WO2022217450A1

WO2022217450A1 - Carbon solid target for generating soft x-rays by means of laser plasma acceleration mechanism, and application

Info

Publication number: WO2022217450A1
Application number: PCT/CN2021/086839
Authority: WO
Inventors: 李韫慧; 谢耀钦; 欧阳效芸; 颜学庆; 马文君; 寿寅任; 孔德峰; 潘卓; 梅竹松; 曹正轩
Original assignee: 中国科学院深圳先进技术研究院
Priority date: 2021-04-13
Filing date: 2021-04-13
Publication date: 2022-10-20

Abstract

Provided in the present application is a carbon solid target for generating soft X-rays by means of a laser plasma acceleration mechanism. The carbon solid target comprises a carbon nanotube layer, wherein the carbon nanotube layer comprises a vertical carbon nanotube array. The energy conversion efficiency of the carbon solid target interacting with an ultra-short and ultra-strong laser to generate soft X-rays is high, and the generated soft X-rays have high brightness, a short pulse width and good coherence, thereby facilitating the application of soft X-rays in water window imaging and carbon window imaging. Further provided in the present application is a method for generating soft X-rays by means of a laser plasma acceleration mechanism.

Description

Carbon solid target for generating soft X-rays by laser plasma acceleration mechanism and its application

technical field

The present application relates to the field of laser plasma acceleration, in particular to a carbon solid target for generating soft X-rays by a laser plasma acceleration mechanism and its application.

Background technique

Ultrashort pulse high-brightness laser radiation in the soft X-ray (SXR, 0.1nm-10nm) band can be used for "water window" (2.3nm-4.4nm) and "carbon window" (4.5nm-5.0nm) imaging, for detection Macromolecular structure, diagnostic chemical reaction process, real-time live cell imaging, etc. are of great significance. Existing soft X-ray light sources are based on traditional accelerator synchrotron radiation devices or free electron lasers, which have the limitation of small electric field acceleration gradients. However, in practical applications, light radiation with high brightness, short pulse width and good coherence is required. In addition, the above-mentioned radiation source devices based on traditional accelerators are large in scale and expensive, which limits the application of soft X-ray optical radiation.

With the rapid development of laser accelerators that generate plasma from the interaction of ultra-short and ultra-intensive lasers with matter, the devices based on ultra-short ultra-intensive lasers to generate optical radiation are not only small in size and low in cost, but also the interaction between ultra-intensive pulsed lasers and solid targets can Produces short pulses of high-brightness light radiation. However, the solid target materials used in the existing laser accelerators have low energy conversion efficiency for generating soft X-rays, especially in the "water window" and "carbon window" wavelength bands. Therefore, it is necessary to provide a solid target that can generate high-brightness soft X-ray light radiation after interacting with an ultra-intensive laser, so as to promote the application of soft X-rays in water window imaging and carbon window imaging.

SUMMARY OF THE INVENTION

In view of this, the present application provides a carbon solid target for generating soft X-rays by a laser plasma acceleration mechanism. The high brightness and short pulse width promote the application of soft X-rays in water window imaging and carbon window imaging. The present application also provides a method for generating soft X-rays by a laser plasma acceleration mechanism and a laser plasma accelerator.

A first aspect of the present application provides a carbon solid target for generating soft X-rays by a laser plasma acceleration mechanism, the carbon solid target includes a carbon nanotube layer, and the carbon nanotube layer includes a vertical carbon nanotube array.

The carbon solid target of the present application adopts the vertical carbon nanotube array as the target body, and the interaction between the carbon solid target and the ultra-short ultra-intensive laser can generate ultra-high electron density and ultra-high electron temperature; and the ultra-intensive laser incident on the vertical carbon nanotubes The electrons generated during the array are in rotational motion, and the ultrafast electrons undergo electron-induced acceleration resonance and gain high energy during their movement around the carbon nanotubes, thereby obtaining high-brightness soft X-ray light radiation.

Optionally, the carbon solid target further includes a carbon nano-film layer disposed on the surface of the carbon nanotube layer, and the carbon nano-film layer includes one or more of a graphene layer, a diamond layer and a diamond-like carbon layer. .

