A multi-channel wide-spectrum scattered light energy simultaneous measurement device and method

Abstract

The application discloses a kind of multi-channel wide spectrum scattered light energy simultaneous measurement device and method, wherein multi-channel wide spectrum scattered light energy simultaneous measurement device mainly includes target chamber, spectrometer, gate camera and multiple scattered light imaging light paths.The present multi-channel wide spectrum scattered light energy simultaneous measurement device and method are used, by setting multiple scattered light imaging light paths, realize multi-channel measurement capability, can accurately give the energy of different wavelengths and total energy, realize the simultaneous measurement of stimulated brillouin scattering and stimulated raman scattering scattered light, provide more reliable diagnostic techniques for the scattered light generated by laser target shooting;At the same time, the present measurement method greatly reduces the use of energy probe, not only saves cost, but also improves diagnostic efficiency;And, the present measurement method can be used not only for high-energy scattered light measurement, but also for other light source intensity analysis and comparison.

Description

Technical Field

[0001] This invention relates to the field of photoelectric detection technology, specifically to a device and method for simultaneously measuring the energy of multi-channel broadband scattered light. Background Technology

[0002] In laser-driven inertial confinement fusion research, a laser is incident on a black cavity (target) to generate plasma and couple with it. During the interaction between the laser and the plasma, in addition to absorption and transmission through the inverse bremsstrahlung mechanism, laser energy also excites various parametric instabilities such as stimulated Brillouin scattering, stimulated Raman scattering, dual-plasma decay, filamentation, and self-focusing. These instabilities significantly reduce the coupling efficiency between the laser and the cavity target and disrupt the symmetry of the radiation field. When these parametric instabilities develop to a certain level, they can also couple and correlate with each other, making the parametric instability process highly complex and difficult to predict. Studying and suppressing parametric instabilities, mainly stimulated Brillouin scattering and stimulated Raman scattering, has always been a core scientific problem that needs to be studied in laser fusion. The main physical quantity used to characterize the scattered light generated during the laser-plasma interaction process is the fraction of scattered light.

[0003] Because the scattered light generated from the physical process has relatively high energy, approximately 1% to 20% (10J-500J) of the incident laser energy, and exhibits a large distribution angle, its energy is difficult to measure directly. Current methods involve using a concave mirror of appropriate aperture to converge the scattered light, then using various mirrors with attenuation capabilities to form a long reflection path to attenuate the scattered light, and finally using a lens group to transmit it to an energy calorimeter for measurement. This type of scattered light measurement often involves complex optical path components, occupies a large volume, uses many elements, and makes the analysis of measurement results difficult. Especially for stimulated Raman scattering, which has a wide spectral distribution, an energy calorimeter alone cannot accurately measure the broadband light energy. Furthermore, existing measurement techniques cannot simultaneously measure stimulated Brillouin scattering and stimulated Raman scattering; experiments often require multiple measurements of multiple broadband light streams.

[0004] Solving these problems is now a top priority. Summary of the Invention

[0005] To address the technical problems of existing measurement techniques that cannot accurately measure broadband light energy using energy calorimeters and cannot simultaneously measure stimulated Brillouin scattering and stimulated Raman scattering, this invention provides a multi-channel broadband scattered light energy simultaneous measurement device and method.

[0006] The technical solution is as follows:

[0007] A multi-channel broadband scattered light energy simultaneous measurement device includes a target chamber, a spectrometer, and a gated camera. The gated camera is located at the output end of the spectrometer. The key feature is that it also includes multiple scattered light imaging optical paths.

[0008] The scattered light imaging optical path includes an optical path channel, a dichroic mirror, a target lens, a diffuse reflector, a filter group, an imaging lens group, a scattering sheet, and an optical fiber. The optical path channel is located between the target chamber and the diffuse reflector, and one end of the optical path channel is connected to the target chamber. The dichroic mirror and the target lens are both installed in the optical path channel. A target laser inlet is opened on one side of the optical path channel. The dichroic mirror is located inside the target laser inlet. The target lens is located between the dichroic mirror and the target chamber. The filter group and the imaging lens group are sequentially arranged between the diffuse reflector and the scattering sheet. The surface of the imaging lens group is coated with a coating that can filter out light with wavelengths less than 340nm and wavelengths greater than 700nm. The incident end face of the optical fiber faces the side of the scattering sheet away from the imaging lens group.

[0009] A multi-channel fiber optic coupler is installed at the entrance slit of the spectrometer, and the exit ends of each fiber are coupled to the multi-channel fiber optic coupler in a longitudinal arrangement.

