阅读说明：本技术 一种高产额自成靶d-d中子管及其制作方法 (High-yield self-targeting D-D neutron tube and manufacturing method thereof ) 是由 刘洋 李康 汪永安 于轶鹏 李刚 于 2021-07-16 设计创作，主要内容包括：本发明提出一种高产额自成靶D-D中子管及其制作方法,以解决在测井、在线分析等应用中,现有同位素中子源存在设备维修和操作防护困难、14MeV可控中子源存在防护困难和防护装置庞大、D-D可控中子源存在中子产额不高的技术问题。中子管包括管壳组件、芯柱组件、气压调节组件、潘宁离子源组件、加速电极及自成靶组件；通电加热气压调节组件释放出一定量的氘气,潘宁离子源组件使氘气电离而产生氘离子,氘离子经加速电极加速后轰击自成靶靶面,发射出快中子；同时还提出上述高产额自成靶D-D中子管的制作方法。本发明D-D中子管在不使用情况下可以关断电源,其工作温度可达到175℃,D-D中子产额达到1×10～(7)n/s以上。(The invention provides a high-yield self-target-forming D-D neutron tube and a manufacturing method thereof, and aims to solve the technical problems that an existing isotope neutron source is difficult to maintain and operate and protect, a 14MeV controllable neutron source is difficult to protect, a protection device is large, and a D-D controllable neutron source is low in neutron yield in logging, online analysis and other applications. The neutron tube comprises a tube shell assembly, a core column assembly, an air pressure adjusting assembly, a penning ion source assembly, an accelerating electrode and a self-targeting assembly; the power-on heating air pressure adjusting assembly releases a certain amount of deuterium gas, the penning ion source assembly enables the deuterium gas to be ionized to generate deuterium ions, and the deuterium ions bombard the self-forming target surface after being accelerated by the accelerating electrode to emit fast neutrons; meanwhile, a manufacturing method of the high-yield self-targeting D-D neutron tube is also provided. The D-D neutron tube can be powered off when not in use, the working temperature can reach 175 ℃, and the D-D neutron yield reaches 1 multiplied by 10 7 n/s or more.)

1. A high yield self-targeting D-D neutron tube, which is characterized in that: comprises a tube shell component, a core column component, an air pressure regulating component, a penning ion source component, an accelerating electrode (181) and a self-targeting component;

the pipe shell assembly comprises an upper sealing ring (5), a neutron pipe shell (17) and a lower sealing ring (182) which are sequentially connected from top to bottom;

the accelerating electrode (181) is of a conical cylinder structure, is arranged at the upper end of the inner wall of the lower sealing ring (182) and is arranged upwards, and the top end of the accelerating electrode is provided with a through hole;

the core column assembly is arranged in the upper sealing ring (5) and comprises a core column (4), a process exhaust pipe (1), a low-voltage electrode (2), a high-voltage electrode (3) and a grounding electrode (25); the core column (4) comprises a hollow cylindrical core column base (41) and a core column supporting column (42) which are integrally designed, and the outer wall of the core column base (41) is sealed with the inner wall of the upper sealing ring (5); the process exhaust pipe (1), the low-voltage electrode (2), the high-voltage electrode (3) and the grounding electrode (25) are arranged on the core column base (41); the upper end of the process exhaust pipe (1) is closed; the grounding electrode (25) is connected with the stem base (41);

the penning ion source assembly comprises an ion source cover (8) arranged in a neutron tube shell (17) and connected with an upper sealing ring (5), an ion source sealing ring (7) arranged at the upper end of the ion source cover (8), and a main magnetic steel (10), a cathode (12), an anode (13), an output cathode (15) and a magnetic ring (16) which are sequentially arranged in the ion source cover (8) from top to bottom; a first through hole is formed in the ion source sealing ring (7); the upper end surface of the ion source sealing ring (7) is connected with a core column supporting column (42); the main magnetic steel (10) is arranged between the lower end surface of the ion source sealing ring (7) and the cathode (12); the cathode (12) is connected with the ion source cover (8); a gap is arranged between the cathode (12) and the anode (13) along the axial direction, an anode lead (22) of the anode (13) penetrates out of a first through hole in the ion source sealing ring (7) and is connected with the high-voltage electrode (3), an anode lead insulating ceramic tube (9) is sleeved outside the anode lead (22), and a gap is formed between the anode lead insulating ceramic tube (9) and the first through hole; the bottom of the ion source cover (8) is provided with a second through hole, the magnetic ring (16) and the output cathode (15) are sequentially arranged above the second through hole, and the edge of the output cathode (15) is connected with the inner wall of the ion source cover (8); the output cathode (15), the magnetic ring (16) and the second through hole form a deuterium ion beam flow channel;

the air pressure adjusting assembly is positioned between the upper end surface of the ion source sealing ring (7) and the lower end surface of the core column base (41), and comprises a heater (24) and a getter (6) wrapped outside the heater (24); one end of the heater (24) is connected with the low-voltage electrode (2), and the other end of the heater is connected with the grounding electrode (25); deuterium gas is absorbed in the getter (6);

the self-targeting assembly is arranged in the lower sealing ring (182) and comprises a target base (19), and the outer wall of the target base (19) is sealed with the inner wall of the lower sealing ring (182); target magnetic steel (20) is arranged in the target base (19); the upper surface of the target base (19) is plated with a target film (23), and deuterium gas is adsorbed on the target film (23).

2. The high yield self-targeting D-D neutron tube of claim 1, wherein: the upper surface of the target base (19) is provided with a plurality of inwards concave conical surface structures.

3. A high yield self-targeting D-D neutron tube according to claim 1 or 2, wherein: the acceleration distance of the acceleration electrode (181) is 10-12 mm.