Optionally, the density of the carbon nanotube layer is 0.1 g/cm ³ -2.5 g/cm ³ .

Optionally, the diameter of the vertical carbon nanotubes is 0.1 nm-200 nm.

Optionally, the height of the vertical carbon nanotubes is 1 μm-20 μm.

Optionally, the thickness of the carbon nanotube layer is 1 μm-20 μm.

Optionally, the thickness of the carbon nano-film layer is 0.1 nm-200 nm.

Optionally, the carbon solid target further includes a substrate, and the carbon nanotube layer is disposed on the surface of the substrate.

Optionally, the substrate surface has one or more raised structures.

Optionally, the height of the raised structures is less than or equal to 50 μm.

Optionally, the protruding structure includes one or more of a hemispherical structure, a columnar structure and a frustum-like structure.

Optionally, the protruding structure includes a cylindrical structure, and the diameter of the cylindrical structure is 1 nm-100 μm.

Optionally, the energy conversion efficiency of the carbon solid target interacting with the laser to generate soft X-rays is greater than or equal to 6%. Further, the energy conversion efficiency of the interaction between the carbon solid target and the laser to generate soft X-rays is greater than or equal to 20%.

The interaction between the carbon solid target in this application and the ultra-short ultra-intensive laser can generate high-brightness soft X-ray light radiation, and the energy conversion efficiency of this process is high. X-ray light sources provide a new method with promising application prospects.

In a second aspect, the present application provides a method for generating soft X-rays by a laser plasma acceleration mechanism. The method uses an ultra-short and ultra-intensive laser to interact with a carbon solid target to generate plasma to generate soft X-rays, the carbon solid target A carbon nanotube layer is included, the carbon nanotube layer including a vertical carbon nanotube array.

Optionally, in the method for generating soft X-rays by a laser plasma acceleration mechanism, the peak power of the laser is greater than or equal to 1×10 ¹⁸ W/cm ² .

In a third aspect, the present application provides a laser plasma accelerator, which includes the carbon solid target provided in the first aspect of the present application.

The laser plasma accelerator provided by the third aspect of the present application can form soft X-ray light radiation with high brightness and high quality due to the use of the carbon solid target of the present application.

Description of drawings

1 is a schematic structural diagram of a carbon solid target provided by an embodiment of the application;

2 is a schematic structural diagram of a carbon solid target provided by another embodiment of the present application;

3 is a schematic structural diagram of a carbon solid target provided by another embodiment of the present application;

4 is a schematic structural diagram of a carbon solid target provided by another embodiment of the present application;

Fig. 5 is the scanning electron microscope picture of the carbon solid target that the embodiment 1 of this application provides;

Fig. 6 is the scanning electron microscope picture of the carbon solid target that the embodiment 2 of this application provides;

7 is a scanning electron microscope image of the carbon nanotube layer provided in Example 1 of the present application;

8 is a transmission electron microscope image of the vertical carbon nanotubes provided in Example 3 of the present application;

9 is a selected area electron diffraction pattern of a single vertical carbon nanotube provided in Example 2 of the present application;

FIG. 10 is a scanning electron microscope image of the carbon solid target provided in the embodiment of the application, wherein (a) in FIG. 10 is a schematic view of the height of the vertical carbon nanotubes in Example 2, and (b) in FIG. 10 is the vertical diagram in Example 2 SEM images of carbon nanotubes, (c), (d) and (e) in Figure 10 are the SEM images of the vertical carbon nanotubes covered with the diamond-like carbon layer of Example 3, Example 4 and Example 5, respectively;

11 is an analysis diagram of the wavelength band of the optical radiation generated by the laser acceleration experiment provided in Example 1 of the application;

FIG. 12 is a comparison diagram of the light radiation intensity generated by the laser-accelerated carbon solid target of Examples 2-5 provided by the application.

Detailed ways

The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, but not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present application.

