A microchannel device-based plasma generation apparatus and a method of generating

Abstract

The application discloses a kind of plasma preparation device and preparation method based on microchannel device, it is related to plasma preparation field.The preparation device includes ablation laser emitter and microchannel device, wherein, ablation laser emitter is used to emit ablation laser, and microchannel device is used to guide ablation laser transmission;Center hole of set size is equipped on microchannel device;The focal point of ablation laser is aligned with the center hole of microchannel device, and ablation laser is coaxial with microchannel device;Ablation laser is used to ablate the tube wall of microchannel device, and generates plasma.The application prepares plasma by ablation laser ablation microchannel device tube wall, utilizes microchannel device to constrain laser divergence, guides long-distance transmission of laser, to induce plasma to fill in the channel tube transversely, while inhibiting longitudinal expansion of plasma, can obtain state uniform, with steep rising edge Small-size near-critical density plasma.

Description

Technical Field

[0001] This invention relates to the field of plasma preparation, and in particular to a plasma preparation apparatus and method based on microchannel devices. Background Technology

[0002] Near-critical density plasma is a plasma state with a density between 0.1nc and 1nc, where nc is the critical plasma density, which is related to the laser wavelength and is one of the fundamental parameters in the field of laser-plasma interaction. Near-critical density plasma can significantly improve the energy conversion efficiency of laser to electron, and is expected to be used to generate high-energy, highly collimated relativistic electron beams and high-brightness X-ray / gamma-ray sources at the microcoulomb level. Therefore, it has been extensively studied in recent years, and its preparation methods have also attracted much attention.

[0003] Currently, commonly used methods for preparing near-critical density plasma include the high-density gas method based on high-pressure nozzles, the pre-plasma preparation method based on near-critical density foam, and the pre-plasma expansion method based on solid planes. The high-density gas method uses high-pressure supersonic nozzles to eject high-density He or N2 gas, which can prepare large-scale plasmas with lengths and lateral dimensions of several millimeters. The near-critical density foam method uses supercritical drying and other methods to prepare TAC foam, SiO2 foam, or carbon nanotube foam with densities below 10 mg / cc, thereby generating near-critical density plasma. The pre-plasma expansion method uses a laser beam to pre-ablate a CH plane or a metal plane, and then prepares a near-critical density plasma state through the expanding plasma. However, the above-mentioned near-critical density plasma preparation methods suffer from problems such as excessively long low-density rise times (hundreds of micrometers), excessively large lateral plasma dimensions (hundreds of micrometers to several millimeters), and uncontrollable longitudinal plasma length, failing to meet the practical experimental requirements for small-sized (spatial dimensions of tens of micrometers) near-critical density plasmas with steep rise times.

[0004] Therefore, how to improve the near-critical density plasma preparation device and preparation method to obtain small-sized near-critical density plasma with uniform state and controllable density has become a major problem that needs to be solved by those skilled in the art. Summary of the Invention

[0005] The purpose of this invention is to provide a plasma preparation device and method based on microchannel devices to obtain small-sized near-critical density plasma with uniform state and steep rise edge.

[0006] To achieve the above objectives, the present invention provides the following solution:

[0007] A plasma preparation apparatus based on microchannel devices, comprising:

[0008] Ablation laser emitter, used to emit ablation laser;

[0009] A microchannel device is used to guide the transmission of the ablation laser; the microchannel device has a central hole of a predetermined size; the focal point of the ablation laser is aligned with the central hole of the microchannel device, and the ablation laser is coaxial with the microchannel device; the ablation laser is used to ablate the wall of the microchannel device to generate plasma.

[0010] Optionally, the microchannel device is a single-pore micron-scale capillary or a multi-pore array.

[0011] Optionally, the preparation apparatus further includes:

[0012] The beam-target coupling system includes a target holder subsystem and a target-back imaging subsystem;

[0013] The target-back imaging subsystem is used to image the focal point of the ablation laser, the front surface of the microchannel device, and the rear surface of the microchannel device, respectively, to obtain alignment information;

[0014] The target frame subsystem is used to mount the microchannel device and adjust the position and angle of the microchannel device according to the alignment information.

