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RSS2023 Vol. 35, No. 11
Recommend Articles
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- Cover and Contents
- High Power Laser Physics and Technology
- Inertial Confinement Fusion Physics and Technology
- High Power Microwave Technology
- Ion Beam Science and Technology and Its Applications
- Particle Beams and Accelerator Technology
- Pulsed Power Technology
- Nuclear Science and Engineering
- Advanced Interdisciplinary Science
Display Method:
2023,
35: 1-2.
2023,
35: 111001.
doi: 10.11884/HPLPB202335.230308
Abstract:
Temporal coherent combination further extends the pulse duration by assembling many pulses in a train passed through the amplifier into one output pulse, which can improve the peak power and pulse energy effectively and avoid nonlinear effects excited by the high peak power in the amplification. Spatial and temporal pulse combination can overcome limitations in single fiber laser, potentially leading to higher pulse energy, average power and peak power of ultrafast pulses currently only available from bulk amplifiers with low repetition rates. In this paper, the principles and key technologies of temporal coherent combination of ultrafast pulses in fiber lasers are introduced. The current status of temporal coherent combination and their technologies are reviewed. Recent progress of Divided Pulse Amplification (DPA) and Coherent Pulse Stacking (CPS) is emphasized. Different technical ways are compared and analyzed. Several future perspectives are pointed out. The paper can be a reference for research on temporal coherent combination of chirped pulses.
2023,
35: 111002.
doi: 10.11884/HPLPB202335.230073
Abstract:
The single emitter and bars of 780 nm semiconductor laser have been designed and fabricated. The epitaxial layers were prepared by the metal organic chemical vapor deposition technology. GaAsP and GaInP were used as the quantum well and waveguide layer, respectively. The confinement layers were AlGaInP material with low refractive index. The bandgap between the quantum well and the waveguide layer was 0.15 eV, while the bandgap between the waveguide layer and the confinement layer was 0.28 eV. The high bandgap was effective in suppressing carrier leakage. The 1.55 μm thick large optical cavity epitaxy structure increases the beam’s size and alleviates the cavity optical surface damage problem. The asymmetric structure suppresses high-order fast axis modes. Using the ultra-high vacuum cleavage and passivation technology, an amorphous ZnSe passivation layer was deposited on the laser cavity facets. The ZnSe passivated single emitter device with 150 μm width and 4 mm cavity length, did not show COD phenomenon with 16.3 W continuous-wave output, when the current was 15 A. In this case, the slope efficiency reached 1.27 W/A while the electro-optic conversion efficiency was 58%, and the divergence angle of slow-axis was 9.9° and the spectral width was 1.81 nm. The 1-cm laser bar with lateral emitter fill factor of 40%, reached continuous-wave 180 W output power at 192 A, and the electro-optic conversion efficiency was 50.7%, the spectral width was 2.2 nm.
The single emitter and bars of 780 nm semiconductor laser have been designed and fabricated. The epitaxial layers were prepared by the metal organic chemical vapor deposition technology. GaAsP and GaInP were used as the quantum well and waveguide layer, respectively. The confinement layers were AlGaInP material with low refractive index. The bandgap between the quantum well and the waveguide layer was 0.15 eV, while the bandgap between the waveguide layer and the confinement layer was 0.28 eV. The high bandgap was effective in suppressing carrier leakage. The 1.55 μm thick large optical cavity epitaxy structure increases the beam’s size and alleviates the cavity optical surface damage problem. The asymmetric structure suppresses high-order fast axis modes. Using the ultra-high vacuum cleavage and passivation technology, an amorphous ZnSe passivation layer was deposited on the laser cavity facets. The ZnSe passivated single emitter device with 150 μm width and 4 mm cavity length, did not show COD phenomenon with 16.3 W continuous-wave output, when the current was 15 A. In this case, the slope efficiency reached 1.27 W/A while the electro-optic conversion efficiency was 58%, and the divergence angle of slow-axis was 9.9° and the spectral width was 1.81 nm. The 1-cm laser bar with lateral emitter fill factor of 40%, reached continuous-wave 180 W output power at 192 A, and the electro-optic conversion efficiency was 50.7%, the spectral width was 2.2 nm.
2023,
35: 111003.
doi: 10.11884/HPLPB202335.230180
Abstract:
To control the depolarization of incident laser with different polarization states, a liquid crystal depolarizer with random phase distribution structure is designed. For cholesteric liquid crystal device, a model of laser transmission through cholesteric liquid crystal device is established by using finite-difference time-domain method. The theoretical model is verified by experiments, and the polarization change and polarization distribution characteristics of laser through the liquid crystal array unit are analyzed. The simulation results show that the cholesteric liquid crystal device can achieve good depolarization effect for the linear polarized light with different polarization angles under the conditions of suitable liquid crystal material and maximum thickness of the micro-etching pit, and the applicable spectrum is wide.
To control the depolarization of incident laser with different polarization states, a liquid crystal depolarizer with random phase distribution structure is designed. For cholesteric liquid crystal device, a model of laser transmission through cholesteric liquid crystal device is established by using finite-difference time-domain method. The theoretical model is verified by experiments, and the polarization change and polarization distribution characteristics of laser through the liquid crystal array unit are analyzed. The simulation results show that the cholesteric liquid crystal device can achieve good depolarization effect for the linear polarized light with different polarization angles under the conditions of suitable liquid crystal material and maximum thickness of the micro-etching pit, and the applicable spectrum is wide.
