CN1142448C - Miniature neutron tube and its production method - Google Patents
Miniature neutron tube and its production method Download PDFInfo
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- CN1142448C CN1142448C CNB011153261A CN01115326A CN1142448C CN 1142448 C CN1142448 C CN 1142448C CN B011153261 A CNB011153261 A CN B011153261A CN 01115326 A CN01115326 A CN 01115326A CN 1142448 C CN1142448 C CN 1142448C
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Abstract
The present invention belongs to the technical field of a measuring instrument, and provides two miniature neutron tubes and a corresponding making method. One miniature neutron tube is sheathed with a deflection electronic permanent magnet outside s target chamber, has inner pure tritium target or D-T hybrid target with large target area and has the advantages of high temperature resistance, short spacing and broad application. The other miniature neutron tube has a large Penning ion source; the outer diameter of the miniature neutron tube is in sliding matching with the inner diameter of a neutron generator to be assembled; the miniature neutron tube is particularly suitable for assembling the neutron generator of which the diameter is obvious smaller than 30mm. The present invention has the advantages of high neutron productivity and long service life, can be provided with a deuterium memory and a tritium memory at the same time and can be repaired for reuse by a user after failure use.
Description
The invention belongs to the technical field of measuring instruments, and particularly relates to a sealing neutron tube for a small-diameter logging instrument.
Background art in small diameter logging instruments, neutron generators of smaller diameter are assembled; the neutron generator is made of a miniature neutron tube with a smaller diameter. Currently, commercial small-diameter neutron generators have a diameter of about 35mm, and the diameter of the neutron generators is further reduced in the well logging field, so that the development of a miniature neutron tube meeting the requirement is required.
Currently, a representative patent for a miniature neutron tube is U.S. patent No. 4996017, published in 2 months 1991. The neutron tube disclosed by the patent comprises a penning ion source, a high-voltage-resistant insulating sealed shell, a deuterium-tritium mixed self-forming target, a suppression electrode and a deuterium-tritium mixed storage device. The penning ion source is as large as the diameter of the high-voltage-resistant insulating sealing shell; the high-voltage-resistant insulating sealing shell is short, and can bear high voltage of only about 11 ten thousand volts; the suppression electrode is fixed in a sealing metal tube of a high-voltage-resistant insulating sealed shell, and the diameter of the target surface is only about 11 mm due to the structure. The neutron yield of this type of neutron tube is greatly limited by the above factors. The high voltage potential at the target leads to longer source distance, and limits the application range of the neutron tube. After the neutron tube fails to work, the user is difficult to repair the neutron tube by himself. With this type of neutron tube, a neutron generator having a diameter of about 35mm can be assembled, and it is difficult to further reduce the diameter thereof.
The ideal requirements for a miniature neutron tube are: the diameter is small enough, such as can be used for making the neutron generator with diameter less than 35 mm; the neutron yield is sufficiently high, such as greater than 108 neutrons per second; the useful life is long enough, such as greater than 100 hours; the high temperature resistance is enough, such as higher than 170 ℃; in addition, the earthquake-proof performance is good, and the price is easy to be accepted by users. Under the present circumstances, the comprehensive index of the existing commercial products is far from the above requirements.
The invention aims to overcome the defects of the prior art and provides two novel miniature neutron tubes and corresponding manufacturing methods; they can be used to make neutron generators with a diameter equal to or less than 35 mm; and has the advantages of high neutron yield, long effective service life, good high temperature resistance, good earthquake resistance, relatively low price and the like.
The invention provides a miniature neutron tube, which consists of a high-pressure-resistant insulating sealed shell, a penning ion source, a target chamber, an accelerating electrode and a hydrogen isotope storage, wherein the penning ion source is formed by welding a sealing cover and a cup-shaped shell which are made of magnetic conductive metalmaterials, a sealed tube made of nonmagnetic materials and a cathode substrate made of magnetic conductive materials together, and is characterized in that: the high-voltage-resistant insulating sealing shell is formed by respectively sealing two ends of a high-voltage insulating tube with a thick end and a thin end with a thick annular sealing metal part and a thin annular sealing metal part, wherein the thick end and the thin end of the high-voltage insulating tube are respectively provided with a three-layer structure on the side wall; the accelerating electrode is fixed on the thick ring sealing metal part; the target chamber is welded with the thick ring-shaped sealing metal part, and the penning ion source is welded with the thin ring-shaped sealing metal part; the target chamber is a metal cylinder with a bottom made of a non-magnetic metal material with excellent heat conductivity, and the bottom of the metal cylinder is used as a target substrate; the outer diameter of the target substrate is close to the inner diameter of the thick end of the high-voltage insulating tube, and a hydrogen isotope target film with the diameter slightly smaller than that of the inner end surface is manufactured on the inner end surface of the target substrate; a deflection electronic permanent magnet is arranged outside the side wall of the target chamber; the target chamber end is connected with the ground potential; the hydrogen isotope memory is welded on the outer end surface of the target substrate; the penning ion source is thin at one end and thick at the other end, the outer diameter of the thick end of the penning ion source is close to the inner diameter of the thick end of the high-voltage insulating tube, and the anode is contained in the thick end of the penning ion source; plating a metal film with high secondary electron emission coefficient on the end surface of the cathode substrate close to the anode and the inner surface of the cup-shaped shell close to the anode to serve as a cathode; the penning ion source is connected with a positive high-voltage potential; an auxiliary high-voltage insulating cylinder is arranged outside the end of the thin ring type sealing metal part.
