CN114164406B - Particle pressed diode anode target for pulse power device and preparation method - Google Patents

Abstract

The invention provides a particle pressed diode anode target for a pulse power device and a preparation method thereof, which overcome the limitation that the whole anode target is required to be replaced in each experiment, further reduce the experiment cost and improve the service life of the anode. The anode target comprises a formed target formed by pressing one or more target particles; the material of the target particles is tantalum, tantalum carbide, graphite, tungsten carbide or aluminum, and the formed target is formed by selecting different target particles according to the target ray parameters and placing and combining the different target particles for press-bonding; the diameter of the target particles is 0.05-1 mm, and the gaps among the target particles are less than 100 mu m; the thickness of the formed target should be at least 3-4 times the diameter of the target particles. The anode target is formed by pressing and rolling target particles through a machine tool, has long service life, can flexibly adjust target material components according to diode output indexes, and has the capability of adjusting the radiation quality of an output radiation field.

Description

Particle compacted diode anode target for pulse power device and preparation method

Technical field

The invention belongs to the field of interaction between high-power and strong-current pulsed electron beams and matter, and specifically relates to a particle-pressed high-current diode anode target for generating high-dose x-rays or γ-rays through the interaction between strong-current electron beams and matter.

Background technique

The full name of high-current diode is high-current pulsed electron beam diode. Its main function is to generate high-dose large-area x-rays or gamma rays through the interaction between the high-current electron beam emitted from the cathode and the high atomic number (hereinafter referred to as Z) anode target. In the diode anode area, due to the high energy and intensity of the electron beam (0.3~15MeV, 10kA~25MA), the electron beam bombarding the anode target will produce heat deposition on the target, causing extremely strong thermal shock waves and eruptions on the target. Thermal-mechanical destructive effects such as impulse cause the anode to ablate, melt, deform, and crack. As a result, the vacuum layer must be removed and the anode target must be replaced as a whole after each experiment, resulting in low experimental efficiency and economic benefits.

The anode targets used in the high-current diodes of existing pulse power devices are mostly single-layer or multi-layer tantalum targets that are processed as a whole. "Analysis of High Power Radiation Simulation Equipment and Its Application" and "Long Pulse High Impedance High Current" written by Kuai Bin et al. Articles such as "Electron Beam Diode" and "Flash-I Electron Beam Diode" by Hu Kesong et al. introduce the basic structure of accelerators such as "Chenguang", "Qiangguang No. 1" and "Flash No. 1". The various accelerators listed in the article The diodes of the accelerator all use integrally processed single-dielectric tantalum targets, and the entire anode must be replaced after each experiment.

Contents of the invention

In order to overcome the limitation that the entire anode target must be replaced for each experiment, reduce the experimental cost, and extend the life of the anode, the present invention proposes a particle compacted diode anode target for pulse power devices and a preparation method. The anode target is made of target particles pressed and rolled by machine tools. It has a long life and can flexibly adjust the target material composition according to the diode output index. It has the ability to adjust the radiation quality of the output radiation field (dose, spatial distribution, photon proportion )Ability.

In order to achieve the above objects, the present invention adopts the following technical solutions:

The particle compacted diode anode target used in pulse power devices of the present invention includes a shaped target compacted by one or more target particles; the target particles are made of tantalum, tantalum carbide, graphite, tungsten, Tungsten carbide or aluminum, the forming target selects different target particles at different positions for compaction according to the target ray parameters; the diameter of the target particles is 0.05~1mm, and the gap between the target particles is <100 μm; the forming target The thickness should be at least 3 to 4 times the diameter of the target particles.

Further, the shaped target is mainly composed of multiple layers of target particles superimposed in sequence, or is composed of a first type of target particle in the middle and a second type of target particle around it.

Further, the shaped target is composed of tantalum particles on all sides and graphite particles in the center; or tantalum is on all sides and tungsten or tungsten carbide is in the center; or graphite particles, tantalum particles, and aluminum are sequentially superimposed, or graphite particles and tantalum particles are formed. , graphite particles are stacked one after another.

Further, the surface roughness of the shaped target is less than or equal to 1.6.

Further, the shape of the forming target is circular or rectangular.