2023,
35: 111004.
doi: 10.11884/HPLPB202335.230126
Abstract:
To analyze and improve the matrix effect on the quantitative analysis of cadmium (Cd) concentration in soil and rice using laser induced breakdown spectroscopy (LIBS), this article takes the Cd Ⅱ 226.502 nm spectral line as the analysis object, and compares the effects of matrix type, KCl mass concentration, and excitation method on the intensity and quantitative analysis results of Cd Ⅱ 226.502 nm spectral line. The results show that the chemical form of the main components of the matrix and the ionization energy are the main factors that produce the matrix effect. KCl as an additive can significantly improve the spectral line intensity of Cd Ⅱ 226.502 nm in rice. The photoelectric double pulse excitation can significantly enhance the spectral line intensity and stability of Cd Ⅱ 226.502 nm in the matrix, and improve the signal to noise ratio. Compared with the single laser pulse excitation method, the lower detection limit of Cd Ⅱ 226.502 nm in silicon dioxide, soil, and rice matrices decreased from 372, 332 and 2874 mg·kg−1 to 42, 72 and 37 mg·kg−1, respectively, under photoelectric dual pulse excitation. This study has important reference value for the development of LIBS technology and its application and promotion in the field of soil and food pollution detection.
To analyze and improve the matrix effect on the quantitative analysis of cadmium (Cd) concentration in soil and rice using laser induced breakdown spectroscopy (LIBS), this article takes the Cd Ⅱ 226.502 nm spectral line as the analysis object, and compares the effects of matrix type, KCl mass concentration, and excitation method on the intensity and quantitative analysis results of Cd Ⅱ 226.502 nm spectral line. The results show that the chemical form of the main components of the matrix and the ionization energy are the main factors that produce the matrix effect. KCl as an additive can significantly improve the spectral line intensity of Cd Ⅱ 226.502 nm in rice. The photoelectric double pulse excitation can significantly enhance the spectral line intensity and stability of Cd Ⅱ 226.502 nm in the matrix, and improve the signal to noise ratio. Compared with the single laser pulse excitation method, the lower detection limit of Cd Ⅱ 226.502 nm in silicon dioxide, soil, and rice matrices decreased from 372, 332 and 2874 mg·kg−1 to 42, 72 and 37 mg·kg−1, respectively, under photoelectric dual pulse excitation. This study has important reference value for the development of LIBS technology and its application and promotion in the field of soil and food pollution detection.
2023,
35: 111005.
doi: 10.11884/HPLPB202335.230131
Abstract:
The laser damage resistance of fused silica optics is of great significance for the stable operation of high-power laser systems. To improve the laser damage resistance of fused silica optics, and to solve the problem of deposition formed by traditional hydrofluoric acid etching, a method based on organic fluoric acid etching is developed. The advantage of organic fluoric acid etching is that the etching product has good solubility, thus reducing the possibility of forming deposition. Organic fluoric acid solution was used for static etching of fused silica optics, and the surface quality, transmittance, and laser damage density of the opticss were characterized and analyzed. The results of surface quality and transmittance show that the fused silica optics after organic fluoric acid etching have less deposition and impurity, indicating that the organic fluoric acid etching is effective in preventing the formation of deposition. The laser damage tests show that the fused silica optics after 6 μm etching have the average laser damage density of 0.26 cm−2, which is close to those treated by advanced mitigation process (AMP2). Organic fluoric acid based etching for improving the laser damage resistance of fused silica optics has opened up a new pathway in enhancing laser loading capacity.
The laser damage resistance of fused silica optics is of great significance for the stable operation of high-power laser systems. To improve the laser damage resistance of fused silica optics, and to solve the problem of deposition formed by traditional hydrofluoric acid etching, a method based on organic fluoric acid etching is developed. The advantage of organic fluoric acid etching is that the etching product has good solubility, thus reducing the possibility of forming deposition. Organic fluoric acid solution was used for static etching of fused silica optics, and the surface quality, transmittance, and laser damage density of the opticss were characterized and analyzed. The results of surface quality and transmittance show that the fused silica optics after organic fluoric acid etching have less deposition and impurity, indicating that the organic fluoric acid etching is effective in preventing the formation of deposition. The laser damage tests show that the fused silica optics after 6 μm etching have the average laser damage density of 0.26 cm−2, which is close to those treated by advanced mitigation process (AMP2). Organic fluoric acid based etching for improving the laser damage resistance of fused silica optics has opened up a new pathway in enhancing laser loading capacity.
2023,
35: 112001.
doi: 10.11884/HPLPB202335.230161
Abstract:
In view of the measurement requirements of uniformity and areal density parameters of target metal foils, a non-destructive testing technology for high-Z metal foils by obtaining thin film X-ray transmittance and its spatial distribution through a toroidal crystal focusing type X-ray monochromatic imaging device is proposed. This technology not only effectively improves the accuracy of areal density measurement by high-throughput and high-monochromatic imaging, but also realizes high spatial resolution evaluation of thin film uniformity. This paper carries out in-depth research from the aspects of overall scheme design, component preparation and test experiment, and evaluates the influence of various possible factors on measurement uncertainty. The developed toroidal crystal imaging system achieves micro-region resolution better than 5 μm within millimeter scale for 20 keV-level high-energy X-rays, and spectral resolution reaches several eV. The feasibility of the developed technology is verified by surface density measurement experiment of foam gold sample, and relative uncertainty of areal density measurement better than 2% is obtained. This paper provides a new measurement technology for precise non-destructive testing of high-Z target materials for laser inertial confinement fusion, which is also expected to be applied to other fields that require large field of view and high spatial spectral resolution imaging.