Water window imaging is an imaging technology based on the large difference in the absorption rates of soft X-rays in the water window band (2.3nm-4.4nm) between carbon atoms (the main element that constitutes living cells) and oxygen atoms (the main element that constitutes water) Therefore, soft X-rays are of great significance for detecting macromolecular structures, diagnosing chemical reaction processes, and real-time live cell imaging. At present, the soft X-ray light source with the highest brightness is realized based on the synchrotron radiation device of traditional accelerator or free electron laser, which has the limitation of small electric field acceleration gradient. However, in practical application, high brightness, short pulse width and good coherence are required. Optical radiation sources, and radiation source devices based on traditional accelerators are bulky and expensive, limiting the application of soft X-rays. In order to obtain a high-brightness soft X-ray light source, the present application provides a carbon solid target for generating soft X-rays by laser acceleration. Soft X-ray has high brightness, short pulse width and good coherence, which promotes the application of soft X-ray in water window imaging and carbon window imaging.

Please refer to FIG. 1 , which is a schematic structural diagram of a carbon solid target according to an embodiment of the present application. In FIG. 1, the carbon solid target includes a carbon nanotube layer 10, and the carbon nanotube layer 10 includes an array of vertically grown carbon nanotubes. The vertical carbon nanotube layer has a higher specific surface area than the flat carbon solid target, so that the laser can penetrate the target surface and interact with the sidewall of the nano target, increasing the surface area of the interaction between the laser and the solid target, thereby improving the carbon solid target pair. The absorption rate of laser energy; in addition, the carbon nanoarray solid target can generate ultra-high density (two times higher than the typical critical density) under the irradiation of ultra-intense ultra-short laser (peak power greater than or equal to 1×10 ¹⁸ W/cm ² ). order of magnitude) and ultra-high temperature plasma, so that the hydrodynamic cooling time of the high-energy-density plasma is greater than the radiative cooling time, so that a higher ratio of plasma energy is converted into soft X-ray optical radiation; and due to carbon nanotubes In order to be vertically aligned, the ultrafast electrons generated by the ultra-intensive laser incident on the cylindrical nanowire solid target will generate electron-induced acceleration resonance during the movement around the nanowire to obtain high energy, thereby obtaining ultra-short pulse soft X with higher brightness. Ray light radiation. The soft X-ray produced by the application based on the laser acceleration mechanism has high brightness, short pulse width, good coherence and high energy conversion efficiency, which breaks through the current bottleneck of outputting ultra-short pulse optical radiation based on traditional accelerators, and provides high-quality real-time imaging of living organisms. The high-quality soft X-ray light source, and the device for generating optical radiation by the laser acceleration mechanism are small in size and low in cost, which further promotes the application of soft X-rays.

In the embodiment of the present application, the density of the carbon nanotube layer is 0.1 g/cm ³ -2.5 g/cm ³ . The density of the carbon nanotube layer may specifically be, but not limited to, 0.1 g/cm ³ , 0.5 g/cm ³ , 1 g/cm ³ , 2 g/cm ³ or 2.5 g/cm ³ . When the density of the vertical carbon nanotubes is controlled within the above range, the electrons generated by the interaction between the laser and the matter can obtain a strong resonance effect, thereby producing high-brightness soft X-rays. In the embodiments of the present application, the diameter of the vertical carbon nanotubes is 0.1 nm-200 nm. The diameter of the vertical carbon nanotubes can be specifically, but not limited to, 0.1 nm, 1 nm, 10 nm, 20 nm, 40 nm, 60 nm, 100 nm or 200 nm. In some embodiments of the present application, the diameter of the vertical carbon nanotubes is 20nm-40nm. In the embodiment of the present application, the vertical carbon nanotubes may be vertical single-walled carbon nanotubes or vertical multi-walled carbon nanotubes. When the vertical carbon nanotubes are vertical multi-walled carbon nanotubes, the number of layers of the multi-walled carbon nanotubes For 2-100 layers. In some embodiments of the present application, the carbon nanotubes in the carbon nanotube layer are vertical multi-walled carbon nanotubes. When the vertical carbon nanotubes are multi-walled carbon nanotube arrays, they are arranged neatly and have a large specific surface area, which is conducive to the interaction between the laser and the substance. The effect produces ultra-high electron density, which in turn increases the brightness of soft X-rays.