[0010] A measurement method based on the aforementioned multi-channel broadband scattered light energy simultaneous measurement device, the key features of which include the following steps:

[0011] S1. The target is placed in the firing chamber. Then, each laser simultaneously emits laser light to hit the target and generate scattered light. The scattered light is then introduced into the corresponding imaging optical path. Finally, a gated camera records the count P(λ) of each wavelength of the scattered light to be measured. Then, the energy S of each wavelength of the scattered light to be measured is... exp (λ) is represented as:

[0012] P(λ)=S exp (λ)×η×F(λ) (1)

[0013] In equation (1), η represents the response coefficient of the multi-channel broadband scattered light energy simultaneous measurement device, and F(λ) represents the transmittance of the filter group;

[0014] S2. First, the spectral energy S(λ) of the calibration light source is obtained. Then, the calibration light source is placed in the target chamber at the target placement position. At the same time, the filter group (8) in each scattered light imaging optical path is removed. Then, the calibration light source is lit. Finally, the gated camera records the count C(λ) of each wavelength of the calibration light. The calibration relationship between the count C(λ) of the calibration light at the corresponding spectral position and the spectral energy S(λ) of the calibration light source is as follows:

[0015] C(λ)=S(λ)×η (2)

[0016] S3. Based on equations (1) and (2), the energy S of each wavelength of the scattered light to be measured is calculated by the following equation. exp (λ):

[0017]

[0018] The energy S with wavelengths of 349nm-353nm exp (λ) The total energy of the stimulated Brillouin scattering light is obtained by summing the energy of the wavelength 400nm-700nm, S. exp (λ) The total energy of the stimulated Raman scattered light is obtained by summing up the energy.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0020] 1. By setting up multiple scattered light imaging optical paths, multi-channel measurement capability is achieved, which can accurately provide the energy of different wavelengths and the total energy, and realize the simultaneous measurement of scattered light from stimulated Brillouin scattering and stimulated Raman scattering, providing a more reliable diagnostic technology for scattered light generated by laser target shooting;

[0021] 2. This measurement method significantly reduces the use of energy probes, which not only saves costs but also improves diagnostic efficiency;

[0022] 3. This measurement method can be used not only for measuring high-energy scattered light, but also for analyzing and comparing the intensity of other light sources. Attached Figure Description

[0023] Figure 1 A schematic diagram of a multi-channel broadband scattered light energy simultaneous measurement device;

[0024] Figure 2 This is a schematic diagram of the optical path for scattered light imaging;

[0025] Figure 3 A schematic diagram of a multi-channel broadband scattered light energy simultaneous measurement device calibrated without considering vertical and horizontal polarization conditions;

[0026] Figure 4 This is a schematic diagram illustrating the calibration of a multi-channel broadband scattered light energy simultaneous measurement device considering both vertical and horizontal polarization conditions. Detailed Implementation

[0027] The present invention will be further described below with reference to the embodiments and accompanying drawings.

[0028] like Figure 1 and Figure 2As shown, a multi-channel broadband scattered light energy simultaneous measurement device mainly includes a target chamber 1, a spectrometer 2, a gated camera 3, and multiple scattered light imaging optical paths. The number of scattered light imaging optical paths is not limited to the four shown in the figure, and the number can be increased or decreased according to actual needs.

[0029] The scattered light imaging optical path includes an optical path channel 4, a dichroic mirror 5, a target lens 6, a diffuse reflector 7, a filter group 8, an imaging lens group 9, a scattering sheet 10, and an optical fiber 11. The diffuse reflector 7 is a milky-white plate with a diffuse reflection structure, which is simple, reliable, and low-cost. In this embodiment, the target laser uses a 1053nm wavelength laser. The dichroic mirror 5 has high reflectivity for 1053nm light and high transmittance for light with wavelengths of 349-700nm.

[0030] The optical path channel 4 is located between the firing chamber 1 and the diffuse reflector 7, and one end of the optical path channel 4 is connected to the firing chamber 1. That is, the diffuse reflector 7 is located at the end of the optical path channel 4 away from the firing chamber 1. The light in the optical path channel 4 can be emitted from the end close to the firing chamber 1 and then enter the firing chamber 1, or it can be emitted from the end away from the firing chamber 1 and then be directed towards the diffuse reflector 7.