4. A high yield self-targeting D-D neutron tube according to claim 3, wherein: the gap between the cathode (12) and the anode (13) is 1-3 mm; the apertures of the output cathode (15), the magnetic ring (16) and the second through hole at the bottom of the ion source cover (8) are all 3-5 mm;

the aperture of the through hole of the accelerating electrode (181) is 8-10 mm, and the outer surface of the accelerating electrode (181) is polished to a mirror surface degree.

5. The high yield self-targeting D-D neutron tube of claim 4, wherein: the cathode (12) comprises a cathode main body (121) and a cathode groove (122) arranged on the cathode main body (121), and the main magnetic steel (10) is arranged between the lower end surface of the ion source sealing ring (7) and the cathode groove (122); the upper end of the cathode slot (122) is provided with a lug along the radial direction, the outer edge of the lug is connected with the inner wall of the ion source cover (8), and two anode electrode insulating ceramic tubes (11) are symmetrically arranged on the lug along the axial direction;

two anode electrodes (132) are symmetrically arranged on two sides of the anode (13), the two anode electrodes (132) respectively extend into the two anode electrode insulating ceramic tubes (11), and an anode lead (22) is led out from one anode electrode (132);

a positioning ring (14) is arranged at the upper end of the output cathode (15); the outer diameter of the positioning ring (14) is matched with the inner diameter of the ion source cover (8), and the upper end of the positioning ring is connected with the lug edge of the cathode groove (122).

6. The high yield self-targeting D-D neutron tube of claim 5, wherein:

the lower end of the upper sealing ring (5) is provided with a boss inwards along the radial direction, and the upper end of the outer wall of the ion source cover (8) is provided with a flange matched with the boss; the ion source cover (8) is connected with the upper sealing ring (5) through the matching of a flange and a boss;

and the edge of the upper end of the boss is provided with a chamfer.

7. The high yield self-targeting D-D neutron tube of claim 6, wherein:

a circular groove is formed in the middle of the lower end of the target base (19), and the target magnetic steel (20) is arranged in the circular groove; a target magnetic steel support (21) is arranged below the target magnetic steel (20);

the getter (6) is a zirconium-graphite non-evaporable getter material; the target film (23) is made of high-purity zirconium material; the target base (19) material is oxygen-free copper; the ion source cover (8) is made of soft magnetic materials;

the cathode (12) and the anode (13) are made of molybdenum;

the main magnet steel (10) and the target magnet steel (20) are made of samarium-cobalt alloy.

8. A method for manufacturing a high yield self-targeting D-D neutron tube according to any of claims 1 to 7, comprising the steps of:

step 1, carrying out structural assembly of a neutron tube;

step 2, double-vacuum high-temperature exhaust, namely opening the process exhaust pipe (1) of the neutron tube obtained in the step 1 and connecting the process exhaust pipe with a vacuum pump, placing the whole neutron tube in a vacuum environment, setting the temperature of the vacuum environment to be 450-500 ℃, and starting to exhaust, wherein the exhaust time is more than or equal to 20 hours; after the exhaust is finished, deuterium gas is supplied to seal the process exhaust pipe (1);

step 3, performing pressure-resistant exercise, namely after the step 2 is finished, placing the neutron tube in an insulating environment, cooling to normal temperature, then gradually raising the temperature of the environment where the neutron tube is located from the normal temperature to 175 ℃, and gradually increasing the voltage in the tube to over 140KV in the process for 8-10 hours;

and 4, performing target saturation exercise, namely after the step 3 is finished, providing 60-100 KV voltage for an accelerating electrode (181) of the neutron tube, supplying power for a thermion (24) through a low-voltage electrode (2), supplying power for an anode (13) through a high-voltage electrode (3), heating a getter (6) to release deuterium gas, ionizing and accelerating the deuterium gas to bombard a target film (23), and continuing for 8-10 hours until the content of the deuterium gas in the target film (23) is saturated, thereby finishing the manufacturing of the D-D neutron tube.

9. The method for manufacturing a high yield self-targeting D-D neutron tube according to claim 8, wherein the step 1 comprises:

1.1) fixedly connecting a lower sealing ring (182) with an accelerating electrode (181), and then sequentially connecting the lower sealing ring (182), a neutron tube shell (17) and an upper sealing ring (5) from bottom to top to form a tube shell assembly;

1.2) connecting a cathode (12) with two anode electrode insulating ceramic tubes (11), then respectively connecting two anode electrodes (132) with the two anode electrode insulating ceramic tubes (11), wherein an anode lead (22) is led out from one anode electrode (132), and an anode lead insulating ceramic tube (9) is sleeved outside the anode lead (22) to form an electric field assembly; a magnetic ring (16), an output cathode (15), an electric field component, main magnetic steel (10) and an ion source sealing ring (7) are sequentially arranged in an ion source cover (8) from bottom to top and are fixed, and an anode lead (22) and an anode lead insulating ceramic tube (9) are led out from the ion source sealing ring (7); the ion source sealing ring (7) is fixedly connected with the ion source cover (8) to form a penning ion source component;

1.3) respectively sealing the process exhaust pipe (1), the low-voltage electrode (2), the high-voltage electrode (3) and the grounding electrode (25) on a core column base (41) of the core column (4) to form a core column assembly; connecting a core column supporting column (42) of the core column (4) with the upper end face of the ion source sealing ring (7), and then connecting an anode lead (22) with the high-voltage electrode (3) to enable the core column assembly and the penning ion source assembly to be connected into a whole;

1.4) wrapping a getter (6) outside the heater (24) and placing the getter in a space below the core column base (41) to form an air pressure adjusting assembly; one end of the heater (24) is connected with the low-voltage electrode (2), and the other end of the heater is connected with the core column supporting column (42), so that the air pressure adjusting assembly, the core column assembly and the penning ion source assembly are connected into a whole;

1.5) putting the target magnetic steel (20) into a target base (19) plated with a target film (23) and fixing to form a self-target assembly;

1.6) the air pressure adjusting assembly, the core column assembly and the penning ion source assembly which are connected into a whole are arranged together from the upper part of the tube shell assembly, the self-targeting assembly is arranged from the lower part of the tube shell assembly, the outer wall of the core column base (41) is sealed with the inner wall of the upper sealing ring (5), and the outer wall of the target base (19) is sealed with the inner wall of the lower sealing ring (182); and finishing the structural assembly.