The invention provides another miniature neutron tube which is composed of a high-voltage-resistant insulating sealing shell, a penning ion source, a target chamber and a hydrogen isotope storage, wherein the penning ion source is as follows: the sealing cover made of magnetic material, the sealing tube made of nonmagnetic material and the cathode substrate made of magnetic material are sealed and welded together to form a sealing shell; the anode lead, the exhaust pipe and the lead of the hydrogen isotope storage are welded on the sealing cover, a cup-shaped shell made of magnetic conductive material is fixed on the sealing and sealing pipe, and the anode is a metal ring made of nonmagnetic material and fixed on the anode lead; plating a metal film with high secondary electron emission coefficient on the inner end surface of the cathode substrate and the inner surface of the bottom of the cup-shaped shell close to the anode to serve as a cathode; the method is characterized in that: the high-voltage-resistant insulating sealing shell is formed by respectively sealing two ends of a high-voltage insulating tube with a thick end and a thin end with a thick annular sealing metal part and a thin annular sealing metal part with a three-layer structure on the side wall; the outer diameter of the thick ring-shaped sealing metal part is 6-8mm larger than the outer diameter of the thick end of the high-voltage insulating tube and is matched with the inner diameter of a shell of a neutron generator to be assembled in a sliding manner; the thick ring type sealing metal part is also used as a part of the external magnetic circuit of the penning ion source; cathode ground potential of the penning ion source; the hydrogen isotope storage device is welded inside the penning ion source; the target chamber is composed of a target substrate made of metal materials with particularly good heat conducting performance and a suppression electrode, and the suppression electrode is fixed on the target substrate in an insulating mode through a ceramic component; the suppression electrode is connected with a power supply lead through a lead in an inner insulation hole of the target substrate; the inner end of the target substrate is thick, the outer end of the target substrate is thin, the diameter of the inner end surface of the target substrate is slightly smaller than the inner diameter of the thick end of the high-voltage insulating tube, and the diameter of the outer end surface of the target substrate is matched with the inner diameter of the thin ring-shaped sealing metal part in a sliding mode; a hydrogen isotope target film is arranged on the inner end surface of the target substrate; the target substrate is connected with a negative high-voltage potential; an auxiliary high-voltage insulating cylinder is arranged outside the end of the thin ring type sealing metal part.
The hydrogen isotope memory in the miniature neutron tube can comprise a deuterium memory and a tritium memory.
The hydrogen isotope target in the miniature neutron tube is an internal tritium target or a deuterium-tritium mixed target which is manufactured after the neutron tube finishes exhausting and before the exhaust tube is cut off.
The auxiliary high-voltage insulating cylinder is made of aluminum nitride ceramics.
The deflection electronic permanent magnet of the neutron tube is a ring-shaped permanent magnet or a U-shaped permanent magnet in a ring shape.
The accelerating electrode in the miniature neutron tube is made of nonmagnetic material with good sputtering resistance.
The invention also provides a manufacturing method of the miniature neutron tube, which comprises the following steps:
1) the main body of the neutron tube is manufactured according to the conventional process, and comprises the steps of sequentially welding a penning ion source, a high-voltage-resistant insulating sealing shell and a target chamber to form a sealed whole, manufacturing a target film on the inner surface of a target substrate in the neutron tube, and installing a hydrogen isotope storage;
2) sleeving a specially-made heating ring around the target substrate when the neutron tube main body is subjected to racking, baking and exhausting;
3) after the baking and exhausting of the neutron tube main body are finished, cooling the baking oven, and electrifying the heating ring to slowly heat the target substrate;
4) monitoring by a temperature control instrument to ensure that the temperature of the target substrate is above 400 ℃ and other parts of the neutron tube main body are below 180 ℃;
5) closing the exhaust system, starting a deuterium-tritium inflation system, and injecting a predetermined amount of tritium gas or a deuterium-tritium mixed gas into the neutron tube main body, wherein the tritium gas or the deuterium-tritium mixed gas is quickly absorbed by a target film to form a pure tritium target or a deuterium-tritium mixed target;
6) stopping heating the target substrate, and cooling all parts of the whole neutron tube main body to room temperature;
7) filling quantitative deuterium gas or deuterium-tritium mixed gas into the deuterium storage device according to a conventional process;
8) finally, the exhaust pipe is cut off, and the finished neutron tube containing the internal tritium-making target or the deuterium-tritium mixed target is obtained.
The invention has the characteristics that:
the invention provides a first miniature neutron tube, wherein a deflection electron permanent magnet is sleeved outside a target chamber at ground potential and used for inhibiting secondary electrons; the target area is more than three times of the target area of the traditional similar neutron tube; the target substrate can be directly contacted with the neutron generator shell, and the heat conduction and heat dissipation performance of the target substrate are particularly good; an auxiliary high-voltage insulating cylinder with good heat-conducting property is sleeved at the end where the penning ion source is positioned at high potential; deuterium storage and tritium storage can be arranged at the same time; the pure tritium target or the deuterium-tritium mixed target can be manufactured in the manufacturing process of the neutron tube. The application characteristics of the invention are as follows: is particularly suitable for working in high-temperature environment; the source distance is short, and the application range is wide; the neutron yield is high, and the service life is long; after the use fails, the user can repair the device by himself; can be used for manufacturing neutron generators with the diameter equal to or less than 35 mm.