[0015] Optionally, the preparation apparatus further includes:

[0016] A main laser emitter is used to emit a main laser beam toward the microchannel device; the main laser beam is used to interact with the plasma to generate a relativistic electron beam and a radiation source; the radiation source is an X-ray source or a gamma-ray source.

[0017] Optionally, the emission time of the main laser is after the emission time of the ablation laser, and the interval between the emission time of the main laser and the emission time of the ablation laser is a set time.

[0018] Optionally, the peak power density of the ablation laser is 1×10⁻⁶. 10 Wcm -2 ~1×10 12 Wcm -2 .

[0019] Optionally, the pulse width of the ablation laser is less than 1 ns.

[0020] A plasma preparation method based on microchannel devices, wherein the preparation method is applied to the above-mentioned preparation apparatus, comprising:

[0021] Determine the focal point of the ablation laser and the central aperture of the microchannel device;

[0022] Adjust the position and angle of the microchannel device so that the focus of the ablation laser is aligned with the central hole of the microchannel device, and the ablation laser is coaxial with the microchannel device;

[0023] The ablation laser is emitted towards the microchannel device; the ablation laser ablates the wall of the microchannel device, generating plasma.

[0024] Optionally, the preparation method further includes:

[0025] After a predetermined time following the emission of the ablation laser, a main laser is emitted toward the microchannel device; the main laser interacts with the plasma to generate a relativistic electron beam and a radiation source; the radiation source is an X-ray source or a gamma-ray source.

[0026] Optionally, the preparation method further includes:

[0027] The spatial dimensions of the plasma are adjusted according to the dimensions of the microchannel device; the spatial dimensions include: longitudinal length and transverse width.

[0028] The density of the plasma is adjusted according to the peak power density, focal point, and pulse width of the ablation laser;

[0029] The spatial distribution parameters of the plasma are adjusted according to the delay between the main laser and the ablation laser; the spatial distribution parameters include density and spatial size.

[0030] According to specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0031] This invention prepares plasma by ablation of the walls of a microchannel device using laser ablation. The microchannel device can constrain laser divergence and guide the laser to travel long distances, thereby inducing the plasma to fill laterally within the channel tube while suppressing the longitudinal expansion of the plasma. Therefore, it is easier to form near-critical density plasma with uniform state and steep rise edge. Compared with traditional near-critical density plasma preparation methods such as high-density gas method and solid planar target pre-plasma expansion method, this invention has a significant advantage in shortening the low-density rise edge. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1A structural diagram of a plasma preparation apparatus based on microchannel devices provided in an embodiment of the present invention;

[0034] Figure 2 A flowchart of a plasma preparation method based on microchannel devices provided in an embodiment of the present invention.

[0035] Symbol explanation: 1-Main laser, 2-Ablation laser, 3-Microchannel device, 4-Target frame system, 5-Post-target imaging subsystem. Detailed Implementation

[0036] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] The purpose of this invention is to provide a plasma preparation device and method based on microchannel devices to obtain small-sized near-critical density plasma with uniform state and steep rise edge, which can be widely used in the fields of high energy density physics, laboratory astrophysics and novel laser radiation sources.

[0038] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0039] Example 1

[0040] This invention provides a plasma preparation device based on microchannel devices. Figure 1 This is a structural diagram of a plasma preparation apparatus based on microchannel devices provided in an embodiment of the present invention. Figure 1 As shown, the fabrication apparatus includes an ablation laser emitter and a microchannel device 3. The ablation laser emitter emits an ablation laser 2. The microchannel device 3 guides the transmission of the ablation laser 2.

[0041] Specifically, the microchannel device 3 has a central hole of a predetermined size. The focal point of the ablation laser 2 is aligned with the central hole of the microchannel device 3, and the ablation laser 2 is coaxial with the microchannel device 3. The ablation laser 2 is used to ablate the wall of the microchannel device 3, generating plasma.

[0042] In one specific implementation, the ablation laser 2 is a laser pre-pulse or an independent nanosecond laser, which can ablate the solid material of the wall of the microchannel device 3 to generate expanding plasma, and the plasma fills the central hole of the microchannel device 3; the microchannel device 3 is a single-hole micron-scale capillary or a multi-hole array, which can guide laser transmission, induce lateral expansion of plasma, and inhibit longitudinal expansion of plasma, thereby forming a near-critical density plasma with uniform state and steep rise edge.