10. The method of claim 9, wherein the method comprises the steps of: in the step 1.6), the outer wall of the core column base (41) and the inner wall of the upper sealing ring (5) are sealed by adopting an argon arc welding method; the outer wall of the target base (19) and the inner wall of the lower sealing ring (182) are sealed by adopting an argon arc welding method.

Technical Field

The invention relates to a neutron tube, in particular to a high-yield self-targeting D-D neutron tube and a manufacturing method thereof.

Background

The means for measuring and analyzing various components of substances by utilizing the neutron technology has been widely applied in the fields of oil field well logging, coal field well logging, on-line analysis and the like. Compensated neutron logging in oil and coal fields²⁴¹Am-Be、²³⁸Fast neutrons emitted by the Pu-Be isotope neutron source or the 14MeV controllable neutron source are decelerated into thermal neutrons by formation hydrogen elements and then detected by a detector to obtain a formation hydrogen index, so that the porosity of a formation reservoir is obtained through calculation. The on-line analysis includes the application of coal, cement, mine and the like, and mainly utilizes²⁵²The Cf isotope neutron source or the 14MeV controllable neutron source emits neutrons which react with elements in coal, cement and mine to emit characteristic gamma rays in a short time, and the content of the substance can be analyzed by measuring and recording the gamma ray signals. The application is based on an isotope neutron source or a 14MeV controllable neutron source, and the isotope neutron source always emits neutrons no matter whether the isotope neutron source is applied or not, so that great inconvenience is brought to equipment maintenance, and the safety of personnel is affected; the 14MeV controllable neutron source has the defects of large protection device and limited use place due to high neutron energy, and the factors greatly limit the application of the neutron technology in the fields of oil field well logging, coal field well logging, on-line analysis and the like.

In recent years, researchers have attempted neutron logging and on-line neutron analysis using D-D controllable neutron sources, since the neutron energy generated by the D-D controllable neutron source is 2.5MeV, with²⁵²The neutron energies of the Cf isotope neutron source are similar, the D-D controllable neutron source can be switched off under the condition of no use, the equipment maintenance is convenient, the safety of maintenance personnel is ensured, the application technology of the D-D controllable neutron source is substantially improved, but the neutron yield of the current D-D controllable neutron source is generally limited to 4 multiplied by 10⁶About n/s, the actual application effect does not reach the expected value expected by people.

Disclosure of Invention

The invention aims to solve the existing apposition in oil field well logging, coal field well logging, and on-line analysis application of coal, cement and mineThe high yield self-target D-D neutron tube and the manufacturing method thereof are provided, the high yield self-target D-D neutron tube can be shut off when not used, the working temperature reaches 175 ℃, and the D-D neutron yield reaches 1 multiplied by 10⁷n/s or more.

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

a high yield self-targeting D-D neutron tube is characterized in that: the device comprises a tube shell assembly, a core column assembly, an air pressure adjusting assembly, a penning ion source assembly, an accelerating electrode and a self-targeting assembly;

the pipe shell assembly comprises an upper sealing ring, a neutron pipe shell and a lower sealing ring which are sequentially connected from top to bottom;

the accelerating electrode is of a conical cylindrical structure, is arranged at the upper end of the inner wall of the lower sealing ring and is arranged upwards, and the top end of the accelerating electrode is provided with a through hole;

the core column assembly comprises a core column, a process exhaust pipe, a low-voltage electrode, a high-voltage electrode and a grounding electrode; the core column comprises a hollow cylindrical core column base arranged in the upper sealing ring and a core column supporting column arranged at the lower part of the core column base, and the outer wall of the core column base is sealed with the inner wall of the upper sealing ring; the process exhaust pipe, the low-voltage electrode, the high-voltage electrode and the grounding electrode are arranged on the core column base; the upper end of the process exhaust pipe is closed; the grounding electrode is connected with the core column base;

the penning ion source assembly comprises an ion source cover, an ion source sealing ring, a main magnetic steel, a cathode, an anode, an output cathode and a magnetic ring, wherein the ion source cover is arranged in the neutron tube shell and is connected with the upper sealing ring; the ion source sealing ring is provided with a first through hole; the upper end surface of the ion source sealing ring is connected with the core column supporting column; the main magnetic steel is arranged between the lower end face of the ion source sealing ring and the cathode; the cathode is connected with the ion source cover; a gap is axially arranged between the cathode and the anode, an anode lead of the anode penetrates out of a first through hole in the ion source sealing ring and is connected with the high-voltage electrode, an anode lead insulating ceramic tube is sleeved outside the anode lead, and a gap is formed between the anode lead insulating ceramic tube and the first through hole and used for enabling deuterium gas to enter the ion source cover from the upper end of the ion source sealing ring; the bottom of the ion source cover is provided with a second through hole, the magnetic ring and the output cathode are sequentially arranged above the second through hole, and the edge of the output cathode is connected with the inner wall of the ion source cover; the output cathode, the magnetic ring and the second through hole form a deuterium ion beam flow channel;

the air pressure adjusting assembly is positioned between the upper end face of the ion source sealing ring and the lower end face of the core column base and comprises a heater and a getter wrapped outside the heater; one end of the heater is connected with the low-voltage electrode, and the other end of the heater is connected with the grounding electrode; deuterium gas is adsorbed in the getter;

the self-targeting assembly is arranged in the lower sealing ring and comprises a target base, and the outer wall of the target base is sealed with the inner wall of the lower sealing ring; target magnetic steel is arranged in the target base; the upper surface of the target base is plated with a target film, and deuterium gas is adsorbed on the target film.