The outer diameter of the penning ion source at the ground potential of the second miniature neutron tube is larger than that of the high-voltage insulating sealing tube, and the second miniature neutron tube is matched with the inner diameter of a neutron generator to be assembled in a sliding manner; an auxiliary high-voltage insulating cylinder with good heat conduction performance is sleeved outside the end of the target chamber at the high potential; the target area is more than twice of the target area of the traditional similar neutron tube; deuterium storage and tritium storage can be arranged at the same time; the pure tritium target or the deuterium-tritium mixed target can be manufactured in the manufacturing process of the neutron tube. The application characteristics of the invention are as follows: the structure is particularly suitable for manufacturing neutron generators with the diameter of less than 35mm (as small as phi 28mm), the neutron yield is high, the service life is long, and after the neutron generators are used and failed, users can repair the neutron generators by themselves.
Drawings
Fig. 1 is a cross-sectional view along the center axis of embodiment 1 of the present invention.
Fig. 2 is a cross-sectional view along the center axis of embodiment 2 of the present invention.
FIG. 3 is another cross-sectional view along the central axis of the embodiment 2 of the present invention, the cross-section being perpendicular to the cross-section of FIG. 2.
Fig. 4 is a right side view in radial section at 4-4 of fig. 2.
Detailed description of the inventionreference is now made to fig. 1 to 4 for a detailed description of the structure and operation of two embodiments of the present invention. The structure of example 1 is shown in fig. 1. Fig. 1 is a cross-sectional view of the neutron tube along the central axis, which includes a cold cathode penning ion source (hereinafter referred to as penning ion source) 11, a high-pressure-resistant insulating sealed shell 12, a target chamber 13, and a deuterium-tritium gas reservoir 14. The parts are welded and connected in sequence to form a sealed whole.
Wherein, the penning ion source 11 has the structure that: a seal cap 21 made of a magnetically conductive metal material, a seal tube 22 made of a nonmagnetic material, and a cathode base 23 made of a magnetically conductive material are welded together, and an anode high-voltage insulated lead wire 24 and an exhaust pipe 25 are welded to the seal cap 21, thus forming part of a neutron tube sealing system. A cup-shaped housing 26 made of a magnetically permeable metal material is secured to the sealing cover 21, which together form the outer magnetic circuit of the penning ion source. A metal ring 27 made of a nonmagnetic material is an anode and is fixed to a center lead 29 of the anode lead 24. A cylindrical samarium cobalt magnet 28 is inserted into the sealed tube 22 through the central guide hole 51 to establish a longitudinal magnetic field inside the anode 27 through the cathode substrate 23. A metal film with high secondary electron emission coefficient is plated on the concave end surface of the cathode substrate 23 close to the anode and the inner surface of the bottom of the cup-shaped shell 26 close to the anode to serve as a cathode. The cup-shaped housing 26 has a central aperture 52 in the bottom thereof, which is a longitudinal ion exit aperture.
The high-voltage insulating sealed shell 12 is formed by sealing a high-voltage insulating tube 31, a thick ring-shaped sealing metal part 32 and a thin ring-shaped sealing metal part 33. The side wall of the sealing part 33 has a three-layer structure, and the longitudinal section thereof is in a zigzag shape, so that the end can withstand high-temperature baking.
The target chamber 13 is a bottomed metal cylinder made of a metal material excellent in nonmagnetic and heat conductivity, and the bottom of the metal cylinder serves as a target base 37. The concrete structure is as follows: the side wall 36 of the target chamber made of nonmagnetic metal material, the target base 37 made of oxygen-free copper, the deuterium storage 41 and the tritium storage 42 are welded together to form a partof a neutron tube sealing system; a target film 38 of a hydrogen isotope target having a diameter slightly smaller than that of an inner end surface of a target substrate 37 is formed on the inner end surface, and an accelerating electrode 39 is fixed to a target chamber case. As described above, the penning ion source 11, the high voltage resistant insulating sealed envelope 12 and the target chamber 13 are welded together at 6 and 7, respectively, to form a gas-tight neutron tube element.
The present embodiment is characterized in the following aspects:
the neutron tube is characterized in that the penning ion source end is connected with a positive high-voltage potential, and the target chamber end is connected with a ground potential, so that a small-diameter neutron generator assembled by the neutron tube has the characteristic of short source distance and has universality in application; it is especially suitable for the occasions needing smaller and better source distance, such as fast neutron oxygen activation logging instrument. The penning ion source end will be sealed within the main insulating cylinder of the neutron generator (not shown in the figure). Due to the limitation of space, the wall thickness of a general main insulating cylinder is about 3-4 mm, and the breakdown voltage which can be borne is about 10 ten thousand volts; the inner diameter of the main insulating cylinder is almost the same as the outer diameter of the high-voltage insulating tube 31 of the present embodiment, and therefore the diameter of the sealing metal member 32 of the present embodiment is 4mm or more smaller than the inner diameter of the main insulating cylinder of the generator. When the neutron generator is assembled, the penning ion source end needs to be sleeved with an insulating cylinder (not shown in the figure) which has the thickness of about 2.0mm and can bear the voltage of more than 4 ten thousand volts, so that the insulating medium between the high-voltage end of the neutron tube and the metal shell of the neutron generator can bear the high voltage of more than 12 ten thousand volts on the whole, and the safe power supply of the neutron tube can be ensured.