In view of the measurement requirements of uniformity and areal density parameters of target metal foils, a non-destructive testing technology for high-Z metal foils by obtaining thin film X-ray transmittance and its spatial distribution through a toroidal crystal focusing type X-ray monochromatic imaging device is proposed. This technology not only effectively improves the accuracy of areal density measurement by high-throughput and high-monochromatic imaging, but also realizes high spatial resolution evaluation of thin film uniformity. This paper carries out in-depth research from the aspects of overall scheme design, component preparation and test experiment, and evaluates the influence of various possible factors on measurement uncertainty. The developed toroidal crystal imaging system achieves micro-region resolution better than 5 μm within millimeter scale for 20 keV-level high-energy X-rays, and spectral resolution reaches several eV. The feasibility of the developed technology is verified by surface density measurement experiment of foam gold sample, and relative uncertainty of areal density measurement better than 2% is obtained. This paper provides a new measurement technology for precise non-destructive testing of high-Z target materials for laser inertial confinement fusion, which is also expected to be applied to other fields that require large field of view and high spatial spectral resolution imaging.
2023,
35: 112002.
doi: 10.11884/HPLPB202335.230317
Abstract:
In the laser driven inertial confinement fusion experiments, several dozens of diagnostic instruments are needed, located in different sightlines of view. Most of the instruments are required to work inside the giant vacuum target chamber, in distances of centimeters to meters. They are always moved from several meters away, by the general diagnostic instrument manipulator and point the micro target in a precision of about 50 μm. The binocular pointing method is one of the continual alignment methods, which are able to work in the vacuum and in a faraway distance. However, at present this method needs target recognizing by eyes and pointing in a manual operation. Under some situations, such as under low illumination or pointing sightlines with an angle, the target marker may not be accurately recognized, as a result, the precision of the diagnostic alignment degenerates rapidly. In this work, a machine vision aided autonomic alignment method is proposed. The Mask R-CNN algorithm is used to recognize the target marker. Many simulated visual target graphs are created to train the algorithm. The accuracy of the target marker recognizing increases obviously. The error in the test is less than 8 pixels. Furthermore, the relation between the pixel shift in the visual graph and the pointing shift in the coordinate is calibrated in the laboratory. According to the machine vision aided alignment method, the tested alignment precision in pointing direction is estimated to be less than 30 μm, and in axial direction less than 50 μm. With the feedback of the alignment shift, the diagnostic alignment is able to be in an autonomic operation.
In the laser driven inertial confinement fusion experiments, several dozens of diagnostic instruments are needed, located in different sightlines of view. Most of the instruments are required to work inside the giant vacuum target chamber, in distances of centimeters to meters. They are always moved from several meters away, by the general diagnostic instrument manipulator and point the micro target in a precision of about 50 μm. The binocular pointing method is one of the continual alignment methods, which are able to work in the vacuum and in a faraway distance. However, at present this method needs target recognizing by eyes and pointing in a manual operation. Under some situations, such as under low illumination or pointing sightlines with an angle, the target marker may not be accurately recognized, as a result, the precision of the diagnostic alignment degenerates rapidly. In this work, a machine vision aided autonomic alignment method is proposed. The Mask R-CNN algorithm is used to recognize the target marker. Many simulated visual target graphs are created to train the algorithm. The accuracy of the target marker recognizing increases obviously. The error in the test is less than 8 pixels. Furthermore, the relation between the pixel shift in the visual graph and the pointing shift in the coordinate is calibrated in the laboratory. According to the machine vision aided alignment method, the tested alignment precision in pointing direction is estimated to be less than 30 μm, and in axial direction less than 50 μm. With the feedback of the alignment shift, the diagnostic alignment is able to be in an autonomic operation.
2023,
35: 113001.
doi: 10.11884/HPLPB202335.230198
Abstract:
High power microwave devices are investigated extensively, because of their potential applications, such as advanced radars, electromagnetic warfare systems. However, low efficiency, enormous volume, huge weight and short lifetime limit their applications. In this paper, a coaxial grating slow wave structure backward wave oscillator (BWO) driven by radial beam is proposed. The focusing system is eliminated in the particle in cell simulation, which can reduce the volume and the power loss in practice. The lifetime of the BWO can also be improved with the thermionic radial beam cathode instead of the explosive emission cathode. After optimization, the BWO driven by 460 kV, 6 kA radial beam can produce 1.2 GW at frequency 3.8 GHz, with the efficiency of 43.5%.
2023,
35: 113002.
doi: 10.11884/HPLPB202335.230181
Abstract:
During the cathode preheating process of a small amount of space traveling wave tubes(TWTs), there is a fault of periodic fluctuations in the heater current. In response to this problem, the range of fluctuation of heater current is estimated by creating the equivalent circuit of heater, and the natural frequency of heater double-helix structure is measured by using the laser vibration, thereby the localization of the problem is completed, and the mechanism of period fluctuation of heater current is analyzed, and the conditions under which the periodic fluctuation occurs are clarified, and the solutions are put forward. Meanwhile, theoretically, the qualitative analysis is conducted on the influence of heater current on the reliability of the space TWTs, and the correctness of the conclusion of reliability influence analysis is verified through experiments.
