CN113340879B - Laser plasma instability electrostatic wave diagnosis method and diagnosis device - Google Patents
Laser plasma instability electrostatic wave diagnosis method and diagnosis device Download PDFInfo
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Abstract
The invention discloses a laser plasma instability electrostatic wave diagnosis method and a diagnosis device, wherein the diagnosis method comprises the following steps: s1, generating an electron beam probe with energy of more than 100 megaelectron volts and a beam length of 0.1-100 μm; s2, obtaining the original density information of the electron beam probe; s3, exciting unstable electrostatic waves of laser plasma, injecting the electron beam probe with known original density information into the electrostatic waves, and enabling the electron beam probe to generate density modulation under the action of an electrostatic wave electric field when passing through the plasma; s4, obtaining density modulation spatial distribution information of the electron beam probe after passing through the electrostatic wave; and S5, performing inversion reconstruction on the density modulation spatial distribution information to obtain the absolute intensity information of the electrostatic waves. The invention solves the problems that the diagnosis platform is difficult to set up, the absolute intensity information of the electrostatic waves cannot be obtained, two or more laser plasma unstable electrostatic waves simultaneously occurring at the same position cannot be diagnosed at the same time and the like in the prior art.
Description
Technical Field
The invention relates to the technical field of laser plasma instability electrostatic wave diagnosis in laser inertial confinement fusion, in particular to a laser plasma instability electrostatic wave diagnosis method and a diagnosis device.
Background
The instability of laser plasma is one of key factors for restricting the successful ignition of laser inertial confinement fusion, and is a physical process which is restrained by people as much as possible in the laser fusion. The method for effectively inhibiting the laser plasma instability can be obtained theoretically by carefully researching the physical mechanism of the laser plasma instability, and the experimental research on the physical mechanism of the laser plasma instability is mainly carried out by diagnosing two major products, namely scattered light and electrostatic waves. The scattered light signals obtained in the current experiment are the result of path integration, and the position of instability and the growth rule on the path cannot be inferred only by using the scattered light signals, so that an electrostatic wave diagnosis result is required to assist research. However, the only existing electrostatic wave diagnosis method is the hyperthermia coherent thomson scattering method, which requires strict matching of the probe light propagation direction, the electrostatic wave propagation direction and the probe light receiving direction, and the difficulty in building the platform in an experiment is high; meanwhile, the diagnostic method cannot obtain absolute intensity information of the electrostatic wave, is limited to the resolution of the light receiving system, and the measured electrostatic wave signal is also a time integral result of tens of picoseconds.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention provides a laser plasma instability electrostatic wave diagnosis method and a diagnosis device, and solves the problems that the difficulty in building a diagnosis platform is high, the absolute intensity information of electrostatic waves cannot be obtained, two or more laser plasma instability electrostatic waves which simultaneously occur at the same position cannot be diagnosed at the same time, and the like in the prior art.
The technical scheme adopted by the invention for solving the problems is as follows:
a laser plasma instability electrostatic wave diagnosis method comprises the following steps:
s1, generating an electron beam probe with energy of more than 100 megaelectron volts and a beam length of 0.1-100 μm;
s2, obtaining the original density information of the electron beam probe;
s3, exciting unstable electrostatic waves of laser plasma, injecting the electron beam probe with known original density information into the electrostatic waves, and enabling the electron beam probe to generate density modulation under the action of an electrostatic wave electric field when passing through the plasma;
s4, combining the original density information of the electron beam probe obtained in the step S2 to obtain the density modulation spatial distribution information of the electron beam probe after passing through the electrostatic waves;
and S5, performing inversion reconstruction on the density modulation spatial distribution information to obtain the absolute intensity information of the electrostatic waves.
The invention utilizes the ultrafast electron beam probe to diagnose the unstable electrostatic wave of the laser plasma, and can directly diagnose the absolute intensity information of the electrostatic wave; compared with the hyperthermia coherent Thomson scattering, the method has no angle matching requirement, the diagnosis is easier to realize, the diagnosis platform is easy to build, and the debugging difficulty is reduced; the method can diagnose simultaneously various laser plasma unstable electrostatic waves at the same position.