At the same time, the invention also provides a method for preparing a particle compacted diode anode target for pulse power devices, which includes the following steps:

Step 1. Preparation of target particles;

Select the target material according to the target ray parameters, and process the target material into target particles with a diameter of 0.05~1mm;

Step 2: Vacuum bonding;

2.1) Perform recrystallization annealing treatment on the target particles prepared in step 1;

2.2) Mix target particles and binder into a mixture, and the binder should be 5% to 10% of the volume of the mixture;

2.3) According to the volume and density of the anode target, weigh the corresponding mass of the mixture and put it into the compaction mold, and place the compaction mold in a vacuum environment of the order of 10 ^-3 Pa;

2.4) Set the pressing pressure according to the density of the anode target, and press the mixture according to the pressing pressure. When pressing, first fix the side pressing mold, leaving the side convex edge, and perform vertical compression; then fix the upper pressing mold, Carry out lateral compression, and this process is carried out alternately until the mixture is compacted to the preformed anode target, the compression temperature is 35°C to 50°C, and the compression ratio is 2 to 3;

2.5) After the pressing is completed, hold it under the pressing pressure for 3 to 5 minutes, and then leave the preformed anode target in a vacuum environment for 20 to 30 minutes to eliminate stress;

Step 3: Rolling in atmospheric environment;

The preformed anode target is taken out from the vacuum environment and further pressed by rolling with a compression ratio of >2 to further reduce the target particle gap and control the target particle gap to <100 μm;

Step 4. Surface polishing;

Polish the anode target surface to make the surface roughness ≤1.6.

Further, in step 2.4), zinc stearate needs to be applied to the inner surface of the bonding mold before bonding.

Further, in step three, the adhesive is high-purity graphite conductive adhesive.

Further, in step four, a grinder covered with gauze paper is used to grind the surface of the anode target.

Compared with the prior art, the present invention has the following beneficial effects:

1. The particle compacted anode target of the present invention is made of target particles compacted (vacuum environment) and rolled (atmospheric environment). There is a certain gap between the particles, which is conducive to the thermal shock caused by strong current pulse electrons on the target. The dissipation of waves enhances the target's resistance to electron beam thermal-mechanical damage and increases the life of the anode target.

2. The particle compacted anode target of the present invention has strong flexibility. Different target particles can be selected for compaction at different positions of the target according to different application requirements, including tantalum, tantalum carbide, graphite, tungsten, tungsten carbide, and aluminum. etc., so that the compacted target has different characteristics such as ablation resistance, long life, improved radiation field parameters (dose, spatial distribution uniformity, photon proportion), etc., and is suitable for different scenarios.

Description of the drawings

Figure 1 is a schematic diagram of a single-particle compacted high-current diode anode target of the present invention;

Figure 2 is a schematic diagram of two particle compacted high-current diode anode targets according to the present invention;

Figure 3 is a schematic diagram of the multi-layer particle compacted high-current diode anode target of the present invention;

Figure 4 is a schematic diagram of a vacuum bonding mold for a particle-bonded high-current diode anode target according to the present invention.

Reference signs: 1-upper mold, 2-side mold, 3-mixture.

Detailed ways

The present invention will be described in detail below with reference to the drawings and specific embodiments. Those skilled in the art should understand that these embodiments are only used to explain the technical principles of the present invention and are not intended to limit the scope of the present invention.

Most of the existing anode targets are single-use and need to be replaced after each experiment. The invention provides a particle compacted diode anode target for pulse power devices and a preparation method. The anode target has a relatively long service life and can replace the monolithic single-layer tantalum target used in existing high-current diodes. At the same time, this anode target is different from existing ordinary low-energy industrial targets. It is mainly used in the field of high-power pulse technology. This anode target can withstand hundreds of kA, hundreds of kV to several MV high energy in a very short time (tens of ns). The bombardment of electron beams aims to produce instantaneous high-energy x/gamma rays through bremsstrahlung radiation. The instantaneous temperature rise of the anode target can reach thousands of degrees Celsius, the instantaneous stress reaches the GPa level, and the thermo-mechanical damage effect is severe.

The particle compacted high-current diode anode target of the present invention is made of target particles compacted (vacuum environment) and rolled (atmospheric environment). There is a certain gap between the particles, which is beneficial to the heat caused by the high-current pulse electrons on the target. The dissipation of the shock wave enhances the target's resistance to electron beam thermal-mechanical damage and extends the life of the anode target; at the same time, the composition of the anode target can be flexibly selected to achieve the purpose of adjusting the output x/γ ray parameters.