During the cathode preheating process of a small amount of space traveling wave tubes(TWTs), there is a fault of periodic fluctuations in the heater current. In response to this problem, the range of fluctuation of heater current is estimated by creating the equivalent circuit of heater, and the natural frequency of heater double-helix structure is measured by using the laser vibration, thereby the localization of the problem is completed, and the mechanism of period fluctuation of heater current is analyzed, and the conditions under which the periodic fluctuation occurs are clarified, and the solutions are put forward. Meanwhile, theoretically, the qualitative analysis is conducted on the influence of heater current on the reliability of the space TWTs, and the correctness of the conclusion of reliability influence analysis is verified through experiments.
2023,
35: 114001.
doi: 10.11884/HPLPB202335.230179
Abstract:
The negative ion based neutral beam injection (NNBI) system is one of the testing or demonstrating systems in the frameworks of Comprehensive Research Facility of Fusion Technology (CRAFT). The object of the CRAFT NNBI system is to research the key physics and engineering issues around the NNBI, and to accumulate experience for future development and operation of the NNBI system for fusion reactor. The beamlet optics character of a negative ion accelerator determines the divergence of the formed beam, and further influences the beam transmission efficiency through the accelerator and the beamline, which is very important to the high-power, high-energy, and long-pulse operation of the NNBI system. Therefore, the ion beam simulation code IBSimu was used to analyze and estimate the physics design of the beamlet optics of the 400 keV accelerator for the CRAFT NNBI system. The IBSimu code has been successfully benchmarked and applied to many negative ion sources. The current design of the electrode aperture has a similar structure of the ITER negative ion source, the calculation results of the beamlet divergence can meet the design requirement. A higher extracted ion current density (between 100 to 300 A/m2) draws a lower beamlet divergence. When properly increasing the extraction gap (between 5 to 7 mm) or acceleration gap (between 88 to 110 mm), there is a decreasing tendency of the beamlet divergence.
The negative ion based neutral beam injection (NNBI) system is one of the testing or demonstrating systems in the frameworks of Comprehensive Research Facility of Fusion Technology (CRAFT). The object of the CRAFT NNBI system is to research the key physics and engineering issues around the NNBI, and to accumulate experience for future development and operation of the NNBI system for fusion reactor. The beamlet optics character of a negative ion accelerator determines the divergence of the formed beam, and further influences the beam transmission efficiency through the accelerator and the beamline, which is very important to the high-power, high-energy, and long-pulse operation of the NNBI system. Therefore, the ion beam simulation code IBSimu was used to analyze and estimate the physics design of the beamlet optics of the 400 keV accelerator for the CRAFT NNBI system. The IBSimu code has been successfully benchmarked and applied to many negative ion sources. The current design of the electrode aperture has a similar structure of the ITER negative ion source, the calculation results of the beamlet divergence can meet the design requirement. A higher extracted ion current density (between 100 to 300 A/m2) draws a lower beamlet divergence. When properly increasing the extraction gap (between 5 to 7 mm) or acceleration gap (between 88 to 110 mm), there is a decreasing tendency of the beamlet divergence.
2023,
35: 114002.
doi: 10.11884/HPLPB202335.230263
Abstract:
Coherent transition radiation (CTR) spectroscopy has emerged as a highly productive technique for measuring bunch length and reconstructing longitudinal bunch profiles. However, conventional Michelson interferometry is limited to the amplitude measurement of terahertz radiation spectra, rendering it incapable of directly reconstructing the bunch profile owing to the absence of phase information. Currently, the predominant reconstruction methods encompass the Kramers-Kronig (K-K) phase analysis and algebraic iterative reconstruction algorithms. These two algorithms were employed to validate both Gaussian distribution and Gaussian distribution with tail models, respectively. The outcomes obtained from the K-K algorithm exhibit notable uncertainty, whereas the iterative algorithm showcased superior performance in resolving reconstruction ambiguities and mitigating noise interference. Within the framework of the Lanzhou High Energy Electronic Imaging Platform, a specialized Michelson interferometer was meticulously engineered for the precise measurement of CTR interference spectra. Subsequent to two distinct measurements, the acquired data was subjected to reconstruction and comprehensive analysis employing the aforementioned algorithms. As a result, detailed longitudinal beam cluster reconstructions for the electron beam were successfully obtained. These findings constitute a reference for subsequent beam diagnosis and feedback mechanisms within the High Energy Electron Beam Imaging Platform.
Coherent transition radiation (CTR) spectroscopy has emerged as a highly productive technique for measuring bunch length and reconstructing longitudinal bunch profiles. However, conventional Michelson interferometry is limited to the amplitude measurement of terahertz radiation spectra, rendering it incapable of directly reconstructing the bunch profile owing to the absence of phase information. Currently, the predominant reconstruction methods encompass the Kramers-Kronig (K-K) phase analysis and algebraic iterative reconstruction algorithms. These two algorithms were employed to validate both Gaussian distribution and Gaussian distribution with tail models, respectively. The outcomes obtained from the K-K algorithm exhibit notable uncertainty, whereas the iterative algorithm showcased superior performance in resolving reconstruction ambiguities and mitigating noise interference. Within the framework of the Lanzhou High Energy Electronic Imaging Platform, a specialized Michelson interferometer was meticulously engineered for the precise measurement of CTR interference spectra. Subsequent to two distinct measurements, the acquired data was subjected to reconstruction and comprehensive analysis employing the aforementioned algorithms. As a result, detailed longitudinal beam cluster reconstructions for the electron beam were successfully obtained. These findings constitute a reference for subsequent beam diagnosis and feedback mechanisms within the High Energy Electron Beam Imaging Platform.