Furthermore, the upper surface of the target base is provided with an inwards concave conical surface structure, so that the total area of the target film combined on the surface of the target base can be increased, and the neutron yield is increased.

Furthermore, the acceleration distance of the acceleration electrodes is 10-12 mm, so that sufficient bombardment energy can be ensured after the acceleration of the deuterium ions.

Furthermore, the gap between the cathode and the anode is 1-3 mm, so that the phenomenon that the cathode and the anode are too close to each other to cause discharge ignition can be prevented; the aperture of the output cathode, the aperture of the magnetic ring and the aperture of the second through hole at the bottom of the ion source cover are all 3-5 mm, so that the deuterium ion beam can pass through a larger deuterium ion beam and can be more concentrated;

the aperture of a through hole of the accelerating electrode is 8-10 mm, and the accelerating electrode is used for focusing deuterium ion beam; in order to avoid high-voltage breakdown of the tube shell caused by point discharge, the polishing treatment of the outer surface of the electrode is accelerated to a mirror surface degree.

Furthermore, the cathode comprises a cathode main body and a cathode groove arranged on the cathode main body, and the main magnetic steel is arranged between the lower end face of the ion source sealing ring and the cathode groove; the upper end of the cathode slot is provided with a lug along the radial direction, the outer edge of the lug is connected with the inner wall of the ion source cover, and two anode electrode insulating ceramic tubes are symmetrically arranged on the lug along the axial direction;

two anode electrodes are symmetrically arranged on two sides of the anode, the two anode electrodes respectively extend into the two anode electrode insulating ceramic tubes, and an anode lead is led out of one anode electrode;

a positioning ring is arranged at the upper end of the output cathode; the outer diameter of the positioning ring is matched with the inner diameter of the ion source cover, and the upper end of the positioning ring is connected with the edge of the lug of the cathode slot.

Furthermore, a boss is arranged at the lower end of the upper sealing ring inwards along the radial direction, and a flange matched with the boss is arranged at the upper end of the outer wall of the ion source cover; the ion source cover is connected with the upper sealing ring through the matching of the flange and the boss, so that the stable connection between the ion source cover and the upper sealing ring is ensured;

the upper end edge of the boss is provided with a chamfer, so that the ion source cover is prevented from being worn to generate peak discharge when being placed into the tube shell, and the normal work of the neutron tube is prevented from being influenced.

Furthermore, a circular groove is formed in the middle of the lower end of the target base, and the target magnetic steel is arranged in the circular groove; a target magnetic steel support is arranged below the target magnetic steel and used for fixing the target magnetic steel;

the getter is a zirconium-graphite non-evaporable getter material, has large gas absorption amount and can quickly release gas and absorb gas when the temperature is increased and decreased; the target film is made of a high-purity zirconium material, so that the deuterium adsorption amount in a unit area is improved, the D-D nuclear reaction probability is increased, and the temperature point of deuterium gas release from a self-formed target is also improved; the target base material is oxygen-free copper, the oxygen-free copper has good strength in a deuterium atmosphere, absorbs little deuterium, cannot compete with the target film for deuterium, has good heat dissipation effect, and effectively prevents the target film from being overheated and not releasing gas; the ion source cover is made of soft magnetic materials, so that the magnetic field can be prevented from leaking to weaken the magnetic field intensity in the ion source;

the cathode and the anode are made of molybdenum, so that the high-temperature performance is good, and the normal work of the penning ion source under well logging can be effectively ensured;

the main magnetic steel and the target magnetic steel are made of samarium-cobalt alloy, and the high-temperature performance is good.

Meanwhile, the invention also provides a method for manufacturing the high-yield self-target-forming D-D neutron tube according to any one of claims 1 to 7, which is characterized by comprising the following steps:

step 1, carrying out structural assembly of a neutron tube;

step 2, double-vacuum high-temperature exhaust, namely opening the process exhaust pipe of the neutron tube obtained in the step 1 and connecting the process exhaust pipe with a vacuum pump, placing the whole neutron tube in a vacuum environment, setting the temperature of the vacuum environment to be 450-500 ℃, and starting exhaust, wherein the exhaust time is more than or equal to 20 hours; after the exhaust is finished, deuterium gas is supplied to seal the process exhaust pipe;

step 3, performing pressure-resistant exercise, namely after the step 2 is finished, placing the neutron tube in an insulating environment, cooling to normal temperature, then gradually raising the temperature of the environment where the neutron tube is located from the normal temperature to 175 ℃, and gradually increasing the voltage in the tube to over 140KV in the process for 8-10 hours;

and 4, performing target saturation exercise, namely after the step 3 is finished, providing 60-100 KV voltage for an accelerating electrode of the neutron tube, supplying power for a heater through a low-voltage electrode, supplying power for an anode through a high-voltage electrode, heating a getter to release deuterium gas, ionizing and accelerating the deuterium gas to bombard the target film for 8-10 hours, and completing the manufacturing of the D-D neutron tube, wherein the content of the deuterium gas in the target film is saturated.

