CN102930764A - Ion source negative hydrogen ion beam leading-out experiment table for neutron tube - Google Patents

Abstract

The invention belongs to neutron tube experimental equipment, in particular to a penning neutron tube ion source negative hydrogen ion beam extraction test bench, which is the key experimental equipment for researching and designing long-life and high-stability neutron tubes, and a glass bell jar with high-voltage electrodes For the experimental space, the fine-tuning valve feeds hydrogen and can adjust the vacuum degree to simulate the working pressure inside the neutron tube. The generation of D and T negative ions in the Penning ion source on the test bench is mainly through dissociation and adsorption. There are no negative molecular ions and negative triatomic ions, and the extracted beams are all monatomic negative ions. The extraction beam current of the ion source in the neutron tube is closely related to many factors. Through this experimental platform, various parameters of the ion source system can be adjusted conveniently, the influence of each parameter on the extraction beam can be studied, and good beam quality can be obtained on the accelerating electrode. In addition, the simulation experiment of the neutron tube can be done by using the test bench, and the design of the neutron tube can be checked and corrected, which can greatly shorten the development cycle and save development funds.

Description

Negative hydrogen ion beam extraction test bench for neutron tube ion source

technical field

The invention belongs to experimental equipment for neutron tubes, in particular to an experimental platform for extracting negative hydrogen ion beams from a Penning (PIG) neutron tube ion source.

the

Background technique

The neutron tube and the neutron generator with it as the core is a highly experimental science and technology, which has important applications in many fields. The neutron tube seals the ion source, accelerating focusing electrode, target and air pressure regulation system in an insulating vacuum envelope, forming a small accelerator. The ion source in the neutron tube is one of the core components that determine the output, life and stability of the neutron tube. Penning ion source (referred to as PIG ion source) is widely used in small accelerators such as neutron tubes due to its simple structure, stable operation, long life, simple power supply system, and ability to work under low pressure.

With the continuous expansion of the application fields of neutron tubes and neutron generators, it is urgent to develop neutron tubes with various parameters and characteristics. The extraction beam current of the ion source in the neutron tube is closely related to the selection of the acceleration gap, the size of the extraction aperture, the structure of the ion source, the size and material of each component, the electron temperature, the structure of the extraction electrode, and the air pressure in the tube. Therefore, the development of neutron tubes is based on a large number of experiments. Therefore, it is very necessary for the development of the neutron tube to build an experimental device that can measure the characteristic parameters of the extracted beam and simulate the working state of the neutron tube, taking the extracted beam of the ion source as the core. It can do simulation experiments of neutron tubes, check and correct the design of neutron tubes, greatly shorten the development cycle and save development funds.

At present, the neutron tubes produced in China all use the PIG ion source that extracts positive ions, and a negative high voltage of -60KV ~ -120KV is added to the target end to accelerate the deuterium (D) ions and tritium (T) ions generated by the ion source, and A nuclear reaction on the target produces neutrons. The neutron tube with this structure has the disadvantages of low utilization rate of the extracted beam, secondary electrons will be generated on the target, field emission points of electrons are easily formed on the surface of the Faraday cylinder, and the sputtering damage of the target is large. Adopt PIG type negative ion source to generate deuterium (D) and tritium (T) negative ions. Positive high voltage is added to the target. In the case of removing electrons in the extracted beam, the extracted beam is all monatomic negative ions, and the beam utilization rate of neutrons can reach 100%, which can overcome the above-mentioned shortcomings.

Contents of the invention

In order to improve the success rate and efficiency of developing neutron tubes for different purposes, and improve the life and stability of neutron tubes, the purpose of this invention is to provide a negative hydrogen ion beam extraction test platform for Penning (PIG) neutron tube ion sources.

Penning neutron tube ion source negative hydrogen ion beam extraction test bench is composed of Penning ion source negative hydrogen ion beam extraction part, vacuum system and environment part.