In the embodiment of the present application, the height of the vertical carbon nanotubes is 1 μm-20 μm. The height of the vertical carbon nanotubes can be specifically, but not limited to, 1 μm, 3 μm, 5 μm, 8 μm, 10 μm, 15 μm or 20 μm. In this application, the height of the vertical carbon nanotubes is the thickness of the carbon nanotube layer. In the embodiment of the present application, the thickness of the carbon nanotube layer is 1 μm-20 μm. The thickness of the carbon nanotube layer may specifically be, but not limited to, 1 μm, 3 μm, 5 μm, 8 μm, 10 μm, 15 μm or 20 μm. In some embodiments of the present application, the thickness of the carbon nanotube layer is 5 μm-10 μm. When the thickness of the carbon nanotube layer is 5 μm-10 μm, the laser can have a higher energy conversion efficiency when acting on the carbon solid target.

In some embodiments of the present application, the carbon solid target further includes a carbon nanofilm layer disposed on the surface of the carbon nanotube layer. Please refer to FIG. 2 , which is a schematic structural diagram of a carbon solid target provided by another embodiment of the present application. In FIG. 2 , the carbon solid target includes a carbon nanotube layer 10 and a carbon nanofilm layer 20 disposed on the surface of the carbon nanotube layer 10 . In the present application, the carbon nano-thin film layer can be arranged to adjust the carbon atom density of the target material, thereby improving the energy conversion efficiency of soft X-ray light radiation. In the embodiments of the present application, the carbon nano-film layer includes one or more of a graphene layer, a diamond layer, and a diamond-like carbon layer. In some embodiments of the present application, a diamond-like carbon layer is used as the carbon nano-film layer. The diamond-like carbon layer has the advantages of high density, good uniformity and high hardness. Using the diamond-like carbon layer as the carbon nano-film layer can not only optimize the energy conversion efficiency of light radiation, but also the obtained carbon solid target has good structural stability.

In the embodiment of the present application, the thickness of the carbon nano film layer is 0.1 nm-200 nm. The thickness of the carbon nano-film layer may specifically be, but not limited to, 0.1 nm, 1 nm, 5 nm, 10 nm, 30 nm, 50 nm, 100 nm or 200 nm. In this application, the carbon density of the carbon solid target increases with the increase of the thickness of the carbon nano-film layer, so the carbon density of the carbon solid target can be adjusted by adjusting the thickness of the carbon nano-film layer. When the density of carbon atoms reaches a certain value, the brightness of ultra-short pulse soft X-ray light radiation generated by the interaction between laser and matter can reach the maximum value. In the present application, when the carbon nanotube layer is provided with a carbon nanofilm layer, it can be understood that the surface of the vertical carbon nanotubes in the carbon nanotube layer is covered by the carbon nanofilm layer.

In some embodiments of the present application, the carbon solid target further includes a substrate. In some embodiments of the present application, the substrate is a silicon substrate, and the thickness of the substrate is 500 μm. Please refer to FIG. 3 , which is a schematic structural diagram of a carbon solid target provided by another embodiment of the present application. In FIG. 3 , the carbon solid target includes a substrate 30 , a carbon nanotube layer 10 disposed on the surface of the substrate 30 , and a carbon nanofilm layer 20 disposed on the surface of the carbon nanotube layer 10 , wherein the substrate 30 is a planar structure. In some embodiments of the present application, the surface of the substrate has one or more raised structures. Please refer to FIG. 4 , which is a schematic structural diagram of a carbon solid target provided by another embodiment of the present application. In FIG. 4, the carbon solid target includes a substrate 30, a carbon nanotube layer 10 disposed on the surface of the substrate 30, and a carbon nanofilm layer 20 disposed on the surface of the carbon nanotube layer 10, and the surface of the substrate 30 has a plurality of periodically arranged protrusions structure. On the one hand, the protruding structure on the surface of the substrate can increase the specific surface area of the carbon solid target, and increase the depth of the laser incident on the carbon solid target, thereby increasing the absorption rate of the carbon solid target to the laser; on the other hand, the protruding structure can adjust the carbon nanometer. The morphology of the tube layer, and the surface carbon atom density of the carbon tube clusters was optimized. In the embodiments of the present application, the protruding structure includes one or more of a hemispherical structure, a columnar structure, and a frustum-shaped structure. In some embodiments of the present application, the surface of the substrate has a plurality of cylindrical protruding structures arranged in an array, the diameter of the cylindrical protruding structures is 5 μm-20 μm, the height of the cylindrical protruding structures is less than or equal to 50 μm, and the cylindrical protruding structures are The pitch is 5μm-15μm.