As shown in Figures 1 to 3, the particle compacted diode anode target used in the pulse power device of the present invention includes a shaped target formed by compacting one or more target particles in a vacuum. Different selections are made at different positions. The target particles are compacted to adjust the output x/γ ray parameters; the material of the target particles can be tantalum, tantalum carbide, graphite, tungsten, tungsten carbide or aluminum; the distance between target particles is less than 100 μm. The gap; the target particle diameter is 0.05~1mm, and the thickness of the formed target should be at least 3~4 times the particle diameter.

The particle compacted anode target proposed by the present invention is highly flexible, and different target particles can be selected and compacted at different locations according to different application requirements, for example: ① "Tantalum particles around the edges, graphite particles in the center" configuration , can be used to improve the uniformity of the spatial distribution of target output rays, and is suitable for irradiation diodes; ② "Tantalum is surrounded by tantalum, and tungsten or tungsten carbide is in the center" configuration, which can increase the radiation dose output at the center of the target and is suitable for focusing diodes; ③" "Pure tantalum or tantalum carbide particles" configuration, suitable for soft X-ray scenarios; ④ Multi-layer configuration, the surface layer is graphite particles, the center is tantalum particles, and the back layer is aluminum or graphite particles, making the compacted target resistant to ablation, Features such as long life and increased photon ratio in the radiation field make it suitable for large-area irradiation diodes.

When making the above anode target, the particle size, target particle type and configuration are selected according to the application scenario and the size of the formed anode target. Target particles with a diameter of 0.05 to 1mm are pressed into a monolithic circular or rectangular anode target with a thickness of 0.2 to 10mm using a machine tool under vacuum conditions according to the application scenario.

Generally speaking, the thickness of the formed target should be at least 3 to 4 times the diameter of the target particles. For example, for a target with a thickness of 0.2mm, the selected target particles should be 0.05mm. According to the selected configuration, the corresponding tooling mold is made, pressed using a machine tool in a vacuum environment, and then rolled and polished in an atmospheric environment. After polishing, the surface roughness is required to be less than or equal to 1.6. The specific preparation process is as follows:

Step 1. Particle preparation;

Select the target material according to the ray parameters required for the experiment and prepare the corresponding target particles, such as tantalum, tantalum carbide, graphite, tungsten, tungsten carbide, aluminum, etc. The particle diameter is 0.05~1mm. The particle diameter in this size range is smaller than the powder commonly used in industry for metallurgy, and the preparation difficulty is reduced;

Step 2: Vacuum bonding;

2.1) Perform recrystallization annealing treatment on the target particles prepared in step 1. The annealing temperature varies depending on the recrystallization temperature of the material. For tantalum particles, the recrystallization annealing temperature is generally between 800°C and 1000°C;

2.2) Mix target particles and binder (high-purity graphite conductive glue). The total amount of graphite glue is about 5% to 10% (volume) of Mixture 3;

2.3) According to the volume and density of the anode target, weigh the corresponding mass of mixture 3 and put it into the compaction mold, and place the compaction mold in a vacuum environment of the order of 10 ^-3 Pa;

The structure of the compaction mold is shown in Figure 4; when the compaction mold is compacted, the corresponding mass of mixture 3 is weighed according to the volume and density of the preformed anode target, and the compression ratio (height of mixture 3 before compaction) is generally taken The ratio to the compression height after molding) is 2 to 3. Multiple particles or multi-layer anode targets need to be positioned in advance or the particles should be placed in layers;

2.4) Set the pressing pressure according to the density of the anode target, and press the mixed target particles and adhesive according to the pressing pressure. The entire bonding process is carried out in a vacuum environment of the order of 10 ^-3 Pa. The side is fixed first. Press mold 2, leave side convex edges, and perform vertical compression; then fix the upper mold 1, perform lateral compression, and proceed alternately until the mixture 3 is compacted to the preformed size, and the particles are in the vertical and horizontal directions. are compressed;

Before bonding, zinc stearate needs to be applied to the inner surface of the bonding mold to lubricate the mold wall and release the bonding target. The compression temperature during bonding is 35℃~50℃. At this temperature, graphite glue has better bonding ability. The above-mentioned pressing pressure is related to the required target density. Taking pure tantalum target as an example, the compacted target density is generally 10g/cm ³ when 100MPa ~ 160MPa is used, and the compacted target density is about 11g/cm ³ when 190MPa ~ 270MPa is used;