The glass bell jar with high-voltage electrodes on the test bench is the test space, which is connected to the molecular pump unit through the vacuum flange. It can be used to conduct ion source beam extraction experiments and simulation experiments of the overall working state of the neutron tube, or to check the design size of a certain component and the selection of materials and magnetic fields. The vacuum flange has insulated electrodes to introduce ion source voltage and collection voltage. A round high voltage electrode on a glass bell introduces the accelerating high voltage. The trimmer valve feeds hydrogen and can adjust the degree of vacuum to simulate the working pressure inside the neutron tube. Lead glass is placed in front of the experimental table to block the X-rays generated during the experiment. The discharge of the ion source and the shape of the extracted beam can be directly observed through the lead glass. The generation of D and T negative ions in the PIG ion source on the test bench is mainly through dissociation and adsorption. The reaction formula is H ₂ +e →H ₂ ^- →H ₁ ^- +H ₁ , and there is no negative molecular ion (negative Molecular ions are unstable and have a lifetime of about 10 ^-15 s-10 ^-13 s) and negative triatomic ions, the extracted beams are all monatomic negative ions, and the beam utilization rate of neutrons can reach 100%. Moreover, due to the high beam utilization rate, the amount of D and T negative ions required to produce neutrons with the same yield in the future when packaged into a neutron tube is relatively small, the sputtering damage to the target is very small, and the life of the target can be significantly extended . Another advantage of adding a positive high voltage to the target is that the secondary electrons generated by the negative ions knocking down the target will immediately return to the target, so there is no need to consider measures to suppress the secondary electrons. However, when negative ions are extracted from the PIG type negative ion source, some electrons are also drawn out. If they are allowed to knock down the target, they will account for most of the accelerating current and increase the load of the accelerating high-voltage power supply. Therefore, this part of electrons must be extracted from the separated from the stream. Here we adopt the careful setting of the corresponding transverse deflection magnetic field and collecting electrodes on the path of the beam to realize it.

The technical solution adopted by the present invention to solve its technical problems is:

Penning neutron tube ion source negative hydrogen ion beam extraction test bench is composed of Penning ion source negative hydrogen ion beam extraction part, vacuum system and environment part.

The experimental space is limited inside the glass bell jar with high-voltage electrodes. The lower part of the glass bell jar is a flange plate, and an insulating electrode, a ground electrode, a vacuum gauge, a thermometer, an air inlet pipe, and a connection to the molecular pump are arranged on the flange plate. Catheter etc. The electrodes are used to provide the anode voltage, collection voltage, and acceleration voltage required for the experiment; the vacuum gauge is used to measure the vacuum plating inside the glass bell jar; the air inlet tube is used to fill the glass bell jar with working gas, and can realize fine adjustment. The beam extraction of the negative hydrogen ion source located inside the glass bell jar adopts the eccentric extraction method. During the eccentric extraction, the central axis of the anode cylinder coincides with the central axis of the copper head, the counter cathode, and the extraction cathode, and the negative ions in the area deviated from the axis of the ion source of the highest density. Positive high voltage is applied to the collecting electrode and the accelerating plate, the accelerating voltage is higher than the collecting voltage, and the extracted beam includes negative ions and electrons, and the negative ions are all monatomic negative ions. Since electrons in the extracted beam do not contribute to neutron production and would increase the load on the high voltage power supply, they must be removed. We use a set of transverse deflection magnetic fields plus collecting electrodes, or two sets of transverse deflection magnetic fields with a mutual angle of 90 ^° plus collecting electrodes. The thickness of the magnetic field along the axis of the beam is greater than the radius of gyration of the electrons. Theoretical calculations show that the magnetic field strength is hundreds of Gs, and the collection voltage is several thousand volts. The collecting electrodes are embedded in two sets of magnetic steels, and the collecting electrodes are also used as extraction electrodes. The configuration of the two sets of magnetic fields can not only ensure the sufficient removal of electrons, but also ensure the axisymmetric shape of the extracted beam.