[0031] Both the dichroic mirror 5 and the target lens 6 are installed in the optical path channel 4. A target laser inlet is opened on one side of the optical path channel 4. The dichroic mirror 5 is located inside the target laser inlet, and the target lens 6 is located between the dichroic mirror 5 and the target chamber 1. The filter group 8 and the imaging lens group 9 are arranged sequentially between the diffuse reflection plate 7 and the scattering plate 10. The surface of the imaging lens group 9 is coated with a coating that can filter out light with wavelengths less than 340nm and wavelengths greater than 700nm. The incident end face of the optical fiber 11 faces the side of the scattering plate 10 away from the imaging lens group 9.

[0032] Therefore, the target lasers excited by each laser 15 first enter the corresponding optical path channel 4 from the corresponding target laser inlet, and are then reflected by the dichroic mirror 5 to the target lens 6. The target lens 6 then focuses the target laser onto the target 14. The target laser interacts with the target 14 to generate plasma. At the same time, the interaction between the target laser and the plasma causes the laser to scatter. Some of the scattered light enters the optical path channel 4 and passes through the target lens 6 and the dichroic mirror 5 in sequence before exiting from the other end of the optical path channel 4. The outgoing scattered light is intercepted by the diffuse reflection plate 7 and reflected to the filter group 8. After the filter group 8 filters out stray light, it is directed to the imaging lens group 9. The imaging lens group 9 images the light with wavelengths of 340nm-700nm onto the scattering plate 10, and then the light is directed from the scattering plate 10 to the incident end face of the optical fiber 11, and finally transmitted to the spectrometer 2 through the optical fiber 11. Among them, the light with wavelengths of 340nm-700nm includes the scattered light generated by stimulated Brillouin scattering with wavelengths of 349nm-353nm and the scattered light generated by stimulated Raman scattering with wavelengths of 400nm-700nm.

[0033] The slit built into the spectrometer 2 is removed. Then, a multi-channel fiber optic coupler 12 is installed at the entrance slit position of the spectrometer 2. The fiber optic coupler 12 consists of multiple longitudinally arranged optical fibers. The exit ends of each optical fiber 11 are coupled to the multi-channel fiber optic coupler 12, and the exit faces of each optical fiber 11 are fixed to the spectrometer 2 as the entrance slit. The multi-channel fiber optic coupler 12 is imaged onto the gated camera 3 by the spectrometer 2, at which point the image is longitudinally arranged. After being diffracted by the grating inside the spectrometer 2, the scattered light forms a scattered light spectrum on the gated camera 3. The spectra of each channel are longitudinally arranged. By selecting the gate width of the gated camera 3, non-target signals can be effectively blocked.

[0034] In this embodiment, the difference in contribution between the center and edge of the diffuse reflector 7 is less than 20%, and each optical fiber 11 is placed 15 cm behind its corresponding scattering plate 10, thereby reducing the influence of dispersion on the measurement results while ensuring the light collection efficiency of the optical fiber 11. The surface of the diffuse reflector 7 is coated with a high-reflectivity Lambertian reflective coating with a reflectivity greater than 98%, thereby ensuring the quality of the final image and improving the measurement accuracy.

[0035] The overall transmittance of the surface coating of the imaging lens group 9 is ≥50%. Under both vertical and horizontal polarization conditions, the transmittance of the horizontal and vertical polarization film layers of a single lens is ≥98%, ensuring imaging quality.

[0036] The filter group 8 consists of multiple neutral attenuation plates. The filter group 8 can make the transmittance of light with wavelengths of 349nm-353nm 1%, while the transmittance of light with wavelengths of 400nm-700nm 10%, thereby filtering out stray light as much as possible and improving measurement accuracy.

[0037] In this embodiment, the diameter of the optical fiber 11 is preferably 200 μm and the numerical aperture is 0.22. The output end face of each optical fiber 11 is coupled to the multi-channel optical fiber coupler 12. The spacing between adjacent optical fibers 11 on the multi-channel optical fiber coupler 12 is 1 mm, which ensures the acquisition of multiple signals from the gated camera 3.

[0038] Spectrometer 2 is an aberration-corrected spectrometer with a focal length of approximately 200 mm to ensure the imaging quality of each signal arranged longitudinally. The grating in spectrometer 2 is set to 150 line pairs / mm to ensure appropriate spectral resolution across the entire recording surface.

[0039] The gated camera 3 is located at the output end of the spectrometer 2. The gated camera 3 has both single-shot and continuous acquisition modes. Single-shot mode is used for scattered light measurement, while continuous acquisition mode is used for calibration. During actual measurement, the gate width is 50 ns, covering the entire signal region while shielding stray light from other times. The gated camera's image area is no less than 13*13mm, and the number of pixels is no less than 1024*1024.