2.5) After reaching the pressing pressure, maintain the pressure for 3 to 5 minutes. The purpose is to fully transmit the pressure and reduce the impact of elastic aftereffects. Then slowly remove the pressure and leave it in a vacuum environment for 20 to 30 minutes to eliminate the stress;

Step 3: Rolling in atmospheric environment;

The preformed anode target is taken out from the vacuum environment and further compacted by rolling. The purpose is to further shape the particle target, improve the surface flatness, and further reduce the particle gap, control the particle gap to <100 μm, and compress Ratio (thickness of preformed target and thickness of target after rolling)>2.

Step 4. Surface polishing;

Use a grinder (coated sandpaper) to grind the anode target surface to make the surface roughness ≤ 1.6.

Install the target on the pulse power device. After each experiment, it is necessary to check the thermo-mechanical damage of the target in time. If the particles on the target surface fall off, there is no need to replace it. Just polish it with sandpaper as appropriate.

Claims (8)

1. A particle pressed diode anode target for a pulsed power device, characterized by: comprises a forming target formed by pressing and bonding a plurality of target particles; the middle of the formed target is provided with first-class target particles, and the periphery of the formed target is provided with second-class target particles;

the material of the target particles is tantalum, tantalum carbide, graphite, tungsten carbide or aluminum, and the formed target selects different target particles at different positions according to the target ray parameters for press-bonding;

the diameter of the target particles is 0.05-1 mm, and the gaps among the target particles are less than 100 mu m; the thickness of the formed target is at least 3-4 times of the diameter of the target particles.

2. A particle pressed diode anode target for a pulsed power device according to claim 1, characterized by: the forming target consists of tantalum particles at the periphery and graphite particles at the center; or tantalum is arranged around, and tungsten or tungsten carbide is arranged in the center.

3. A particle pressed diode anode target for a pulsed power device according to claim 2, characterized by: the surface roughness of the molded target is 1.6 or less.

4. A particle pressed diode anode target for a pulsed power device according to claim 3, characterized by: the shape of the formed target is round or rectangular.

5. A method for preparing a particle pressed diode anode target for a pulse power device, comprising the steps of:

step one, preparing target particles;

selecting a target material according to the target ray parameters, and processing the target material into target particles with the diameter of 0.05-1 mm;

step two, vacuum pressing and bonding;

2.1 Carrying out recrystallization annealing treatment on the target particles prepared in the step one;

2.2 Mixing target particles with an adhesive to form a mixture, wherein the adhesive accounts for 5-10% of the volume of the mixture;

2.3 According to the volume and density of the anode target, weighing the mixture with corresponding mass, putting the mixture into a compacting die, and putting the compacting die into 10 ^-3 In a vacuum environment of the order of Pa;

2.4 Setting pressing pressure according to the density of the anode target, pressing the mixture according to the pressing pressure, fixing a side pressing die, leaving a side convex edge, and compressing in the vertical direction; fixing the upper pressing die, and performing lateral compression, wherein the process is alternately performed until the mixture is pressed and bonded to a preformed anode target, the compression temperature is 35-50 ℃, and the compression ratio is 2-3;

2.5 After the pressing is finished, maintaining the pressure for 3-5 minutes under the pressing pressure, and then standing the preformed anode target in a vacuum environment for 20-30 minutes to eliminate the stress;

step three, rolling in the atmospheric environment;

taking out the preformed anode target from the vacuum environment, further compacting by adopting a rolling method, wherein the compression ratio is more than 2, so that the gaps among target particles are further reduced, and the gaps among the target particles are controlled to be less than 100 mu m;

step four, polishing the surface;

polishing the surface of the anode target to ensure that the surface roughness is less than or equal to 1.6.

6. The method of manufacturing according to claim 5, wherein: in the step 2.4), zinc stearate is required to be smeared on the inner surface of the compacting die before compacting.

7. The method of manufacturing according to claim 6, wherein: in the third step, the adhesive is high-purity graphite conductive adhesive.

8. The method of manufacturing according to claim 7, wherein: and step four, polishing the surface of the anode target by adopting a polishing machine coated with gauze.