As a preferred technical solution, the step S2 includes the following steps:
s21, focusing the electron beam probe generated in step S1 using the magnetic field;
s22, injecting the focused electron beam probe into the plasma without exciting electrostatic waves, and enabling the electron beam probe to penetrate through the plasma;
s23, collecting the electron beam probe by using the transition radiation medium, and generating transition radiation after the electron beam probe passes through the transition radiation medium;
and S24, obtaining the original density information of the electron beam probe by the transition radiation space distribution and the time spectrum distribution.
The method is convenient for obtaining the influence of the background plasma (the background plasma is also called as diagnostic plasma) on the density spatial distribution of the electron beam probe, thereby improving the signal-to-noise ratio of the density spatial distribution information of the electron beam probe and enabling the diagnosis to be more accurate and reliable.
As a preferable technical solution, the direction in which the electron beam probe injects the electrostatic wave in step S3 is perpendicular to the propagation direction of the electrostatic wave.
Therefore, the electron beam probe can generate density modulation space distribution information vertical to the propagation direction of the electron beam probe under the action of the electrostatic wave electric field when passing through the plasma, so that the density modulation space distribution information is more accurate, and the diagnosis effect is better.
As a preferable mode, the density modulation spatial distribution information generated in step S4 includes wave number information, absolute intensity information, and phase velocity information of one or more types of electrostatic waves.
If the density modulation spatial distribution information generated in step S4 includes wave number information, absolute intensity information, and phase velocity information of an electrostatic wave, the absolute intensity information of the electrostatic wave can be obtained;
if the density modulation spatial distribution information generated in step S4 includes the wave number information, the absolute intensity information, and the phase velocity information of a plurality of types of electrostatic waves, the absolute intensity information and the frequency information of the electrostatic waves can be obtained, and the temperature information and the density information of the plasma can be obtained, so that two or more types of laser plasma unstable electrostatic waves occurring at the same position at the same time can be diagnosed at the same time.
As a preferred technical solution, the step S4 includes the following steps:
s41, collecting the electron beam probe passing through the plasma by using a transition radiation medium, and generating transition radiation after the electron beam probe passes through the transition radiation medium;
s42, obtaining density information of the electron beam probe passing through the electrostatic wave through transition radiation space distribution and time spectrum distribution;
s43, imaging the transit radiation signal by using the transit radiation imaging device, and performing inverse solution on the imaged transit radiation signal;
and S44, combining the original density information obtained in the step S2 to obtain the spatial distribution information of the electron beam probe density at different moments.
Therefore, the density modulation spatial distribution information of the electron beam probe can be conveniently obtained, and reference is provided for the selection of a reconstruction model.
As a preferred technical solution, in step S1, a laser-driven accelerator or a linear accelerator is used to generate the electron beam probe.
Laser drive acceleration, especially tail field acceleration, is convenient for generating electron beam probes with reliable quality; the linear accelerator is more traditional and has stronger universality.
As a preferable technical solution, in the inversion reconstruction process in step S5, the structure of the electrostatic wave is assumed to have a waveform conforming to one of a sine function structure, a cosine function structure, a superposition structure of a plurality of sine functions and/or cosine functions.
Since the electric field distribution generating the same density modulation is not unique, the structure of the electrostatic wave is properly assumed in the process of inversion reconstruction, and the structure of the electrostatic wave is assumed to be the above structure, so as to obtain more accurate absolute intensity information of the electrostatic wave. In addition, accurate electrostatic wave frequency and electrostatic wave phase velocity information can be obtained conveniently.
As a preferred technical solution, the step S5 further includes the following steps:
and (3) performing wave number analysis on the density modulation spatial distribution information to obtain frequency information of the electrostatic waves and/or obtain temperature information and density information of the plasma.
Therefore, frequency information of the electrostatic waves is obtained, and besides, temperature information and density information of plasmas are obtained, so that two or more laser plasma unstable electrostatic waves which simultaneously occur at the same position can be diagnosed at the same time.
As a preferred technical solution, the method further comprises the following steps:
s6, if the wave number analysis in step S5 obtains two or more differences of more than 8.5 μm-1The wave number of (2) is obtained by using the correlation between the electrostatic wave phase velocity and the plasma temperature and the plasma density to obtain the temperature and the plasma density information of the plasma.
If the wave number analysis in step S5 obtains two or more differences greater than 8.5 μm-1The wave number of the plasma is the same as that of the conventional plasma, which means that when various instabilities occur simultaneously, the invention realizes additional functions, can be used for calculating local plasma temperature, density and other information, and can realize the purpose of calculating the local plasma temperature, density and other informationCan diagnose two or more laser plasma unstable electrostatic waves simultaneously occurring at the same position.