[0043] In practical applications, the number of ablation lasers 2 is equal to the number of central holes in the microchannel device 3, and they correspond one-to-one. When the microchannel device 3 is a single-hole micron-sized capillary, there is one ablation laser 2; when the microchannel device 3 is a multi-hole array, there are multiple ablation lasers 2.

[0044] Preferably, the peak power density of the ablation laser is 1×10⁻⁶. 10 Wcm -2 ~1×10 12 Wcm -2 The pulse width of the ablation laser is less than 1 ns.

[0045] Furthermore, the fabrication apparatus also includes a beam-target coupling system. The beam-target coupling system includes a target holder subsystem 4 and a target-back imaging subsystem 5, with the target-back imaging subsystem 5 located behind the microchannel device 3; the target holder subsystem 4 is located below the microchannel device 3. The target-back imaging subsystem 5 is used to image the focal point of the ablation laser 2, the front surface of the microchannel device 3, and the rear surface of the microchannel device 3, respectively, to obtain alignment information. The target holder system 4 is used to mount the microchannel device 3 and adjust the position and angle of the microchannel device 3 according to the alignment information, so that the focal point of the ablation laser 2 is aligned with the central hole of the microchannel device 3, and that the ablation laser 2 and the microchannel device 3 are coaxial.

[0046] In practical applications, the target frame subsystem 4 is a high-precision target-tracking system, and the target-back imaging subsystem 5 consists of multiple high-precision imaging systems. The high-precision beam-target coupling system composed of the two is used to ensure that the focal point of the ablation laser 2, the center of the front surface of the microchannel device 3, and the center of the rear surface of the microchannel device 3 overlap, thereby accurately injecting the ablation laser 2 into the central hole of the microchannel device 3.

[0047] The target imaging subsystem 5 includes a set of six-dimensional stepper motors, which can image the focal point of the ablation laser 2, the front surface of the microchannel device 3 (such as a capillary), and the rear surface of the microchannel device 3 (with an imaging spatial resolution better than 2μm). This is used to guide the target holder subsystem 4 to adjust the position and angle of the target (i.e., the microchannel device 3). Through multiple iterations, the focal point of the ablation laser 2 can be precisely overlapped with the center of the front surface of the capillary and the center of the rear surface of the capillary, ultimately achieving precise alignment between the focal point of the ablation laser 2 and the central hole of the capillary, while ensuring high-precision coaxiality between the laser and the capillary axis.

[0048] Furthermore, the fabrication apparatus also includes a main laser emitter. The main laser emitter emits a main laser 1 towards the microchannel device 3; the main laser 1 interacts with the plasma to generate a relativistic electron beam and a radiation source; the radiation source is an X-ray source or a gamma-ray source (i.e., a gamma-ray source). Since the prepared plasma is a small-sized, near-critical-density plasma, its interaction with the main laser 1 can produce a high-energy, highly collimated relativistic electron beam and a high-brightness X-ray / gamma-ray source at the microcoulomb level, which can then be used for research in high-energy-density physics, laboratory astrophysics, and novel laser radiation sources.

[0049] Preferably, the emission time of the main laser 1 is after the emission time of the ablation laser 2, and the interval between the emission time of the main laser 1 and the emission time of the ablation laser 2 is a set time. The set time can be several nanoseconds (ns).

[0050] Example 2

[0051] The present invention also provides a plasma preparation method based on microchannel devices, wherein the preparation method is applied to the preparation apparatus described in Example 1. Figure 2 A flowchart of a plasma preparation method based on microchannel devices provided in an embodiment of the present invention is shown below. Figure 2 As shown, the preparation method includes:

[0052] Step S1: Determine the focal point of the ablation laser and the central hole of the microchannel device.

[0053] Step S2: Adjust the position and angle of the microchannel device so that the focus of the ablation laser is aligned with the center hole of the microchannel device, and the ablation laser is coaxial with the microchannel device.

[0054] Step S3: Emit the ablation laser to the microchannel device; the ablation laser ablates the wall of the microchannel device, generating plasma.