The larger the volume of the interior of the anode of the penning ion source in the neutron tube, the larger the intensity of the extracted beam current. The penning ion source of the present embodiment has an outer diameter that is relatively close to the inner diameter of the high voltage insulating tube 31, and the ion extraction intensity is sufficient to generate more than 108 neutrons per second.
In order to prevent secondary electrons emitted by the bombardment of the target from being emitted to the penning ion source under the acceleration of an electric field, the embodiment is provided with a deflection electron permanent magnet 49 outside the side wall 36 of the annular target chamber, a magnetic field containing a radial component is generated in front of the target, and the electrons moving to the penning ion source are deflected under the action of the magnetic field and absorbed by the surrounding metal conductor. The magnet can be in various shapes, such as a circular ring shape or an annular U shape, and the embodiment adopts a circular ring shape.
The neutron tube target chamber 13 of the present embodiment further includes an accelerating electrode 39 installed in front of the target film 38. The target film 38 is formed by vapor depositing a titanium film on the inner surface of the target substrate 37 in accordance with conventional techniques. The accelerating electrode 39 is made of a nonmagnetic material having a high sputtering resistance and has an ion accelerating entrance hole 53. Two O-grooves 55 on the left end of the chamber side wall 36 are used to place a rubber seal. When assembling the small-diameter neutron generator, the neutron tube is inserted from one end of the shell of the neutron generator, and air-tight connection is formed at the O-shaped groove. Thus the high voltage part of the neutron tube to the left from the part 33 is inside the main insulating cylinder of the generator, while the target chamber is outside the main insulating cylinder of the generator. This has the following benefits: firstly, the diameter of the target chamber is not restrained by the inner diameter of the main insulating cylinder any more, and can be made larger, so that a larger target surface can be obtained conveniently. The diameter of the target of the embodiment can reach 22mm, which is quite ideal for a miniature neutron tube adopting a penning ion source; the target chamber is positioned outside the sealing area of the neutron generator, and a deflection electronic permanent magnet can be freely placed; thirdly, the size and the structure of the target substrate can be conveniently changed, so that the target substrate has the best heat conduction and heat dissipation performance. In the neutron logging instrument, the 'cold source' for absorbing the heat of the target is the shell of the neutron generator and the shell of the logging instrument, and the good heat conduction between the target substrate and the 'cold source' can be easily realized by adopting the design. In summary, the present embodiment will have the best high temperature resistance. The deuterium memory 41 of the present embodiment employs a zirconium memory, and has a strong hydrogen absorption capability. The tritium storage 42 is made of a hydrogen absorption metal wire, the hydrogen absorption capacity is relatively poor, and hydrogen absorption can be started only when the temperature is very high (higher than 300 ℃); the normal temperature saturated hydrogen absorption rating of the tritium memory 42 is small and much smaller than that of the deuterium memory 41. Their outer shells 43, 44 are made of non-magnetic stainless steel, the outer ports are welded with ceramic leads 45, 46 which are resistant to high temperature baking, and the inner channels 56, 57 of the target substrate connect the inner space of the memory and the inner space of the target chamber into a whole. The temperature of the deuterium storage heater wire 47 and the gas storage wire 48 of the storage 42 is controlled by adjusting the current. The manufacturing method of the embodiment is as follows: the penning ion source 11, the high-voltage resistant insulating sealing shell 12 and the target chamber 13 are welded together at 6 and 7 respectively to form an airtight neutron tube main part. At this time, no permanent magnet is arranged in the penning ion source, the target film 38 does not adsorb hydrogen isotopes, and no deflection electron permanent magnet is arranged outside the target chamber 13, so that the whole main part allows the adoption of ultrahigh-temperature baking exhaust. The original neutron tube is connected with an exhaust station through an exhaust pipe 25, and the exhaust station is provided with a quantitative deuterium-tritium inflation system. Through long-time high-temperature and high-vacuum exhaust, all parts in the neutron tube main part are nearly completely degassed; thorough degassing is essential to improve the high temperature resistance and prolong the service life of the neutron tube. After the exhaust of the neutron tube main part is finished, the hydrogen-containing isotope target film 38 is manufactured, and besides the conventional manufacturing technology of 'deuterium-tritium mixed self-target', the manufacturing method of the invention can also be adopted as follows:
1. manufacturing technology of 'deuterium-tritium mixed target' on platform
The term "on-table" as used herein means that the exhaust pipe is not cut and the neutron tube is not removed from the exhaust table.
When the neutron tube is arranged on the rack for exhausting, a special heating ring is sleeved on the periphery of the target substrate, and when the temperature of the baking furnace is reduced after exhausting, the heating ring is electrified. The target substrate is a good thermal conductor, and the target film and other parts of the neutron tube can be at different temperatures by monitoring through a temperature control instrument, and the value of the target substrate is that the temperature of the target substrate is high enough (above 400 ℃) so that the target film has good enough air suction rate; the temperature of other parts of the neutron tube is as low as possible (below 180 ℃), and the air suction interference is negligible. After the temperature is proper, the exhaust system is closed, the deuterium-tritium inflation system is started, a predetermined amount of deuterium-tritium mixed gas is injected into the neutron tube, and the deuterium-tritium mixed gas are quickly absorbed by a target film to form a target containing the deuterium-tritium mixed gas, which is called as a deuterium-tritium mixed target. After the neutron tube is cooled to the room temperature, filling a predetermined amount of deuterium-tritium mixed gas into the deuterium storage according to the conventional process, and finally cutting off the exhaust pipe 25 to obtain the finished product neutron tube.