Preferably, the transit radiation signal is imaged with a framing camera in step S43.
The high space-time resolution capability of the framing camera is better, and the imaging effect of the transit radiation signals is convenient to ensure.
The high space-time resolution capability of the framing camera is good, the imaging effect of the transit radiation signals is convenient to ensure, the high space-time resolution electrostatic wave signals can be obtained, and meanwhile, the time resolution and the space resolution of electrostatic wave diagnosis are convenient to ensure to be higher.
Therefore, the invention can diagnose the unstable electrostatic wave of the laser plasma by using the ultrafast electron beam probe, can be used for diagnosing the electrostatic wave with high time resolution, and can diagnose the absolute intensity information, the frequency, the phase speed and other information of various unstable electrostatic waves of the laser plasma at the same spatial position at the same time; the invention has the electrostatic diagnosis function of high space-time resolution and can directly diagnose the absolute intensity information of the electrostatic waves, and the invention perfects the problems of insufficient time resolution and single effect of the existing diagnosis method.
The laser plasma instability electrostatic wave diagnosis device comprises an electron beam probe generation device, a magnetic field generation device, plasma to be diagnosed, a transition radiation medium and transition radiation imaging devices, wherein the electron beam probe generation device, the magnetic field generation device, the plasma to be diagnosed and the transition radiation medium are sequentially arranged along the propagation direction of an electron beam probe.
The invention utilizes the ultrafast electron beam probe to diagnose the unstable electrostatic wave of the laser plasma, and can directly diagnose the absolute intensity information of the electrostatic wave; compared with the hyperthermia coherent Thomson scattering, the method has no angle matching requirement, the diagnosis is easier to realize, the diagnosis platform is easy to build, and the debugging difficulty is reduced; the method can diagnose simultaneously various laser plasma unstable electrostatic waves at the same position.
Compared with the prior art, the invention has the following beneficial effects:
(1) the invention utilizes the ultrafast electron beam probe to diagnose the unstable electrostatic wave of the laser plasma, and can directly diagnose the absolute intensity information of the electrostatic wave;
(2) compared with the hyperthermia coherent Thomson scattering, the method has no angle matching requirement, the diagnosis is easier to realize, the diagnosis platform is easy to build, and the debugging difficulty is reduced;
(3) the method is convenient for obtaining the influence of the background plasma on the density spatial distribution of the electron beam probe, thereby improving the signal-to-noise ratio of the density spatial distribution information of the electron beam probe and ensuring that the diagnosis is more accurate and reliable;
(4) in the step S3, the direction of the electrostatic wave injected by the electron beam probe is vertical to the propagation direction of the electrostatic wave, so that the electron beam probe can generate density modulation spatial distribution information vertical to the propagation direction of the electron beam probe under the action of an electrostatic wave electric field when passing through the plasma, thereby enabling the density modulation spatial distribution information to be more accurate and the diagnosis effect to be better;
(5) the invention can obtain the absolute intensity information and frequency information of the electrostatic wave, and can also obtain the temperature information and density information of the plasma, thereby being capable of diagnosing the unstable electrostatic wave of two or more laser plasmas which simultaneously occur at the same position;
(6) the invention is convenient to obtain the density modulation space distribution information of the electron beam probe and provides reference for the selection of a reconstruction model;
(7) in step S1, a laser drive accelerator or a linear accelerator is adopted to generate the electron beam probe, and laser drive acceleration, particularly tail field acceleration, is convenient to generate the electron beam probe with reliable quality; the linear accelerator is more traditional and has stronger universality;
(8) the invention can obtain more accurate absolute intensity information of electrostatic waves; in addition, accurate electrostatic wave frequency and electrostatic wave phase velocity information can be obtained conveniently;
(9) the invention carries out wave number analysis on the density modulation spatial distribution information to obtain the frequency information of the electrostatic waves and/or obtain the temperature information and the density information of the plasma; therefore, frequency information of the electrostatic waves is obtained, and besides, temperature information and density information of plasmas are obtained, so that two or more laser plasma unstable electrostatic waves which simultaneously occur at the same position can be diagnosed at the same time.