In the embodiments of the present application, the pulse width of the laser is 1fs-1000fs, and the pulse width of the laser may specifically be, but not limited to, 1fs, 10fs, 20fs, 100fs, 500fs, or 1000fs. In the embodiment of the present application, the peak power of the laser light is greater than or equal to 1×10 ¹⁸ W/cm ² . The peak power of the laser can be specifically, but not limited to, 1×10 ¹⁸ W/cm ² , 5×10 ¹⁸ W/cm ² , 1×10 ¹⁹ W/cm ² , 5×10 ¹⁹ W/cm ² or 1×10 ²⁰ W/cm ² . In some embodiments of the present application, the experimental parameters for the generation of soft X-rays by accelerated laser targeting are set as follows: the central wavelength of the laser is 800 nm, the pulse width is 30 fs, the energy is 1 J, the laser focal spot is 4.0 μm×4.5 μm, and the peak power of the laser is It is 4×10 ¹⁹ W/cm ² , and the contrast ratio of the laser is 10 ⁻¹⁰ .

In the embodiment of the present application, the wavelength of the characteristic peak of light radiation generated by the action of the carbon solid target and the laser is 2nm-5nm, which is consistent with the water window wavelength band, and can be well applied in water window imaging. In the embodiment of the present application, the energy conversion efficiency of the carbon solid target and the laser to generate soft X-rays is greater than or equal to 6%. In some embodiments of the present application, the energy conversion efficiency of the carbon solid target and the laser to generate soft X-rays is greater than or equal to 20%. The energy conversion efficiency of the carbon solid target and the laser to generate soft X-rays can be specifically, but not limited to, 6%, 10%, 12%, 15%, 20%, 23%, 27% or 30%.

The carbon solid target provided in the present application can generate high-brightness and high-quality soft X-rays by interacting with the ultra-intense laser, and the energy conversion efficiency of the process is high, which is beneficial to the application of soft X-rays in water window imaging.

The present application also provides a method for preparing the carbon solid target, including: providing a substrate, preparing a carbon nanotube layer on the surface of the substrate by chemical vapor deposition, and depositing a carbon nanofilm layer on the surface of the carbon nanotube layer to obtain a carbon solid target.

In the embodiments of the present application, the substrate includes a low-resistance silicon wafer substrate. In some embodiments of the present application, the surface of the substrate has one or more protruding structures, and the protruding structures on the surface of the substrate can be obtained by reactive ion etching, and different shapes and sizes can be obtained by adjusting the mask pattern and the etching depth raised structure. In some embodiments of the present application, the carbon nanotube layer is prepared by a phthalocyanine cracking method. The phthalocyanine cracking method is beneficial to form carbon nanotubes with good vertical orientation, and the length and diameter of the carbon tubes are uniform.

In the embodiment of the present application, the steps of the phthalocyanine cracking method include: using an independent dual temperature control heating system, placing the phthalocyanine salt in the low temperature area of the heating furnace, and placing the substrate in the high temperature area of the heating furnace; after the system is evacuated to a vacuum, the argon gas is The mixed gas with hydrogen is introduced into the reaction chamber; the high temperature zone is heated to 700°C-1000°C, and the low temperature zone is heated to 550°C-650°C, and the phthalocyanine salt is cracked in the low temperature zone by entering the high temperature zone with the mixed gas and in the high temperature zone. To generate vertical carbon nanotubes, the growth time of the vertical carbon nanotubes is 15min-30min. After the growth is completed, the gas source is turned off when the temperature is lowered to 200°C, and the carbon nanotube layer is obtained by cooling to room temperature in a vacuum state. In the embodiment of the present application, the phthalocyanine salt includes one or more of iron phthalocyanine, cobalt phthalocyanine, and nickel phthalocyanine, and the flow rate of the mixed gas of argon and hydrogen is 5 sccm-150 sccm. In some embodiments of the present application, the growth time of the vertical carbon nanotubes is 20 minutes, and controlling the growth time of the vertical carbon nanotubes is beneficial to control the diameter and length of the carbon nanotubes, thereby adjusting the optical radiation energy conversion rate of the carbon solid target.