2023,
35: 114003.
doi: 10.11884/HPLPB202335.230117
Abstract:
With the increasing demand on higher precision control of beams in modern particle accelerators, higher requirements are raised for the design and survey of engineering control network. In this paper, the layout and survey scheme of the first-level surface control network for the engineering survey of High Energy Photon Source (HEPS) are introduced in detail. The permanent points of the surface control network are arranged in the tunnel of the particle accelerator building, and the vertical view hole is aligned with the instrument plumb on the top surface of the online station hall, and the observation condition of plane mutual view is formed, the transmission and contact of plane coordinates are realized. In the elevation direction, the communication between the leveling station and the elevation coordinates is realized by means of horizontal viewing holes and doors and windows. Therefore, the three-dimensional view and observation structure is formed, which is unique in the construction of synchrotron radiation light source in China, and effectively ensures the accurate control of accelerator orbit. The scheme that the plane control network adopts the GNSS control network and the corner network of the total station respectively is proposed. The elevation control network adopts the scheme of indoor tunnel ground and outdoor ground level survey scheme. Before the installation of the accelerator tunnel equipment, two surface control network surveys were carried out. The data processing was adjusted in plane + elevation mode, and the accuracy of the measurement process is verified by comparing different survey schemes, and the reliability is verified by comparing the measurement results of two control networks. The average point position standard deviation is 2 mm, which indicates that the survey results are reliable and meet the requirements of subsequent control network survey and equipment installation collimation. The stability of the point is improved by optimizing the design of permanent point marker structure. As HEPS requires high stability of permanent control points, through optimal design and special construction, the ultra-high fine and stable bedrock spacer pile was successfully built in the narrow tunnel space, forming a stable three-dimensional permanent control point for the storage ring. It provides a benchmark for long-term monitoring of beam orbit stability, and provides a reference for the subsequent construction of synchrotron radiation light source.
With the increasing demand on higher precision control of beams in modern particle accelerators, higher requirements are raised for the design and survey of engineering control network. In this paper, the layout and survey scheme of the first-level surface control network for the engineering survey of High Energy Photon Source (HEPS) are introduced in detail. The permanent points of the surface control network are arranged in the tunnel of the particle accelerator building, and the vertical view hole is aligned with the instrument plumb on the top surface of the online station hall, and the observation condition of plane mutual view is formed, the transmission and contact of plane coordinates are realized. In the elevation direction, the communication between the leveling station and the elevation coordinates is realized by means of horizontal viewing holes and doors and windows. Therefore, the three-dimensional view and observation structure is formed, which is unique in the construction of synchrotron radiation light source in China, and effectively ensures the accurate control of accelerator orbit. The scheme that the plane control network adopts the GNSS control network and the corner network of the total station respectively is proposed. The elevation control network adopts the scheme of indoor tunnel ground and outdoor ground level survey scheme. Before the installation of the accelerator tunnel equipment, two surface control network surveys were carried out. The data processing was adjusted in plane + elevation mode, and the accuracy of the measurement process is verified by comparing different survey schemes, and the reliability is verified by comparing the measurement results of two control networks. The average point position standard deviation is 2 mm, which indicates that the survey results are reliable and meet the requirements of subsequent control network survey and equipment installation collimation. The stability of the point is improved by optimizing the design of permanent point marker structure. As HEPS requires high stability of permanent control points, through optimal design and special construction, the ultra-high fine and stable bedrock spacer pile was successfully built in the narrow tunnel space, forming a stable three-dimensional permanent control point for the storage ring. It provides a benchmark for long-term monitoring of beam orbit stability, and provides a reference for the subsequent construction of synchrotron radiation light source.
2023,
35: 114004.
doi: 10.11884/HPLPB202335.230217
Abstract:
The samples of the China Spallation Neutron Source (CSNS) Engineering Material Diffraction Spectrometer (EMD) are very large and have different shapes. The neutron collimation aperture needs to be designed as a pointed-mouth slit to be close to these abnormal components. The main function of the pointed-mouth slit is to provide the beam size is needed by the sample experiment, and ensure that the beam size has high accuracy. The pointed-mouth slit is continuous, and it can be changed according to the experimental requirements. The blade uses enriched boron carbide, which can reduce the deformation of the slit cantilever structure. The slit has a very long mouth, which can approach the special-shaped components and enter into the long tubes. The deformation problem of the cantilever was simulated and analyzed using finite element software. The slit adopts a dual safety design, which can effectively prevent from being damaged by large samples. This slit has been applied to the CSNS engineering material spectrometer. It has made remarkable contributions to residual stress measurement. The application of this slit provides a very important reference for the design of the pointed-mouth slits.
The samples of the China Spallation Neutron Source (CSNS) Engineering Material Diffraction Spectrometer (EMD) are very large and have different shapes. The neutron collimation aperture needs to be designed as a pointed-mouth slit to be close to these abnormal components. The main function of the pointed-mouth slit is to provide the beam size is needed by the sample experiment, and ensure that the beam size has high accuracy. The pointed-mouth slit is continuous, and it can be changed according to the experimental requirements. The blade uses enriched boron carbide, which can reduce the deformation of the slit cantilever structure. The slit has a very long mouth, which can approach the special-shaped components and enter into the long tubes. The deformation problem of the cantilever was simulated and analyzed using finite element software. The slit adopts a dual safety design, which can effectively prevent from being damaged by large samples. This slit has been applied to the CSNS engineering material spectrometer. It has made remarkable contributions to residual stress measurement. The application of this slit provides a very important reference for the design of the pointed-mouth slits.