(10) If the wave number analysis in step S5 obtains two or more differences of more than 8.5 μm-1The wave number of the laser plasma instability electrostatic wave is the same as that of the laser plasma instability electrostatic wave, and the method can be used for calculating local plasma temperature, density and other information and diagnosing two or more laser plasma instability electrostatic waves simultaneously occurring at the same position.
Drawings
FIG. 1 is a diagram of the steps of the diagnostic method of the present invention;
fig. 2 is a schematic structural diagram of the diagnostic device of the present invention.
Reference numbers and corresponding part names in the drawings: 1. an electron beam probe generating device 2, a magnetic field generating device 3, plasma to be diagnosed 4, a transition radiation medium 5 and a transition radiation imaging device.
Detailed Description
The present invention will be described in further detail with reference to examples and drawings, but the present invention is not limited to these examples.
Example 1
As shown in fig. 1 and fig. 2, a method for diagnosing laser plasma instability electrostatic waves includes the following steps:
s1, generating an electron beam probe with energy of more than 100 megaelectron volts and a beam length of 0.1-100 μm;
s2, obtaining the original density information of the electron beam probe;
s3, exciting unstable electrostatic waves of laser plasma, injecting the electron beam probe with known original density information into the electrostatic waves, and enabling the electron beam probe to generate density modulation under the action of an electrostatic wave electric field when passing through the plasma;
s4, combining the original density information of the electron beam probe obtained in the step S2 to obtain the density modulation spatial distribution information of the electron beam probe after passing through the electrostatic waves;
and S5, performing inversion reconstruction on the density modulation spatial distribution information to obtain the absolute intensity information of the electrostatic waves.
The invention utilizes the ultrafast electron beam probe to diagnose the unstable electrostatic wave of the laser plasma, and can directly diagnose the absolute intensity information of the electrostatic wave; compared with the hyperthermia coherent Thomson scattering, the method has no angle matching requirement, the diagnosis is easier to realize, the diagnosis platform is easy to build, and the debugging difficulty is reduced.
As a preferred technical solution, the step S2 includes the following steps:
s21, focusing the electron beam probe generated in step S1 using the magnetic field;
s22, injecting the focused electron beam probe into the plasma without exciting electrostatic waves, and enabling the electron beam probe to penetrate through the plasma;
s23, collecting the electron beam probe by using the transition radiation medium, and generating transition radiation after the electron beam probe passes through the transition radiation medium;
and S24, obtaining the original density information of the electron beam probe by the transition radiation space distribution and the time spectrum distribution.
The method is convenient for obtaining the influence of the background plasma (the background plasma is also called as diagnostic plasma) on the density spatial distribution of the electron beam probe, thereby improving the signal-to-noise ratio of the density spatial distribution information of the electron beam probe and enabling the diagnosis to be more accurate and reliable.
As a preferable technical solution, the direction in which the electron beam probe injects the electrostatic wave in step S3 is perpendicular to the propagation direction of the electrostatic wave.
Therefore, the electron beam probe can generate density modulation space distribution information vertical to the propagation direction of the electron beam probe under the action of the electrostatic wave electric field when passing through the plasma, so that the density modulation space distribution information is more accurate, and the diagnosis effect is better.
As a preferable mode, the density modulation spatial distribution information generated in step S4 includes wave number information, absolute intensity information, and phase velocity information of one or more types of electrostatic waves.
If the density modulation spatial distribution information generated in step S4 includes wave number information, absolute intensity information, and phase velocity information of an electrostatic wave, the absolute intensity information of the electrostatic wave can be obtained;
if the density modulation spatial distribution information generated in step S4 includes the wave number information, the absolute intensity information, and the phase velocity information of a plurality of types of electrostatic waves, the absolute intensity information and the frequency information of the electrostatic waves can be obtained, and the temperature information and the density information of the plasma can be obtained, so that two or more types of laser plasma unstable electrostatic waves occurring at the same position at the same time can be diagnosed at the same time.
As a preferred technical solution, the step S4 includes the following steps:
s41, collecting the electron beam probe passing through the plasma by using a transition radiation medium, and generating transition radiation after the electron beam probe passes through the transition radiation medium;
s42, obtaining density information of the electron beam probe passing through the electrostatic wave through transition radiation space distribution and time spectrum distribution;
s43, imaging the transit radiation signal by using the transit radiation imaging device, and performing inverse solution on the imaged transit radiation signal;
and S44, combining the original density information obtained in the step S2 to obtain the spatial distribution information of the electron beam probe density at different moments.