Further, step 1 specifically comprises:

1.1) fixedly connecting a lower sealing ring with an accelerating electrode, and then sequentially connecting the lower sealing ring, a neutron tube shell and an upper sealing ring from bottom to top to form a shell component;

1.2) connecting the cathode with two anode electrode insulating ceramic tubes, and then respectively connecting the two anode electrodes with the two anode electrode insulating ceramic tubes, wherein an anode lead is led out from one anode electrode, and the anode lead insulating ceramic tubes are sleeved outside the anode lead to form an electric field assembly; sequentially installing a magnetic ring, an output cathode, an electric field assembly, main magnetic steel and an ion source sealing ring into an ion source cover from bottom to top and fixing, and simultaneously leading an anode lead and an anode lead insulating ceramic tube out of the ion source sealing ring; fixedly connecting the ion source sealing ring with the ion source cover to form a penning ion source component;

1.3) respectively sealing the process exhaust pipe, the low-voltage electrode, the high-voltage electrode and the grounding electrode on a core column base of the core column to form a core column assembly; connecting a core column supporting column of the core column with the upper end face of the ion source sealing ring, and connecting an anode lead with a high-voltage electrode to connect the core column assembly and the penning ion source assembly into a whole;

1.4) wrapping the getter outside the heater and placing the getter in a space below the core column base to form an air pressure adjusting assembly; connecting one end of the thermionic resistor with the low-voltage electrode and connecting the other end of the thermionic resistor with the core column supporting column so that the air pressure adjusting assembly, the core column assembly and the penning ion source assembly are connected into a whole;

1.5) the target magnetic steel is arranged in the target base plated with the target film and fixed to form a self-target assembly;

1.6) the air pressure adjusting assembly, the core column assembly and the penning ion source assembly which are connected into a whole are arranged together from the upper part of the tube shell assembly, the self-targeting assembly is arranged from the lower part of the tube shell assembly, the outer wall of the core column base is sealed with the inner wall of the upper sealing ring, and the outer wall of the target base is sealed with the inner wall of the lower sealing ring; and finishing the structural assembly.

Further, in the step 1.6), the outer wall of the core column base and the inner wall of the upper sealing ring are sealed by adopting an argon arc welding method; the outer wall of the target base and the inner wall of the lower sealing ring are sealed by adopting an argon arc welding method.

The invention has the beneficial effects that:

1) the high-yield self-target-forming D-D neutron tube is characterized in that a heater of a heating air pressure adjusting assembly is electrified to enable the heater to emit a certain amount of deuterium gas, a penning ion source enables the deuterium gas to be ionized to generate deuterium ions, the deuterium ions bombard the surface of a self-target-forming target after being accelerated by an accelerating system and generate nuclear reaction with deuterium on the surface of the target, and fast neutrons with the emission energy of 2.5MeV are emitted; the working temperature can reach 175 ℃, and the D-D neutron yield reaches 1 multiplied by 10⁷n/s or more, canFor replacing compensation neutron well logging of oil field and coal field and on-line analysis of coal, cement and mine²⁴¹Am-Be、²³⁸Pu-Be、²⁵²A Cf isotope neutron source and a 14MeV controllable neutron source; the power supply can be turned off under the condition of no use, the safety is good, and the device has the characteristics of small volume, long service life, convenience in transportation, convenience in equipment maintenance and the like.

2) The high-yield self-target D-D neutron tube enlarges the volume of main magnetic steel in the ion source, enhances the magnetic field intensity and improves the ion beam density; the target magnetic steel is placed at the bottom of the self-forming target, and the generated magnetic field can change the motion direction of secondary electrons emitted by the target surface, so that the secondary electron current is reduced, and the unit effective beam current is improved; the self-target-forming target surface is designed into an inwards-concave conical surface structure, the surface area of the self-target-forming target surface is nearly doubled compared with that of a plane target, and the area bearing ion beam bombardment is doubled compared with that of the plane target; the target film material is made of high-purity zirconium, so that the deuterium adsorption amount in a unit area is improved, the D-D nuclear reaction probability is increased, the temperature point of deuterium gas release from a target is increased, and the measures can effectively improve the D-D neutron yield of the neutron tube.

3) According to the invention, samarium cobalt material is used for magnetic steel of the high-yield self-targeting D-D neutron tube, molybdenum material is used for the cathode and the anode, soft magnetic material is used for the ion source cover, oxygen-free copper material is used for the self-targeting target base, and zirconium-graphite getter material is used for the getter, so that the self-targeting D-D neutron tube can work in an environment of 175 ℃ for a long time, and the improvement of the secondary neutron yield of the D-D neutron tube is guaranteed.

4) According to the manufacturing method of the high-yield self-targeting D-D neutron tube, after the structure is assembled, the double-vacuum exhaust mode is adopted, and the impurity gas deep on the inner surface and the outer surface of the D-D self-targeting neutron tube can be effectively removed, so that the temperature resistance of the neutron tube is improved.

Drawings

FIG. 1 is a schematic diagram of the structure of a high-yield self-targeting D-D neutron tube according to the present invention;

fig. 2 is a top view of fig. 1.

Description of reference numerals:

1-process exhaust pipe, 2-low voltage electrode, 3-high voltage electrode, 4-core column, 41-core column base, 42-core column support column, 5-upper sealing ring, 6-getter, 7-ion source sealing ring, 8-ion source cover, 9-anode lead insulating ceramic tube, 10-main magnetic steel, 11-anode electrode insulating ceramic tube, 12-cathode, 121-cathode main body, 122-cathode slot, 13-anode, 132-anode electrode, 14-positioning ring, 15-output cathode, 16-magnetic ring, 17-neutron tube shell, 181-accelerating electrode, 182-lower sealing ring, 19-target base, 20-target magnetic steel, 21-target magnetic steel support, 22-anode lead, 23-target film, 24-thermion, 25-ground electrode.

Detailed Description

In order to more clearly explain the technical solution of the present invention, the following detailed description of the present invention is made with reference to the accompanying drawings and specific examples.