2. Technique for preparing "internal tritium-making target" on platform
The term "on-table" as used herein means that the exhaust pipe is not cut and the neutron tube is not removed from the exhaust table.
The term "internal tritium target" refers to a pure tritium target formed by absorbing tritium gas in a target film at the later stage of neutron tube production. The basic process is the same as the process for manufacturing the deuterium-tritium mixed target on the platform, except for the filled gas. Cooling the baking oven after the neutron tube finishes exhausting; electrifying the heating ring, and controlling the target substrate and other parts of the neutron tube to be at proper temperatures respectively; and closing the exhaust system, starting a deuterium-tritium inflation system, and allowing the titanium film to absorb a certain amount of tritium to form the tritium-titanium target. After the neutron tube is cooled to the room temperature, the deuterium storage 41 is filled with quantitative deuterium according to the conventional process, then the tritium storage 42 is filled with quantitative tritium, and finally the exhaust pipe 25 is cut off, so that the finished product of the neutron tube is obtained. The tritium reservoir 42 is tritiated to repair the neutron tube when the tritium target fails.
The internal tritium-making target and the deuterium-tritium mixed target (including the existing deuterium-tritium mixed self-forming target) have characteristics.
In the early stage of operation of a neutron tube containing an internal tritium target, a nuclear reaction for generating 14MeV neutrons mainly exists: under the condition of setting the neutron yield, the required intensity of the incident ion beam is much smaller than that of a neutron tube containing the deuterium-tritium mixed target. With the operation of the neutron tube, deuterium ions injected into the target are accumulated continuously, so that the pure tritium target is gradually changed into a 'deuterium-tritium mixed target', and the process of course needs a long time. The neutron tube containing the deuterium-tritium mixed target has the advantage of good neutron yield stability. Overall, "intrinsic tritium targets" are superior to "mixed deuterium and tritium targets"; the 'deuterium-tritium mixed target' is superior to the 'deuterium-tritium mixed self-forming target'; the three are all superior to the traditional 'preset tritium target'.
After the neutron yield is reduced to critical, a tritium storage 42 can be used for reconstructing a new tritium target or reconstructing the neutron tube containing a deuterium-tritium mixed target, so that the neutron yield is improved, and the service life of the neutron tube is prolonged. The method comprises the following steps:
1. heating the target substrate to allow the titanium film to rapidly release deuterium and tritium, and heating the deuterium reservoir 41 to increase its hydrogen absorption capacity, the temperature criteria being: the equilibrium gas pressure of the titanium film is more than 10 times higher than that of the deuterium storage device 41, so that the deuterium and tritium emitted from the titanium film will be absorbed by the deuterium storage device. Then stopping heating the deuterium memory and allowing it to cool to room temperature; the target substrate is also cooled to a certain degree, but has stronger hydrogen absorption capacity; then, the tritium storage is heated to a high temperature, so that the tritium contained in the tritium storage is rapidly discharged and absorbed by the titanium film. The final result is that the titanium target becomes pure tritium target, the tritium storage device releases stored tritium, the deuterium storage device absorbs deuterium and tritium of the original titanium target, and the overall deuterium content is far larger than that of tritium. The performance of the repaired neutron tube is close to the initial use characteristic. The above operations can be performed in a user laboratory with the necessary conditions.
2. Heating the tritium storage 42 to rapidly release the tritium contained therein, and simultaneously heating the deuterium storage 41 to make it have strong tritium absorption capability; after a short period of time, the tritium transfer is basically finished, the deuterium storage device is cooled first, the remaining tritium is further absorbed, and then the tritium storage device is stopped being heated. The final result is that the titanium target is unchanged, corresponding to the deuterium-tritium mixed target; the deuterium storage device stores deuterium-tritium mixed gas. The performance of the repaired neutron tube is close to that of a newly prepared neutron tube containing the deuterium-tritium mixed target. The above operations may be performed in a user laboratory. Is very safe, reliable and convenient.
The micro neutron tube described in the embodiment 1 is particularly suitable for working in a high-temperature environment, wherein the neutron yield is high, the working life is long, and a user can repair the tube by himself after the tube is used and failed; can be used for manufacturing neutron generators with the diameter equal to or less than 35 mm. It has these significant advantages, the main techniques are: the whole element is allowed to adopt ultra-high temperature baking exhaust; although the outer diameter of the high-voltage-resistant insulating tube is small, the diameter of the penning ion source is relatively small; the target chamber is designed to ensure that the diameter of a target surface is large, and the heat conduction and heat dissipation performance of a target substrate is particularly good; using a deflection electron permanent magnet to suppress secondary electrons; the overall design allows for application of operating voltages of up to 12 kilovolts; in particular, both deuterium and tritium memories may be provided; an "internal tritium-producing target" or a "deuterium-tritium mixed target" is prepared.
The structure of embodiment 2 is shown in fig. 2, 3 and 4, and fig. 2 and 3 are cross-sectional views of the sub-pipe of this embodiment along the central axis, the cross-sections being perpendicular to each other. Fig. 4 is a right side view in radial cross-section at 4-4 of fig. 2. The neutron tube of the present embodiment is composed of a penningion source 71, a high voltage resistant insulating sealed shell 72, a target chamber 73, a hydrogen isotope storage 74 and a suppression electrode 75.