The beneficial effect of the present invention is that, as an experiment and test platform, the Penning neutron tube ion source negative hydrogen ion beam extraction test platform can conveniently optimize and combine various parameters, and obtain the best beam current quality on the target and accelerating electrode plates . Through the improvement of components, the Penning ion source works in the best state, and the results can be used in the research and design of neutron tubes for various purposes. The development cycle can be greatly shortened and development funds can be saved.

Description of drawings

Accompanying drawing 1 is the schematic diagram of the negative hydrogen ion beam extraction part structure of the Penning neutron tube ion source negative hydrogen ion beam extraction test bench of the Penning ion source.

Among them 1. Ion source magnet, 2. Leading out cathode, 3. Counter cathode, 4. Anode cylinder, 5. Ion source cover, 6. Collecting electrode, 7. Deflection magnet, 8. Glass tube, 9. Target and acceleration Electrode plate, 10. Anode terminal, 11. Ground electrode terminal, 12. Upper mask, 13. Copper head.

Attached Figure 2 is a schematic diagram of the structure of the vacuum system and the environment of the negative hydrogen ion beam extraction test bench of the Penning neutron tube ion source.

14. Accelerating high voltage electrode, 15. Negative hydrogen ion beam extraction part of Penning ion source, 16. Insulation support, 17. Glass bell jar, 18. Ion source electrode, 19. Ground electrode, 20. Vacuum gauge, 21. Collection Electrode, 22. Thermometer, 23. Exhaust pipe, 24. Manual valve, 25. Fine-tuning valve, 26. Working gas delivery pipe, 27. Molecular pump unit, 28. Flange.

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

Detailed ways

The penning neutron tube ion source negative hydrogen ion beam extraction test bench of the present invention is composed of the negative hydrogen ion beam extraction part of the Penning ion source, a vacuum system and an environment part. Adopting a cylindrical axisymmetric structure, it puts the ion source, accelerating electrode, collecting electrode, deflection magnet, air pressure adjustment system, etc. in the glass bell jar to form a compact and easy-to-use ion source beam extraction experimental device. Its structure and position relationship are shown in accompanying drawing 1 and accompanying drawing 2. 

Negative hydrogen ion beam extraction part of Penning ion source: As shown in Figure 1, clean all parts and install them from bottom to top. First put the counter cathode 3 into the copper head 13, then put the ion source magnetic steel 1 into the copper head 13, draw the cathode 2 and the ion source cover 5 and weld them together, and place them on the copper head 13. Inside the ion source cover 5, the anode cylinder 4 connected by the anode terminal 10 is housed. Cover the copper head 13 with the upper cover 12, and keep in good contact with the ion source cover 5. Place a section of glass tube 8 on the upper cover, place a pair of deflection magnets 7 in the glass tube 8, and wrap a layer of valveable material on the outside of the deflection magnets 7 as the collecting electrode 6. Place a target and acceleration on the upper end of the glass tube 8 The electrode plate 9 and the ground electrode terminal 11 are connected to the negative pole of the power supply. The above is the core part of the test bench, which is the negative hydrogen ion beam extraction part of the Penning ion source. All parts in this part must be coaxial, and the coaxiality tolerance is not greater than 0.02mm. 

Vacuum system and environment part, as shown in accompanying drawing 2, first place the lead-out part 15 of the negative hydrogen ion beam of the Penning ion source on the insulating support 16, the ion source electrode 18, the ground electrode 19, the collecting electrode 21, respectively and Panning ion source The corresponding electrodes of the negative hydrogen ion beam extraction part 15 of the Ning ion source are connected, the glass bell jar 17 is fastened on the flange plate 28, and the target and the accelerating electrode plate of the negative hydrogen ion beam extraction part 15 of the PIG ion source are connected to the accelerating high voltage on electrode 14. Then connect the various power supplies, connect the vacuum gauge 20, and open it. Connect the thermometer 22 and turn it on. Turn on the molecular pump unit 27, open the manual valve 24, evacuate the inner space of the glass bell jar 17 through the exhaust pipe 23, and when the vacuum degree reaches above 10 ^-4 Pa, slowly open the fine-tuning valve 25, and introduce the gas through the working gas delivery pipe 26 Working gas, here we choose hydrogen as the working gas. The fine-tuning valve 25 controls the introduction amount of the working gas, and the vacuum degree inside the glass bell jar 17 is measured by a vacuum gauge. Then, turn on the ion source power supply, the collector power supply, and the accelerating high-voltage power supply in sequence. At this time, the test bench enters the working state, and experiments, measurements and observations can be carried out.