2023,
35: 114005.
doi: 10.11884/HPLPB202335.230074
Abstract:
Accurate measurement of the transverse phase space distribution of electron beams is of great importance in the design and optimization of accelerators. The computerized tomography theoretically provides the true transverse phase space distribution. However, to understand the details of the distribution more accurately, it is necessary to solve the problems of limited range of rotation angle and insufficient number of projections. In this paper, a neural network model is proposed to address these two problems in the hybrid domains, which combines interpolation and artifact removal neural networks in the sinogram and tomogram domains, respectively. Even with a simple diagnostic beamline and a small number of projections (7), the network model can reconstruct the transverse phase space distribution of beams with high quality. Moreover, since the selection of angles is independent of the normalized phase space, Twiss parameters do not need to be measured. Using the proposed method to measure the transverse phase space improves reconstruction quality to a certain extent and simplifies the measurement process.
Accurate measurement of the transverse phase space distribution of electron beams is of great importance in the design and optimization of accelerators. The computerized tomography theoretically provides the true transverse phase space distribution. However, to understand the details of the distribution more accurately, it is necessary to solve the problems of limited range of rotation angle and insufficient number of projections. In this paper, a neural network model is proposed to address these two problems in the hybrid domains, which combines interpolation and artifact removal neural networks in the sinogram and tomogram domains, respectively. Even with a simple diagnostic beamline and a small number of projections (7), the network model can reconstruct the transverse phase space distribution of beams with high quality. Moreover, since the selection of angles is independent of the normalized phase space, Twiss parameters do not need to be measured. Using the proposed method to measure the transverse phase space improves reconstruction quality to a certain extent and simplifies the measurement process.
2023,
35: 115001.
doi: 10.11884/HPLPB202335.230124
Abstract:
To reduce the energy loss of the air-core pulse alternator and the heating of the field winding, a field circuit topology with the function of recovering residual magnetic energy is proposed. By setting the adjustable inductance in the capacitor branch, the capacitor after the discharge has a reverse voltage, forcing the thyristor and the diode to turn off, and switching the current flow path to realize the transfer of the remaining excitation energy to the capacitor. The circuit uses the thyristor as the main switch, and its high current turn-off capability gives it an advantage in the application of high-power pulse alternator. The working process of the proposed excitation energy recovery circuit is introduced, the influence of residual energy recovery on the energy loss and heat generation of the field winding is simulated and analyzed, and the working principle of the circuit topology is verified experimentally. The results show that the circuit can quickly recover the residual energy in the field winding, shorten the freewheeling time of the excitation current, and reduce the excitation loss and energy loss. The law reflected by the simulation and experimental results is consistent with the circuit principle, which shows the validity of the circuit method.
To reduce the energy loss of the air-core pulse alternator and the heating of the field winding, a field circuit topology with the function of recovering residual magnetic energy is proposed. By setting the adjustable inductance in the capacitor branch, the capacitor after the discharge has a reverse voltage, forcing the thyristor and the diode to turn off, and switching the current flow path to realize the transfer of the remaining excitation energy to the capacitor. The circuit uses the thyristor as the main switch, and its high current turn-off capability gives it an advantage in the application of high-power pulse alternator. The working process of the proposed excitation energy recovery circuit is introduced, the influence of residual energy recovery on the energy loss and heat generation of the field winding is simulated and analyzed, and the working principle of the circuit topology is verified experimentally. The results show that the circuit can quickly recover the residual energy in the field winding, shorten the freewheeling time of the excitation current, and reduce the excitation loss and energy loss. The law reflected by the simulation and experimental results is consistent with the circuit principle, which shows the validity of the circuit method.
2023,
35: 116001.
doi: 10.11884/HPLPB202335.230102
Abstract:
Print circuit heat exchanger (PCHE) is widely used in the present supercritical carbon dioxide (S-CO2) Brayton cycle to support its superiority in compactness when compared with other energy conversion cycles. The maintenance and overhaul of PCHE are hard to be carried out when leakage and fouling appear because of the integral structure of the core. A microtube and shell heat exchanger (MSTE) is proposed in this research. The structure of the MSTE is similar to that of the conventional shell-and-tube heat exchanger except that the tube diameter is reduced to microchannel level. The cross-section area of the flow channel in MSTE takes more counts than that in PCHE, thus the volume and weight of MSTE can be reduced by more than 30% when compared with PCHE under typical design conditions of recuperator and precooler. Sensitivity analysis results show that if the designed recuperator and precooler with MSTE structure are adopted, the inlet temperature of compressor changes less than 1 ℃ when the hot or cold inlet temperature of recuperator increased by about 20 ℃. It can be concluded from the analysis results that the heat transfer capacity of MSTE is sufficient to adjust the general working condition fluctuations of the energy conversion cycle.