Therefore, the density modulation spatial distribution information of the electron beam probe can be conveniently obtained, and reference is provided for the selection of a reconstruction model.
As a preferred technical solution, in step S1, a laser-driven accelerator or a linear accelerator is used to generate the electron beam probe.
Laser drive acceleration, especially tail field acceleration, is convenient for generating electron beam probes with reliable quality; the linear accelerator is more traditional and has stronger universality.
As a preferable technical solution, in the inversion reconstruction process in step S5, the structure of the electrostatic wave is assumed to have a waveform conforming to one of a sine function structure, a cosine function structure, a superposition structure of a plurality of sine functions and/or cosine functions.
Since the electric field distribution generating the same density modulation is not unique, the structure of the electrostatic wave is properly assumed in the process of inversion reconstruction, and the structure of the electrostatic wave is assumed to be the above structure, so as to obtain more accurate absolute intensity information of the electrostatic wave. In addition, accurate electrostatic wave frequency and electrostatic wave phase velocity information can be obtained conveniently.
As a preferred technical solution, the step S5 further includes the following steps:
and (3) performing wave number analysis on the density modulation spatial distribution information to obtain frequency information of the electrostatic waves and/or obtain temperature information and density information of the plasma.
Therefore, frequency information of the electrostatic waves is obtained, and besides, temperature information and density information of plasmas are obtained, so that two or more laser plasma unstable electrostatic waves which simultaneously occur at the same position can be diagnosed at the same time.
As a preferred technical solution, the method further comprises the following steps:
s6, if the wave number analysis in step S5 obtains two or more differences of more than 8.5 μm-1The wave number of (2) is obtained by using the correlation between the electrostatic wave phase velocity and the plasma temperature and the plasma density to obtain the temperature and the plasma density information of the plasma.
If the wave number analysis in step S5 obtains two or more differences greater than 8.5 μm-1The wave number of the laser plasma instability electrostatic wave is the same as that of the laser plasma instability electrostatic wave, and the method can be used for calculating local plasma temperature, density and other information and diagnosing two or more laser plasma instability electrostatic waves simultaneously occurring at the same position.
Preferably, the transit radiation signal is imaged with a framing camera in step S43.
The high space-time resolution capability of the framing camera is good, the imaging effect of the transit radiation signals is convenient to ensure, the high space-time resolution electrostatic wave signals can be obtained, and meanwhile, the time resolution and the space resolution of electrostatic wave diagnosis are convenient to ensure to be higher.
Preferably, the time resolution of the transit radiation imaging device is selected to be 1 femtosecond to 200 femtoseconds.
Preferably, the spatial resolution of the transit radiation imaging device is selected to be 0.1 μm to 100 μm.
The selection of the time resolution and the space resolution of the transit radiation imaging device is convenient to ensure the imaging effect of transit radiation signals and simultaneously is convenient to ensure that the time-space resolution of electrostatic wave diagnosis reaches the femtosecond and micron magnitude.
Preferably, the transition radiation medium in the step S3 is a metal plate, and the thickness of the metal plate is 10 μm to 200 μm.
The selection of the transition radiation medium is convenient for ensuring the effect of transition radiation.
Therefore, the invention can diagnose the unstable electrostatic wave of the laser plasma by using the ultrafast electron beam probe, can be used for diagnosing the electrostatic wave with high time resolution, and can diagnose the absolute intensity information, the frequency, the phase speed and other information of various unstable electrostatic waves of the laser plasma at the same spatial position at the same time; the invention has the electrostatic diagnosis function of high space-time resolution and can directly diagnose the absolute intensity information of the electrostatic waves, and the invention perfects the problems of insufficient time resolution and single effect of the existing diagnosis method.
Example 2
As shown in fig. 1 and fig. 2, the laser plasma instability electrostatic wave diagnosis device includes an electron beam probe generation device 1, a magnetic field generation device 2, a plasma 3 to be diagnosed, a transition radiation medium 4, and transition radiation imaging devices 5 disposed on two sides of the transition radiation medium 4.