The structure of the high yield self-targeting D-D neutron tube is shown in figure 1, and comprises a tube shell assembly, a core column assembly, an air pressure adjusting assembly, a penning ion source assembly, an accelerating electrode 181 and a self-targeting assembly; the pressure regulating assembly releases a certain amount of deuterium under the condition of heating and electrifying, the penning ion source enables the deuterium to be ionized to generate deuterium ions, the accelerating electrode 181 extracts, shapes and accelerates the deuterium ions and then bombards the self-targeting target surface, and the deuterium-deuterium nuclear reaction is generated on the target surface to generate fast neutrons with the energy of 2.5 MeV.

The pipe shell assembly comprises an upper sealing ring 5, a neutron pipe shell 17 and a lower sealing ring 182 which are sequentially connected from top to bottom; the neutron tube shell 17 is a ceramic tube shell. The tube shell assembly is used for sealing the penning ion source assembly, the accelerating electrode 181, the self-targeting assembly and the air pressure adjusting assembly in a cylindrical barrel.

The core column assembly comprises a core column 4, a process exhaust pipe 1, a low-voltage electrode 2, a high-voltage electrode 3 and a grounding electrode 25, as shown in fig. 2, the core column 4 comprises a hollow cylindrical core column base 41 arranged in an upper sealing ring 5 and a core column supporting column 42 arranged at the lower part of the core column base 41, and the outer wall of the core column base 41 is sealed with the inner wall of the upper sealing ring 5; the process exhaust pipe 1, the low-voltage electrode 2, the high-voltage electrode 3 and the grounding electrode 25 are arranged on the core column base 41, wherein the upper sealing ring 5 and the core column 4 are arranged to be a common ground; after the neutron tube is subjected to double vacuum exhaust, the upper end of the process exhaust tube 1 can be closed; the ground electrode 25 is connected to the stem base 41 and is common to both.

And the air pressure adjusting component is used for storing deuterium gas and adjusting the working air pressure in the neutron tube. The air pressure adjusting assembly is positioned between the lower end face of the stem base 41 and the penning ion source assembly and comprises a heater 24 and a getter 6 wrapped outside the heater 24; the heater 24 has one end connected to the low voltage electrode 2 and the other end connected to the ground electrode 25, i.e., to the common ground, and in fig. 1, the ground electrode 25 is not shown in a cross-sectional view, so that the other end of the heater 24 is connected to the stem base 41 which is also the common ground; deuterium gas is adsorbed in the getter 6. The getter is made of zirconium-graphite non-evaporable getter material, has large gas absorption amount, can quickly release gas and absorb gas when the temperature rises and falls, and can quickly and effectively regulate the gas pressure in the tube at 175 ℃. After the neutron tube is powered off, the getter 6 absorbs deuterium gas in the sealed cavity along with the reduction of temperature, so that deuterium ions disappear, and the neutron tube stops emitting neutrons. In this example, the getter of the non-evaporable getter material of zirconium-graphite has the overall dimensions ofActivating at 850 deg.C for 10min, and allowing deuterium absorption rate to reach 900ml/s cm²The total amount of deuterium absorption can reach 898 Pa.ml/cm²。

The penning ion source component is used for generating deuterium ions and comprises an ion source cover 8, an ion source sealing ring 7, main magnetic steel 10, a cathode 12, an anode 13, an output cathode 15 and a magnetic ring 16. The ion source cover 8 is arranged in the neutron tube shell 17 and is connected with the upper sealing ring 5; a boss is arranged at the lower end of the upper sealing ring 5 in the radial direction, and a flange matched with the boss is arranged at the upper end of the outer wall of the ion source cover 8; the ion source cover 8 is connected with the upper sealing ring 5 through the matching of a flange and a boss, and the connection structure ensures the stable connection between the ion source cover and the upper sealing ring; the upper end edge of the boss is provided with a chamfer, so that the ion source cover is prevented from being worn to generate peak discharge when being placed into the tube shell, and the normal work of the neutron tube is prevented from being influenced. The ion source cover 8 is made of soft magnetic material, so that the phenomenon that the magnetic field leaks out to weaken the magnetic field intensity inside the ion source, and deuterium ions are not concentrated to form effective beam current can be avoided.

The ion source sealing ring 7 is arranged at the upper end of the ion source cover 8, the upper end surface of the ion source sealing ring is connected with the core column supporting column 42, and a first through hole is formed in the ion source sealing ring 7. The main magnetic steel 10, the cathode 12, the anode 13, the output cathode 15 and the magnetic ring 16 are sequentially arranged in the ion source cover 8 from top to bottom; the main magnet steel 10 is arranged between the lower end surface of the ion source sealing ring 7 and the cathode 12. The cathode 12 comprises a cathode body 121 and a cathode slot 122 arranged on the cathode body 121, and the main magnet steel 10 is arranged in the cathode slot 122; the upper end of the cathode slot 122 is provided with a lug along the radial direction, the outer edge of the lug is connected with the inner wall of the ion source cover 8, and two anode electrode insulating ceramic tubes 11 are symmetrically arranged on the lug along the axial direction. The main magnet steel 10 is made of samarium cobalt, the working temperature is 300-350 ℃, and the Curie temperature is 800 ℃. The invention increases the volume of the main magnetic steel 10, enhances the magnetic field intensity and improves the ion beam density.

The gap is formed between the cathode 12 and the anode 13 along the axial direction, which can prevent the cathode main body and the anode main body from being too close to cause discharge ignition, the gap cannot be too large, otherwise sufficient deuterium ions cannot be generated due to insufficient electric field energy, the gap is usually 1-3 mm, and in the embodiment of the invention, the gap between the cathode and the anode is 2 mm.