Print circuit heat exchanger (PCHE) is widely used in the present supercritical carbon dioxide (S-CO2) Brayton cycle to support its superiority in compactness when compared with other energy conversion cycles. The maintenance and overhaul of PCHE are hard to be carried out when leakage and fouling appear because of the integral structure of the core. A microtube and shell heat exchanger (MSTE) is proposed in this research. The structure of the MSTE is similar to that of the conventional shell-and-tube heat exchanger except that the tube diameter is reduced to microchannel level. The cross-section area of the flow channel in MSTE takes more counts than that in PCHE, thus the volume and weight of MSTE can be reduced by more than 30% when compared with PCHE under typical design conditions of recuperator and precooler. Sensitivity analysis results show that if the designed recuperator and precooler with MSTE structure are adopted, the inlet temperature of compressor changes less than 1 ℃ when the hot or cold inlet temperature of recuperator increased by about 20 ℃. It can be concluded from the analysis results that the heat transfer capacity of MSTE is sufficient to adjust the general working condition fluctuations of the energy conversion cycle.
2023,
35: 116002.
doi: 10.11884/HPLPB202335.230253
Abstract:
Due to electricity needs of scenarios such as remote areas and emergency situations, mobile nuclear power sources with high reliability and long life are needed. A conceptual design scheme of a small mobile helium-xenon cooled solid reactor has been proposed in previous work. This study aims to obtain a lightweight and compact core design and improve the design scheme of sliding reflector segments for reliable reactivity control. Firstly, under the design constraints of reactor life and thermal safety, the core geometry optimization analysis was performed using OpenMC, and a design scheme to obtain minimal mass of core was achieved. Secondly, the study analyzed the influence of burnable poison on power distribution and by adding a 2% mass fraction of Gd2O3 to the fuel rods near the reflector region, the radial power factor was reduced from 2.22 to 1.43 at the beginning of life. Finally, by partitioning the sliding reflector, a linear introduction of reactivity was achieved, and it can also ensure the reactor safety in case of accidents. This study provides a certain reference for the design of small gas-cooled solid reactor.
Due to electricity needs of scenarios such as remote areas and emergency situations, mobile nuclear power sources with high reliability and long life are needed. A conceptual design scheme of a small mobile helium-xenon cooled solid reactor has been proposed in previous work. This study aims to obtain a lightweight and compact core design and improve the design scheme of sliding reflector segments for reliable reactivity control. Firstly, under the design constraints of reactor life and thermal safety, the core geometry optimization analysis was performed using OpenMC, and a design scheme to obtain minimal mass of core was achieved. Secondly, the study analyzed the influence of burnable poison on power distribution and by adding a 2% mass fraction of Gd2O3 to the fuel rods near the reflector region, the radial power factor was reduced from 2.22 to 1.43 at the beginning of life. Finally, by partitioning the sliding reflector, a linear introduction of reactivity was achieved, and it can also ensure the reactor safety in case of accidents. This study provides a certain reference for the design of small gas-cooled solid reactor.
2023,
35: 116003.
doi: 10.11884/HPLPB202335.230047
Abstract:
To study the oxidation and phase structure of fuel pellets for both intact and leak pressurized water reactors fuel rods with different burnup, Raman spectroscopy was used to analyze the intact fuel rods with 14 GW·d·t−1 and 41 GW·d·t−1 burnup as well as the leak fuel rods with 14 GW·d·t−1 and 41 GW·d·t−1 burnup. Evaluation of the reactivity and structural changes of the fuels based on different laser powers are provided locally. The results show that the increase in laser power would not cause oxidation of UO2. The intact fuel rod UO2 pellets with 14 GW·d·t−1 and 45 GW·d·t−1 burnup consist of UO2, U4O9 and U3O8, and the oxidation of fuel pellet in peripheral zone is higher than that of the internal area. The leak fuel rod UO2 pellets with 14 GW·d·t−1 and 41 GW·d·t−1 burnup have undergone restructuring and formed columnar grains, which consist of UO2 and U3O8. The increase of burnup and leakage of fuel rods can promote the oxidation of UO2 pellets, but the main phase structure of the fuel pellets will not change.
To study the oxidation and phase structure of fuel pellets for both intact and leak pressurized water reactors fuel rods with different burnup, Raman spectroscopy was used to analyze the intact fuel rods with 14 GW·d·t−1 and 41 GW·d·t−1 burnup as well as the leak fuel rods with 14 GW·d·t−1 and 41 GW·d·t−1 burnup. Evaluation of the reactivity and structural changes of the fuels based on different laser powers are provided locally. The results show that the increase in laser power would not cause oxidation of UO2. The intact fuel rod UO2 pellets with 14 GW·d·t−1 and 45 GW·d·t−1 burnup consist of UO2, U4O9 and U3O8, and the oxidation of fuel pellet in peripheral zone is higher than that of the internal area. The leak fuel rod UO2 pellets with 14 GW·d·t−1 and 41 GW·d·t−1 burnup have undergone restructuring and formed columnar grains, which consist of UO2 and U3O8. The increase of burnup and leakage of fuel rods can promote the oxidation of UO2 pellets, but the main phase structure of the fuel pellets will not change.