[0055] Furthermore, the preparation method further includes:

[0056] Step S4: After the ablation laser emission time is set, a main laser is emitted towards the microchannel device; the main laser interacts with the plasma to generate a relativistic electron beam and a radiation source; the radiation source is an X-ray source or a gamma-ray source.

[0057] In practical applications, the above preparation method is as follows:

[0058] First, the laser focus and the center of the microchannel hole (i.e. the central hole of the microchannel device) are located using a beam-target coupling system. The microchannel device is then moved to the laser focus using a high-precision target holder system. Through multiple iterations, the laser focus is injected into the center of the microchannel hole, ensuring that the laser and the microchannel hole are as coaxial as possible.

[0059] Secondly, the experiment provides an ultrashort pulse laser. The pre-pulse (i.e., ablation laser 2) precedes the main pulse (i.e., main laser 1) by several nanoseconds, and the delay between the pre-pulse and the main pulse can be adjusted according to specific circumstances. The pre-pulse interacts with the microchannel device 3 to ablate the microchannel wall, generating expanding plasma. The plasma laterally fills the microchannel pores, forming a near-critical density plasma structure with a uniform state and a steep leading edge.

[0060] Subsequently, the interaction between the main pulse and the near-critical density plasma can generate high-energy, highly collimated relativistic electron beams and high-brightness X-ray / gamma-ray sources at the microcoulomb level, which can be used for research in fields such as high-energy-density physics, laboratory astrophysics, and novel laser radiation sources.

[0061] Here, the density of the filling plasma can be controlled by changing the peak power density of the pre-pulse. Similarly, the state of the filling plasma (spatial distribution parameters such as plasma density, longitudinal length, and transverse width) can be controlled by changing the delay of the main pulse and the pre-pulse. In addition, the spatial size of the near-critical density plasma is completely determined by the size of the microchannel device. Therefore, it is easier to generate small-sized near-critical density plasma compared with traditional methods.

[0062] In this embodiment, since the peak power density, focal point, and pulse width of the ablation laser, the size of the microchannel device, and the delays of the main laser and the ablation laser are all adjustable and controllable, the spatial distribution parameters of the prepared plasma can be adjusted by adjusting the above parameters, specifically:

[0063] (1) Adjust the spatial dimensions of the plasma according to the dimensions of the microchannel device; the spatial dimensions include: longitudinal length and transverse width. The transverse width is the aperture of the microchannel device, that is, the size of the central aperture, which is equivalent to the focal spot size of the ablation laser, specifically 5 micrometers to 100 micrometers; the longitudinal length is the length of the microchannel device, which is on the order of micrometers, specifically 50 micrometers to 500 micrometers.

[0064] (2) Adjust the density of the plasma according to the peak power density, focal point and pulse width of the ablation laser.

[0065] (3) Adjust the spatial distribution parameters of the plasma according to the delay between the main laser and the ablation laser; the spatial distribution parameters include density and spatial size.

[0066] This invention provides a method for preparing small-sized near-critical density plasmas with uniform state and controllable density. This method can be used for preparing near-critical density plasmas in research on high-energy, highly collimated relativistic electron beam generation at the microcoulomb level and in research on high-brightness X-ray / gamma-ray source generation. Through ingenious design, this invention combines the advantages of adjustable microchannel device size, adjustable pre-pulse intensity and delay, and suppressed lateral filling and longitudinal expansion of the pre-plasma. This effectively achieves the preparation of small-sized near-critical density plasmas with uniform density, adjustable density, and controllable spatial dimensions, solving problems such as excessively long low-density rise times, excessively large lateral dimensions, excessively long longitudinal lengths, and poor adjustability in existing plasma preparation techniques. Therefore, compared with existing technologies, this invention represents a significant advancement with outstanding substantive features and remarkable progress.

[0067] Compared with the prior art, the present invention has the following beneficial effects:

[0068] (1) This invention prepares near-critical density plasma by laser ablation of microchannel devices. Microchannel devices can constrain laser divergence, guide laser long-distance transmission, induce plasma to fill laterally in the channel tube, and suppress plasma longitudinal expansion. Therefore, it is easier to form near-critical density plasma with uniform state and steep front. Compared with traditional near-critical density plasma preparation methods such as high-density gas method and solid planar target pre-plasma expansion method, this method has obvious advantages in shortening the low-density rise edge.