Wherein the penning ion source 71 has the structure: a sealing cover 81 made of magnetic conductive material, a sealing tube 82 made of nonmagnetic material and a cathode substrate 83 made of magnetic conductive material are sealed and welded together to form a sealed shell; the anode lead 84, the exhaust pipe 85, and the leads 105 and 106 of the two hydrogen isotope storage containers 101, 102 are welded to the seal cover 81, thus forming part of the neutron tube sealing system. A cup-shaped shell 86 made of a magnetically permeable material is secured to the sealing and sealing tube 92, which together form the outer magnetic circuit of the penning ion source. A metal ring 87 made of nonmagnetic material is an anode and is fixed to a center lead 89 of the anode lead 84. A cylindrical samarium cobalt magnet 88 is inserted into the interior from the central guide hole 111 to create a longitudinal magnetic field. A metal film with a high secondary electron emission coefficient is plated on the concave inner end surface of the cathode base 83 and the inner surface of the bottom of the cup-shaped case 86 near the anode to serve as a cathode. The bottom central aperture 112 of the cup-shaped housing 86 is a longitudinal ion extraction aperture.
The high-voltage-resistant insulating sealing shell 72 is formed by sealing an insulating tube 91 and thick and thin annular sealing metal parts 92 and 93. The side wall of the thin annular sealing part 93 is of a three-layer structure, so that the end can bear high-temperature baking.
The target chamber 73 has the structure: the target substrate 97 is made of oxygen-free copper with particularly good heat conduction performance, the diameter of the inner end face of the target substrate is larger than thatof the outer end of the target substrate so as to obtain a larger target area, and the target 98 is made by evaporating a titanium film on the inner end face of the target substrate 97 according to the traditional process; welding a suppressor electrode insulated lead wire 99 at the outer end of the target substrate, applying a voltage to the suppressor electrode 75 through the target substrate's inner insulated via 116 using its center wire 100; the suppression electrode 75 is made of a non-magnetic material with good sputtering resistance, is provided with an ion acceleration entry hole 113, and is fixed on the target base 97 through a ceramic sealing member 96; the suppression electrode is coupled to a power supply lead by a wire in an inner insulating channel of the target substrate.
As described above, the penning ion source 71, the high voltage resistant insulating sealed envelope 72 and the target chamber 73 are welded together at 8, 9 to form a hermetically sealed neutron tube element. It is characterized in the following aspects.
The neutron tube is at penning ion source cathode earth potential, the target substrate is connected with negative high-voltage potential, and the end of the target chamber is sealed in a main insulating cylinder of the neutron generator; due to the limitation of space, the wall thickness of a main insulating cylinder of the neutron generator is about 3 to 4mm, and the breakdown voltage of about 10 ten thousand volts can be borne. The outer diameter of the neutron tube high-voltage insulating tube 91 is close to the inner diameter of the main insulating cylinder, so the outer diameter of the thin ring type sealing metal part 93 must be 4 to 5mm smaller than the inner diameter of the neutron generator main insulating cylinder. When assembling the small-diameter neutron generator, an auxiliary high-voltage insulating cylinder (not shown in the figure) with the thickness of more than 2mm and capable of bearing thebreakdown voltage of more than 4 kilovolts is arranged on the end sleeve. Therefore, the insulating medium between the high-voltage end of the neutron tube and the metal shell of the neutron generator can bear the bulk breakdown voltage of more than 12 ten thousand volts in the whole view, and the necessary reliable high-voltage power supply of the neutron tube can be ensured. In order to dissipate the heat on the target more quickly, special ceramics (such as aluminum nitride ceramics) with high pressure resistance and good heat conductivity can be used for manufacturing the auxiliary high-pressure insulating cylinder.
The suppression electrode 75 is powered by an insulated lead wire 99, which advantageously allows the diameter of the target surface to be as large as the inner diameter of the insulating tube 91, facilitating the fabrication of a neutron tube and neutron generator of a smaller diameter.
The existing neutron tube is generally that the outer diameter of a penning ion source is smaller than or equal to that of a high-voltage insulating tube of the neutron tube; the neutron tube is characterized in that the outer diameter of the penning ion source 71 is about 6-8mm larger than that of the high-voltage insulating tube 91 of the neutron tube, and is matched with the inner diameter of a metal shell (not shown in the figure) of a neutron generator to be assembled in a sliding mode. This is based on the following considerations: supposing that a neutron generator with the diameter of 30mm is manufactured, the wall thicknesses of a shell of the neutron generator, a main insulating cylinder of the generator and a high-voltage insulating tube 91 are removed, and the inner diameter of a cavity of the neutron tube is only about 15 mm; difficult to make for generating 10 in a cavity of 15mm8Penning ion source for neutrons per second. It is therefore necessary to place the penning ion source outside one end of the high voltage insulating tube 91 of the neutron tube, at ground potential, and to have its diameter as large as possible, up to the inner diameter of the housing of the neutron generator. At this time, although the diameter of the neutron generator is as small as 30mm, penning can be producedDiameter of ion sourceBut around 29mm, which is very advantageous for obtaining a high neutron yield. The solution adopted by this embodiment opens up the possibility of making neutron generators with a diameter substantially less than 35 mm. Analysis shows how small the diameter of the small-diameter neutron generator can be after the neutron tube is adopted, and the small-diameter neutron generator can not be limited by the neutron tube any more.
The deuterium storage device 101 and the tritium storage device 102 of the embodiment are arranged inside the penning ion source, and two ends of a heating wire of the deuterium storage device and two ends of a heating wire of the tritium storage device are respectively connected with a penning ion source sealing shell and central leads of ceramic leads 105 and 106.