Two anode electrodes 132 are symmetrically arranged on two sides of the anode 13, the two anode electrodes 132 respectively extend into the two anode electrode insulating ceramic tubes 11, an anode lead 22 is led out from one anode electrode 132, and the anode lead 22 penetrates out of a first through hole on the ion source sealing ring 7 and is connected with the high-voltage electrode 3; an anode lead insulating ceramic tube 9 is sleeved outside the anode lead 22, and when the anode lead insulating ceramic tube 9 penetrates out of the ion source sealing ring 7, a gap exists between the anode lead insulating ceramic tube and the first through hole, so that deuterium gas released by the getter 6 enters the ion source cover 8 from the upper end of the ion source sealing ring 7.

The cathode 12 and the anode 13 are made of molybdenum, so that the high-temperature performance is good, and the normal work of the penning ion source under well logging can be effectively ensured.

The bottom of the ion source cover 8 is provided with a second through hole, a magnetic ring 16 and an output cathode 15 are sequentially arranged above the second through hole, the edge of the output cathode 15 and the ion sourceThe inner wall of the cover 8 is connected; a positioning ring 14 is arranged at the upper end of the output cathode 15; the outer diameter of the retaining ring 14 matches the inner diameter of the ion source housing 8 and its upper end is attached to the ledge edge of the cathode slot 122. Wherein, the output cathode 15, the magnetic ring 16 and the second through hole form a deuterium ion beam flow channel; the aperture of the output cathode 15 is 3-5 mm, so that the deuterium ion beam can pass through a larger deuterium ion beam and can be concentrated. In this embodiment, the aperture of the output cathode 15 is determined by experiments and takes the value of

Fifthly, the upper end of the inner wall of the lower sealing ring 182 is upwards provided with an accelerating electrode 181 with a cone-shaped structure, the accelerating distance of the accelerating electrode 181 is 10-12 mm, the distance can ensure that the accelerated deuterium ions reach enough bombardment energy, and if the accelerating distance is too short, the accelerating electrode is too close to a ion source cover, which may cause discharge ignition; the top end of the accelerating electrode 181 is provided with a through hole for enabling the deuterium ion beam to enter, the aperture of the through hole is 8-10 mm, the through hole is used for focusing the deuterium ion beam, the deuterium ion beam is poorly focused when the aperture is too large, the deuterium ion beam is easily shot on the inner wall of the accelerating electrode instead of a target in the accelerating process, the deuterium ion beam accelerated when the aperture is too small cannot cover the whole target surface, and the deuterium-deuterium nuclear reaction efficiency is low. In this embodiment, the acceleration distance is theoretically calculated and is determined by experimental verification to be 12mm, and the aperture of the through hole at the top end of the acceleration electrode 181 isIn order to avoid high-voltage breakdown of the tube shell caused by the point discharge, the through hole of the accelerating electrode 181 is designed to be circular arc, and the outer surface of the accelerating electrode 181 is polished to a mirror surface degree.

The self-targeting assembly is arranged in the lower sealing ring 182 below the accelerating electrode 181 and comprises a target substrate 19, and the outer wall of the target substrate 19 is sealed with the inner wall of the lower sealing ring 182; a circular groove is arranged in the middle of the lower end of the target base 19, target magnetic steel 20 is placed in the circular groove, and a target magnetic steel support 21 is arranged below the target magnetic steel 20; the target magnetic steel 20 and the magnetic steel support 21 form a target pole secondary electron suppression system, secondary electrons generated in the target are suppressed in a cone formed by the accelerating electrode 181, secondary electron current is reduced, and unit effective beam current is improved. Samarium cobalt alloy is selected as the material of the target magnetic steel 20, and the high-temperature performance of the samarium cobalt alloy material is good, so that the normal work of the penning ion source under the well logging can be effectively ensured.

A target film 23 is plated on the upper surface of the target substrate 19, and deuterium gas is adsorbed on the target film 23; the target film 23 is made of high-purity zirconium material, the zirconium material is used as the target film, the air suction amount is large, the deuterium adsorption amount in unit area is improved, the D-D nuclear reaction probability is increased, the temperature point of deuterium gas release from the target is also improved, and normal gas release can be realized at 175 ℃ under logging.

The target base 19 is made of oxygen-free copper material, the oxygen-free copper has high melting point and low oxygen content, has good strength in deuterium atmosphere, absorbs little deuterium, cannot compete with the target film for deuterium, has good heat dissipation effect, and effectively prevents the target film from being overheated and not releasing gas. The upper surface of the target base 19 is provided with an inward-concave conical surface structure, and the structure can increase the total area of a target film combined on the surface of the target base, thereby increasing the deuterium adsorption capacity, increasing the deuterium and deuterium reaction probability and increasing the neutron yield; the structure also increases the surface area of the target base, is beneficial to the heat dissipation of the target base, and prevents deuterium and deuterium nuclei from reacting to release a large amount of heat so as to prevent the target film from releasing deuterium gas due to overheating.

The space inside the cartridge assembly from the lower end face of the stem base 41 to the upper end face of the target base 19 is a vacuum environment.

The manufacturing method of the high-yield self-target D-D neutron tube comprises the following steps:

1) structural assembly

1.1) will seal ring 182, ceramic tube 17 and last seal ring 5 from the bottom up and weld in proper order down, form the tube, and concrete operation is: and sequentially installing the lower sealing ring 182, the accelerating electrode 181, the ceramic tube shell 17 and the upper sealing ring 5 into a positioning tool from bottom to top, placing silver-copper solder sheets on the upper end surface and the lower end surface of the ceramic tube shell 17, and welding the components into a tube shell assembly in a brazing mode.