[0040] A measurement method for the above-mentioned multi-channel broadband scattered light energy simultaneous measurement device includes the following steps:

[0041] S1, please refer to Figure 1 and Figure 2 The target 14 is placed in the target chamber 1. Then, each laser 15 simultaneously emits laser light to hit the target and generate scattered light, which is introduced into the corresponding scattered light imaging optical path. The light output from each scattered light imaging optical path is finally recorded by the gated camera 3. The count P(λ) of each wavelength of the scattered light to be measured recorded by the gated camera 3 is then used to determine the energy S of each wavelength of the scattered light to be measured. exp (λ) is represented as:

[0042] P(λ)=S exp (λ)×η×F(λ) (1)

[0043] In equation (1), η represents the response coefficient of the multi-channel broadband scattered light energy simultaneous measurement device, and F(λ) represents the transmittance of filter group 8;

[0044] S2, please refer to Figure 3 First, the spectral energy S(λ) of the calibration light source 16 is obtained. Then, the calibration light source 16 is placed in the target chamber 1 at the position where the target 14 is placed. At the same time, the filter group 8 in each scattered light imaging optical path is removed to increase the light transmission. Then, the calibration light source 16 is lit up. Finally, the gated camera 3 records the count C(λ) of each wavelength of the calibration light. At this time, the gated camera 3 adopts a continuous working mode. In order to obtain a better signal-to-noise ratio, the lighting time of the calibration light source 16 is 5-10 minutes and the gated camera 3 works continuously.

[0045] In this embodiment, the calibration light source 16 is preferably a halogen lamp or a xenon lamp. Halogen lamps, as stable and reliable broadband sources, enable accurate calibration. Xenon lamps, on the other hand, have a flatter spectral intensity range (340nm-700nm) compared to tungsten halogen lamps, which helps improve the signal-to-noise ratio of the calibration.

[0046] The calibration relationship between the count C(λ) of the calibration light at the corresponding spectral position and the spectral energy S(λ) of the calibration light source 16 is as follows:

[0047] C(λ)=S(λ)×η (2)

[0048] S3. Based on equations (1) and (2), the energy S of each wavelength of the scattered light to be measured is calculated by the following equation. exp (λ):

[0049]

[0050] The energy S with wavelengths of 349nm-353nm exp (λ) The total energy of the stimulated Brillouin scattering light is obtained by summing the energy of the wavelength 400nm-700nm, S. exp (λ) The total energy of the stimulated Raman scattered light is obtained by summing up the energy.

[0051] Further, please see Figure 4 When it is necessary to consider the scattered light of polarized light, in step S3, the spectral energy S of the calibration light source 16 under vertical polarization conditions is first calibrated. ⊥ (λ) and the spectral energy S under horizontal polarization conditions || (λ), then vertical polarizers 17 or horizontal polarizers 18 are set in both the calibration light source 16 and each optical path channel 4. At the same time, the filter group 8 in each scattered light imaging optical path is removed. After completion, the calibration light source 16 is lit. Finally, the gated camera 3 records the count C under vertical polarization conditions. ⊥ (λ) or the count C of each wavelength under horizontal polarization conditions. || (λ), where C is the count for each wavelength under vertical and horizontal polarization conditions. ⊥ (λ) and C || (λ) Spectral energy S of the same calibration light source 16 under vertical polarization conditions ⊥ (λ) and the spectral energy S under horizontal polarization conditions || The scaling relations for (λ) are as follows:

[0052] C ⊥ (λ)=S ⊥ (λ)×η (4)

[0053] C || (λ)=S|| (λ)×η (5)

[0054] In step S4, based on equations (2) and (4), the total energy of stimulated Brillouin scattering and stimulated Raman scattering under vertical polarization can be calculated; based on equations (2) and (5), the total energy of stimulated Brillouin scattering and stimulated Raman scattering under horizontal polarization can be calculated.

[0055] In this embodiment, to ensure polarization quality, the distance between the vertical polarizer 17 and the horizontal polarizer 18 and the calibration light source 16 is preferably 15cm, and the diameter of the vertical polarizer 17 and the horizontal polarizer 18 is not less than 10cm.

[0056] Finally, it should be noted that the above description is merely a preferred embodiment of the present invention. Those skilled in the art, under the guidance of the present invention, can make various similar representations without departing from the spirit and claims of the present invention, and such modifications all fall within the protection scope of the present invention.