The penning ion source 71, the high voltage resistant insulating sealing shell 72 and the target substrate 97 are welded together at 8 and 9 respectively, so that an airtight neutron tube element is formed. The subsequent baking exhaust and the method for producing the hydrogen-containing isotope target are the same as those described in connection with example 1.
The micro neutron tube described in this embodiment 2 is particularly suitable for manufacturing a neutron generator with a very small diameter (as small as 28mm), wherein the neutron yield is high, the working life is long, and after the use failure, a user can repair the neutron tube by himself. It has these significant advantages, the main techniques are: the whole element is allowed to adopt ultra-high temperature baking exhaust; although the outer diameter of the high-voltage resistant insulating tube is small, the diameter of the penning ion source is quite large and is very close to the inner diameter of a neutron generator to be assembled; the suppression electrode allows the diameter of the target surface to be made larger by internal power supply; the overall design allows for application of operating voltages of up to 12 kilovolts; in particular, the deuterium storage device and the tritium storage device can be simultaneously arranged, and an 'internal tritium-making target' or a 'deuterium-tritium mixed target' can be manufactured and prepared.
Claims (10)
1. A miniature neutron tube, it is formed by insulating sealed shell of high pressure resistant, penning ion source, target chamber, accelerating electrode and hydrogen isotope memory, the penning ion source is sealed lid and cup-shaped shell made of magnetic conductive metal material, sealed tube made of nonmagnetic material and negative pole base body made of magnetic conductive material are welded together, characterized by that: the high-voltage-resistant insulating sealing shell is formed by respectively sealing two ends of a high-voltage insulating tube with a thick end and a thin end with a thick annular sealing metal part and a thin annular sealing metal part, wherein the thick end and the thin end of the high-voltage insulating tube are respectively provided with a three-layer structure on the side wall; the accelerating electrode is fixed on the thick ring sealing metal part; the target chamber is welded with the thick ring-shaped sealing metal part, and the penning ion source is welded with the thin ring-shaped sealing metal part; the target chamber is a metal cylinder with a bottom made of a non-magnetic metal material with excellent heat conductivity, and the bottom of the metal cylinder is used as a target substrate; the outer diameter of the target substrate is close to the inner diameter of the thick end of the high-voltage insulating tube, and a hydrogen isotope target film with the diameter slightly smaller than that of the inner end surface is manufactured on the inner end surface of the target substrate; a deflection electronic permanent magnet is arranged outside the side wall of the target chamber; the target chamber end is connected with the ground potential; the hydrogen isotope memory is welded on the outer end surface of the target substrate; the penning ion source is thin at one end and thick at the other end, the outer diameter of the thick end of the penning ion source is close to the inner diameter of the thick end of the high-voltage insulating tube, and the anode is contained in the thick end of the penning ion source; plating a metal film with high secondary electron emission coefficient on the end surface of the cathode substrate close to the anode and the inner surface of the cup-shaped shell close to the anode to serve as a cathode; the penning ion source is connected with a positive high-voltage potential; an auxiliary high-voltage insulating cylinder is arranged outside the end of the thin ring type sealing metal part.
2. The miniature neutron tube of claim 1, wherein said hydrogen isotope storage means comprises a deuterium storage means and a tritium storage means.
3. The miniature neutron tube of claim 1, wherein: the hydrogen isotope target is an internal tritium target or a deuterium-tritium mixed target which is manufactured after the neutron tube finishes exhausting and before the exhaust tube is cut off.
4. The miniature neutron tube of claim 1, wherein said secondary high voltage insulating cylinder is made of aluminum nitride ceramic.
5. The miniature neutron tube of claim 1, wherein said deflection electron permanent magnet is a ring-type permanent magnet or a U-type permanent magnet in a ring shape; the accelerating electrode is made of nonmagnetic material with good sputtering resistance.
6. A miniature neutron tube, it is formed by insulating sealed shell of high pressure resistant, penning ion source, target chamber and hydrogen isotope memory, the ion source of said penning is: the sealing cover made of magnetic material, the sealing tube made of nonmagnetic material and the cathode substrate made of magnetic material are sealed and welded together to form a sealing shell; the anode lead, the exhaust pipe and the lead of the hydrogen isotope storage are welded on the sealing cover, a cup-shaped shell made of magnetic conductive material is fixed on the sealing and sealing pipe, and the anode is a metal ring made of nonmagnetic material and fixed on the anode lead; plating a metal film with high secondary electron emission coefficient on the inner end surface of the cathode substrate and the inner surface of the bottom of the cup-shaped shell close to the anode to serve as a cathode; the method is characterized in that: the high-voltage-resistant insulating sealing shell is formed by respectively sealing two ends of a high-voltage insulating tube with a thick end and a thin end with a thick annular sealing metal part and a thin annular sealing metal part with a three-layer structure on the side wall; the outer diameter of the thick ring-shaped sealing metal part is 6-8mm larger than the outer diameter of the thick end of the high-voltage insulating tube and is matched with the inner diameter of a shell of a neutron generator to be assembled in a sliding manner; the thick ring type sealing metal part is also used as a part of the external magnetic circuit of the penning ion source; cathode ground potential of thepenning ion source; the hydrogen isotope storage device is welded inside the penning ion source; the target chamber is composed of a target substrate made of metal materials with particularly good heat conducting performance and a suppression electrode, and the suppression electrode is fixed on the target substrate in an insulating mode through a ceramic component; the suppression electrode is connected with a power supply lead through a lead in an inner insulation hole of the target substrate; the inner end of the target substrate is thick, the outer end of the target substrate is thin, the diameter of the inner end surface of the target substrate is slightly smaller than the inner diameter of the thick end of the high-voltage insulating tube, and the diameter of the outer end surface of the target substrate is matched with the inner diameter of the thin ring-shaped sealing metal part in a sliding mode; a hydrogen isotope target film is arranged on the inner end surface of the target substrate; the target substrate is connected with a negative high-voltage potential; an auxiliary high-voltage insulating cylinder is arranged outside the end of the thin ring type sealing metal part.