[0069] (2) The present invention prepares near-critical density plasma by laser ablation of microchannel devices. The density of the filled plasma can be easily controlled by adjusting parameters such as the peak power density, laser focal spot, and pulse width of the ablation laser. In addition, the state of the filled plasma can also be controlled by adjusting the delay between the ablation laser and the main laser.

[0070] (3) This invention prepares near-critical density plasma by laser ablation of microchannel devices. By changing the aperture, length and other parameters of the microchannel devices, the spatial size of the near-critical density plasma can be precisely adjusted. Compared with traditional preparation methods, it is easier to prepare small-sized near-critical density plasma with uniform density, adjustable density and controllable spatial size.

[0071] (4) The present invention is reasonably designed, easy to use and highly practical, and is very suitable for large-scale application in the preparation of small-sized near-critical density plasma.

[0072] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0073] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the core ideas of the present invention. Furthermore, those skilled in the art will recognize that, based on the ideas of the present invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the present invention.

Claims

1. A microchannel device based plasma production apparatus, characterized by, The application relates to a preparation device and a preparation method thereof. The preparation device comprises: an ablation laser emitter for emitting an ablation laser; a micro-channel device for guiding the ablation laser transmission; the micro-channel device is provided with a center hole with a set size; a focal point of the ablation laser is aligned with the center hole of the micro-channel device, and the ablation laser is coaxial with the micro-channel device; the ablation laser is used for ablating a pipe wall of the micro-channel device to generate plasma; a beam target coupling system comprises a target frame subsystem and a post-target imaging subsystem; the post-target imaging subsystem is used for imaging the focal point of the ablation laser, a front surface of the micro-channel device and a rear surface of the micro-channel device respectively to obtain alignment information; and the target frame subsystem is used for erecting the micro-channel device and adjusting the position and angle of the micro-channel device according to the alignment information. The micro-channel device is a single-hole micro-capillary or a multi-hole array. The application further relates to a preparation method of the preparation device.

2. The microchannel device based plasma production apparatus of claim 1, wherein, The preparation method comprises the following steps: determining the focal point of the ablation laser and the center hole of the micro-channel device; imaging the focal point of the ablation laser, the front surface of the micro-channel device and the rear surface of the micro-channel device to obtain alignment information; adjusting the position and angle of the micro-channel device according to the alignment information so that the focal point of the ablation laser is aligned with the center hole of the micro-channel device, and the ablation laser is coaxial with the micro-channel device; and emitting the ablation laser to the micro-channel device; the ablation laser ablates the pipe wall of the micro-channel device to generate plasma.

3. The microchannel device based plasma production apparatus of claim 1, wherein, The application further relates to a preparation method of the preparation device. The preparation method comprises the following steps: emitting the ablation laser to the micro-channel device after a set time; the ablation laser ablates the pipe wall of the micro-channel device to generate plasma; emitting the main laser to the micro-channel device after the ablation laser is emitted for a set time; the main laser interacts with the plasma to generate a relativistic electron beam and a radiation source; the radiation source is an X-ray source or a gamma-ray source. The application further relates to a preparation method of the preparation device.

4. The microchannel device based plasma production apparatus of claim 3, wherein, The preparation method comprises the following steps: adjusting the spatial size of the plasma according to the size of the micro-channel device; the spatial size comprises a longitudinal length and a transverse width; adjusting the density of the plasma according to the peak power density, the focal point and the pulse width of the ablation laser; and adjusting the spatial distribution parameters of the plasma according to the time delay between the main laser and the ablation laser; the spatial distribution parameters comprise the density and the spatial size.

5. The microchannel device based plasma production apparatus of claim 1, wherein, The peak power density of the ablation laser is 1 x 10 10 Wcm -2 ~1 x 10 12 Wcm -2 .

6. The microchannel device based plasma production apparatus of claim 1, wherein, ​ 7. A method of plasma production based on a microchannel device, characterized in that, ​ ​ ​ ​ ​ 8. The microchannel device-based plasma production method according to claim 7, wherein, ​ ​ 9. The microchannel device-based plasma production method according to claim 8, wherein, ​ ​ ​ ​ ​

Images