In some embodiments of the present application, the carbon solid target further includes a carbon nano-film layer, and the carbon nano-film layer includes one or more of a graphene layer, a diamond layer, and a diamond-like carbon layer. In some embodiments of the present application, the carbon nano-film layer is a diamond-like carbon layer. The preparation methods of the diamond-like layer include magnetron sputtering, plasma enhanced chemical vapor deposition and magnetic filtration cathode vacuum arc deposition. In the present application, the diamond-like carbon layer is prepared by the magnetic filtration cathode vacuum arc deposition method. The magnetic filtration cathode vacuum arc deposition method filters out neutral carbon clusters through a 90-degree diverter elbow. Compared with the film deposition device without magnetic filtration, it has the advantages of high ionization rate, high ion energy, and high deposition rate. In addition, the method can precisely control the thickness of the diamond-like carbon layer, and the prepared diamond-like carbon layer has high density, uniform structure and good bonding force.

In the embodiment of the present application, the magnetic filtration cathode vacuum arc deposition method adopts a cylindrical high-purity (99.9%) graphite rod as the cathode, the trigger voltage of the pulse trigger power supply is 12kV, the trigger anode voltage is less than 90V, and the substrate DC/pulse negative bias voltage Adjustable, the initial vacuum degree is lower than 9.9×10 ^-4 Pa, the working gas is high-purity argon, the deposition temperature is room temperature (25℃), the thickness of the prepared diamond-like layer is proportional to the pulse count of the cathode arc source , so the thickness of the diamond-like carbon layer can be controlled by adjusting the pulse count to ensure that the thickness of the diamond-like carbon layer is in the range of 0.1 nm-200 nm.

The preparation method of the carbon solid target provided by the present application is simple to operate, the obtained carbon solid target has good stability, and can generate high-brightness and high-quality soft X-rays when interacted with a super-strong laser.

The present application also provides a laser plasma accelerator, which includes the above-mentioned carbon solid target. Since the laser plasma accelerator provided in the present application adopts the carbon solid target of the present application, high brightness and high-quality soft X-ray emission can be realized.

The technical solutions of the present application will be further described below by dividing into multiple embodiments.

Example 1

A preparation method of a carbon solid target, comprising the steps:

a) The heavily doped n-type silicon wafer substrate is etched by reactive ion etching, and a plurality of silicon cylinders are formed on the surface of the substrate. The diameter of the silicon cylinder is 10 μm, the height of the silicon cylinder is 7 μm, and the space between the silicon cylinders The pitch is 10μm;

b) A carbon nanotube layer (CNT) is formed on the surface of the substrate by a phthalocyanine cracking method, and the average thickness of the carbon nanotube layer is 8.3 μm to obtain a carbon solid target.

Example 2

The difference between Example 2 and Example 1 is that the height of the silicon cylinder is 10 μm.

Example 3

The difference between Example 3 and Example 2 is that after the carbon nanotube layer is prepared, in Example 3, a magnetic filtration cathode vacuum arc deposition (FCVA) is used to form a diamond-like carbon layer (DLC) on the carbon nanotube layer (CNT) to obtain Carbon solid target with a diamond-like layer thickness of 7.5 nm.

Example 4

The difference between Example 4 and Example 3 is that the thickness of the diamond-like carbon layer in Example 4 is 15 nm.

Example 5

The difference between Example 5 and Example 3 is that the thickness of the diamond-like carbon layer in Example 5 is 30 nm.

Effect Example

In order to verify the structure and performance of the carbon solid target prepared in the present application, the present application also provides effect examples.

1) The morphology of the carbon solid targets in Examples 1-5 was characterized by scanning electron microscopy and transmission electron microscopy.

