insulating sleeve; in the embodiment, the distance between two wall penetrating holes of the tooling flanges 6 and 7 is 42.3mm, the section of the ceramic insulating sleeve is a rectangular frame with the wall thickness of 2mm, and the size of the inner wall rectangle is 10mmx20 mm; the temperature thermocouple jack is positioned at the circle centers of the tool flanges 6 and 7 and is a through round hole with the diameter of 8 mm.

In a word, the thin-wall tin source crucible 4, the tool flange 6, the two heating electrodes 2,3 and 6 are assembled and then pass through the superconducting cavity 1; the assembly between the tool flange 6 and the beam pipeline flange at one end of the superconducting cavity is completed through M8 pure tungsten fastening screws; the assembly of the two heating electrodes 2 and 3 and the tool flange 7 is completed; the assembly between the tool flange 7 and the beam pipeline flange at the other end of the superconducting cavity is completed through M8 pure tungsten fastening screws; inserting a probe of a tungsten-rhenium thermocouple into the superconducting cavity 1 through an insertion hole of a tool flange 6, wherein the probe of the thermocouple is tightly close to a first thin-wall tin source crucible 4; and (3) putting the assembled superconducting cavity system into a film coating cavity, closing the furnace door after completing the electric connection between the heating power supply and the heating electrode and the electric connection between the thermocouple lead and the tungsten-rhenium thermocouple, vacuumizing in advance, and heating and coating according to a specified process curve.