2023,
35: 116004.
doi: 10.11884/HPLPB202335.230096
Abstract:
During the normal operation of pressurized water reactors, tritium contributes more than 95% of the total activity of liquid phase effluent from pressurized water reactors, and it is one of the key radionuclides in reactor design and operation. Through in-depth data cleaning and analysis of tritium emission data from eight units operating in the United States with very similar core designs from 2000 to 2019, it is concluded that tritium emission from Sb-Be secondary neutron sources using stainless steel cladding is one of the important sources of tritium source terms for pressurized water reactor units. According to statistics, the average contribution of tritium production from secondary neutron sources in the units is 7.5 TBq·a−1, combined with theoretical calculations, The penetration ratio in line with the current cladding material development and operation management level is 10%−20%. The elimination of secondary neutron sources can reduce the public dose caused by tritium emissions by about 20%, and can also reduce the constraints of tritium source terms on the number of units planned for the plant site. In addition, it also found that significant fluctuations in tritium emissions are significantly affected by concentrated liquid emissions, especially before or during the overhaul of pressurized water reactors in the United States, which will help optimize the management of radioactive emissions from future units.
During the normal operation of pressurized water reactors, tritium contributes more than 95% of the total activity of liquid phase effluent from pressurized water reactors, and it is one of the key radionuclides in reactor design and operation. Through in-depth data cleaning and analysis of tritium emission data from eight units operating in the United States with very similar core designs from 2000 to 2019, it is concluded that tritium emission from Sb-Be secondary neutron sources using stainless steel cladding is one of the important sources of tritium source terms for pressurized water reactor units. According to statistics, the average contribution of tritium production from secondary neutron sources in the units is 7.5 TBq·a−1, combined with theoretical calculations, The penetration ratio in line with the current cladding material development and operation management level is 10%−20%. The elimination of secondary neutron sources can reduce the public dose caused by tritium emissions by about 20%, and can also reduce the constraints of tritium source terms on the number of units planned for the plant site. In addition, it also found that significant fluctuations in tritium emissions are significantly affected by concentrated liquid emissions, especially before or during the overhaul of pressurized water reactors in the United States, which will help optimize the management of radioactive emissions from future units.
2023,
35: 119001.
doi: 10.11884/HPLPB202335.230103
Abstract:
In this work, the temperature-dependent behavior of CH3NH3PbBr3 (MAPbBr3) crystal powder is experimentally investigated using steady-state photoluminescence (PL) spectroscopy. Under 405 nm continuous-wave laser excitation, the fluorescence peak is at 560 nm with a full width at half maximum of 123 meV. There is a good linear increase in the luminescence intensity with increasing pump laser fluence, which indicates induced single-photon absorption. The MAPbBr3 crystal powder-induced PL exhibits different temperature-dependent behaviors at temperatures ranging from 80−310 K. As the temperature increases, the photon energy of the line width gets greater and the PL integral intensity gradually decreases because of the enhanced exciton phonon interaction. The peak of the PL spectrum shows a linear blue shift at 80−145 K. There is a very shallow slot around 150 K, while the peak position of the spectrum remains almost constant when the temperature exceeds 150 K. These temperature-dependent induced PL behaviors are mainly due to the contribution of phase transition and thermal expansion from orthogonal to tetragonal phases occurring at around 150 K. In addition, exciton binding energies of about 49.8 meV and longitudinal optical phonon energies of about 60.4 meV are derived from the temperature dependent PL experimental dataset.
In this work, the temperature-dependent behavior of CH3NH3PbBr3 (MAPbBr3) crystal powder is experimentally investigated using steady-state photoluminescence (PL) spectroscopy. Under 405 nm continuous-wave laser excitation, the fluorescence peak is at 560 nm with a full width at half maximum of 123 meV. There is a good linear increase in the luminescence intensity with increasing pump laser fluence, which indicates induced single-photon absorption. The MAPbBr3 crystal powder-induced PL exhibits different temperature-dependent behaviors at temperatures ranging from 80−310 K. As the temperature increases, the photon energy of the line width gets greater and the PL integral intensity gradually decreases because of the enhanced exciton phonon interaction. The peak of the PL spectrum shows a linear blue shift at 80−145 K. There is a very shallow slot around 150 K, while the peak position of the spectrum remains almost constant when the temperature exceeds 150 K. These temperature-dependent induced PL behaviors are mainly due to the contribution of phase transition and thermal expansion from orthogonal to tetragonal phases occurring at around 150 K. In addition, exciton binding energies of about 49.8 meV and longitudinal optical phonon energies of about 60.4 meV are derived from the temperature dependent PL experimental dataset.
2023,
35: 119002.
doi: 10.11884/HPLPB202335.230130
Abstract:
A series of reliability design work is carried out for a scintillation detector which can detect pulsed neutrons in complex environment. In the design, the inherent reliability of the detector is improved by means of redundant backup of test channels and anti-vibration design. The mission reliability objectives of each component of the detector are defined by means of reliability modeling and index assignment. Through FMECA analysis method, the failure modes and their effects of each component of the detector are studied, and the important component of reliability is determined. The reliability of the detector is further improved by using environmental stress screening test and reliability enhancement test. It is proved that the mission reliability of the pulsed neutron detector with the above reliability design assurance technology is not less than 0.999.
A series of reliability design work is carried out for a scintillation detector which can detect pulsed neutrons in complex environment. In the design, the inherent reliability of the detector is improved by means of redundant backup of test channels and anti-vibration design. The mission reliability objectives of each component of the detector are defined by means of reliability modeling and index assignment. Through FMECA analysis method, the failure modes and their effects of each component of the detector are studied, and the important component of reliability is determined. The reliability of the detector is further improved by using environmental stress screening test and reliability enhancement test. It is proved that the mission reliability of the pulsed neutron detector with the above reliability design assurance technology is not less than 0.999.