The electron beam probe generating device 1 is used for generating an electron beam probe; the magnetic field generating device 2 is used for focusing the electron beam probe and improving the quality of the electron beam; the plasma 3 to be diagnosed has the function of generating plasma, and is divided into two types, wherein one type is excited by electrostatic waves, the other type is excited by non-electrostatic waves, when the original density information of the electron beams is obtained, the electron beams pass through the plasma which is not excited by the electrostatic waves, and when the electrostatic waves are diagnosed, the electron beams pass through the plasma which is excited by the electrostatic waves; the function of the transit radiation medium 4 is to collect the electron beam probe and generate secondary radiation, such as transit radiation; the function of the transit-radiation imaging device 5 is to collect secondary radiation by which the density information of the electron beam probe is deduced.
When in specific use, the following steps can be adopted:
s1, generating an electron beam probe with energy of more than 100 MeV and beam length of 0.1-100 μm by using the electron beam probe generating device 1;
s2, obtaining the original density information of the electron beam probe;
s3, exciting unstable electrostatic waves of laser plasma, injecting the electron beam probe with known original density information into the electrostatic waves, and enabling the electron beam probe to generate density modulation under the action of an electrostatic wave electric field when passing through the plasma;
s4, combining the original density information of the electron beam probe obtained in the step S2 to obtain the density modulation spatial distribution information of the electron beam probe after passing through the electrostatic waves;
and S5, performing inversion reconstruction on the density modulation spatial distribution information to obtain the absolute intensity information of the electrostatic waves.
The invention utilizes the ultrafast electron beam probe to diagnose the unstable electrostatic wave of the laser plasma, and can directly diagnose the absolute intensity information of the electrostatic wave; compared with the hyperthermia coherent Thomson scattering, the method has no angle matching requirement, the diagnosis is easier to realize, the diagnosis platform is easy to build, and the debugging difficulty is reduced; the method can diagnose simultaneously various laser plasma unstable electrostatic waves at the same position.
It should be noted that, in practical use, the selection of the quality of the electron beam probe, the selection of the transit radiation target, the design of the transit radiation signal imaging system, the wave number and phase velocity analysis of the electron beam probe density modulation, and the reconstruction model of the electrostatic wave spatial distribution are preferably directed to the electrostatic wave characteristics.
Example 3
As shown in fig. 1 and 2, the present embodiment provides a more detailed technical solution on the basis of embodiments 1 and 2.
Taking the stimulated raman scattering excited in the plasma with critical density of 0.1 times by the laser with the wavelength of 1 μm as an example, the wavelength, the phase velocity and the frequency of the generated electrostatic wave can be pre-evaluated, according to theoretical calculation and numerical simulation, the beam length of an electron beam probe required for diagnosing the electrostatic wave in the example is less than 10 μm, the energy of the electron beam probe can be 200 Mega electron volts, a copper plate with the thickness of 100 μm is selected as a transition radiation medium for generating transition radiation, the time resolution of the transition radiation diagnostic equipment is less than 6 femtoseconds (about 2 times of the laser period), and the spatial resolution is less than 1 μm.
In specific implementation, the following steps can be adopted:
firstly, generating an electron beam probe with energy of hundreds of megaelectron volts and a beam length of several microns to hundreds of microns by utilizing laser driving acceleration (such as tail field acceleration) or a traditional accelerator acceleration mode; secondly, focusing the electron beam probe by using a magnetic field, and injecting the electron beam probe into the excited plasma with the electrostatic wave, wherein the injection direction of the electron beam probe is perpendicular to the propagation direction of the electrostatic wave (the propagation direction of the more common electrostatic wave is the same as the propagation direction of the laser generating the electrostatic wave), so that when the electron beam probe passes through the plasma, transverse (the direction perpendicular to the propagation direction of the electron beam probe) density modulation can be generated under the action of an electrostatic wave electric field, and the generated transverse density modulation can carry the following information: 1) the wave number information of the electrostatic wave, 2) the intensity information of the electrostatic wave, 3) the phase velocity information of the electrostatic wave is also included when the density modulation of the electron beam probe is subjected to time resolution diagnosis; collecting an electron beam probe passing through the plasma by using a metal (such as aluminum, copper, gold and the like) thin plate with the thickness of several microns, wherein the electron beam probe can generate transition radiation on the front surface and the rear surface of the thin plate after passing through the metal thin plate, and the density information of the electron beam probe can be obtained through the spatial distribution and the time spectrum distribution of the transition radiation; fourthly, a framing camera and other cameras with high space-time resolution capability are used for imaging the transit radiation signals, and then the spatial distribution of the electron beam probe density at different moments is obtained through inverse solution; fifthly, obtaining the absolute intensity, frequency and phase velocity information of the electrostatic wave by performing inversion reconstruction and wave number analysis on the density modulation information, wherein due to the fact that the distribution of the electric field generating the same density modulation is not unique, proper assumption needs to be made on the structure of the electrostatic wave in the inversion reconstruction process, and a sine function or a cosine function is generally assumed according to the physical characteristics of the electrostatic wave; and sixthly, if multiple instabilities occur simultaneously (namely, wave number analysis obtains multiple wave numbers with larger differences), calculating to obtain the information of the temperature, the density and the like of the plasma by using the correlation between the phase velocity of the electrostatic wave and the temperature and the density of the plasma.