Claims (4)

1. Penning neutron tube ion source negative hydrogen ion beam extraction test bench is characterized in that it is composed of ion source negative hydrogen ion beam extraction part 15 and vacuum system and environment. Among them, Penning ion source negative hydrogen ion beam extraction Part 15 is composed of copper head 13, upper cover 12, anode cylinder 4, ion source cover 5, ion source magnet 1, deflection magnet 7, collecting electrode 6, glass tube 8, target and accelerating electrode plate 9; the vacuum system and The environment is composed of accelerating high voltage electrode 14, Penning ion source negative hydrogen ion beam extraction part 15, glass bell jar 17, vacuum gauge 20, thermometer 22, manual valve 24, fine-tuning valve 25, molecular pump unit 27, flange plate 28, The negative hydrogen ion beam extraction part 15 of the Penning ion source is to place the opposite cathode 3 in the copper head 13, then place the ion source magnet 1 in the copper head 13, and weld the drawn cathode 2 and the ion source cover 5 together, and Placed above the copper head 13, inside the ion source cover 5, the anode cylinder 4 connected by the anode terminal 10 is housed. Use the upper cover 12 to cover the copper head 13, keep in contact with the ion source cover 5, and place on the upper cover 12 A section of glass tube 8, a pair of deflection magnets 7 are placed in the glass tube 8, and a layer of valveable material is wrapped outside the deflection magnets 7 as a collecting electrode 6, and a target and an acceleration electrode plate 9 are placed on the upper end of the glass tube 8, grounded The electrode terminal 11 is connected to the negative pole of the power supply, and all parts of the negative hydrogen ion beam extraction part 15 of the Penning ion source are kept coaxial, and the vacuum system and the environment part are placed on the insulating support 16 for the negative hydrogen ion beam extraction part 15 of the Penning ion source Above, the ion source electrode 18, the ground electrode 19, and the collecting electrode 21 are respectively connected to the corresponding electrodes of the negative hydrogen ion beam extraction part 15 of the Penning ion source. The target of the hydrogen ion beam extraction part 15 and the accelerating electrode plate 9 are connected to the accelerating high-voltage electrode 14, connected to various power supplies, a vacuum gauge 20 and a thermometer 22 are arranged in the glass bell jar 17, and the glass bell jar 17 passes through the exhaust pipe 23 and the manual valve 24 It communicates with the molecular pump unit 27, and at the same time, the glass bell jar 17 is provided with a fine-tuning valve 25 to connect the gas delivery pipe 26. 2. Penning neutron tube ion source negative hydrogen ion beam extracting experimental platform according to claim 1 is characterized in that: the beam current of Penning ion source is drawn out and adopts eccentric extracting mode, and the central axis of anode cylinder 4 is connected with copper head 13, The central axes of the opposite cathode 3 and the extraction cathode 2 are coincident, the negative ion flow is extracted from the Penning ion source, and a pair of deflection magnets are arranged outside the collecting electrodes. 3. The negative hydrogen ion beam extracting test bench of the Penning neutron tube ion source according to claim 1, characterized in that: the concentricity tolerance of all parts of the beam extracting part in the glass bell jar 17 is not greater than 0.02mm. 4. Penning neutron tube ion source negative hydrogen ion beam extracting test bench according to claim 1 is characterized in that: under the condition of removing collecting electrode 6 and deflection magnet 7, and changing the accelerated high voltage polarity, deuterium can be carried out , Beam extraction experiment of positive tritium ions.

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