1.2) connecting the cathode 12 with the two anode electrode insulating ceramic tubes 11 by brazing, then connecting the two anode electrodes 132 with the two anode electrode insulating ceramic tubes 11 by brazing respectively, wherein one anode electrode 132 is connected with an anode lead 22, and the anode lead insulating ceramic tube 9 is sleeved outside the anode lead 22 to form an electric field assembly; a magnetic ring 16, an output cathode 15, a positioning ring 14, an electric field assembly, main magnetic steel 10 and an ion source sealing ring 7 are sequentially arranged in an ion source cover 8 from bottom to top and are tightly pressed, an anode lead 22 and an anode lead insulating ceramic tube 9 are led out from the ion source sealing ring 7, and a gap exists between the anode lead insulating ceramic tube 9 and the ion source sealing ring 7; and spot welding and sealing the ion source sealing ring 7 and the ion source cover 8 at the joint of the upper end surface by using a spot welding machine to form the penning ion source assembly.

1.3) respectively connecting the process exhaust pipe 1, the low-voltage electrode 2, the high-voltage electrode 3 and the grounding electrode 25 on a core column base 41 of a core column 4 in a brazing mode to form a core column assembly; the core column supporting column 42 of the core column 4 is connected with the upper end surface of the ion source sealing ring 7 in a soldering way, and the anode lead 22 is connected with the high-voltage electrode 3 in a spot welding way; the stem assembly and the penning ion source assembly are connected into a whole.

1.4) wrapping the getter 6 outside the heater 24, connecting one end of the heater 24 with the low-voltage electrode 2 by using a spot welding machine, and connecting the other end of the heater 24 with the stem supporting column 42 (on the public ground) to form a gas supply assembly, wherein the gas supply assembly, the stem assembly and the penning ion source assembly are connected into a whole.

1.5) putting the core column assembly, the gas supply assembly and the penning ion source assembly which are connected into a whole into the tube shell assembly from the upper part of the tube shell obtained in the step 1.1), and sealing the outer wall of the core column base 41 and the inner wall of the upper sealing ring 5 by using an argon arc welding method.

1.6) plating a target film 23 on the target substrate 19; the target magnetic steel 20 is arranged in a circular groove on the lower end face of the target base, and the target magnetic steel 20 is fixed on the target base 19 through a target magnetic steel support 21.

1.7) putting the self-target assembly into the tube shell assembly from the lower part of the tube shell obtained in the step 1.1), and sealing the outer wall of the target base 19 and the inner wall of the lower sealing ring 182 by using an argon arc welding method, thus finishing the structural assembly of the neutron tube.

2) Double vacuum high temperature exhaust

And removing the impurity gases on the inner surface, the outer surface and the deep layer of the neutron tube by double-vacuum high-temperature exhaust. Opening the process exhaust pipe 1 of the neutron tube obtained in the step 1) and connecting the process exhaust pipe with a vacuum pump, placing the whole neutron tube in a vacuum environment, setting the temperature of the vacuum environment to be 450-500 ℃ because the self-targeting target film does not adsorb any gas before exhausting, and starting exhausting for more than 20 hours. In the present embodiment, the exhaust gas temperature is set to 470 ℃. After the exhaust is completed, deuterium gas is supplied to seal the process exhaust pipe 1.

The quality of the exhaust gas directly influences the performance of the neutron tube, the degassing is not thorough, besides the pressure resistance of the tube is influenced, the residual miscellaneous gas in the tube can also reduce the effective components of ion flow, the neutron yield is naturally reduced, and under the condition of the same other conditions, the difference of the neutron yield due to the difference of the exhaust gas quality can be more than one time.

3) Aging test

Pressure-resistant exercise

And (3) placing the neutron tube subjected to the double-vacuum high-temperature exhaust in an insulating environment, cooling to normal temperature, then gradually raising the temperature of the environment where the neutron tube is located from the normal temperature to 175 ℃, gradually raising the voltage in the tube in the process, and finally enabling the working withstand voltage of the D-D neutron tube to reach over 140KV at the high temperature of 175 ℃ for 8-10 hours. The pressure-resistant exercise can eliminate burrs and conductive particles in neutrons of the tube and remove miscellaneous gases released by parts in the tube at the high temperature of 175 ℃, so that the temperature resistance of the tube is improved, and the D-D neutron tube is favorable for outputting higher neutron yield in a larger working high-pressure range.

② target saturation exercise

After the pressure-resistant exercise is finished, 60 KV-100 KV voltage is provided for an accelerating electrode 181 of the neutron tube, the low-voltage electrode 2 supplies power for the heater 24, the high-voltage electrode 3 supplies power for the anode 13, the getter 6 is heated to release deuterium gas, the deuterium gas bombards the target film 23 after ionization and acceleration, deuterium ions are gradually injected into the self-forming target film, the duration is 8-10 hours, the content of the deuterium gas in the target film 23 is saturated, and the self-forming target with stable neutron yield is formed.

Third, index testing

After the first two processes were completed, the D-D neutron yield at high temperature of 175 ℃ was testedAnd various power supply parameters, and tests show that the D-D neutron yield of the high-yield self-target D-D neutron tube reaches 1 x 10⁷n/s or more.

The high-yield self-target D-D neutron tube can emit fast neutrons with the energy of 2.5MeV by electrifying, can be turned off when not in use, has good safety, and the D-D neutron yield reaches 1 multiplied by 10⁷More than n/s, can replace the compensation neutron logging of oil fields and coal fields and the on-line analysis of coal, cement, mines and the like²⁴¹Am-Be、²³⁸Pu-Be、²⁵²The Cf isotope neutron source and the 14MeV controllable neutron source have the advantages of small volume, long service life, convenient transportation, convenient equipment maintenance and the like.

The above description is only for the purpose of describing the preferred embodiments of the present invention and is not intended to limit the technical solutions of the present invention, and any known modifications made by those skilled in the art based on the main technical concepts of the present invention are within the technical scope of the present invention.