As described above, the present invention can be preferably realized.
All features disclosed in all embodiments in this specification, or all methods or process steps implicitly disclosed, may be combined and/or expanded, or substituted, in any way, except for mutually exclusive features and/or steps.
The foregoing is only a preferred embodiment of the present invention, and the present invention is not limited thereto in any way, and any simple modification, equivalent replacement and improvement made to the above embodiment within the spirit and principle of the present invention still fall within the protection scope of the present invention.
Claims (8)
1. A laser plasma instability electrostatic wave diagnosis method is characterized by comprising the following steps:
s1, generating an electron beam probe with energy of more than 100 megaelectron volts and a beam length of 0.1-100 μm;
s2, obtaining the original density information of the electron beam probe;
s3, exciting unstable electrostatic waves of laser plasma, injecting the electron beam probe with known original density information into the electrostatic waves, and enabling the electron beam probe to generate density modulation under the action of an electrostatic wave electric field when passing through the plasma;
s4, combining the original density information of the electron beam probe obtained in the step S2 to obtain the density modulation spatial distribution information of the electron beam probe after passing through the electrostatic waves;
step S4 includes the following steps:
s41, collecting the electron beam probe passing through the plasma by using a transition radiation medium, and generating transition radiation after the electron beam probe passes through the transition radiation medium;
s42, obtaining density information of the electron beam probe passing through the electrostatic wave through transition radiation space distribution and time spectrum distribution;
s43, imaging the transit radiation signal by using the transit radiation imaging device, and performing inverse solution on the imaged transit radiation signal;
s44, combining the original density information obtained in the step S2 to obtain the spatial distribution information of the electron beam probe density at different moments;
and S5, performing inversion reconstruction on the density modulation spatial distribution information to obtain the absolute intensity information of the electrostatic waves.
2. The method of claim 1, wherein step S2 includes the following steps:
s21, focusing the electron beam probe generated in step S1 using the magnetic field;
s22, injecting the focused electron beam probe into the plasma without exciting electrostatic waves, and enabling the electron beam probe to penetrate through the plasma;
s23, collecting the electron beam probe by using the transition radiation medium, and generating transition radiation after the electron beam probe passes through the transition radiation medium;
and S24, obtaining the original density information of the electron beam probe by the transition radiation space distribution and the time spectrum distribution.
3. The method of claim 1, wherein the direction of injecting the electrostatic wave by the electron beam probe in step S3 is perpendicular to the propagation direction of the electrostatic wave.
4. The method of claim 1, wherein the density modulation spatial distribution information generated in step S4 includes wave number information, absolute intensity information, and phase velocity information of one or more electrostatic waves.
5. The method as claimed in claim 1, wherein step S1 is performed by using a laser-driven accelerator or a linear accelerator to generate the electron beam probe.
6. The method of claim 1, wherein the structure of the electrostatic wave is assumed to conform to one of a sine function structure, a cosine function structure, a superposition structure of sine functions and/or cosine functions in the waveform during the inversion reconstruction in step S5.
7. The method of claim 1, wherein step S5 further comprises the steps of:
and (3) performing wave number analysis on the density modulation spatial distribution information to obtain frequency information of the electrostatic waves and/or obtain temperature information and density information of the plasma.
8. The method of claim 7, further comprising the steps of:
and S6, if the wave number analysis in the step S5 obtains two or more wave numbers with the difference larger than 8.5 μm, the correlation between the electrostatic wave phase velocity and the plasma temperature and the plasma density is utilized to obtain the information of the plasma temperature and the plasma density.
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