Please refer to FIG. 5 , FIG. 6 and FIG. 7 , FIG. 5 is a scanning electron microscope image of the carbon solid target provided in Example 1 of the application, FIG. 6 is a scanning electron microscope image of the carbon solid target provided in Example 2 of the application, and FIG. 7 is a The scanning electron microscope image of the carbon nanotube layer provided in Example 1 of the present application. It can be seen from Figure 5 and Figure 6 that carbon nanotube layers were successfully prepared in Example 1 and Example 2. Since the carbon nanotubes prepared by phthalocyanine cracking grow vertically along the top, bottom and sidewalls of the silicon cylinder, the silicon The growth direction of carbon nanotubes on the sidewall of the cylinder is horizontal with respect to the top and bottom of the silicon cylinder. Please refer to Figure 5. When the height of the silicon cylinder (7μm) is smaller than the vertical carbon nanotube height (8.3μm), the sidewall of the silicon cylinder grows horizontally. The horizontally grown carbon nanotubes are extruded into a vertical shape by the vertical carbon nanotubes grown vertically at the bottom of the silicon substrate, see Figure 6, when the silicon cylinder height (10 μm) is larger than the carbon nanotube height (8.3 μm), the silicon cylinder side The carbon nanotubes grown on the top part of the wall will not be squeezed and thus maintain a horizontal growth state, so the carbon nanotube clusters grown on silicon cylinders with different heights will form different surface morphologies. It can be seen from FIG. 7 that the diameter of the vertical carbon nanotubes in Example 1 is 25 nm-40 nm. Please refer to FIG. 8. FIG. 8 is a transmission electron microscope image of the vertical carbon nanotubes provided in Example 3 of the present application. It can be seen from FIG. 8 that the surface of the carbon nanotubes is covered with a diamond-like carbon layer, the thickness of the diamond-like carbon layer is about 7.5 nm, and the diamond-like carbon layer is well combined with the carbon nanotubes, which shows that Example 3 is successful in the carbon nanotube layer. The surface is coated with a diamond-like layer. Please refer to FIG. 9. FIG. 9 is a selected area electron diffraction pattern of a single vertical carbon nanotube provided in Example 2 of the present application. From FIG. 9, it can be seen that the vertical carbon nanotube is an ordered structure in which single-layer carbon atoms are closely arranged.

Please refer to FIG. 10, FIG. 10 is a scanning electron microscope image of the carbon solid target provided in the embodiment of the application, wherein, (a) in FIG. 10 is a height schematic diagram of the vertical carbon nanotubes of Embodiment 2, and (b) in FIG. 10 is The scanning electron microscope image of the vertical carbon nanotubes of Example 2, (c), (d) and (e) in Figure 10 are the vertical carbon nanotubes covering the diamond-like layer of Example 3, Example 4 and Example 5, respectively SEM image. It can be seen from (a) in Figure 10 that the height of the vertical carbon nanotubes is 8.3 μm, that is, the thickness of the carbon nanotube layer is 8.3 μm; it can be seen from (b) in Figure 10 that the vertical carbon nanotubes in Example 2 The diameter of the tube is about 30nm; it can be seen from (c) in Figure 10 that in Example 3, the surface of the vertical carbon nanotubes is covered with a diamond-like layer, and after calculation, it can be concluded that the thickness of the diamond-like layer is 7.5nm; from Figure 10 In (d), it can be seen that in Example 4, the thickness of the diamond-like layer is 15 nm; from (e) in FIG. 10, it can be seen that in Example 5, the thickness of the diamond-like layer is 30 nm.

2) A laser acceleration experiment was performed on the carbon solid target of Example 1-5, and the radiation intensity of the Ly-α and He-α peaks of the carbon atoms in the carbon solid target of Example 1-5 and the accelerated proton energy were obtained.

The experimental parameters of the laser acceleration experiment in this application are as follows: the central wavelength of the laser is 800nm, the pulse width is 30fs, the energy is 1J, the laser focal spot is 4.0μm×4.5μm, and the peak power of the laser is 4×10 ¹⁹ W/cm ² , the contrast ratio of the laser is 10 ^-10 . Please refer to FIG. 11 , which is an analysis diagram of the wavelength band of the optical radiation generated by the laser acceleration experiment provided in Example 1 of the present application. It can be seen from Fig. 11 that the characteristic peak wavelength of the light radiation of the carbon solid target of the present application is within the water window band, and the peak value of the carbon element Ly-α is about 7.0×10 ⁵ , and the peak value of He-α is about 5.2×10 ⁵ .