Claims

1. A multi-channel broadband scattered light energy simultaneous measurement device, comprising a target chamber (1), a spectrometer (2), and a gated camera (3), wherein the gated camera (3) is located at the output end of the spectrometer (2), characterized in that: It also includes multiple scattered light imaging optical paths; The scattered light imaging optical path includes an optical path channel (4), a dichroic mirror (5), a target lens (6), a diffuse reflector (7), a filter group (8), an imaging lens group (9), a scattering sheet (10), and an optical fiber (11). The optical path channel (4) is located between the target chamber (1) and the diffuse reflector (7), and one end of the optical path channel (4) is connected to the target chamber (1). The dichroic mirror (5) and the target lens (6) are both installed in the optical path channel (4). A target laser inlet is opened on one side of the optical path channel (4). The dichroic mirror (5) is located inside the laser inlet of the target, the target lens (6) is located between the dichroic mirror (5) and the target chamber (1), the filter group (8) and the imaging lens group (9) are arranged sequentially between the diffuse reflector (7) and the scattering plate (10), the surface of the imaging lens group (9) is coated with a coating that can filter out light with wavelengths less than 340nm and wavelengths greater than 700nm, and the incident end face of the optical fiber (11) faces the side of the scattering plate (10) away from the imaging lens group (9); The spectrometer (2) has a multi-channel fiber optic coupler (12) installed at the entrance slit position, and the exit ends of each fiber (11) are coupled to the multi-channel fiber optic coupler (12) in a longitudinal arrangement.

2. The multi-channel broadband scattered light energy simultaneous measurement device according to claim 1, characterized in that: The filter group (8) is composed of multiple neutral attenuation plates. The filter group (8) can make the transmittance of light with wavelengths of 349nm-353nm 1% and the transmittance of light with wavelengths of 400nm-700nm 10%.

3. A measurement method based on the multi-channel broadband scattered light energy simultaneous measurement device according to any one of claims 1-2, characterized in that, Includes the following steps: S1. Place the target (14) in the target chamber (1), and then each laser (15) simultaneously emits laser light to hit the target and generate scattered light, which is then introduced into the corresponding scattered light imaging optical path. Finally, the gated camera (3) records the count of each wavelength of the scattered light to be tested. The energy of each wavelength of the scattered light to be measured is... Represented as: （1） In equation (1), This represents the response coefficient of a multi-channel broadband scattered light energy simultaneous measurement device. This indicates the transmittance of the filter assembly (8); S2. First, calibrate the spectral energy of the calibration light source (16). Then, the calibration light source (16) is placed in the target chamber (1) at the position where the target (14) is placed. At the same time, the filter groups (8) in each scattered light imaging optical path are removed. Then, the calibration light source (16) is lit. Finally, the gated camera (3) records the count of each wavelength of the calibration light. Among them, the counting of the calibration light at the corresponding spectral position Spectral energy of the calibration light source (16) The scaling relationship between them: （2） S3. Based on equations (1) and (2), the energy of each wavelength of the scattered light to be measured is calculated by the following equation. : （3） Energy with wavelengths of 349nm-353nm The total energy of the stimulated Brillouin scattering light is obtained by summing the energy of the wavelengths 400nm-700nm. The total energy of the stimulated Raman scattered light is obtained by summing them up.

4. The measurement method according to claim 3, characterized in that: The calibration light source (16) is a halogen lamp or a xenon lamp.

5. The measurement method according to claim 3, characterized in that: In step S3, the lighting time of the calibrated light source (16) and the working time of the gated camera (3) are 5-10 minutes.

6. The measurement method according to claim 3, characterized in that: In step S3, the spectral energy of the calibration light source (16) under vertical polarization conditions is first determined. and spectral energy under horizontal polarization conditions Then, vertical polarizers (17) or horizontal polarizers (18) are set on the calibration light source (16) and each optical path channel (4). At the same time, the filter group (8) in each scattered light imaging optical path is removed. After completion, the calibration light source (16) is lit. Finally, the gated camera (3) records the count under vertical polarization conditions. Or, counting each wavelength under horizontal polarization conditions. Among them, the count for each wavelength under vertical polarization conditions and under horizontal polarization conditions. and Spectral energy of the same calibration light source (16) under vertical polarization conditions and spectral energy under horizontal polarization conditions The scaling relationships are as follows: （4） （5） Based on equations (2) and (4), the total energy of stimulated Brillouin scattering and stimulated Raman scattering under vertical polarization can be calculated; based on equations (2) and (5), the total energy of stimulated Brillouin scattering and stimulated Raman scattering under horizontal polarization can be calculated.

Images