7. The miniature neutron tube of claim 6, wherein said hydrogen isotope storage means comprises a deuterium storage means and a tritium storage means.
8. The neutron tube of claim 6, wherein: the hydrogen isotope target is an internal tritium target or a deuterium-tritium mixed target which is manufactured after the neutron tube finishes exhausting and before the exhaust tube is cut off.
9. The neutron tube of claim 6, wherein said secondary high voltage insulating cylinder is made of aluminum nitride ceramic.
10. Amanufacturing method of a miniature neutron tube is characterized by comprising the following steps:
1) the main body of the neutron tube is manufactured according to the conventional process, and comprises the steps of sequentially welding a penning ion source, a high-voltage-resistant insulating sealing shell and a target chamber to form a sealed whole, manufacturing a target film on the inner surface of a target substrate in the neutron tube, and installing a hydrogen isotope storage;
2) sleeving a specially-made heating ring around the target substrate when the neutron tube main body is subjected to racking, baking and exhausting;
3) after the baking and exhausting of the neutron tube main body are finished, cooling the baking oven, and electrifying the heating ring to slowly heat the target substrate;
4) monitoring by a temperature control instrument to ensure that the temperature of the target substrate is above 400 ℃ and other parts of the neutron tube main body are below 180 ℃;
5) closing the exhaust system, starting a deuterium-tritium inflation system, and injecting a predetermined amount of tritium gas or a deuterium-tritium mixed gas into the neutron tube main body, wherein the tritium gas or the deuterium-tritium mixed gas is quickly absorbed by a target film to form a pure tritium target or a deuterium-tritium mixed target;
6) stopping heating the target substrate, and cooling all parts of the whole neutron tube main body to room temperature;
7) filling quantitative deuterium gas or deuterium-tritium mixed gas into the deuterium storage device according to a conventional process;
8) finally, the exhaust pipe is cut off, and the finished neutron tube containing the internal tritium-making target or the deuterium-tritium mixed target isobtained.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNB011153261A CN1142448C (en) | 2001-04-20 | 2001-04-20 | Miniature neutron tube and its production method |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNB011153261A CN1142448C (en) | 2001-04-20 | 2001-04-20 | Miniature neutron tube and its production method |
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| CN1329461A CN1329461A (en) | 2002-01-02 |
| CN1142448C true CN1142448C (en) | 2004-03-17 |
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| CNB011153261A Expired - Fee Related CN1142448C (en) | 2001-04-20 | 2001-04-20 | Miniature neutron tube and its production method |
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Families Citing this family (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102548181B (en) * | 2012-01-19 | 2016-01-06 | 哈尔滨市源盛达电子技术有限公司 | Small-diameter radio-frequency drive deuterium-deuterium neutron pipe |
| CN102930764B (en) * | 2012-11-01 | 2015-02-11 | 东北师范大学 | Ion source negative hydrogen ion beam leading-out experiment table for neutron tube |
| CN104093261B (en) * | 2014-07-16 | 2017-02-15 | 中国工程物理研究院核物理与化学研究所 | Helium processing device of high yield neutron generator |
| CN104602438B (en) * | 2014-12-29 | 2017-07-14 | 中国原子能科学研究院 | One kind inhales tritium target piece preparation method |
| CN104966448B (en) * | 2015-07-09 | 2018-04-27 | 东北师范大学 | Radio frequency neutron tube ion gun line draws tabletop experiments platform |
| CN105407621B (en) * | 2015-11-13 | 2018-01-16 | 兰州大学 | A kind of compact D D accelerators for neutron production |
| CN106098507B (en) * | 2016-06-30 | 2018-01-12 | 西安冠能中子探测技术有限公司 | A kind of setl-target neutron tube fills tritium platform and its fills tritium method |
| CN106057614B (en) * | 2016-08-12 | 2018-10-12 | 兰州大学 | A kind of cold-cathode Penning ion source |
| CN107356981A (en) * | 2017-07-28 | 2017-11-17 | 秦佑胜 | Accelerator for neutron production detection system |
| CN107708284A (en) * | 2017-09-11 | 2018-02-16 | 中国工程物理研究院核物理与化学研究所 | A kind of deuterium deuterium accelerator for neutron production target chamber |
| CN109275254B (en) * | 2018-09-14 | 2019-10-08 | 珠海市纽创科技有限公司 | A kind of production method of microminiature neutron tube |
| CN109041397B (en) * | 2018-09-14 | 2019-07-26 | 珠海市纽创科技有限公司 | A kind of microminiature neutron tube |
| CN113099600A (en) * | 2021-04-02 | 2021-07-09 | 西京学院 | Neutron pipe target pole structure with adjustable target distance |
-
2001
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