Please refer to Table 1 and FIG. 12. Table 1 is the experimental data table of the light radiation generated by the interaction between the ultra-short and ultra-intensive laser and the laser and the carbon solid target of Examples 2-5 of the present application, and FIG. 12 is the example 2- 5. Comparison of light radiation intensity produced by laser accelerated carbon solid target. It can be seen from Table 1 and Figure 12 that in Examples 2-5, as the thickness of the diamond-like carbon layer increases, the Ly-α and He-α light radiation intensity of carbon element first increases and then decreases, and the proton energy decreases monotonically. It shows that the deposition of diamond-like carbon layers with different thicknesses on the carbon nanotube layer can modulate the carbon atom density, light radiation intensity and particle acceleration energy of the carbon solid target. In the embodiment of the present application, when the thickness of the diamond-like carbon layer is 15 nm, the light radiation intensity of the carbon solid target is the highest, and the energy conversion efficiency is the highest.

Table 1 Example 2-5 Laser-accelerated carbon solid target produces optical radiation experimental data

In this application, the interaction between ultra-short and ultra-intensive laser and carbon solid target is used to generate soft X-ray band light radiation, and the effect of the structure and density of carbon solid target on the characteristic spectral brightness of carbon elements Ly-α and He-α is analyzed through the experiments of the embodiment. modulation effect. The carbon solid target includes a carbon nanotube layer, and the atomic density of the carbon solid target can be changed by covering the surface of the carbon nanotube with a diamond-like carbon layer. As the thickness of the diamond-like carbon layer increases from 0 nm to 30 nm, the brightness of the Ly-α and He-α lines of carbon element first increases and then decreases, indicating that the density of the carbon solid target has an optimal value. Under the density, the energy conversion efficiency of the soft X-ray optical radiation generated by the relativistic laser incident on the carbon solid target is the highest, thus providing an experimental basis for modulating the target density to improve the energy conversion efficiency of the soft X-ray optical radiation.

The above description is the preferred embodiment of the present application, but should not be construed as a limitation on the scope of the present application. It should be pointed out that for those skilled in the art, without departing from the principles of the present application, several improvements and modifications can also be made, and these improvements and modifications are also regarded as the protection scope of the present application.

Claims

A carbon solid target for generating soft X-rays by a laser plasma acceleration mechanism, characterized in that the carbon solid target includes a carbon nanotube layer, and the carbon nanotube layer includes a vertical carbon nanotube array.
The carbon solid target according to claim 1, wherein the carbon solid target further comprises a carbon nano film layer disposed on the surface of the carbon nanotube layer, the carbon nano film layer comprising a graphene layer, a diamond layer and one or more of diamond-like layers.
The carbon solid target according to claim 1 or 2, wherein the density of the carbon nanotube layer is 0.1 g/cm 3 -2.5 g/cm 3 ; the diameter of the vertical carbon nanotube is 0.1 nm -200nm.
The carbon solid target according to any one of claims 1-3, wherein the vertical carbon nanotubes have a height of 1 μm-20 μm.
The carbon solid target according to claim 2, wherein the thickness of the carbon nano film layer is 0.1 nm-200 nm.
The carbon solid target according to any one of claims 1-5, wherein the carbon solid target further comprises a substrate, the carbon nanotube layer is disposed on the surface of the substrate; the substrate surface has one or more There are protruding structures, and the height of the protruding structures is less than or equal to 50 μm.
The carbon solid target according to any one of claims 1 to 6, wherein the energy conversion efficiency of the carbon solid target interacting with the laser to generate soft X-rays is greater than or equal to 6%.
A method for generating soft X-rays by a laser plasma acceleration mechanism, characterized in that an ultra-short and ultra-intensive laser is used to interact with a carbon solid target to generate plasma to generate soft X-rays, and the carbon solid target includes a carbon nanotube layer, The carbon nanotube layer includes a vertical carbon nanotube array.
A method for generating soft X-rays by a laser plasma acceleration mechanism, the method comprising using the carbon solid target according to any one of claims 2-7.
The method for generating soft X-rays by a laser plasma acceleration mechanism according to claim 8 or 9, wherein the peak power of the laser is greater than or equal to 1×10 18 W/cm 2 .
A laser plasma accelerator, characterized in that the laser plasma accelerator comprises the carbon solid target according to any one of claims 1-7.